Failure Behavior of Zircaloy-4 Cladding After

Journal of Nuclear Materials 362 (2007) 36–45

www.elsevier.com/locate/jnucmat

Failure behavior of Zircaloy-4 cladding afteroxidation and water quench

Jun Hwan Kim *, Myoung Ho Lee, Byoung Kwon Choi, Yong Hwan Jeong

Advanced Core Materials Laboratory, Korea Atomic Energy Research Institute, P.O. Box 105, Yuseong, Daejeon 305-600, Republic of Korea

Received 2 March 2006; accepted 25 October 2006

Abstract

Simulated LOCA (loss of coolant accident) tests and subsequent mechanical tests on Zircaloy-4 cladding were carriedout to evaluate the failure behavior of the cladding. Zircaloy-4 claddings were oxidized in a steam environment from 900 to1250 �C for a given time period followed by a flooding of cool water to simulate LOCA tests. After the simulated LOCAtest, the ductility of the oxidized cladding was evaluated by mechanical tests such as ring compression test and 3-point bendtest. Evaluation of the absorbed contents such as hydrogen and oxygen were also carried out. The results showed thatZircaloy-4 cladding failed during thermal shock when the ECR (equivalent cladding reacted) value exceeded 20%. Lowerboundary of brittle failure at thermal shock corresponds to 20% of ECR line calculated by the Baker–Just equation regard-less of test temperature. On the other hand, boundary of ductile failure by the mechanical test did not followed after theECR line. It rapidly decreased above 1000 �C to show that all Zircaloy-4 claddings behaved brittle fracture above 1150 �Cwhen it oxidized at 300 s. Microstructural analysis revealed that boundary of ductile failure by the mechanical test fittedwell when the absorbed oxygen content inside the prior-b layer was below 0.5 wt%.� 2006 Published by Elsevier B.V.

1. Introduction

Fuel cladding is a component which containsfuel pellets to prevent fission products from beingreleased outside. Because of the advantage of a neu-tron economy, zirconium alloy is used for the fuelcladding. It is of importance that the fuel claddingshould maintain its fuel integrity in a postulateddesign-based accident, as well as during a normaloperation. In terms of this, a loss of coolant acci-dent (abbreviated as LOCA) is treated as one of

0022-3115/$ - see front matter � 2006 Published by Elsevier B.V.

doi:10.1016/j.jnucmat.2006.10.026

* Corresponding author.E-mail address: [email protected] (J.H. Kim).

the most important design-basis accidents in a lightwater reactor (LWR). When a LOCA occurs, thetemperature of the fuel system rises so that the clad-ding undergoes an oxidation caused by the reactionof the mixture of water and steam. After a certaintime interval, the emergency core cooling systemactivates, and water is injected to cool down thehot core, which is inevitably accompanied by a ther-mal shrinkage of the cladding. When the embrittledcladding cannot stand the stress involved, the clad-ding fragments, which results in a release of radioac-tive fission product. To maintain the fuel integrityunder postulated LOCA conditions, the NuclearRegulatory Commission (NRC) established the fuelsafety criteria related to a LOCA, where the peak

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Fig. 1. Illustration of the LOCA simulation test: (a) test facility;(b) test scheme.

J.H. Kim et al. / Journal of Nuclear Materials 362 (2007) 36–45 37

fuel temperature and the total oxidation cannotexceed 1204 �C and 17% level respectively [1]. How-ever, such criteria have been founded by applying asafety margin based on the Hobson’s ring compres-sion test [2], and it is reported that there exist differ-ences between the existing safety criteria and thebehavior of a actual cladding [3,4].

The objectives in this study are to quantitativelyanalyze the failure behavior of the fuel cladding andto construct a failure map of the fuel cladding undera simulated LOCA situation. Cladding was oxidizedat various temperatures and times followed by aninjection of cool water. Mechanical tests, such asthe ring compression test and the 3-point bend testwere carried out at the oxidized cladding. Finally,mechanical test result after LOCA test was incorpo-rated into the conventional failure map and therevised failure diagram of the fuel cladding wasevaluated to quantitatively evaluate the failurebehavior of the oxidized cladding.

2. Experimental

2.1. Simulated LOCA test

Fig. 1(a) shows an illustration of a facility usedfor simulated LOCA test. A 200 mm-long Zirca-loy-4 tube, which respectively has 9.5 mm outerdiameter and 0.57 mm of thickness, was used in thisstudy. Composition of Zircaloy-4 was Zr–1.3Sn–0.2Fe–0.1Cr, whose microstructure was stress-relieved. A direct heating by the ohmic resistancewas applied to heat the specimen up to 1265 �C.The length of the heated section of the specimenwas 160 mm. Specimen temperature was measuredby a pyrometer. Before the test, a temperature cali-bration of the pyrometer was performed by using anattached thermocouple on the specimen at the sametime. The temperature profile of the pyrometer andthe thermocouple calibration revealed that the dif-ferences were no more than about 3–5 �C duringthe entire test period. In addition, axial temperatureprofile along the specimen was measured. Tempera-ture value at the point ±80 mm from the midpointrevealed no more than ±20 �C.

To simulate a LOCA condition, the specimenwas oxidized in a flowing steam at a desired temper-ature and time. The steam injected before turningon the power. During the initial stage of heating,an overshoot of the temperature may occur thatcould affect the high temperature oxidation behav-ior of the specimen. To minimize the overshoot, a

two-step heating was adopted. That is, a specimenwas heated below the desired temperature in a shorttime to maintain the peak temperature below thetest temperature, then it was heated to the desiredtemperature. When the cladding is exposed to anemergency coolant at the refill regime, a violent heattransfer between the hot cladding and cold watermakes the coolant vaporize into steam, and thecladding temperatures do not abruptly drop untilthe sufficient coolant flooded the core. To simulatesuch a transient, the specimen was cooled at anintermediate temperature of 700 �C for 100 s afterbeing oxidized, and then quenched. Such a transientis depicted in Fig. 1(b). During the test, the speci-men may be subjected to unnecessary loads due to

Fig. 2. Illustration of the mechanical tests: (a) ring compressiontest; (b) 3-point bend test.

38 J.H. Kim et al. / Journal of Nuclear Materials 362 (2007) 36–45

an attached electrode, wire and connecting rod, etc.In order to compensate for such a load, a sameweight was applied with a reverse direction to bal-ance the net force in the test specimen to zero. Allthe data and procedures were collected and con-trolled by a computer.

In this study, two kinds of tests were introduced.First, the cladding was oxidized at the different tem-peratures but kept at the same time such as 300 s [5].When the cladding is oxidized for the identical timebut at the different temperature, the temperaturewhere the material property abruptly decreases overthe value is expected to be found, such as DBTT.Oxidized claddings were tested by using differentkinds of mechanical tests to see which mechanicaltest was effective for assessing the embrittlementbehavior (called ‘1-dimensional failure analysis’).Second, the claddings were oxidized at the differenttemperatures and times then the mechanical proper-ties of the oxidized cladding was evaluated to con-struct a revised failure map of the zirconiumcladding (called ‘2-dimensional failure analysis’).Detailed test schemes are shown in Table 1.

2.2. Mechanical tests

After the thermal shock test, ring compressiontest and 3-point bend test were performed to evalu-ate the oxidized cladding ductility. Ring com-pression test was selected because of its easiness.3-point bend test was also selected because it isregarded to be more realistic than the ring compres-sion. It is reported that it can simulate the axialbuckling behavior of the cladding which is inducedby an inadvertent operation during the handlingof fuel bundles after the LOCA event [8]. Fig. 2shows a schematic illustration of the mechanicaltests. In the ring compression test, the oxidized clad-ding was cut into 15 mm length, and compressed byan Instron-type test machine at the rate of 1 mm perminute until a fracture. In the ring compression test,three specimens were collected at the middle part of

Table 1Experimental variables used in this study

1-Dimensional failure evaluation

Oxidation temperature(�C)

900, 950, 1000, 1050, 1100, 1150, 1200, 121265 �C

Oxidation time (s) Same at 300 sMechanical test Ring compression test 3-point bend testMicrostructrual analysis Hydrogen analysis oxygen analysis

the cladding then three identical tests were con-ducted. All data relating to the ring compressiontest were the average value of the three test results.In the case of the 3-point bend test, the oxidizedcladding with a length of 180 mm was put into thebending jig then it was bent at the rate of 1 mm/min until a fracture. Span (distance between theloading jigs) length of the test was 70 mm. All thetests were performed at room temperature.

2.3. Microstructural analysis

When cladding is exposed to a high temperaturesteam environment, a diffusion of the oxygen resultsin the development of three distinct layers across theZircaloy-4 cladding thickness, namely zirconiumoxide, a stabilized alpha phase, and a prior-b phase[3]. Fig. 3 shows the microstructure and localoxygen value of Zircaloy-4 cladding after oxidationand water quench. It can be shown that both oxygencontent and local microhardness value decreasedalong the cladding thickness. Oxygen contentsinside the prior-b phase were constant throughoutthe thickness.

To determine the oxidation rate more quantita-tively, the term ECR (equivalent cladding reacted)was introduced to be defined as the ratio of the con-verted metal thickness to the initial cladding thick-ness. Converted metal thickness can be defined asthe equivalent metal thickness that would be

2-Dimensional failure evaluation

50, 900, 950, 1000, 1050, 1100, 1125, 1150, 1175, 1200, 1225,1250 �C300, 500, 1000, 2000, 3000, 5000, 7000, 10000, 15000 s3-Point bend testHydrogen analysis oxygen analysis

Fig. 3. Local microhardness, oxygen content, and the micro-structure of Zircaloy-4 cladding after oxidation and waterquench.


converted to oxide if all the oxygen absorbed by andreacted with the cladding is locally converted tostoichiometric zirconium [1]. Using a dimensionalconversion, the ECR value of zirconium can bederived according to the relationship

ECRð%Þ ¼ tm

ti

� 100 ¼ DmZr

qZr � ti

� 100

¼ 2:693� 10�3DmZr

¼ 2:693� 10�3 � ð3:36� 1011

� expð�22900=T Þ � tÞ0:5; ð1Þ

where ti: initial thickness of zirconium cladding; tm:thickness of zirconium reacted during oxidation;DmZr: total mass change of zirconium metal (inmg/dm2); qZr: density of the zirconium; T: oxidationtemperature (in K); t: oxidation time (in s).

To calculate the ECR value, the Baker–Justequation [6], which is used as a reference oxidationmodel of zirconium by NRC, was adopted as theweight gain formula in this study. Hydrogen andoxygen pickup occur at the cladding surface as the

oxidation proceeds, and they diffuse and penetrateinto the cladding to play an important role in themechanical properties. Absorbed hydrogen contentin the oxidized cladding was measured by a gasanalysis method. Three or four specimens weresampled at the middle part of the cladding. Priorto the hydrogen analysis, they were ultrasonicallytreated in the acetone to remove surface grease thenthey were treated in the carbon tetrachloride solu-tion to remove the surface moisture that greatlyaffects hydrogen content. Regarding the absorbedoxygen, the thickness of the prior-b phase and itsassociated oxygen content have a great influenceon the cladding integrity against a thermal shock[3]. Since the local oxygen value measured by anEDX shows only the relative value, it was decidedto measure the ‘absolute’ oxygen value at theprior-b phase by removing surface oxide then ana-lyzing it by gas analysis. Several specimens afterthermal shock test were sampled and cut into smallparts. They were ground on both sides to removethe surface oxide, leaving up to a thickness of50 lm, and an attempt to measure the oxygen con-tent inside the prior-b layer was initiated. As shownin Fig. 3, thickness of prior-b phase was in the rangeof 200–400 lm so that ‘the pure prior-b layer’ isexpected to obtain once it has carefully groundmuch at outer surface but little at inner surface tothin it down to 50 lm. Similar to the hydrogen anal-ysis, several oxygen contents from the single speci-men were analyzed and averaged.

3. Results and discussion

3.1. Mechanical test

Fig. 4 shows the load–displacement curves of theoxidized cladding from the ring compression testand the 3-point bend test. In the ring compressionresult, the cladding oxidized at 900 �C exhibited aductile compression during the test. In the claddingoxidized over 950 �C, however, the cladding showedan abrupt load drop then it showed a plastic defor-mation at the rest of the curve. Such a load drop ismainly due to a fracture of the brittle oxide outsidethe cladding surface. Thickness of the oxide below900 �C was so thin that it cannot affect the defor-mation behavior of the cladding. However, whenoxidized above 950 �C, the oxide growth and itsthickness became so significant that the load dropcannot be neglected. Even when a load dropoccurred, the prior-b layer was so stable that it

Fig. 4. Load–displacement curve of the Zircaloy-4 cladding after the thermal shock test using both ring compression and 3-point bendtest: (a) ductile deformation; (b) load drop at plastic region; (c) load drop at elastic region.


can sustain an additional compression load. Addi-tional load after load drop gradually decreased asthe oxidation temperature increases to 1100 �C. In

the oxidized cladding beyond 1150 �C, the thicknessof prior-b layer was so thin as well as brittle that itshowed a load drop at the elastic region. However,

Fig. 5. Changes of the mechanical properties of the fuel claddingwith the oxidation temperature: (a) ring compression test; (b) 3-point bend test.


load increases again after the first load drop toresult in a sawtooth-type pattern. The reason whythe successive load increase and drop occur is thatring compression specimen can resist further com-pression because the specimen, although it frac-tured, still maintains cylindrical shape rather thanbreaks in pieces. When oxidized over 1200 �C, thecladding was severely embrittled such that it couldnot maintain the first load drop and it showed abrittle failure.

In the case of the 3-point bend test as shown inFig. 4, the overall trends do not much differ fromthat of the ring compression test. In the claddingoxidized below 1000 �C, the cladding shows asimple bending without showing any load drop orbrittle failure. Cladding oxidized at 1000 �C showeda smaller load when compared to the 900 �C speci-men, which is due to a reduction of the load bearingarea inside the zirconium cladding. When oxidizedbetween 1050 �C and 1100 �C, it failed after itreaches above maximum load. Above 1150 �C, thecladding exhibited a brittle failure without showingany sawtooth pattern as in the ring compressiontest. It failed at a small flexural displacement beforereaching the maximum load.

Fig. 5 shows the changes of the mechanical prop-erties such as the maximum load and displacementwith the oxidation temperature. Ductile compres-sion or bending is shown when the cladding isoxidized at a relatively low temperature (‘ductiledeformation’ region). Load drops caused by a frac-ture of the surface oxide occurred at the plasticregion when the cladding was oxidized at the inter-mediate temperature region (‘load drop at plasticregion’ region). Finally, a load drop occurred atthe elastic region to show that brittle fracture whichcould not sustain the first load drop appeared whenthe cladding was oxidized at a high temperature(‘brittle failure at elastic region’ region). Maximumload in the ring compression decreased slowly asthe temperature increased then it decreased rapidlyabove the brittle failure region. On the other hand,the maximum load in the 3-point bend specimendecreases slowly until 1200 �C.

Besides the maximum load, the maximum dis-placement also decreased with the oxidation tem-perature. Maximum displacement was taken at thepoint where the first load drop occurred from theload–displacement curve. Maximum displacementcannot be measured at the specimen like 900 �C inring compression and below 1000 �C in 3-pointbend test, because no load drop is found at the clad-

ding which shows ductile deformation. Maximumdisplacement in the ring compression specimen con-tinuously decreased with the oxidation temperature,whereas the 3-point bend specimen showed anabrupt decrease of the displacement above the ‘brit-tle failure region’. In the ring compression test, ringgeometry is maintained throughout the test to exhi-bit sawtooth pattern in load–displacement curve. Inthe case of 3-point bend test, however, cladding willbreak in pieces above the fracture load, which leadsto the abrupt displacement decrease over the ‘loaddrop’ region.

3.2. 1-Dimensional failure analysis

Fig. 6 shows the behavior of the absorbed energyduring the mechanical test with the oxidation tem-perature, where oxidation time was set constantfor 300 s. Absorbed energy can be defined as thearea under the load–displacement curve which hasa dimension of the energy. Both energies obtained

Fig. 6. Changes of the absorbed energy and the absorbed contents of the fuel cladding with the oxidation temperature.


by the ring compression and 3-point bend testsdecreased with the oxidation temperature, and theyshowed an abrupt decrease between 1100 and1150 �C. Energy of the 3-point bend specimen waslarger than that of the ring compression becausethe specimen size of the bend test is larger than thatof the compression test. From this result, one canconclude that the 3-point bend test is more sensitivefor evaluating the failure criterion in that thechanges of the absorbed energy are more distinctthan in the ring compression test.

Fig. 6 also shows the changes of the absorbedcontents of the Zircaloy-4 cladding with the oxida-tion temperature. Both the absorbed hydrogen con-tent and the oxygen content inside the prior-b layerincreased with the oxidation temperature. Absorbedhydrogen content gradually increased in all thetemperature regions. Hydrogen content, whenthe Zircaloy-4 cladding oxidized at the 1150 �Cabove which it exhibited a brittle fracture, shows270 ppm. Oxygen content inside the prior-b layerincreased slowly below 1200 �C then it increasedrapidly above this temperature. Oxygen content at1150 �C, above which it showed brittle fracture,was 0.5 wt%. It can be said that the oxygen contentof the cladding to show a brittle fracture is above0.5 wt%. Thus the cladding cannot withstand theload to show nil ductility when the absorbed oxygencontent inside the b layer exceeds 0.5 wt%. Whencompared to the oxygen content inside the prior-bphase from the pseudo-binary phase diagram ofZircaloy-4 and oxygen [7], the absorbed oxygencontent in this study was similar to the theoreticaloxygen solubility below 1200 �C. At 1250 �C, theactual oxygen value increased so high as to reach

around 1.6 wt%, whereas the maximum oxygensolubility corresponding to this temperature is0.7 wt%. It seemed that the temperature was so highas to result in the accelerated oxygen diffusionoccurred above 1200 �C to exceed in the oxygencontent inside the prior-b phase in which the clad-ding leads to a brittle failure.

3.3. 2-Dimensional failure analysis

Fig. 7 shows the failure behavior of Zircaloy-4cladding after the thermal shock test with variousoxidation temperatures and times. Open and closedsymbols respectively denote the specimens whichsurvived and failed after a cold water injectionfollowed by a high temperature oxidation. Whenthe heated cladding was quenched by the cold water,the cladding undergoes thermal shrinkage so thatthe length of the cladding abruptly reduced. Slightlyoxidized cladding which has either low temperatureor short oxidation time can accommodate suchshrinkage to maintain its integrity during thequench. However, heavily oxidized cladding likeeither high temperature or long oxidation timecannot maintain the shrinkage then it fails duringthe water quench. Oxidized cladding during quench-ing usually fails by cutting in halves across the clad-ding diameter. In the case of heavily oxidizedcladdings, they are shattered in pieces immediatelyafter cold water injection. Solid curve representsthe ECR value calculated from the Baker–Justequation. Zircaloy-4 cladding oxidized at 1000 �Cdoes not fail until the oxidation time exceeds10 000 s. As the oxidation temperature increases,oxidation time to cause a failure decreases such as

Fig. 7. Failure map of the Zircaloy-4 cladding after the thermalshock test.


1100 �C in 5000 s and 1200 �C in 2000 s. The mini-mum ECR which is defined as the minimum pointwhere a cladding fails, lies between 20% and 30%,indicates that the conventional 17% ECR criteriafor a cladding failure is somewhat conservative.

Fig. 8 is the 2-dimensional failure diagram of theZircaloy-4 cladding according to the Arrheniusform when collated with the calculated 3-point bendenergy based on the previous section. Same in theFig. 7, closed symbol represents the failed claddingduring the water quench. The ductile bending canbe easily distinguished from the brittle fracture inthat absorbed energy in the ductile bending lies inthe value over 1200 kgf-mm, whereas 100 kgf-mmranges in the brittle failure region. When separatingeach region based on the fracture energy, one can

Fig. 8. Changes of the 3-point bend fracture energy of the fuelcladding with the oxidation temperature and time.

obtain the empirical failure behavior of the Zirca-loy-4 cladding under the LOCA condition. ‘Ductilebending’ (blue1 region in Fig. 8) means that thecladding can assure its mechanical ductility after athermal shock, not to mention a survival during awater quenching. ‘brittle fracture at the mechanicaltest’ (green region in Fig. 8) means that although thecladding at first survived the water quenching, it hasalready lost its mechanical ductility so that it couldbe failed during a handling, such as refueling ortransporting the fuel bundles to the spent fuelstorage [8]. ‘Brittle failure at a thermal shock’ (redregion in Fig. 8) indicates that the cladding is toobrittle to withstand even a thermal stress during awater quenching. From the diagram, ‘ductile bend-ing’ region decreases with the oxidation tempera-ture. For instance, a ductile bending occursirrespective of the oxidation time when oxidizedbelow 950 �C. However, it loses its mechanical duc-tility above 5000 s when oxidized at 1000 �C.Finally, oxidized cladding at 1150 �C shows itsmechanical ductility only at 300 s. The maximumECR to withstand a ductile bending is around15% when oxidized at 1000 �C. It graduallydecreases to have a ECR below 10% when oxidizedabove 1100 �C.

Fig. 9 shows the changes of the absorbed contentwhen collated with the Arrhenius form of the failuremap. When connecting each of the same values,such as drawing the contours, an empirical diagramof each absorbed contents can be obtained. In thisdiagram, the effect of the hydrogen on the failurebehavior of the Zircaloy-4 cladding was low.Instead, the trends of the absorbed oxygen insidethe prior-b layer fit well with the cladding ductilityregion (refer to the blue region in Fig. 8). Claddingwhose oxygen contents in the prior-b layer are lessthan 0.5 wt% showed a ductile failure, which exactlycorresponds to the result of the 1-dimensional fail-ure analysis as mentioned in the previous section.

So far, the approach on the construction of therevised failure diagram, where the thermal shocktest was combined with the mechanical test, can beextended to the other studies. That is, revised failurediagram as proposed in this study can be extendedto the condition where cladding ballooned prior tohigh temperature oxidation, axially constrainedcondition, high-burnup condition such as pre-hyd-

1 For interpretation of color in Fig. 8, the reader is referred tothe web version of this article.

Fig. 9. Changes of the material properties of the fuel claddingwith the oxidation temperature and time: (a) absorbed hydrogencontent (b) oxygen content inside prior-b layer.


rided cladding, and Nb-contained advanced clad-ding. Quantitative evaluation how each region (duc-tile bending, brittle fracture at the mechanical test,and brittle fracture at thermal shock) will be chan-ged with the change of condition (ballooning, axialstress, pre-hydride, and Nb content, and so on) willbe of importance. For example, the existence ofhydride inside zirconium matrix generated duringnormal operation will induce small decrease in theminimum ECR above which cladding will fail dur-ing thermal shock (red region would be little chan-ged compared to the as-received condition).However, it is expected that large decrease in thethreshold ECR above which oxidized cladding willshow brittle failure at the mechanical test (blueregion would shrink rapidly compared to the as-received condition), because pre-hydride increasesoxygen content inside the prior-b layer to rapidlydecrease mechanical ductility of the oxidized andquenched cladding [9].

4. Conclusion

To analyze the failure behavior of Zircaloy-4cladding under a LOCA condition, a simulatedLOCA test and subsequent mechanical tests wereconducted. After conducting the thermal shock testat the temperature ranges from 900 to 1250 �C withvarious times followed by mechanical tests and amicrostructure analysis, the following wereobtained:

(1) 3-Point bend test is more sensitive than thering compression test in assessing the failurebehavior of an oxidized cladding.

(2) The minimum ECR of the Zircaloy-4 claddingto cause a brittle fracture during thermalshock is around 20%, regardless of oxidationtemperature. On the other hand, thresholdECR, below which mechanical ductility ofthe cladding can be assured, decreased as theoxidation temperature increased.

(3) The absorbed oxygen contents in the prior-blayer had an influence on the 3-point absorbedenergy. When the absorbed oxygen contentwas less than 0.5%, the cladding maintainedits mechanical ductility after the LOCA test.

Acknowledgement

This study was supported by Korea Science andEngineering Foundation (KOSEF) and Ministryof Science and Technology (MOST), Korean Gov-ernment, through its national nuclear technologyprogram.

References

[1] Nuclear Regulatory Commission, 10 CFR 50.46, AcceptanceCriteria for Emergency Core Cooling Systems for Light WaterNuclear Power Reactors, 1973.

[2] D.O. Hobson, P.L. Rittenhouse, Embrittlement of ZircaloyClad Fuel Rods by Steam during LOCA Transients ORNL-4758, 1972.

[3] H.M. Chung, T.F. Kassner, Embrittlement Criteria forZircaloy Fuel Cladding Applicable to Accident Situations inLight-Water Reactors: Summary Report NUREG/CR-0344,1980.

[4] F. Nagase, T. Fuketa, recent results from LOCA study inJAERI, in: Proceedings of the 2003 Nuclear Safety ResearchConference NUREG/CP-0185, 2003.

[5] C. Vitanza, Consideration on LOCA Criteria including HighBurn-up Effect, SEGFSM Topical Meeting on LOCA Issues,Argonne National Laboratory, May 25–26, 2004.


[6] L. Baker, L.C. Just, Studies of Metal–Water Reactionsat High Temperatures III. Experimental and Theoreti-cal Studies of the Zirconium–Water Reactions, ANL-6548,1962.

[7] H.M. Chung, T.F. Kassner, J. Nucl. Mater. 84 (1979) 327.

[8] A. Machiels, Perspective on Requirements for Spent FuelStorage and Transportation, Nuclear Safety Research Con-ference 2004, 2004.

[9] J.H. Kim, B.K. Choi, J.H. Baek, Y.H. Jeong, Nucl. Eng. Des.236 (2006) 2386.

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Failure Behavior of Zircaloy-4 Cladding After