General-Purpose Heat Source Safety Verification Test Series: SVT-1

LA—10353-MS

DE85 017956

LA-10353-MS

UC-33AIssued: June 1985

General-Purpose Heat SourceSafety Verification Test Series:

SVT-1 Through SVT-6

D. PavoneT. G. GeorgeC. E. Frantz

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United StatesGovernment. Neither the United States Government nor any agency thereof, nor any of theiremployees, makes any warranty, express or implied, or assumes any legal liability or responsi-bility for the accuracy, completeness, or usefulness of any information, apparatus, product, orprocess disclosed, or represents that its use would not infringe privately owned rights. Refer-ence herein to any specific commercial product, process, or service by trade name, trademark,manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom-mendation, or favoring by the United States Government or any agency thereof. The viewsand opinions of authors expressed herein do not necessarily state or reflect those of theUnited States Government or any agency thereof.

u Los Alamos National LaboratoryLos Alamos, New Mexico 87545

OF THIS COft'SKKT

yLos Alamos National LaboratoryLos Alamos. New Mexico 87545 memorandum

TO Holders of LA-10353-MS

FROM I S — 1 1

DATE J u l y 2 6 , 1985

MAIL STOP/TELEPHONE D 4 1 8 / 7 - 5 4 6 9

SUBJECT Addendum

Addendum, p . 37.

Fig. A-l. Particle-size distributions of selectedimpacted plutonia pellets.

GENERAL-PURPOSE HEAT SOURCESAFE! Y VERIFICATION TEST SERIES:

SVT-1 THROUGH SYT-6

bv

D. Pavone, T. G. George, and C. E. Frantz

ABSTRACT

The General-Purpose Heat Source (GPHS) is a modular heat source that "ill supplyenergy for Radioisotope Thermoelectric Generators (RTGs) in space missions. TheSafety Verification Tests (SVTs) are performed to assess the plutonia containmentcapability of heat source modules subjected to certain accident environments. Thisinterim report describes the GPHS module configuration, 'he test environment, and theresponse of the module components following simulated reentry and solid Earthimpact. The specific test environment of these initial six tests results from failure of thebooster rocket to place the spacecraft in a proper trajectory and subsequent reentry ofthe GPHS modules from Earth orbit.

I. INTRODUCTION

The General-Purpose Heat Source (GPHS) is a mod-ular radioisotopic heal source that produces heal fromthe a-decay of the 238 isotope of plulonium. The heai-source modules have been designed so thai they may beused as individual heat sources in RadioisolopcThermoelectric Generators (RTGs) of various finalpower outputs and as a heat source for turbine-typegenerators if such equipment were developed. The in-itial application of the GPHS will be in RTGs to furnishelectric power for the NASA Galileo mission and theUlysses mission (formerly the Internationa! Solar-Polarmission). The RTGs for these missions each use eight-een 250-W(t: .nodules.

The GPHS module was primarily designed at the LosAlamos National Laboratory: however, that design wasmodified by the General Electric Company, systemcontractor for the RTG. tc reduce the weight for thenbo\e-mentioncd missions. A short series of DesignIteration Tests (DITs) was conducted in the modifieddesign configuration and then the design was acceptedfor use in the Galileo and Ulysses missions. An ex-tensive series of tests is being conducted io assess thecapability of the system to contain piutonium in theevent of an aborted mission from orbit with subsequentreentry and Earth impact. This interim report describes

the planned Safely Verification Test (SVT) series andthe results of the initial six impact lests.

The GPHS module contains four right circular cylin-drical pellets of 238-plutonia nominally 27.7-mm d.amX 27.7-mm height, which weigh approximately 150 gand generate 62.5 W(t). Each plutonia pellet is clac! in awelded DOP-26 iridium-alloy capsule 29-mm diam x29.4-mm height X 0.64-mm wall thickness. One end ofthe iridium capsule is fitted with a vent of sinterediridium powder through which the decay producthelium is released. This assembly, referred to as a fueledclad (FC). is the basic unit of plutonia containment.Two fueled clads are loaded into a cylindrical. Fine-weave-Pierced Fabric* (FWPF) composite graphite im-pact shell (GIS). 39.4-mm diam X 78.7-mm length. Tocomplete the GPHS module, two GISs. each sur-rounded by a cylinder and two disks of carbon-bondedcarbon-fiber (CBCF) insulation, are contained withincavities of a rectangular parallelepiped FWPF aeroshell(A/S) 98 mm X 94 mm X 54 mm. A schematic view ofthe module is shown in Fig. 1.

Reentry analysis' indicated that if an RTG reentercdthe atmosphere, the RTG case and thermoelectric mod-ules would be stripped from the heat source and the heat

*Fineweave-Pierced Fabric 3-D carbon/cr.rbon composite, aproduct of AVCO Systems Division. 201 Lowell Si Wil-mington. MA 01887. '

1

source modules would reenter as single entities. Thus,individual modules were selected for testing in the testprogram.

II. TEST OBJECTS

Objects to be tested in this phase of the program werecomplete GPHS modules assembled from flight-qualitycomponents except as noted below. The source andfabrication responsibilities of the components were asfollows:

A. Iridium Clad

clad at that site. A process change during the producirun resulted in two classes of plutonia pellets, omwhich had been fired in an argon atmosphere andother in an Ar/O; atmosphere. Both pellet groupsconsidered to be of flight quality. Table 1 listsproduction history of the pellets.

Because weld cracking occurred in some test weSRP developed an ultrasonic, nondestructive vevaluation procedure (NDE). An arbitrary sccalibrated against standard defects, was established,those FCs with ultrasonic reflections <8 were dcnated as flight quality.

C. CBCF Insulation

Iridium-allov sheet for the cladding was produced byOak Ridge National Laboratory. Circular blanks andfoil were supplied lo Monsanto Research CorporationMound Plant (MRC-Mound).

MRC-Mound formed cups from the blanks: formedvent assemblies, decontamination covers, and weldshields from the foil: and assembled these pieces loconstitute the pellet cladding.

B. Plutonia

Plutonia pellets were fabricated ai the SavannahRiver Plant (SRP) and were encapsulated in the iridium

Carbon-based ca'bon-fiber insulation componwere manufactured to final configuration at Oak RNational Laboratory and were supplied directlyMRC-Mound.

D. Aeroshell and Impact Shell

Fineweave-Pierced Fabric composite graphite cponents were machined at two locations. Los AlaNational Laboratory and Tcledyne IsotopesTimonium. Maryland. Items produced by Tcieccarry an identification code of PAT or PGT followea four-digit number. PAT-XXXX or PGT-XX

FWPFAEROSHuLL

FWPFFLOATING

MEMBRANE

PLUTONIAPELLET

•' IRIDiUM— js' \CLAD C B C F ^ - - F W P F

INSULATION IMPACT SHELL

Fig. 1. Schcmalic diagram of a GPHS module.

TABLE I.

Pellet No.

HF-232HF-238HF-261HF-410

HF-273HF-355HF-369HF-449

HF-343HF-350HF-454HF-457

HF-139HF-162HF-348HF-354

HF-260HF-267HF-415HF-426

HF-189HF-225HF-361HF-373

Production History of the SVTFuel Pellets

Firing Atmosphere

Ar/OiAr/O3

Ar/O,Argon

Ar/O:

ArgonArgonArgon

ArgonArgonArgonArgon

Ar/O;Ar/O:

ArgonArgon

Ar/O;Ar/O:

Ar/O:

Argon

Ar/O,Ar/O:

ArgonArgon

Test

SVT-1SVT-1SVT-1SVT-1






Those produced at Los Alamos are identified with acode of PAL or PGL followed by a three-digit number.PAL-XXX or PGT-XXX. Aeroshclis used in the testmodules of this series were machined at Los Alamos toremove twice the thickness of expected ablation for thereentry mode of the test. The RTG contractor. GeneralElectric Company, described two reentryconfigurations: a minimum-gamma and an orbital-decay reentry mode.

E. Module Assembly

Components of the test modules were asemblcd atMRC-Mound. After the vents of the fueled dads wereactivated and the module was assembled, the assembledmodule was treated in the Mound Reduction and Moni-toring Facility (MRMF). Then the module was sub-jected to two cycles of flight-acceptance vibration spec-tra and transient accelerations, radiographed, andshipped to Los Alamos in welded stainless steel con-tainers. Table II identifies the components ofthc mod-ules SVT-1 through SVT-6.

III. TEST PROGRAM

The test program was designed to simulate the se-quence of environments and events that a modulewould experience during an aborted mission.

Thirteen modules were allocated for testing in theSVT series. Each module was fueled with two GISs: oneGIS, designated the primary impact assembly (PIA).contained flight-quality FCs, and the other GIS. orsecondary impact assembly (SIA), contained non-flight-quality FCs. The FCs in the SIA arc not flight-qualitybecause weld-inspection NDE indications exceeded 8(arbitrary units). No FC with an NDE indication >14was used in the SVT series.

In addition to the reentry mode and the fuel process-ing variables, various impact orientations of the modulewere included. Schematic representation of possibleorientations is depicted in Fig. 2. and the Impact TestPlan is depicted in Fig. 3. Orientations of tests followingthe initial five (SVT-1 through 5) were determined by aTechnical Review Board consisting of R. W. Zocher(Los Alamos National Laboratory). C. T. Bradshaw(General Electric Company), and R. W. Englehan(NUS).

IV. EXPERIMENTAL PROCEDURES

A. Receiving and Inspection

Assembled modules were received from MRC-Mound in welded stainless steel containers. Three of themodules had been disassembled at MRC-Mound andthe impact assemblies shipped in stainless steel con-tainers separate from the aeroshell/insulation compo-nents.

The test articles were radiographed to establish thecondition of the fuel pellet before further test opera-lions. Test modules were removed from the shippingcan in an argon-atmosphere glove box (O : = <150ppm). were disassembled to the extent of removal ofthcimpact assemblies from the aeroshell. and were visually-examined.

B. Aging

A !/16-in.-diam optical pyrometer sight hole wasdrilled through the cap of the primary impact assembly,and both GISs were loaded into an AT.) graphite fumacefixture. The aging assembly was transported to thefurnace in a covered can and loaded into the furnacewith minimum exposure to air.

Aging treatments were performed in high-vacuumfurnaces with tungsten mesh heating elements and tan-talum radiation shields. Most of the GISs were aged inBrew Model 424C furnaces, which have a 4-in.-diam hot

I VH1 1 11. Components of CPUS SV'T Series

Component

Aeroshel!

Prime impact assemblyInsulation cylinderInsulation discs

Impact shellFueled clad—open end

Fuel pelletVent cupShield cup

Fueled clad—blind endFuel pelletVent cupShield cup

Secondary impact assembly-Insulation cylinderInsulation discs

Impact shellFueled clad—open end

Fuel pelletVent cupShield cup

Fueled clad—blind endFuel pelletVent cupShield cup

SVT-1

PAL-012

C40-4P8-2-4:P8-2-15PGL-013FC-232HF-232LR-313-1LR-316-1FC-238HF-238LR-315-2LR-318-6

C31-3P8-2-2:P12-1-18PGL-014FC-261HF-261P709-6Q804-1FC-410HF-410S2-4S2-5

Test Modules

SVT-2

PALO 15

C40-5P8-2-44:P12-1-17PGL-018FC-355HF-355Q806-2Q80G-5FC-369HF-369NR528-2NR528-3

C33-9PI1-1-10:PI 1-1-11PGL-018FC-449HF-449S27-2S25-3FC-273HF-273PR718-4MER19-4

SVT-3

PAL-014

C40-7P8-2-59:P8-2-60PGL-020FC-343HF-343PR718-5PR719-5FC-350HF-350R904-7R904-5

C30-4PI 1-1-24:P11-1-3IPGL-027FC-457HF-457P40-5P41-4FC-454HF-454S36-4S39-5

SVT-4

PAT-1007

(40-6P3-2-51:P8-:-54PGT-1015FC-348HF-348QR820-IQR820-6FC-354HF-354QR820-3QR820-2

C30-8Pll-11-12:P1J-1-23PGT-1017FC-139HF-139N510-CMER14-5FC-162HF-162MER19-2MER1-5

SVT-5

PAT-1008

C41-3Pll-2-12:PU-2-20PGT-1027FC-267HF-267P701-5P708-5FC-260HF-260PP717-3PR717 4

C34-2PI 1-2-18:PI 1-2-29PGT-1029FC-415HF-415S8-3S7-2FC-426HF-426S25-4S25-5

SVT-6

PAT-1009

C40-8PI 1-1-30Pll-2-8PGT-1023FC-361HF-361PR726-1PR725-5FC-373HF-373PR727-3Q803-6

C29-5PI 1-2-7PI 1-2-9PGT-1026FC-189HF-189P705-3P705-5FC-225HF-225MER1-4MER7-4

FiR. 2. T h r e e ang le s descr ibe the o r i e n t a t i o n sens i l iv i i s of the ( I I ' H S m o d u l e to impac t .

zone and accommodate the two GISs from a singlemodule. A 6-in.-diarn Brew Model 426C. which couldaccommodate four GISs from two modules, was usedfor the aging heat treatment of some test pieces.

Two of the 4-in.-diam furnaces were equipped tomonitor the helium released from the FCs during theaging treatment. Those modules treated in thesefurnaces were continuously monitored, but modules tobe handled in this manner were not preselected.

Aging treatments were conducted at a pressure of<1 X 10 h torr and a clad temperature of 1287°C asmeasured with a calibrated optical pyrometer sighted onthe end of one of the GIS fueled dads. This temperaturerepresented a weighted average of the iridium-clad tem-perature at the operating conditions of the heat source inthe Galileo and Ulysses RTGs. Aging time was 200 h forGISs from modules to be tested in the minimum-gamma reentry mode, and 90 days for GISs from mod-ules to be tested in the orbital-decay reentry mode. The90-day aging reflects the expected elapsed time for anaborted Galileo mission.2 however, the data obtainedare considered applicable to the Ulysses mission as well.which would have a 38-day operational period before anorbital-decay reentry.

C. Reentry Simulation

When the aging treatment was completed, the GISswere returned to the inert-atmosphere glove box. andtwo additional holes were drilled in the cap of theimpact shells to accommodate the legs of a split-junc-tion thermocouple. The appropriate reentry tempera-ture profile was applied in an electron-beam furnace.Figure 4 illustrates the temperature profiles for theminimum-gamma and orbital-decay reentry conditions.

D. Preimpact Inspection

Before the GISs were reassembled into the aeroshell.they were again radiographed to document the pre-impact condition of the plutonia pellet.

E. Impact Test

Holes were drilled in the aeroshell and the primaryGIS for thermocouples used to monitor the temperatureof the impact assembly. A split-junction. Chromcl-Alumel thermocouple was installed with its legs contact-ing a primary FC. and two beaded-junction thermocou-ples were placed in contact with the outer surface of theprimary GIS. The instrumented module was trans-ported to the test site in a helium-filled container thatwas cooled by forced air.

Test modules in these reported tests were impacted atthe Los Alamos Isotope Fuels Impact Test Facility(IFIT) against a hardened steel target at the designatedtemperature and velocity corresponding to the reentrymode of the test. The impact test conditions, specifiedby General Electric Company, were a velocity of 54 m/sand a clad impact temperature of 919°C for minimum-gamma reentries and 975°C for orbital-decay entries.

The IFIT. a 178-mm-diam gas gun with provision forcontainment of the impacted test article in a catch tube,is described in detail in Los Alamos Scientific Labora-tory report LA-6013 (January 1976). entitled "IsotopeFuels Impact Tester." Tests of GPHS SVT modulesdiffered from that shown for the Multihundred-WattFuel Sphere Assemblies (MHW FSAs): The moduleswere not enclosed in an impact can, iridium-cladtemperatures were measured directly, and the desiredimpact temperatures and thermal inventory of a module

AGE: 200 HAT 1287°C

RRENTERMTN. GAMMA

IMPACT919 C 54 m/s

( = e = o°

= 6 = 0°

ABLATIONSIMULATION

13

MODULEASSEMBLY

MODULEREDUCTION

RECEIVEAND

INSPECT

11

AGE: 90 DAYSAT 1287°C

REENTERORBTT DECAY

|

IMPACT975°C, 54 m/s

7

IMPACTTBD

ct= 90° , Y = 0 c

13

POSTMORTEM

Fig. 3. Tesl scheme fur aging reentry-impact poriion of (iPHS SVT series.

1600

ooIt?

onUJa.

UJh-

1500

MOOooLJ 1300

?ATU

R

Fo o o

EM

PE

F

o o

I00Q

9 0 0

/

/

J\

0

\

\

MINIMUM GAMMA

\

400 800

/

/

J\

1200

V

\1600

1500

TIME.s.

1400

1300

1200

1100

1000

9 0 0

ORBI"r DEC.

\

\

•

100 2 0 0 300 4 0 0 5 0 0

TIME, s.

Fig. 4. Clad tcmpcralurc histories during reentry of a GPHS module.

were such that the impact temperatures were reached byself-heating.

For modules in the a = p1 = 0° (broad-face) impactorientation, geometric considerations pre\ented thedirect use of split-junction thermocouple measurementof the clad temperature. In these cases, a temperaturecalibration was made in the gun, in which the surfacetemperature of the impact shell was determined tocorrespond to the iridium-clad temperature measuredw nh the split-junction thermocouple. The split-junctionthermocouple was removed, and the lest was conductedat the calibrated impact-shell surface temperature.

F. Postmortem Examination

Because the schedule for Safety Analysis Reviewsallowed only a limited time to complete the impact testsand postmortem examinations, we adopted the protocolof performing complete postmortem examinations onlyof the primary FC's. This protocol was later amended toinclude investigation of failures of the secondary FCs.and since the fuel pellet would be processed for plutoniarecovery, chemical analyses of the secondary fuel pelletswere obtained.

The principal objectives of the postmortem examina-tion were to determine the quantity of plutonium re-leased, if any. and the fraction in the <l(j-um particle-sizc range: to document the damage sustained by allcomponents: and to characterize the iridium andplutonia with respect to chemical composition andmicrostructure. The following nine steps summarize thepostmortem examination.

(1) Obtain documentary photographs of the post-impact condition of the aeroshell. the impactshells, and the fueled clads.

(2) Recover all graphitic components, including thecatch-tube debris, and determine the total pluto-nium content and the fraction in the particle-sizerange <l()-um.

O) Measure the principal dimensions of the im-pacted FCs.

(4) Estimate the area of fractures from suitably or-iented photographs.

(5i Defuel the FC's. obtain documentary photographsot the nlutonia fracture pattern, and performsieve analysis of the impacted plutonia pellets ofselected unfailcd FC's.

CS) Select a sample of each cup of the iridium clad foremission specirographic analysis and select twosamples for Auger electron spectroscopy (AES)analysis.

(?) Select mctallographic cross sections through anyfailures or severe localized deformation of theindium clad, select an axial cross section throughthe weld, and select other cross sections so that

both transverse and axial microstructure and thegrain size of each cup may be determined.

(8) Cross section the vent assembly and metallo-graphically examine the vent-assembly weldmicrostructures. vent deposits, and vent ef-fusates.

(9) Select samples of the plutonia fuel pellet for emis-sion spectrographic analysis, colorimetric phos-phorus analysis, and ceramographic microstruc-tural examination.

The experimental procedures for conducting most ofthe postmortem operations involve generally wellknown equipment and techniques and need not bedescribed in any further detail. However, the procedurefor obtaining the total plutonium and the <10-u.m frac-tion contained in the graphitic materials warrantsfurther discussion.

In previous test programs involving the MHW FSAs.the FSAs were impacted with the FSA contained withina welded tantalum can. All graphite debris was re-covered after sawing the can open, and the debris wasburned in air at about 850-900°C. The resulting ash wasdissolved in acid, and the solution was analyzed forplutonium by radiochemical techniques.

For most of the initial tests (SVT-1 through 5) de-scribed here, the debris remaining in the catch tube wasrecovered by washing with ethyl alcohol, then was driedand combined with the aeroshell and impact shells.Processing of this material then followed the techniqueused previously, except that the ash resulting from thecombustion was sieved into fractions greater than andless than 10 urn. and each fraction was analyzedseparately.

To investigate possible agglomeration of plutoniaparticles into larger aggregates by sintering at the com-bustion temperature of graphite, an extraction replicawas made of a sample from the <20-um. >10-umfraction of the ash. and this replica was examined byelectron microscopy. Figure 5 shows that very smallparticles, a few tenths of a micron in diameter, didindeed form aggregates larger than 10 urn. To circum-vent this problem, the procedure for handling higraphitic materials was modified according to a schemasuggested by E. W. Johnson (MRC). In this procedure,large pieces of aeroshell. impact shells, and insulationwere cleaned ultrasonically in ethyl alcohol before com-bustion in the usual manner. Material recovered fromthe washing operation was combined with the catch-tube debris and burned in oxygen in a plasma-assistedcombustion furnace. The rate of oxidation is very slowin this apparatus, but the temperature remains low(~50°C) so that particle sintering is not a problem. Theash is sieved into <10-um and >IO-|im fractions andanalyzed as before. The plutonium remaining on the

Fig. 5. Agglomerates of plutonia particles and ash were formedduring combustion of the graphitic materials. 10.000X.

aeroshell and impact shells is considered to be OO-ummaterial.

V. TEST RESULTS

Results will be presented narratively as a descriptionof observations, with illustration of significant features.For ease of comparison and ready reference, analyticalresults are tabulated as follows in the Appendix:

Table A-I. Impact Test Summary—GPIIS SITSeries

This table lists the NDE value, the gross deforma-tion of each FC, the number of failures, and theestimated area of the fractures.

Table A-I 1. GPHS SYT Fuel ReleaseThis table lists the total plutonium released in thetest and the distribution between the <10-um and>10-um size range.

Table A-III. Particle-Size Distribution (ifthe<l(l-\imFraction of Selected Impacted Pellets

The size distribution of the < 10-um fraction of theplutonia pellets from selected unfailed fuel clads isshown in this tr.ble. Figure A-l graphically showsthe results of the sieve analysis of these pellets.

Table A-IV. Iridium Grain Size—GPHS SVTSeriesThis table lists the grain size of the iridium cups inaxial and transverse cross section expressed asgrains/640 um thickness.

Table A-l'. Summary of AFS Analyses of GPUSSVT Iridium

This table summarizes the results of AES analysisof the primary iridium clads and a few of thesecondary elads. The Th^/lr.;,) intensity ratios aregiven for the interior, center, exterior, and for theaverage. The average intensity ratios are given forother elements.

Table A-l'I. Results of Spectrographic Inalvsis ofGPHS SIT Iridium

The concentrations are tabulated r^r \-r,r;\ir'----- clc-rv.e.M.-k i-.-.'itc..i :-. ; i ie i n d i v i d u a l i n d i u m c u p s as

determined by emission spectroscopy.Table A-\ II. Plutonia Analyses, GPIIS .VI 7'Scries

This table summarizes the results of emissionspectrographic analysis of the plutonia pellets andgives the phosphorus content as determined by acolorimetri'; procedure.

A. SVT-1

This assembly was tested to simulate minimum-gamma reentry conditions in a broad-face (o = |i = ()")orientation. The impact temperature was 919"C (clad)and the impact velocity was 54.4 m/s. The target washardened 4340 steel.

Figure 6 shows the module as recovered from thecatch tube. There were nearly full length cracks on bothnonclosurc narrow faces of the aeroshell and two cracksparallel to the axes of the impact assemblies on theimpact face. The back face was dented and cracked.Although forces exerted on the back face during impactmay account for the deformation and cracking of theaeroshell back face, the observed deformation andcracking might also result when the module reboundsagainst thermocouple extension wires that arc fedthrough the center of the inner projectile cylinder. Thecondition of the P1A impact shell is shown in Fig. 7Both of the GISs had slightly bowed profiles and irregu-lar cracks on the impact face extending about 85% of thelength from the closure end. These postimpact featuresare typical of the FWPF components of a module im-pacted in the a = (3 = 0° orientation.

No failures were observed in cither of the FC's of'.hoP1A, FC-232 and FC-238. The overall deformation wassymmetrical and only modest localized iridium de-formation was observed, principally on the impact face.

Failures occurred in both fueled clads of the SIA.Figure 8 illustrates a major failure located on the backside in both cups of the iridium clad of FC-261 andshows a small failure on the impact face of the shield cupabout 180° from the back-side fracture. The vent-endprofile view shows the overall distortion of the iridiumclad caused by plutonia fragments sliding along a planeoriented at an angle near 45° to the impact plane. Thefailure in FC-410 apparently originated at the corner ofthe shield-cup back side and extended axially through

(a) (b)

Fig. 6. The aeroshell of SVT-1. There were cracks on the impact face, on both nonclosure narrow faces, and on the bai;k. (a)Impact face forward, (b) back forward.

(a) (b)

Fig. 7. The graphite impact shell of the PIA of SVT-1 was cracked on the impact face and had a slightly bowed profile, (a)Impact face, (b) profile view.

10

(a) (b)

(c)

Fig. 8. Fuel push-lhrough failures occurred on the impact face o f FC-261 and on the back side of FC-261. (a) Impact face, (b)back side, and (c) vent-end view.

the weld into the vent-cup wall, as well as into the edgeof the shield-cup bottom. Figure 9 illustrates the lo-cation and the extent of the failure.

Metallographic transverse cross sections through thefailures in FC-261 are shown in Figs. 10 and 11. Thefracture mode at the fracture site on the vent-cup backside (Fig. 10) was intergranular, although a small reduc-tion in thickness, about 4%, indicates limited ductility.The radial displacement of opposite sides of the fractureindicates the effect of fuel-fragment push-through. Thephotomacrograph of the cross section through the im-pact-face fracture of the shield cup (Fig. 11) shows asharp bend at the point of the fuel-fragment push-through and the fracture nearby in the reverse-bend

rep;.>n. The etched microstructure indicates that thefdlure occurred where some relatively large, columnargrains normal to the surface were present. This micro-structure is similar to that observed in some vent-assembly welds and is probably the location at which theweld-shield tab was wJded to the cup interior.

Transverse metallographic cross sections through theshield-cup failure of FC-410 are shown in Fig. 12. Again,the effect of fuel-fragment push-through is evident. Thefracture mode was intergranular, but the reduction ofthickness of about 6% indicates modest ductility

Auger electron spectroscopy analysis of fracture sur-faces indicated that small quantitites of grain-boundarysulfur were present in both samples of the FC-261 ventcup.

11

(a) (b)

Fig. 9. The failure in FC-410 originated al corner on the shield-cup back side, and it extended axially through the wall of theshield cup into the vent cup as well as into the edge of the capsule bottom.

(a) (b)

Fig. 10. Radial displacement of the two sides of the fracture on the back side of the FC-261 vent cup indicates the effect of fuel-fragment push-through. The fracture mode was inlergranular.

12

(a) (b)

Fig. I I . The fracture on the shield-cap import face occurred in the reverse-bend region near the point of fuel-fragmentindentation. Large grains on the interior of the wall thickness result from welding of the weld-shield tab to the capsule wall, (a)7X. (b)50X.

The calcium content of the plutonia pellets HF-238.HF-261, and HF-410 exceeded the SRP guideline limits.The microstructuresof pelli is HF-238 and HF-239 weretypical of SRP material.

The iridium microstructure was uniform; however,the grain size varied from 20 grains/640 u.m thicknessfor cup LR315-2 to 28 grains/640 um thickness for cupLR318-6.

Metallographic examination of an axial cross sectionthrough the weld bead indicated that the microstructureconsisted of randomly oriented, equiaxed grains in thecenter of the weld bead, that there was no porosity, andthat the penetration was complete.

Metallographic examination of the vent-assemblycross sections of FC-232 and FC-238 showed that bothvent orifices were free of deposits, that the entrance tothe filter element of the vents contained only a smallquantity of plutonia, and that the decontaminationcover and vent-assemblv welds were sound.

B. SVT-2

This module was also tested in the minimum-gammareentry mode at an orientation of a =(3 = 0°. The impacttemperature was 919°C (clad) and the velocity was 55m/s against a target of hardened steel.

The condition of tne graphitic components wassimilar to that of graphitic components in SVT-1. Theaeroshell had impact-face cracks about parallel to theGIS axes, and it was fractured on both nonclosurcnarrow faces. Both impact shells had bowed profiles andirregular impact-face cracks along about 80% of thelength.

There were no failures or severe localized iridiumdeformation in either FC-355 or FC-369. the fueledclads of the primary impact assembly, or in clad FC-273of the secondary impact assembly.

The fueled clad positioned in the closure end of thesecondary impact shell, FC-449, suffered three failures:

13

(a) (b)

Fig. 12. The fraciure on the back side of the shield cup of FC-410 was also of the fuel-fragment push-through type, (a) 7X. (b)50X.

an axial failure on the back side, a failure on thecenterline of the weld bead, and a failure on the vent-cupradius on the back side. Figure 13 illustrates the ob-served failures. The weld-bead failure was in a single-pass region of the weld bead, about 180" from the weldoverlap and about 90-100° from the center of the impactface.

Metallographic cross sections through the failures ofboth cups on the back side of FC-449 (Fig. 14) show thatthe fracture mode was intergranular with no significantreduction of thickness; however, radial displacement ofthe sides of the fractures indicates fuel-fragment push-through.

Figure 15 shows the metallographic cross sectionthrough the fractured weld bead. The microstructure ofthe weld consists of small, randomly oriemed grains thatwould not be particularly subject to failures along thecenterlinc of the bead; however, relative displacementof the two sides of the fracture suggests that the failure

was caused by fuel push-through effects similar to thoseseen on the impact face and back side of the cylinderportion of other assemblies. An AES avialysis of the weldbead did not show any unusual impurities, though thethorium Content on the vent-cup side of the weld washigher than that on the shield-cup side.

The metallographic cross section through the fracturein the vent-cup corner is shown in Fig. 16. The fracturemode is intergranular with no indication of reducedthickness and no displacement of the two sides of thefracture. This is a low-strain region of the capsule, so thereason for failure at this location is not evident.

Examination of the microstructure cf the FC-355weld bead (Fig. 17) revealed a crack that extended about25% of the thickness from the interior surface. The weldsample cross section was located on the side of theimpacted fuel clad and by chance included the weldoverlap region. The observed crack is doubtlessly a pre-existing fabrication defect and not an impact-induced

14

(a) (b)

(c)

Fig. 13. Th ree failures o c c u r r e d in I-( -44 >: an axial failure o n the hack side, a cen te r i i nc we ld -head failure, and a failure mi iheven t - cup radius on the hack s ide , (a) Back side, (b) s ide profi le , a n d (e) ven t -end view.

failure. The micros'.ructure of the center of the weldbead includes undesirable elongated grains oriented ap-proximately normal to the thickness of the capsule wall.

The microstructures of the iridium clads were uni-form. The observed grain sizes ranged from 28grains/640 urn thickness for cup NR528-3 to 21grains/640 |im thickness for ^up Q806-2.

Vent-assembly metallographic examination ofFC-355 and FC-369 showed that the vent orifices werefree of deposits and that only a small quantity ofplutonia was deposited in the entrance to the vent filterelement. The decontamination cover and vent-assembly welds to the clad were free of defects.

AES analysis of the grain-boundary chemistry of theiridium clad revealed expected concentrations of

thorium. Small amounts of phosphorus were present insamples from FC-355 and FC'-3ht) (prime). Iron was theprincipal impurity element detected by emission spec-troscopy.

The microstructurc of the prime plutonia pellets wasnormal, and no impurities exceeding the SKP guidelineswere present.

C. SVT-3

This assembly was processed for simulation of anorbital-decay reentry and was impacted in the u = |i = (Vorientation. The impact temperature was 975"C" (clad)and the impact velocity was 54.4 m/s fainst a steeltarget. Continuous monitoring of the 1 :i m released

t5

(a) (h)

(c) (d)

Fig. 14. Failures on the back side of FC-449 occurred in areas of mild localized iridium deformation. Shield cup (a) 7X and (b)50X. Vent cup (c) 7X and (d) 50X.

16

Fig. 15. The niicrostructure of the center of the FC-449 weldbead consisted of small, randomly orier.k-d grains. Radial dis-placement of the two sides of the fracture suggests unequalstrain across the weld. 50X.

(a) (b)

i. The failure on the vent-cup radius of FC-449 exhibited no evidence of fuel-fragment push-through, and the fractureu urred with no indication of ductility, (a) Photomacrograph 7X, (b) 50X.

17

Fig. 17. The microstruclure of the weld head of" FC-355 con-tained elongated grains oriented normal to the wall thickness; acack extending about 25% of the thickness in the weld overlapwas present. 50X.

from the test assembly showed that there were severalperiods during the initial 680 h of the 90-day agingexposure in which the helium released was equivalent to75% of the generation rate, indicating intermittent ventplugging of one fueled clad.

There were no fractures on the impact face or narrowfaces of the acroshcll. but a diagonal crack was presenton the back side. Boih impact shells had bowed profilesand impact-face cracks spanning about 70% of thelength.

No fractures of the iridium dads of the primaryimpact assembly. FC-343 and FC-350. or of the secon-dary impact assembly clad. FC-457. were observed.

Figure 18a shows a small fracture in the center of theback side of the Ft"-454 shield cup. This capsule alsodisplayed a significant quantity of vent effusate sur-rounding the \eni hole as shown in Fig. 18b.

Metallographic examination of a transverse cross sec-tion through the back-side fracture of the FC-454 shieldcup revealed thai the fracture mode was intcrgranularwith a small reduction in thickness of about 4% near thefracture. The photomicrographs of Fig. 19 show nosevere localized deformation of the iridium in this cladarea and no radial displacement by fuel fragments toaccount for the fracture.

Auger electron spectroscopy analysis of the grain-boundary chemistry of samples taken adjacent to thefracture in the FC-454 shield cup revealed high sulfur

concentrations. Small quantities of sulfur were alsoobserved r' some locations in samples from FC-355 andFC-369. Thorium concentrations at all sample interiorswere lower than in the center and exterior locations. Theprincipal impurity clement detected by emission spec-troscopy was iron.

Figure 20 shows a mciallographic cross sectionthrough the vent orifice and the intermetallic reactionproducts on the exterior surface surrounding the orificeof FC-454. A porous deposit of iridium-tungsten alloywas present on the wall of the orifice, particularly nearthe interior. The four phases on the clad exterior wereidentified as (1) iridium, tungsten, and iron; (2) iridium.plutonium, and titanium: (3) iridium and plutonium:and (4) iridium and iron. The venl orifices of the otherfueled clads did not show any effused materials, there-fore FC-454 probably was responsible for the observedperiods of vert plugging.

The vent orifices of FC-343 and FC-350 were free ofvapor-transported material, and only small quantities ofplutonia were deposited at the vent entrance. The de-contamination cover nnd vent-assembly welds ofFC-350 were free of defects or abnormal microstruc-tures. The weld areas of FC-454 exhibited a large grainsize, and in FC-343 large grains were observed on oneside of the sample while normal microstructure existedon the other. These features arc illustrated in Fig. 21.

18

(a) (b)

Fig. 18. A small fracture ir the center of the back si Je of FC-454 was the only failure in SV F-3 (a). Effusate surrounding thevent onfice indicates thai this vent was plugging iluring the aging treatment (b).

(a) (b)

Fig. 19. Failure in the shield cup of FC-454 occurred in an area without severe localized iridium delbrmalion or indicalinns offuel-tiagnr-nl push-through, (a) 7X. (h) 50X.

19

(a)

(b)

FIR. 20. The orifice of the FC-4'4 vent had a deposit of iridium-tungstcn allo\. Intermctallic reaction prodirls were present onthe clad exterior, (a) 50x. (h) 25OX.

20

(a) (b)

(d)

Fig. 21. Abnormal grain growth occurred in the vent-assembly welds of FC-454 (a,b) and FC-343 (c,d). 50X.

21

FiR. 22. The micrnsmicuiiv nt indium aip STW-? had isolatedlargo grains on ihi- i-xu-rmi in addition I" lariu' inu-riur grainsize U •

The indium microstruclures observed werenonuniform across the thickness. Typically, the interior20-25% of the thickness showed a large grain size.Isolated occurrences of large grain si/e were also ob-served on the exterior of cup S31)-5 (Ft'-454). as il-lustrated in Fig. 22.

Mctallographic examination of the cross sectionthrough the welds of Ft -343 and Ft'-3 50 indicated thatthe welds were free of porosity, had penetrated com-pletely, and had microstructurcs consisting of randomlyoriented grains in ihe center of the weld bead.

The microstruclure of the primary fueled-cladplutonia pellets was typical. Pellets MF-350 tind HF-454each had a calcium concentration of 200 ppm. whichshghth exceeds the SKP guideline.

D. SVT--4

!" - .s ".-jst duplicated SVT-3. that is. with orbital-decay:i ' i :"i! reentry an(i impact in an a = (3 = 0° orienta-

- -.!.•,%.-••,: a steel target. The impact temperature was•" ' ; ": : and the impact velocity was 54 m/s.

Irij". 23. FC-.WK sustained a fuel-fragment push-through crackon ihe impact lace, principally in ihc shield cup.

Continuous monitoring of the helium released fromthe four fueled dads showed no evidence of vent plug-ging throughout ihe 90-day aging exposure.

Damage sustained by the aeroshell was similar to thatobserved in the previous three tests conducted in the a =P = 0° orientation. Then, were irregular cracks on theimpact face near both edges of the aeroshell body and afracture the full length of the narrow face on the PI.A sideof the aeroshell. The fracture on the other narrow sideextended only about 50% of the length. A dent waspresent on the back side with cracks radiating to thecorners. Several longitudinal cracks distributed over theimpact face occurred in the impact shell of the primaryimpact assembly. This failure mode differs from thesingle crack on the center of the impact face usuallyobserved. Both impact shells exhibited the typicalbowed profiles.

No failures occurred in the iridium clad of FC-354 ofthe PIA or in eithei of the fueled dads. FC-139 andFC-162. of the SIA. Only mild to moderate localizediridium deformation was observed in these units.

A longitudinal fuel push-through failure in a reverse-bend area was present on the impact face of FC-348. Thefracture extended nearly the full length of the shield cupand a short distance into the vent cup, with a discon-tinuity at the weld: Fig. 23 illustrates the location andextent of the failure.

Metallographic cross-sections taken transverselythrough the fractures of the shield cup and the vent cupare shown in Figs. 24 and 25. respectively. The

(a)

(b) (c)

Fig. 24. The impact-face failure in the shield cup of FC-348 occurred in a region of severe reverse bending near a fuel-fragmentindentation, (a) 7X. (b) and (c) 50X.

23

(a) (b)

Fig. 25. Deformation in the vent cup of FC-348 also exhibited the fuel-fragment push-through characteristics. Failure occurredafter modest reduction in thickness.

photomacrographs clearly illustrate the point of fuel-fragment indentation, with failure occurring in the re-verse-bend region nearby. The shield-cup cross sectionalso shows a crack progressing from the exterior surfacethrough about two-thirds of the wall thickness. Theprimary fracture in the shield cup exhibits negligiblereduction of thickness at the fracture site and about 15%reduction of thickness at the point of fuel-fragmentindentation. A reduction of thickness of about 9-10% atthe fracture site in the vent cup indicates a limitedamount of ductility. The fracture appears to lack aboutone grain thickness of full penetration on this plane, butquite likely penetrated through the thickness some-where along its length.

Though no failures were observed in FC-354 of theprimary1 impact assembly, a crack progressing throughabout 40% of the wall thickness occurred in the reverse-bend region of the impact face, as illustrated in Fig. 26.The degree of fuel-tragment indentation and reversebending at this location was comparatively mild.

AES analysis of the iridium grain-boundarychemistry of FC-345 and FC-354 showed thai in mo;:samples, the thorium concentration was depleted at theinterior surface. Small concentrations of sulfur weredetected in samples from the shield cup of FC-354. CupQR820-2 had higher concentrations of chromium, iron,and nickel impurities than did the other cups of theprimary fueled clads.

The iridium microstructures observed were similar tothose of cups in SVT-3, with large interior grains occu-pying 20-25% of the wall thickness. The range of ob-served grain sizes was 18 grains/640 um thickness forcup QR820-1 to 15 grains/640 um thickness for cupQR820-6.

Examination of vent-assembly cross sections in-dicated similar conditions for both FC-343 and FC-350.The vent orifices were free of vapor-transported de-posits, a small quantity of plutonia was deposited at theentrances to the vent assemblies, and the decontamina-tion cover and vent-assembly welds were free of defects.

24

(a) (b)

Fig. 26. A crack observed in FC-354 traversed about 40% of the wall thickness from the interior at a location of mild reversebending, (a) 7X, (b) SOX.

Axial cross sections through the capsule closure weldsshowed that these welds were of high quality. There wasno porosity, the weld penetrated completely, and themicrostructure did not contain any undesirablecharacteristics.

All impurity elements in the plutonia pellets werewell below SRP guidelines. The microstructures weretypical, though HF-354 had a somewhat smaller grainsize.

E. SVT-5

This lest module was designated for impact testing inthe orbital-decay reentry mode with impact against asteel target on the narrow, nonclosure face of the aero-shell (a = 90°, y = 0°). The impact temperature was975°C and the impact velocity was 54.0 m/s.

Figure 27 shows the module in the catch tube and theaeroshell after the impact assemblies have been re-moved. The impact face of the aeroshell was separated

from the body along fractures parallel to the axis of thelead impact assembly. The aeroshell closure cap of tbelead impact assembly was not retained and a circulardisk was torn from the opposite end, leaving the leadimpact assembly free to be ejected from th? aeroshell.The closure cap of the lead impact shell was not retainedin the body, and one of the fueled clads was partially outof the impact shell. Damage to the lead impact shell wasgreater than that sustained in the a = (3 = 0° orientation.In addition to a crack on the impact-face centerline thatwas wider than is usually observed, there were cracks oneach side about midway between the centerline and edgeof the impact face. The trailing impact shell had atypical irregular crack on the impact face and a trans-verse crack on the back side about 8 mm from theclosure end.

No failures were observed in any of the fueled clads.As expected, the gross deformations of the fueled cladsin the lead impact assembly were greater than (abouttwice) those of the clads in the trailing impact assembly.

25

(a)

(b)

Fig. 27. The narrow impacl face was torn from the aeroshell.permitting the lead IA to be ejected in SVT-5. A crack waspresent on the impact face.

26

(a) (b)

Fig. 28. Fuel-fragment push-through deformation occurred on the back of the shield cup of FC-267. The crack in the reverse-bend location progressed only three grains.

Localized iridium deformation of the clads was mod-erate, occurring principally on the center of the FC-260and FC-267 impact faces. Figure 28 illustrates the mostsevere localized iridium deformation, which occurredon the back side of the FC-267 shield cup. A small crackwas initiated at the interior surface, but it progressedonly three grains into the wall.

AES analyses showed that thorium concentrations atthe iridium grain boundaries were lower at the inieriorthan at the center and exterior. Low levels of sulfur werefound in one sample of the shield cup of FC-267.Emission spectroscopy analysis showed iron to be theprincipal impurity element in the iridium clads.

The microstructure of the iridium clads wasnonuniform across the thickness. Large interior grainsoccurred to a depth of 20-25% of the thickness. Theaverage grain-size range was narrow at 14 grains/640 urnthickness for cup P701-5 to 16 grains/640 urn thicknessfor cups P708-5 and PR717-4.

Axial cross sections through the welds of FC-260 andFC-267 showed that the weld beads had a desirablemicrostructure, no porosity, and full penetration.

Emission spectrographic analysis of samples of theplutonia pellets showed that pellet HF-260 had analuminum content of 320 ppm, which exceeds the SRPguideline. Colorimetric phosphorus analysis for samplesof HF-260 and HF-267 showed 40 to 55 ppm, respec-tively. Subsequent y-sean analysis of these two pelletsindicated that phosphorus content was below the detect-ion limit (20 ppm). The chemical samples were possiblycontaminated inadvertently. The absence of phos-phorus in the grain boundaries of the iridium wouldsupport this hypothesis.

The microstructure of the plutonia pellets HF-260and HF-267 was typical of SRP material.

F. SVT-6

The SVT-6 test assembly was aged for 90 days at1287°C; monitoring of the helium release revealed noevidence of vent plugging. Following the aging heattreatment, the module was given a simulated reentry at1375°C. Post-reentry radiography indicated that all fourfuel pellets were badly cracked.

27

The test module impacted "side-on" at 54.6 m/s and975°C against a hardened 4340 steel plate (Fig. 29). Theaeroshell walls fractured along the axial contact lines ofthe prime GIS, 90° to the impact face {Fig. 30). Damageto the impact shells was moderate. Both GISs had abowed profile and were partially fractured on the impactface.

The primary clads (HF-361 and HF-373) deformed,and capsule HF-373 breaci.ed (Fig. 31). The impact faceof HF-373 contained a large axial crack (22.5 mm X 1.7mm) and a smaller parallel crack (3.7 mm X 0.3 mm) onthe vent-cup radius. Both cracks apparently resulted from the differential displacement of a large fuelfragment.

Metallographic examination of sections removedfrom the primary clads revealed localized excessivegrain growth. Although the average grain sizes wereacceptable (see Table A-IV). areas in both vent cupscontained as few as 2 grains/thickness. The largestgrains were observed on the vent-cup radii (Figs. 32 and

33) and adjacent to the vent-cover welds (Figs. 34 and35). Although the breach in HF-373 did not occur in acoarse-grained region, cracks on the vent-cup radii wereassociated with excessively large grains (Fig. 36).

The plutonia in the primary' clads was broken intomassive chunks that were held tightly by the deformedindium. Fuel in the trailing capsules fractured intonumerous small fragments. Particle-size analyses of thefuel in capsule HF-361 is given in Fig. A-l and Table A-III, and the fines released by HF-373 are given in TableA-II.

VI. DISCUSSION OF RESULTS

In the four modules tested in the a = p = 0° orienta-tion, failures were observed in five fueled clads for anoverall failure rate of 31%. One failure of a PIA fueledclad occurred for a failure rate of 12.5%, and fourfailures occurred in a SIA fueled clad for a failure rate of

O P P O S I T E F A C E

S P L I T J U N C T I O N T C H O L E T O F CD I M P L E L O C A T I O N

I M P A C T SURFACE

2 - 2 5 0 1 .340

G I S T C H O L E S

S P L I T J U N C T I O N

B E A D E D T C H O L E T O F C

Fig. 29. SVT-6 impact orientation.

28

Fig. 31. A wide axial crack was present on the impact face ofcapsule FC-373: 2X.

Fig. 30. The SVT-6 aeroshell fraciured along the axial conlacllines of the pnme GIS.

Fig. 32. Abnormal grain growth was observed on the FC-36Ivent-cup radius; 100X.

29

Fig. 33. Grain coarsening also occurred on the FC-373 vent-cupradius: 100X.

Fig. 34. Abnormal grain growth was also observed on theimpact-face side of the FC-361 vent-crver weld: 40X.

30

(a)

(b)

Fig. 35. Excessive grain growth was observed on the FC-273vent-cover weld, (a) Impact-face side and (b) opposite face; bothat 40X.

31

(a)

(b)

Fig. 36. Crr.cks on the FC-373 vent-cup radius were associaledwilh abnormally large grains, (a) As polished and (b) etched:both at 50X.

32

50%. The principal cause of failures was fuel-fragmentpush-through. For a few of the failures, a direct causecould not be identified: however, these were small frac-tures and did not significantly contribute to the totalfracture area. Except for axial failures that traversed thegirth weld, only one weld failure was observed. Thefailure occurred about 180° from the weld-overlap re-gion, a common site of weld cracking, and thereforefabrication defects probably were not involved in thefailure. In the two modules tested in the a = 90°, y = 0"orientation, one failure was observed for an overallfailure rate of 12.5%. The single failure occurred in theprimary impact assembly for a failure rate of 25% in theleading impact assembly. The failure was of the fuel-fragment push-through type.

Evidence of vent plugging was observed in 1 of 3modules that were subjected to continuous monitoringof the helium release; only 1 capsule of the 12 exhibitedsignificant vent effusate. Performance was good primar-ily because the impurity content of the plutonia wasgenerally low. Positioning the vents of the two fueledclads in opposition at the center of the IA (highesttemperature) probably helped avoid deposits thatwould plug the vent.

Iridium transport was not significant in the FCsexamined (except FC-454). Processing the modules inthe MRMF to slightly reduce the stoichiometry of theplutonia appears to have been beneficial in lowering thepartial pressure of oxygen within the fueled clad andlimited the tendency for iridium transport.

The concentration of impurity elements found in theiridium-alloy capsules was, in general, low. Iron was theprincipal impurity found, but only at levels of a fewhundred parts per million, which is not expected tosignificantly affect the mechanical properties. A fewsamples showed sulfur contamination at the grainboundaries. These instances were not consistent in allsamples from a given capsule, and therefore it is difficultto account for their source. The effect of sulfur segre-gation to grain boundaries is not well established, but itmay have contributed to the minor failure of FC-454.

The average grain size of the iridium in capsules agedfor 90 days was smaller than that which would bepredicted from prior MHW data (7-8 grains/640 urn).Though the iridium-clad temperature during aging wasslightly lower (1287°C vs 1310°C). the absence of phos-phorus contamination at the grain boundaries may also

have helped restrict the abnormal grain growth to theclad interior where thorium depletion inevitably occurs.The excessive grain growth associated with the decon-tamination cover and the vent-assembly welds in somecapsules suggests that this effect is a function of weldingprocedures and is not an inherent property of the designor the materials.

ACKNOWLEDGMENT

The authors gratefully acknowledge the cooperationand contributions of the following to the conduct of thetest program reported herein:

• G. H. Brooks and J. P. Lucero—Radiographic in-spection.

• M. D. Anstey and A. R. Herrcra—Impact Tests.• L. R. Bergamo and J. 1. Archulcta—Foaimortem

assistance and metallography.• O. R. Simi, D. L. Gallimore. and .1. D. Mon-

toya—Emission spectrographic analysis ofirridium.

• J. D. Farr—Auger electron spectroscopy ofiridium.

• W. M. Myers. C. B. Collier, and D.Hedrick—Emission spectrographic analysis ofplutonia.

• T. K. Marshall and T. R. Hahn—Colorimetricphosphorus analysis.

• T. R. Hahn. J. Bubcrnak, and E. M.Hodge—Analysis of plutonium in graphiticmaterials.

• Helen Bustos for manuscript preparation.

REFERENCES

1. "Updated Safety Analysis Report For The GalileoMission and The International Solar-PolarMission," General Electric document GEST-7186(April, 1984), Section 3.4 (GPHS Reentry Response).

2. "Estimates for the Orbital Lifetime for Galileo andSolar Polar," Applied Physics Laboratory documentATD-RL-82-081/ANSP-L-662 (November 18.1982).

3 3/

APPENDIX

Tabulation of Analytical Resultsfor the GPHS SVT Test Series

-177-125-74,-44,-30,-20,-10

, +125, +74+44+30+ 20+ 10

I1 . : ' : • • : • : . . : > . , • : • . _ • • : :

1-

| :^;-V.x:;;-;i;.i.:x:,:;;;:;-:;:>

+ 6000-6000, +2000-2000, +841-841. +420-420, +177-177, +125-125, +74-74. +44-44, +30-30, +20-20, +10-10

+ 6000-6000, +2000-2000, +841-8-.1. +420-420, +177

+6000-6000, +2000-2000, +841-841, +420-420. +177-177, +125-125. +74-74. +44-44. +30-30, +20-20. +10-10

+6000-6000. +2000-2000. +841-841. +420-420, +177-177. +125-125. +74-74. +44-44, +30-30. +20-20. +10-10

+6000-6000. +2000-2000. +841~-841, +420-420, +17/-177. +125-125. +74-74. +44-44. +30-30. +20-20, +10-10

^iSS::;:|:;S;i;i:^:::i:i:::''i': l'1?^.- ;:::|;;':: ::^::^":^::ir:,jr>E :i:: -^L^ ::::::;1:::::^:: •>.:.•...::.'.

;--,

^ i ^ - : ^ . : : ' j :••:'! J:A:.::i.:.. •' ' ' :;.' : V .

M.

•^•^.••v-.^^S^^^-l^^

jH'S:SSi-SS:'Siv::;'^:^ :

0.001 0.01 0.1 1.0

WEIGHT FRACTION

37

TABLE A-I. Impact Test Summary, GPHS SVT Series

Test No.

SVT-1

SVT-2

SVT-3

SVT-4

SVT-5

SVT-6

•Aged 200 i.

ReentryMode

Min-Y*

Face-on

Min-y"

Face-on

OrbitalDecayb

Face-on

OrbitalDecay11

Face-on

OrbitalDecayb

Side-on

OrbitalDecay"Side-on

FueledClads

FC-232FC-238FC-261FC-410

FC-355FC-369FC-449FC-273

FC-343FC-350FC-457FC-454

FC-348FC-354FC-139FC-162

FC-267FC-260FC-415FC-426

FC-373FC-361FC-225FC-189

NDEValue

3.05.08.7

12.6

6.86.0

13.710.7

2.91.19.8

12.8

1.03.2

13.710.7

3.04.09.49.6

4.14.4

13,213.3

. ! 1287°C (clad); impact 919°C and 54 m/s.bAged 90 days at 1287°C (clad); impact 975"C and 54 m/s.

Gross Deformation

Diam (%)

+13.5+9.6

+11.7+9.8

+10.0+9.1

+12.5+10.3

+12.3+10.0+10.8+9.5

+11.5+8.5

+12.5+10.3

+10.4+10.9

+5.5+5.0

+11.2+12.3

+7.8+6.4

Height (%)

-11.1-7.3

-11.1-9.6

-10.4-9.3

-10.3-10.5

-9.0-8.5-7.2-6.4

-11.3-8.2-8.5-9.3

-9.1-13.7

-4.5-6.9

-14.9-17.6

-8.8-7.2

Axial (%)

+5.8+3.8+5.6+1.4

+4.1+4.1+5.6+4.4

+5.7+2.6+5.6+2.9

+6.4+4.0+5.1+3.4

+5.5+4.1+1.2nil

+6.2+ 8 *-r3.7+2.9

Failures

Number

0021

0030

0001

1000

0000

2000

Area (mm2)

25.4

8.4

0.4

1.8

0

24.1

38

Table AH. GPHS SVT Fuel Release

Pu Content (g)*

Module

SVT-1SVT-2SVT-3SVT-4SVT-5SVT-6

Mode

Min-YMin-y

O-DecayO-DecayO-DecayO-Decay

<10um

0.01280.00410.00510.00760.00200.0091

>10um

0.09720.02480.01260.0181

00.0056

Total

0.11000.02890.01770.02570.00200.0147

"SVT-1 to -5: Combust graphitics ai 850-900X. sieve ash, and analyze.SVT-6: Ultrasonic wash of A/S and GIS, plasma-assisted combustion of smallfragments and Tines, sieve a h , and analyze.

Table A-III. Particle-Size Distribution of the <10-nm Fraction of Selected Impacted Pellets

Max. Size(um)

1.002.003.004.005.006.007.008.009.00

10.00

Ace. VVt. Frac.<10um

SVT-1HF-232

0.0015930.0003980.0005790.0004410.00038?0.0009920.0002630.0007840.0011160.001531

0.00808

Weight Fraction

SVT-3HF-343

0.0005110.0002600.0002350.0003410.0003150.0002420.0001920.0008610.0014300.002523

0.00691

SVT-4HF-139

0.0003090.0003870.0003360.0003440.0004280.0004220.0004190.0003750.0005340.001955

0.00551

SVT-5HF-260

0.0004170.0002430.0002530.0003130.0002290.0003080.0001400.0004170.0005940.001834

0.00475

SVT-6HF-361

0.0008460.0004920.0006350.0008000.0010000.0009720.0001720.0007680.0010940.003001

0.00978

39

TABLE

FCNo.

SVT-1

232232238238261261410

SVT-2

355355369369449449

SVT-3

343343350350454

SVT-4

348348354354

SVT-5

267267260

260

SVT-6

361361373373ana = not

A-IV. Iridium

Cup No.

LR313-1LR316-1LR315-2LR318-6

P709-6Q804-1

S205

Q806-2Q806-5

NR528-2NR528-3

S27-2S25-3

PR718-5PR719-5

R704-7R904-5

S39-5

QR820-1QR820-6QR820-3QR820-4

P701-5P708-5

PR717-3

PR717-4

PR725-5PR726-1

Q803-6PR727-3

analyzed.

Grain Size—GPHS SVT

Transverse

25212028222220

212522282323

2016181815

18151917

141615

16

16141516

Axial

20222028na"22na

19232229nana

17181617na

1617i716

151615

14

15131617

Series, Grains per Nom. 640 urn

Comments

UniformUniform except for tab weldUniformUniformUniformUniformUniform

UniformUniform except for tab weldUniformUniform except for tab weldUniformUniform

Lg. interior grains, 20-25% of thk.Lg. interior grains, 20-25% of thk.Lg. interior grains, 20-25% of thk.Lg. interior grains, 20-25% of thk.Lg. interior grains, 20-25% of thk.+ isolated lg. exterior grains.

Lg. interior grains, 20-25% of thk.Lg. interior grains, 20% of thk.Lg. interior grains, 20% of thk.Lg. interior grains, 20% of thk.

Lg. interior grains, 30-35% of thk.Lg. interior grains, 20-25% of thk.Lg. interior grains and isolated lg.exterior grains.Lg. interior grains, 20-25% of thk.

Lg. interior trains to 30% of thk.Lg. interior grains to 30% of thk.Lg. interior grains to 30% of thk.Lg. interior grains to 30% of thk.

40

TABLE A-V. Summary of AES Analyses of GPHS SVT Iridium

Specimen

SVT-1

FC-232: Vent cup-1Vent cup-2Shield cup-1Shield cup-2


SVT-2

FC-449: Vent cup-1Vent cup-2Shield cup-1Shield cup-2Weld VC sideWeld SC side


FC-369: Vent cup-1Vent cup-2

SVT-3



FC-454: Shield cup-1Shield cup-2

SVT-4


FC-354- Vent cup-1Vent cup-2Shield cup-1Shield c<p-2

and—not delected.hv5—very strong

Th6S/Ir,,9

Int. Center

0.070.460.360.71

0.450.550.410.80

0.600.820.430.45

—

0.820.650.550.37

0.480.46

0.380.170.210.35

0.190.460.200.14

0.320.16

0.190.350.630.44

0.110.270.340.37

0.400.560.650.75

0.760.650.500.88

0.690.970.320.68——

0.930.850.860.53

0.630.53

0.680.480.350.76

0.630.740.440.75

0.480.28

0.490.560.760.49

0.520.360.460.68

Ext.

0.160.610.570.60

0.440.410.430.80

0.640.660.430.65——

0.760.630.560.54

0.400.46

0.410.390.410.55

0.470.840.410.65

0.590.36

0.420.240.630.39

0.710.470.520.43

Ave.

0.210.540.530.69

0.550.560.450.83

0.610.820.390590.620.23

0.840.710.660.48

0.500.48

0.490.350.320.55

0.430.680.350.51

0.460.24

0.400.380.670.44

0.450.370.440.49

Ave.

nda

ndndnd

ndndndnd

ndndndndndnd

0.050.080.050.04

0.030.05

ndndndnd

ndndndnd

ndnd

ndndndnd

ndndndnd

C27«/Ir,M

Ave.

0.470.350.170.12

0.440.301.450.17

0.160.090.590.320.190.92

0.H0O i l0.120.24

0.310.39

0.230.480.330.35

0.87nd

1.540.06

0.980.72

0.950.13nd

0.37

0.460.4G0.311.91

O510/Ir1M

Ave.

0.650.760.430.20

0.690.591.17nd

0.470.081.010.570.490.88

0.310.110.360.54

0.740.79

0.460.700.850.01

0.70nd

0.960.09

0.810.95

1.190.53nd

0.82

0.940.750.831.19

SI5o/Ir«9 '

Ave.

ndndndnd

ndnd

0.04nd

nd

ndndndndnd

ndndndnd

ndnd

ndndndnd

ndnd

0.01nd

0.15vsb

ndndndnd

ndnd

0.040.04

Clin/Irnt

Ave.

ndndndnd

ndnd

0.04nd

ndndndndndnd

nd

ndndnd

ndnd

ndndndnd

ndndndnd

ndnd

ndndndnd

ndndndnd

41

TABLE A-V

Specimen

(cont). Summary of

Int.

AES Analyses of GPHS SVT Iridium

Th65/Ir229 Pr.o/Ii-229 C

Center Ext. Ave. Ave.

270/1*229

Ave.O5I0/Ir229

Ave.SI50/Ir229

Ave.

Cl180/Ir229

Ave.

SVT-5

FC-260: Vent cup-1 0.20 0.56 0.38 0.39Vent cup-2 0.36 0.77 0.49 0.54Shield cup-1 0.35 0.36 0.52 0.43Shield cup-2 0.05 0.37 0.42 0.28


SVT-6



ndndndnd

ndndndnd

ndndndnd

ndndndnd

0.460.120.210.79

ndnd

0.740.91

0.090.110.090.78

0.180.120.231.25

0.170.250.431.07

0.22nd

1.081.10

0.520.980.680.86

0.560.570.630.60

nd0.02ndnd

ndnd

0.050.29

nd0.08ndnd

ndndnd

0.30

rJndndnd

ndndnd

0.05

ndnd

0.11

ndndndnd

42

TABLE A-VI. Results of Spectrographic Analysis of GPHS SVT Iridium

FCNo.

SVT-1

232

238

261

410

SVT-2

355

369

449

SVT-3

343

350

SVT-4

348

354

SVT-5

267

260

SVT-6

361

373

Cup No.

LR313-1LR316-1LR315-2LR318-6

P709-6Q804-1

S2-4S2-5

Q806-2Q806-5

NR528-2NR528-3

S27-2S25-2

PR718-5PR719-5

R904-7R904-5

QR820-1QR820-6QR820-3QR820-2

P701-5P708-5

PR717-3PR717-4

PR725-5PR726-1Q803-6

PR727-3

Cu

3201515151535

nd103

nd2010

402066

5nd1540

15152020

15533

Mg

ndb

7107

15151520

35

ndndndnd

ndndndnd

ndndndnd

7ndndnd

ndndndnd

"Elements present in excess of the detection limit.bnd—not detected.

Selected 1

Ca

nd5

201520252030

nd3

ndndndnd

ndndndnd

ndndnd

3

43

ndnd

ndndnd

3

Al

4050505050505050

506040504050

40506060

50504060

50606070

60505050

Elements" (ppm)

Si

nd2525105030

100140

nd150ndndndnd

ndndndnd

ndnd1010

50ndndnd

10ndnd30

Cr

nd30nd10ndndndnd

nd15ndnd1015

nd151515

10101550

nd1010nd

30154030

Fe

80150120120150150150120

200200100150200200

150200300300

200200150400

150150120120

150200200200

Ni

1040404545355020

3040nd103030

30605040

40303080

60505050

40404040

Pt

ndndndnd50

150nd

100

ndndndndndnd

ndndndnd

ndndnd30

ndndndnd

30ndndnd

43

TABLE A-VII.

Pellet No.

SVT-1

HF-232HF-238HF-261HF-410

SVT-2

HF-355HF-369HF-273HF-449

SVT-3

HF-350HF-343HF-454HF-457

SVT-4

HF-348HF-354HF-139HF-162

SVT-5

HF-260HF-267HF-415HF-426

SVT-6

HF-189HF-225HF-361HF-373aColorimetric Analys

Plutonia Analyses, GPHS SVT Series

pa

5552

433

3523

4332

40b

55"66

398?

is.S-Scan indicates <2ll ppm for

Mg

11

nd3

2?

22

nd10ndnd

3322

nd2

ndnd

31020

4

Selected

Ca

130200200400

40304040

200100200150

40503030

30402030

nd60

150130

Al

20252025

25152535

35356035

40402520

320754060

65453015

HF-260 and HF-267.

Elements (ppm)

Si

15702545

30157050

20305010

101588

1535

810

25303545

Fe

607085

110

65455580

35207020

30352025

2030

710

20151020

Cr

15154035

30102530

10106015

1525259

56

nd15

ndnd15nd

Ni

nd5nd5

ndnd7

nd

ndndndnd

ndndndnd

ndndndnd

ndndndnd

Ti

5577

1055

10

201520

3

77

105

15151520

20102020

44 SUSGPO 1985-576-1

Documents

General-Purpose Heat Source Safety Verification Test Series: SVT-1