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YGR OLUTIONSENE S
8-120B RAI#2 Meeting
April 18th, USNRC, Rockville, MD
E YGREN S ITULO ONS
2
Agenda
• Meeting objectives
• RAIs that are basis of new analysis method (5-6 and 5-7)
– New analysis methodology description
– New approach for payload specification
– Shielding analysis details
• Other RAIs
• Conclusion
2
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New Analysis Methodology
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New Analysis Method Discussion
• New method primarily driven by RAIs 5-6 and 5-7
• We will discuss:
– Our understanding of RAIs 5-6 and 5-7
– Primary features of new analysis method
– Fundamental principles that form basis of new methodology
– How the new method addresses concerns raised in RAIs 5-6 and 5-7
4
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Our Understanding of RAI 5-6
• Distributed-case analyses modeled uniform source
distribution
• Loading spec allowed source density variation
• Analysis did not consider potential source distribution
changes under HAC
• We agree that the last shielding analysis/qualification
method made it difficult to demonstrate conservatism
under NCT and HAC conditions.
5
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Our Understanding of RAI 5-7
• Distributed source analyses specified maximum source
strength (gammas/sec)
– Adjusted based on payload density
– Not adjusted based on payload volume
• RAI questioned that this approach was bounding for
partial-cavity payloads
6
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Our Understanding of RAI 5-7
• We concur that smaller payload volumes may not be
bounded
– Source (gammas/sec) not reduced
– Less self-shielding (for given density)
– Distributed-Case analysis did not account for shifting of
smaller payloads under HAC
• Source limit (gammas/sec) based on full-cavity analysis
• Same total source could be concentrated in section of cavity
7
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New Analysis Approach – Primary Features
• Point Source Analyses
– Same general approach used
– Used to establish limits on source strength for concentrated
sources
– Non-centered NCT point source case added
• Distributed Source Analyses
– Determine limits on activity density, in gammas/sec per gram
of material
– Maximum activity density of the payload material must meet
limit (not smeared density)
– Analysis conservatively based on cavity filled with maximum
activity density material
– Centrally shored small-volume containers evaluated for NCT
8
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New Analysis – Basic Principles
• Point source bounding for a given activity (gammas/sec)
– Concentrated (higher local dose rates)
– No self-shielding
– Worst-case location within cavity
• Cavity filled with maximum activity density material
bounding for any distributed source
– Bounds lower source strength density material
– Bounds any partially filled cavity
– Issues of source strength variation within payload, or
location of payload within cavity all disappear
• For a given activity density (Ci/g), lower g/cc payloads are
bounded when modeled at a higher g/cc
– Objects with g/cc higher than that analyzed must be qualified
as point sources. 9
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New Analysis – Basic Principles
• Demonstration of effect of g/cc changes while holding
specific activity (Ci/g) constant
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New Analysis Addresses RAIs
• RAI 5-6 (source distribution)
– Distributed source qualification based on maximum activity
density material within payload
– HAC distributed source analyses conservatively assume
cavity filled with maximum activity density material
• RAI 5-7 (smaller volume payloads)
– Analyses determine limit on activity density (γ/sec per gram),
not activity (γ/sec).
– Reducing payload volume reduces allowable activity
– Reducing payload density reduces allowable activity
– Full cavity bounds smaller volume of “same stuff”
– Reduced g/cc payloads bounded by modeled g/cc
11
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Analyzed Configurations
• Point Source Cases
– Centered NCT
– Non-centered NCT (worst-case location)
– Non-centered HAC (worst-case location)
• Distributed Source Cases
– Full Cavity - NCT
– Centered 55 gallon (drum) - NCT
– Centered 2.5 ft3 container – NCT
– Full Cavity - HAC
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Analyzed Configurations Basis
• Full Cavity Cases
– Bounding for any waste configuration that meets Ci/g limit
– Do not rely on shoring
• Reduced Volume Container NCT Cases (55 gal & 2.5 ft3)
– Assume waste is placed within smaller, shored container
– Allows higher source density
– HAC still based on full cavity case (no reliance on shoring)
• Point Source Cases
– Centered NCT: Shored container allows higher source
– Non-Centered NCT: Allows loose concentrated sources
– HAC: Non-centered (no shoring credit)
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New Approach for Payload Specification
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Basis for Payload Qualification
• For analyzed configuration, source limit is based on NCT
or HAC case, whichever is worse
– HAC cases do not take credit for shoring
• Gamma-energy-dependent activity and activity density
limits are determined for payload configuration
– Payload size (full, 55 gal, 2.5 ft3)
– Shored at cavity centroid, or not
• 7 analyzed configurations – 5 columns of source limits
– One set for each configuration (governed by NCT or HAC)
– Full cavity, center 55 gal, center 2.5 ft3, center pt., gen pt.
• Payload must meet source strength density or source
strength limit
15
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Shielding Analysis – Analyzed Configurations
• Allowable sources based on conservative modeling
assumptions
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New Approach – Qualification (User’s Standpoint)
• Qualification
Flowchart
• 5 Columns in
Allowable Source
Table
– Ci limit
– Ci/g limit
• 2 Qualification
Paths
– General
– Discrete/shored
Payload
Qualification
Type
Determine payload
activity and mass data.
Discrete Sources
(shored at centroid)
General Sources
(most conservative)
Meets
Ci/g Limit
?
Meets
Applicable
Ci/g Limit
? No
Yes
SHIP
STOP
Centered Activity Limit (Ci)
Centered Activity Density Limit (Ci/g), 2.5 ft3
Centered Activity Density Limit (Ci/g), 55 gal
General Activity Density Limit (Ci/g)
No
Yes
SHIP
STOP
General Activity Limit (Ci)
Meets
Ci limit
?Yes
No
SHIP Meets
Ci limit
? Yes
No
SHIP
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Preview of Payload Qualification Table
Energy
(MeV)
G
en
era
l A
ctivity L
imit (
Ci)
C
en
tere
d A
ctivity L
imit (
Ci)
G
en
era
l A
ctivity D
en
sity
Lim
it (
Ci/g
)
C
en
tere
d A
ctivity D
en
sity
Lim
it,
2.5
ft3
Pa
ylo
ad (
Ci/g
))
C
en
tere
d A
ctivity D
en
sity
Lim
it,
55
-ga
l P
aylo
ad (
Ci/g
)
0.5 TBD TBD TBD TBD TBD
0.7 TBD TBD TBD TBD TBD
0.9 TBD TBD TBD TBD TBD
1.17 TBD TBD TBD TBD TBD
1.5 TBD TBD TBD TBD TBD
1.83 TBD TBD TBD TBD TBD
2.25 TBD TBD TBD TBD TBD
2.75 TBD TBD TBD TBD TBD
3.5 TBD TBD TBD TBD TBD
Co-60 1.3E+11 5.8E+11 8.1E+06 5.8E+07 3.3E+07
Cs-137 TBD TBD TBD TBD TBD
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New Approach – Example 1
• Sealed source,
centrally shored
– Discrete source
path
– Check Column 2
for allowable
source
– Sum fractions
for each energy
• We’ll return to this
example to
discuss the
shielding models
Payload
Qualification
Type
Determine payload
activity and mass data.
Discrete Sources
(shored at centroid)
General Sources
(most conservative)
Meets
Ci/g Limit
?
Meets
Applicable
Ci/g Limit
? No
Yes
SHIP
STOP
Centered Activity Limit (Ci)
Centered Activity Density Limit (Ci/g), 2.5 ft3
Centered Activity Density Limit (Ci/g), 55 gal
General Activity Density Limit (Ci/g)
No
Yes
SHIP
STOP
General Activity Limit (Ci)
Meets
Ci limit
?Yes
No
SHIP Meets
Ci limit
? Yes
No
SHIP
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New Approach – Example 2
• Resin liner with
small, hot filter
– Find liner
fractions using
Column 3.
– Find filter
fractions using
Column 1
– Sum fractions
• We’ll return to this
example to
discuss the
shielding models
Payload
Qualification
Type
Determine payload
activity and mass data.
Discrete Sources
(shored at centroid)
General Sources
(most conservative)
Meets
Ci/g Limit
?
Meets
Applicable
Ci/g Limit
? No
Yes
SHIP
STOP
Centered Activity Limit (Ci)
Centered Activity Density Limit (Ci/g), 2.5 ft3
Centered Activity Density Limit (Ci/g), 55 gal
General Activity Density Limit (Ci/g)
No
Yes
SHIP
STOP
General Activity Limit (Ci)
Meets
Ci limit
?Yes
No
SHIP Meets
Ci limit
? Yes
No
SHIP
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Shielding Analysis Details
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Method of Determining Source Limits
• Peak per-source-particle dose rate determined on each
regulatory surface
– NCT: 2-meter side plane, package side, bottom and top
– HAC: 1-meter side, top and bottom plane
• Determine maximum per-source-particle dose rate that
applies for each regulatory limit (2-m NCT, Package NCT,
1-m HAC)
• Divide dose rate limit by max per-source-particle dose rate
to yield allowable source strength
• For distributed cases, divide allowable source strength by
modeled payload mass to determine allowable source
strength density
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Example Shielding Results for Co-60
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Preview of Payload Qualification Table
Energy
(MeV)
G
en
era
l A
ctivity L
imit (
Ci)
C
en
tere
d A
ctivity L
imit (
Ci)
G
en
era
l A
ctivity D
en
sity
Lim
it (
Ci/g
)
C
en
tere
d A
ctivity D
en
sity
Lim
it,
2.5
ft3
Pa
ylo
ad (
Ci/g
))
C
en
tere
d A
ctivity D
en
sity
Lim
it,
55
-ga
l P
aylo
ad (
Ci/g
)
0.5 TBD TBD TBD TBD TBD
0.7 TBD TBD TBD TBD TBD
0.9 TBD TBD TBD TBD TBD
1.17 TBD TBD TBD TBD TBD
1.5 TBD TBD TBD TBD TBD
1.83 TBD TBD TBD TBD TBD
2.25 TBD TBD TBD TBD TBD
2.75 TBD TBD TBD TBD TBD
3.5 TBD TBD TBD TBD TBD
Co-60 1.3E+11 5.8E+11 8.1E+06 5.8E+07 3.3E+07
Cs-137 TBD TBD TBD TBD TBD
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Shielding Analysis Details
• General (unshored) NCT and HAC point sources placed in
worst possible location
– Top corner of cask cavity
– Minimum shielding
– Minimum distance to regulatory surfaces
– Lines up with both lid (top) and lead slump (side) gaps
• Distributed case source regions modeled as hypothetical
bounding material: zirconium at ~8 g/cc.
– Minimum attenuation for zirconium (except for 3.5 MeV)
– Max density bounding for a given source density
– If a payload component has a higher density material, must
use activity limit column (based on point models)
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Treatment of Multiple Sources/Energies
• Entire process repeated for….
– Each gamma energy level
– Each payload source component
• Determine fraction of limit for each energy/component
– Using full process described earlier
– May use activity or activity density limit, whichever gives
lower fraction
• Sum fractions for all gamma energies and/or payload
components
• Sum-of-fractions may not exceed 1.0
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Shielding Analysis – Example 1
• Sealed source, centrally shored
– This is not a volumetric source case, so no self-shielding
credit Is taken.
– NCT model based on centrally shored point.
– HAC model based on worst-case point.
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Shielding Analysis – Example 2
• Resin liner with small, hot filter
• Resin fills cavity, but filter could be anywhere.
– Models for the liner
– Models for the filter
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Shielding Analysis – Example 3
• Centered 55 gallon drum
– NCT model assumes drum at cavity centroid
– HAC model assumes full cavity of drum contents
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SAR, Other RAIs
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SAR Presentation
• Chapter 7
– Payload Qualification Flowchart
– Usage rules
– Payload Qualification Table
– Examples
• Chapter 5
– Technical bases for Payload Qualification Table
– Description of shielding approach and conservatisms
• Shielding Calculation Package
– Details of shielding models
– Details of Payload Qualification Table computations
– Backup for modeling assumptions
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Other RAIs
• Structural (2-1)
• Shielding (5-x)
• Operations (7-x)
• Maintenance (8-x)
E YGREN S ITULO ONSStructural Evaluation (2-1)
• Figure 2-50 shows the total deformation of the cask during the end
drop. The relative displacement of the top of the lead-column and the
bottom of the bolting ring is the lead-slump. The data print-out from
ANSYS for this load case is included in Reference 2-15 (ST-627)
Appendix 2, Page 24 of 24.
• In Section 2.7.3 of the SAR it is stated, “A conservative evaluation of
the maximum amount of lead deformation under puncture drop test of
8-120B cask has been performed in Reference 2-15. It has been
shown that the lead shielding deformation is limited to 0.458 inch”.
• This evaluation can be found in Section 7.5 Pages 17 through 19 of
Reference 2-15 (ST-627).
33
E YGREN S ITULO ONSBremsstrahlung Conservatism under HAC (5-4)
• Used HAC MCNP model with a 90Sr/90Y beta source
spectrum in e-p transport mode to simulate the production
of bremsstrahlung radiation. 90Y betas are very energetic
daughters of 90Sr, with a maximum energy of 2.245 MeV.
The bremsstrahlung response for a unit beta source was
2.3E-12 mrem/hr per β/sec. So for a 90Sr/90Y 2x1012 β/sec
source, the HAC dose rate at 1 m due to bremsstrahlung
would be 4.6 mrem/hr, or 0.5% of the HAC 1 m dose limit.
34
E YGREN S ITULO ONSOther Shielding RAIs
• 5-2
Barnwell data package for 77 shipments 2008-2011;
manifest, receipt survey, usually shipper’s survey
• 5-5
• 5-8
Maximum thickness of shield ring specified
35
E YGREN S ITULO ONSGamma Source due to Bremsstrahlung (7-2)
36
E YGREN S ITULO ONSOther RAIs
• Operations (7-x)
• Acceptance Tests and Maintenance (8-x)
37
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Conclusion
• Next actions
• Schedule
• Concluding remarks/questions
YGR OLUTIONSENE S
Thank You