ML19093A955
| ML19093A955 | |
| Person / Time | |
|---|---|
| Site: | Crane, 07200020  |
| Issue date: | 03/19/2019 |
| From: | Gibboney S Orano Federal Services, US Dept of Energy, Idaho Operations Office |
| To: | Office of Nuclear Material Safety and Safeguards |
| References | |
| CLN190779 CALC-3021323 | |
| Download: ML19093A955 (38) | |
Text
Page 1 of 38
(]
orano Orano Federal Services CALCULATION Document No.:
CALC-3021323 Rev. No.
001 Pa e 1 of 38 38 Total Pa es Pro*ect No.:
02029.00.0000.02 Pro*ect Name:
License Renewal Su ort
Title:
TMl-2 Canister To -End Dose Rates for TMl-2 ISFSI License Renewal Summary:
The Nuclear Regulatory Commission (NRC) has requested additional information to support the technical review of the Three Mile Island Unit 2 (TMl-2) Independent Spent Fuel Storage Installation (ISFSI) license renewal.
Request for additional information (RAI) 2-2 questions the dry shielded canister (DSC) basket and its exclusion from the scope of the renewal review. Specifically, RAI 2-2 is concerned with the change in vent and purge port dose rates should TMl-2 Canisters realign.
RAI 3-6 challenges the assertion that Licon degradation within each TMl-2 Canister will cause a "negligible" increase in top-end dose rates.
This calculation reevaluates DSC top-end dose rates, including vent port dose rates, to support the responses to the above RAls.
Revision 1 reevaluates both vent port dose rates and purge port dose rates to confirm Assumption 2. In addition, the purge port dose rates are evaluated with a configuration of TMl-2 Fuel Canisters that does not take credit for the interior purge port block.
Contains Unverified Input/ Assumptions:
Yes: D No: 1'81 Software Utilized (Name and Revision):
Location of Computer Files:
MCNP6.1 COLDStor Excel 2010 Printed Name Signature Preparer:
S. Gibboney Checker:
E. Gonsiorowski Approver:
C. Backus FS-EN-FRM-002 Rev. 11 (Effective January 7, 2019)
Refer to FS-EN-PRC-002 Date Orano Federal Services MAR 19 2019 Records Management
Page 2 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 2 of 38 Revision History Rev.
Changes 000 Initial Release 001 Added Appendix A to provide additional information for RAI 2-2 and 3-6 responses. Revised Assumption 2.
Page 3 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 3 of 38 Table of Contents Page REVISION HISTORY............................................................................................................................. 2 LIST OF TABLES.................................................................................................................................. 4 LIST OF FIGURES................................................................................................................................ 4 1.0 PURPOSE.................................................................................................................................. 5 2.0 METHODOLOGY....................................................................................................................... 5 3.0 ASSUMPTIONS......................................................................................................................... 6 3.1 Unverified Assumptions..................................................................................................................... 6 3.2 Justified Assumptions........................................................................................................................ 6 4.0 DESIGN INPUTS........................................................................................................................ 6 4.1 Design Features................................................................................................................................ 6 4.2 Source Specification.......................................................................................................................... 9 4.3 Material Properties............................................................................................................................ 9 5.0 CALCULATIONS........................................................................................................................ 9 5.1 Methods............................................................................................................................................. 9 5.2 Configuration of Source and Shielding.............................................................................................. 9 5.3 Flux-to-Dose Rate Conversion........................................................................................................ 16 6.0 RESULTS AND CONCLUSIONS............................................................................................. 17 7.0 COMPUTER SOFTWARE USAGE........................................................................................... 19 7.1 In-Use Testing of MCNP6.1............................................................................................................ 19 7.2 File Listing....................................................................................................................................... 19
8.0 REFERENCES
......................................................................................................................... 22 APPENDIX A : RAI 2-2 AND RAI 3-6 FOLLOW-UP TECHNICAL SUPPORT.................................... 24
Page 4 of 38 Orano Federal Services OrQ no
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 4 of 38 List of Tables Page Table 5-1 : ANSI/ANS-6.1.1-1977 Photon Flux-to-Dose Rate Conversion Factors................................ 16 Table 6-1 : Top-End Dose Rates (mrem/hr).......................................................................................... 18 Table A-1: Summary of Top-End Dose Rates (mrem/hr)...................................................................... 37 List of Figures Page Figure 4-1: NUHOMS-12T Canister Basket [4]..................................................................................... 7 Figure 4-2: NUHOMS-12T HSM Rear View [4]..................................................................................... 8 Figure 5-1 : TMl-2 DSC Model, Normal Configuration (with Licon)........................................................ 11 Figure 5-2: TMl-2 DSC Model, Top-End Features................................................................................ 11 Figure 5-3: TMl-2 DSC Model, Configuration 1.................................................................................... 12 Figure 5-4: TMl-2 DSC Model, Configuration 2.................................................................................... 13 Figure 5-5: TMl-2 DSC Model, Normal Configuration without Licon..................................................... 14 Figure 5-6: TMl-2 DSC Model, Configuration 2 without Licon............................................................... 15 Figure A-1 : Model 1: Modified Vent Port Model with Internal Vent Port Block in Configuration #2........ 27 Figure A-2: Model 2: Purge Port Model with Internal Purge Port Block Removed in Configuration #2.. 28 Figure A-3: Model 3: Purge Port Model with Internal Purge Port Block Removed in Configuration #3.. 29 Figure A-4: Vent HEPA Filter Surface Area Tally, xy plane, z = 409.60 cm.......................................... 31 Figure A-5: Vent HEPA Filter Surface Mesh Tallies, xy plane, z = 409.60 cm...................................... 32 Figure A-6: Vent Area Tally, yz plane, x = 4 cm................................................................................... 33 Figure A-7: Vent Mesh Tallies, yz plane, x = 0 cm............................................................................... 33 Figure A-8: Purge Port HEPA Filter Surface Area Tally, xy plane, z = 409.60 cm................................ 34 Figure A-9: Purge Port HEPA Filter Surface Mesh Tallies, xy plane, z = 409.60 cm............................ 35 Figure A-10: Purge Port Area Tally, yz plane, x = 0 cm........................................................................ 36 Figure A-11 : Purge Port Mesh Tallies, yz plane, x = 0 cm.................................................................... 36
Page 5 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 5 of 38 1.0 PURPOSE The Nuclear Regulatory Commission (NRC) has requested additional information to support the technical review of the Three Mile Island Unit 2 (TMI-2) Independent Spent Fuel Storage Installation (ISFSI) license renewal application (LRA) [l]. Request for additional information (RAI) 2-2 questions the dry shielded canister (DSC) basket and its exclusion from the scope of the renewal review. Specifically, RAI 2-2 is concerned with the change in vent and purge port dose rates should TMI-2 Canisters reconfigure. RAI 3-6 challenges the assertion that Licon degradation will cause a "negligible" increase in top end dose rates.
This calculation reevaluates DSC top-end dose rates, including vent port dose rates, following the loss of DSC basket integrity and loss of Licon shielding. The results of this calculation will serve as the technical basis for the responses to RAI 2-2 and RAI 3-6.
Revision 1 adds Appendix A, which reevaluates both vent port dose rates and purge port dose rates to confirm Assumption 2. In addition, the purge port dose rates are evaluated with a configuration ofTMI-2 Fuel Canisters that does not take credit for the interior purge port block.
2.0 METHODOLOGY The DSC basket ( detailed in [2]) is identified as a NITS (Not Important to Safety) subcomponent of an ITS (Important to Safety) structure, system, or component (SSC), the DSC (see Section 2.3.3 of the LRA [3]). Thus, per Table 2-4 of the LRA, the DSC basket is not within the scope of the license renewal. RAI 2-2 is concerned that the basket is relied upon to maintain DSC vent and purge port dose rates. If the basket were to fail, personnel may be seriously affected by increased dose rates resulting from the reconfiguration ofTMI-2 Canisters (meaning the basket needs to be included in the renewal scope as an ITS component).
Similarly, RAI 3-6 is concerned with top-end dose rates following degradation of Licon shielding within the TMI-2 Canisters. Section 3.8.4.5 of [3] asserts that the relative impact of Licon shielding on top-end dose rates is negligible compared to steel shielding within the DSC and TMI-2 Canisters. RAI 3-6 questions whether this statement is sufficiently justified, and thus additional information is necessary to quantify the acceptable degradation of Licon with respect to dose rates.
Shielding analysis of the DSC top-end dose rates, including the vent port, is discussed in part ( d) of Section 7.3.2.2 of the TMI-2 Safety Analysis Report (SAR) [4]. The peak DSC vent port gamma and neutron dose rates of926 mrem/hr and 42 mrern/hr respectively are reported in SAR Table 7.3-1. The gamma dose rate is originally calculated in [5] using MCNP models while the neutron dose rate is originally calculated in Section 6.3 of [6]
using a hand calculation. Purge port dose rates are not independently calculated since vent port dose rates bound purge port dose rates (originally assumed in [5]).
To evaluate the importance of the DSC basket and TMI-2 Canister Licon, the original, design-basis shielding model used in [5] is modified and reevaluated following (1) the reconfiguration ofTMI-2 Canisters due to the loss of DSC basket integrity and (2) the loss ofTMI-2 Canister Licon shielding. Neutron dose rates are not reevaluated since they are relatively small compared to gamma dose rates ( <5% ). MCNP is used to perform the shielding analysis. Modifications to the shielding model are minimized to ensure outputs are comparable to those originally generated. Shielding performance is evaluated in accordance with limits in 10 CFR 20, 10 CFR 72, and the Limiting Conditions for Operation (LCO) 3.2.2 included in the TMI-2 ISFSI Technical Specifications [18].
Page 6 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 6 of 38 3.0 ASSUMPTIONS 3.1 Unverified Assumptions There are no unverified assumptions.
3.2 Justified Assumptions
- 1. Neutron dose rates are not reevaluated. Based on previous analysis [6], neutrons do not significantly contribute to top-end dose rates. In addition, neglecting low neutron dose rates is consistent with Section 7.4.2 of the SAR [4].
- 2. Vent port dose rates bound or are comparable to purge port dose rates, consistent with [5]. This justified assumption is proved by analysis of the vent and purge ports in Appendix A.
- 3. The two TMI-2 Canister reconfiguration scenarios evaluated bound any possible reconfiguration scenario following the loss of DSC basket integrity. The TMI-2 Canister reconfiguration scenarios evaluated assume optimal packing of TMI-2 Canisters and neglect the presence of the purge port block.
- 4. TMI-2 Canisters will not realign directly under the vent port. The vent port shield is long enough that a canister must be at a significant angle (relative to the normal horizontal storage alignment) to align directly under the vent port. This alignment scenario is not plausible due to the initial orientations of the TMI-2 Canisters and the DSCs (see Figure 4-1 and Figure 4-2).
- 5. Point detectors used in the original shielding model [5] are replaced by 1 in. 3 volumetric mesh tallies in the same locations. These mesh tallies are assumed to be sufficiently small enough to yield results similar to point detectors (mesh tally volume is unrelated to exclusion sphere volume). The use of point detectors is reserved for instances where mesh tallies do not sufficiently converge.
- 6.
Large differences in dose rates between original [5] and new shielding models are expected due to the large relative errors in the original model° results.
4.0 DESIGN INPUTS 4.1 Design Features The TMI-2 ISFSI is comprised of concrete horizontal storage modules (HSMs) containing steel DSCs. Within each DSC, a steel basket holds twelve TMI-2 core debris Canisters. The steel basket and DSC assemblies are detailed in [2], [10], [11], and [12]. The TMI-2 Canisters are detailed in [13], [14], and [15]. The orientation of the basket within each DSC is shown in Figure 4-1, while the orientation of each DSC within an HSM is shown Figure 4-2.
No changes are made to the geometry used in [5] except for the removal of the steel basket (and resulting repositioning of the TMI-2 Canisters) or the removal of Licon. The model used in [5] was created before finalization of the SAR drawings, and thus does not fully match the SAR drawings. Differences include the number of spacers in the basket assembly and spacer dimensions. These differences are maintained to keep reanalysis consistent with the design-basis shielding analysis.
Page 7 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support SPACER DISC OPENING FOR TMl-2 CANISTER LlnlNG LUG SUPPORT ROD PURGE PORT BLOCK Figure 4-1 : NUHOMS-12T Canister Basket [4]
Page 7 of 38 CANISTER SHELL SPACER DISC VCNT PORT
Page 8 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support DSC SUPPORT STRUCTURE:
DSC PURGE ASSEMBLY (CONFIGURED FOR STORAGE)
SA~PLE PORT PLUG PURGE ASSEMBLY ACCESS TUBE DRY SHIELDED CANISTER BASE UNIT ACCESS DOOR VENT ASSEMBLY ACCESS TUBE SEAL TEST LINE Page 8 of 38 roR VENT ASSEMBLY (OPTIONAL)
QUJCK-C-ONNECT PANEL (OPTIONAL)
SEAL TEST LINE FOR PURGE ASSEMBLY (OPTIONAL)
Figure 4-2: NUHOMS-12T HSM Rear View [4]
Page 9 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 9 of 38 4.2 Source Specification No changes are made to the source strength and spectrum used in [5]. The design-basis source is originally calculated in [9]. No credit is taken for additional decay of the source.
4.3 Material Properties No changes are made to the material compositions used in [5]. All air is modeled as void.
5.0 CALCULATIONS 5.1 Methods Top-end dose rates for the TMI-2 DSC are computed using MCNP6.1 [16]. The original model used in [5] is contained in the file Original.txt. Due to the high tally errors in [5], various optimizations are made to the original model. The optimizations are as follows:
Splitting layers are added and importance splitting is implemented. Splitting layers are placed within existing cells and do not alter the geometry of the model. Air outside the DSC is converted to void to support importance splitting, but this change does not affect resulting dose rates.
The source definition is rebuilt. The original source definition was very inefficient, wasting significant computational time generating and rejecting invalid source positions. Additionally, the original source definition included ineffective biasing. Cell transformations are reorganized to support the rebuilt source definition.
Point detectors are removed and replaced by mesh tallies of sufficiently small volume ( see Section 3.2, Justified Assumptions). Point detectors result in a significant increase in computational time per particle history, and thus their use is limited to instances where mesh tallies do not sufficiently converge. When used, point detectors are altered to satisfy the guidance on exclusion spheres contained within Section 3.3.5.1.2 of [16].
Enabled the generation of bremsstrahlung photons and improved random number generation based on MCNP6.1 run warnings.
Five unique model geometries are evaluated: the normal configuration originally evaluated in [5] with the TMI-2 Fuel Canister Licon modeled, two TMI-2 Canister reconfiguration scenarios with the DSC basket removed, the normal TMI-2 Canister configuration with Licon removed, and the more-conservative (based on resulting dose rates) TMI-2 Canister reconfiguration scenario with Licon removed. Dose rates are calculated with the surface tallies originally used in [5] and mesh tallies/point detectors based on the point detectors originally used in [5].
5.2 Configuration of Source and Shielding The DSC top-end features are fully modeled, while features at the bottom-end are omitted. Top-end features include the inner shield plug, slanted vent port, and HEPA filter assembly. The purge port is not modeled since vent port dose rates will be similar but conservatively bounding relative to purge port dose rates (see Section 3.2, Justified Assumptions). The normal configuration model is shown in Figure 5-1, with a detailed view of the top-end features shown in Figure 5-2.
Two TMI-2 Canister reconfiguration scenarios (referred to as "Configuration I" and "Configuration 2") are evaluated with the DSC basket modeled as void. TMI-2 Canisters are radially packed as closely as possible around the vent port and shifted axially towards the top-end to maximize dose rates. The "Configuration I" model is shown in Figure 5-3 while the "Configuration 2" model is shown in Figure 5-4.
Page 10 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 10 of 38 Two Licon-removed models are evaluated with TMI-2 Canister Licon modeled as void. The normal configuration model with Licon removed is shown in Figure 5-5, while the "Configuration 2" model with Licon removed is shown in Figure 5-6. Based on the results generated with Licon included, "Configuration 2" is selected for additional analysis with Licon removed due to higher top-end dose rates than "Configuration 1 ".
Page 11 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 11 of 38 Figure 5-1 : TMl-2 DSC Model, Normal Configuration (with Licon)
Figure 5-2: TMl-2 DSC Model, Top-End Features HEPA Filter External Surface Vent Port Entry
Page 12 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 12 of 38 Figure 5-3: TMl-2 DSC Model, Configuration 1
Page 13 of 38
'I orano Orano Federal Services
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Figure 5-4: TMl-2 DSC Model, Configuration 2 Page 13 of 38
Page 14 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 14 of 38 Figure 5-5: TMl-2 DSC Model, Normal Configuration without Licon
Page 15 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 15 of 38 Figure 5-6: TMl-2 DSC Model, Configuration 2 without Licon
Page 16 of 38 Orano Federal Services OrQnO
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 16 of 38 5.3 Flux-to-Dose Rate Conversion ANSI/ ANS-6.1.1-1977 photon flux-to-dose rate conversion factors are used in this analysis. These factors were originally used in [5] and can be obtained from the MCNP6' User's Manual, Appendix D, Table 11-2 [16]. The conversion factors in [ 16] have been multiplied by a factor of 1000 to generate dose rates in units of rnrem/hr rather than rem/hr. The conversion factors are provided in Table 5-1. Run files maintain the style and format of the DE and OF cards used in [5], which neglect the 15 MeV point. This is acceptable since the maximum source photon energy is 9.5 MeV.
Table 5-1: ANSI/ANS-6.1.1-1977 Photon Flux-to-Dose Rate Conversion Factors Energy Gamma Factors Energy Gamma Factors (MeV)
(mrem/hr)/(y/cm2-s)
(MeV)
(mrem/hr)/(y/cm2-s) 0.01 3.96E-03 1.40 2.51 E-03 0.03 5.82E-04 1.80 2.99E-03 0.05 2.90E-04 2.20 3.42E-03 0.07 2.58E-04 2.60 3.82E-03 0.10 2.83E-04 2.80 4.01 E-03 0.15 3.79E-04 3.25 4.41 E-03 0.20 5.01 E-04 3.75 4.83E-03 0.25 6.31 E-04 4.25 5.23E-03 0.30 7.59E-04 4.75 5.60E-03 0.35 8.78E-04 5.00 5.80E-03 0.40 9.85E-04 5.25 6.01 E-03 0.45 1.08E-03 5.75 6.37E-03 0.50 1.17E-03 6.25 6.74E-03 0.55 1.27E-03 6.75 7.11E-03 0.60 1.36E-03 7.50 7.66E-03 0.65 1.44E-03 9.00 8.77E-03 0.70 1.52E-03 11.00 1.03E-02 0.80 1.68E-03 13.00 1.18E-02 1.00 1.98E-03 15.00 1.33E-02
Page 17 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 17 of 38 6.0 RESULTS AND CONCLUSIONS Two sets of surface tallies are used to measure general area dose *rates at two axial locations: the vent port entry and the HEPA filter external surface (see Figure 5-2). Similarly, volumetric meshes (or point detectors when necessary per Section 5.1, Methods) are used to measure point dose rates at the same two axial locations. For a drawing of all tally locations, see Figure 6 in [5]. While all tally locations are reanalyzed, many measured dose rates are in locations of little relevance ( due to the inaccessibility of those locations during storage). All tally results are compiled in the spreadsheet Results.xlsx, but only results of significance (e.g. vent port dose rates) are reported in this section. Dose rates of significance are reported in Table 6-1. All tally relative errors are either less than 10% for flux tallies (except for one tally at 10.7%) or 5% for point detectors.
It can be seen that the optimizations made to the design-basis shielding model result in similar (or at least higher) dose rates near the vent port, with good agreement between maximum values at the vent port entry center.
"Configuration l" and "Configuration 2" do not differ from each other in a statistically significant way, with the higher peak vent port entry and HEP A filter surface dose rates of "Configuration 2" rising to 3,269 mrem/hr and 109 mrem/hr respectively. In isolation (i.e. without TMI-2 Canister reconfiguration), removal of Licon shielding results in a much smaller increase in dose rates, as the same dose rates rise only to 1,278 mrem/hr and 55 mrem/hr. When reconfiguration and Licon removal occur together, peak vent port entry and HEP A filter surface dose rates reach maximum-possible values of 4,344 rnrem/hr and 174 mrem/hr respectively.
RAI 2-2 and RAJ 3-6 requests additional information to ensure compliance with 10 CFR 72 [8], subparts 24(e),
122(h)(5), and 42(a). 10 CFR 72.24(e) is the only subpart to con~ain dose rate limits as it requires compliance with 10 CFR 20 [7]. 10 CFR 20.1201 limits vary depending on the affected part of the body, but total effective dose equivalent is limited to 5,000 mrem/yr for onsite worker personnel. While the vent port entry peak dose rate is greater than 4,000 rnrem/hr, the inaccessibility of the vent port entry (requires disassembly of the HEPA filter to access) means it is not a concern that a worker will exceed this limit. Additional limits are specified in LCO 3.2.2 within the TMI-2 ISFSI Technical Specifications [18]. LCO 3.2.2 requires that "the surface dose rate of each HEPA filter housing shall not exceed 1200 mrem/hr". There is no concern that this limit will be violated, with calculated HEPA filter surface dose rates significantly less than 1200 mrem/hr.
In relation to RAI 2-2, it can be concluded that the classification of the DSC basket as a NITS item is acceptable.
The dose rates resulting from removal of the DSC basket, which bounds any possible degradation or aging of the DSC basket, do not result in the violation of applicable I imits (i.e. 109 rnrem/hr with basket removed in Configuration #2). The margin to the LCO 3.2.2 limit is 1091 mrem/hr. In relation to RAI 3-6, the effect of maximum Licon degradation has been quantified. It can be concluded that the dose rates resulting from the removal of Licon shielding, which bounds any possible degradation or aging of Licon, are similar in magnitude to dose rates with no Licon degradation (i.e. 55 rnrem/hr with Licon removed). The margin to the LCO 3.2.2 limit is 1145 mrem/hr. When bounding DSC basket degradation and bounding Licon degradation are combined, dose rates are still acceptable relative to applicable limits (i.e. 174 rnrem/hr with Licon removed and Configuration #2 of TMI-2 Canister rearrangement without basket). The margin to the LCO 3.2.2 limit is 1026 mrem/hr.
Furthermore, based on final two steps in Table 7.4-1 from the SAR [4] (i.e. "Open Rear Wall Access Door, Remove the Filter Transportation Covers, Visually Check HEPA Filters, and Close Access Door" and "Perform Radiation Survey"), worker exposure time will be two hours per year. Assuming a constant, worst-case dose rate of 17 4 mrem/hr for the two hour period results in an annual dose of 348 mrem per worker. The margin to the 10 CFR 20.1201 limit is 4652 mrem.
Page 18 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 18 of 38 Table 6-1: Top-End Dose Rates (mrem/hr)
Licon Included Licon Removed Normal Normal Configuration Configuration Normal Configuration Configuration [5]
Configuration
- 1
- 2 Configuration
- 2 Tally Result Error Result Error Result Error Result Error Result Error Result Error Location Area 7.253E+01 43%
94 5%
290 1%
291 1%
129 2%
405 1%
Vent Port Center 9.258E+02 15%
1032 5%
3267 2%
3269 2%
1278 5%
4344 1%
Entry Edge 6.505E+01 27%
180 7%
677 6%
679 6%
309 6%
1052 4%
HEPA Area 8.521 E+OO 65%
14 9%
39 2%
39 2%
18 4%
58 1%
Filter Center 3.115E+OO 19%
35 5%
108 3%
109 3%
55 5%
174 3%
Surface Edge 1.724E+OO 16%
15 5%
50 9%
50 9%
23 6%
88 6%
Page 19 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support 7.0 COMPUTER SOFTWARE USAGE Revision 000:
Computer Name:
Hardware Profile of Computer:
Operating System:
Revision 001 :
Computer Name:
Hardware Profile of Computer:
Operating System:
Software Used:
EGONSIOROWSKil Intel Xeon CPU ES-1650 @ 3.50 GHz, 16.0 GB RAM 64-bit Windows 7 Enterprise, Service Pack 1 SGIBBONEYS Intel Xeon CPU ES-1650 @ 3.60 GHz, 32.0 GB RAM 64-bit Windows 7 Enterprise, Service Pack 1 MCNP6. l (SD-MCNP-6.1.00-SRA-3012580-000)
Excel 2010 (Exempt from EASI requirements) 7.1 In-Use Testing of MCNP6.1 Revision 000:
Page 19 of 38 Input fi les buildup Je _5 _ mfp. i and buildup _pb _J _ mfp.i are taken from the MCNP6. l software dedication report
[ 17] for in-use testing. Both files are run on 4/19/2018. The resulting output files are identical to those in [ 17]
except for run-unique parameters (such as date and time of run), indicating that MCNP6. l performs as expected and is acceptable for use.
Revision 001:
Input files buildupJe_5_mfp.i and buildup_pb_l _mfp.i are taken from the MCNP6.l software dedication report
[17] for in-use testing. Both files are run on 2/27/2019. The resulting output files are identical to those in [17]
except for run-unique parameters (such as date and time of run), indicating that MCNP6.1 performs as expected and is acceptable for use.
7.2 File Listing Revision 000:
Directory : Runs \\In-Use Test i ng Mode LastWriteTime Length Name
- a-- -
9/21/2017 2 : 20 PM 2974 buildup fe _ 5_mfp. i
- a ---
4/19/2018 1 : 15 PM 26459 buildup fe _5_mfp. o
- a---
9/21/2017 2 : 20 PM 2706 buildup_pb _l_mfp. i
- a ---
4/19/2018 1 : 22 PM 23750 buildup_pb _l_mfp. o Directory : Runs\\Shielding Mode LastWriteTime Length Name
- a---
4/5/2018 1 : 57 PM 16887 Original. txt Directory : Runs\\Shielding\\Modified Original
Page 20 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Mode LastWriteTime Length Name
- a---
4/10/2018 4:06 PM 20934 modifi e d original f2. i
- a---
4/11/2018 7 : 01 AM 2968 modified original f2. m
- a ---
4/11/2018 7 : 01 AM 2319 modified original f2.mt
- a---
4/11/2018 7 : 01 AM 146145 modifie d _original_f2. o
- a---
4/16/2018 8 : 09 AM 19420 modified _original_f5 - 2. i
- a---
4/16/2018 12 : 43 PM 1614 modified original f5 - 2. m
- a---
4/16/2018 12 : 43 PM 150771 modifi ed original fS - 2. o
- a---
4/13/20 18 8 : 20 AM 19423 modified original fS - 7. i
- a---
4/16/2018 6 : 42 PM 1250 modified _original_ fS - 7. m
- a---
4/16/2018 6 : 42 PM 135295 modified original fS - 7. o Directory : Runs\\Shielding\\No Licon Mode LastWriteTime Length Name
- a -- -
4/19/20 18 10 : 03 AM 21010 no licon config2 f2. i
- a ---
4/20/2018 3 : 35 PM 2448 no licon _config2_f2. m
- a---
4/20/20 18 3 : 35 PM 2319 no licon config2 f2. mt
- a ---
4/20/2018 3 : 35 PM 175271 no licon _config2_f2. o
- a ---
4/17/2018 8 : 28 AM 20933 no licon original f2. i
- a ---
4/18/2018 8 : 32 AM 2864 no licon original f2. m
- a ---
4/18/20 18 8 : 32 AM 2319 no licon original f2. mt
- a ---
4/18/2018 8 : 32 AM 175802 no licon _original_f2. o
- a ---
4/18/2018 1 : 29 PM 19420 no licon _original_f5 - 2. i
- a ---
4/18/2018 4 : 51 PM 1562 no licon original f5 - 2. m
- a ---
4/18/2018 4 : 51 PM 143768 no licon _original_f5 - 2. o
- a ---
4/18/2018 1 : 54 PM 19423 no licon original f5 - 7. i
- a---
4/18/2018 10 : 26 PM 1614 no licon _original_ fS - 7. m
- a---
4/18/2018 10 : 26 PM 152559 no licon _original fS - 7. 0 Directory : Runs\\Shielding\\Reconfigurations Mode LastWriteTime
- a ---
4/13/20 18 10 : 41 AM
- a ---
4/14/2018 2 : 26 PM
- a ---
4/14/20 18 2 : 26 PM
- a ---
4/14/20 18 2 : 2 6 PM
- a ---
4/13/20 18 10 : 42 AM
- a ---
4/15/2018 2 : 53 PM
- a ---
4/15/2018 2 : 53 PM
- a ---
4/15/2018 2 : 53 PM Directory : Spreads heets Mode
- a - - -
- a ---
LastWriteTime 4/11/20 18 3 : 51 PM 4/23/2018 4 : 59 PM Length Name 21038 configl f2. i 2656 configl f2. m 2319 config l f2. mt 174146 config l f 2. o 21010 config2_ f2. i 2656 config2 f2. m 2319 config2 f2.mt 174146 config2 f2. o Length Name 10455 General Tables. xlsx 16732 Results. xlsx Page 20 of 38
Page 21 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Revision 001 :
Directory: Rev 1\\Runs\\In-Use Testing Mode
- a---
- a-- -
- a - --
- a - --
LastWriteT i me 9/21/2017 2/27/2019 9/21/2017 2/27/2019 2 : 20 PM 4 : 24 PM 2 : 20 PM 4 : 25 PM Directory : Rev 1\\Runs\\Shielding Mode LastWriteTime
- a - --
3/5/2019 6 : 18 PM
-a---
3/6/2019 6 : 21 PM
- a ---
3/6/2019 6 : 21 PM
- a - --
3/6/2019 6 : 21 PM
- a ---
2/28/2019 5 : 14 PM
- a - --
3/4/2019 5 : 17 PM
- a - - -
3/4/2019 5 : 17 PM
-a- --
3/4/2019 5 : 17 PM
- a - - -
3/4/2019 5 : 55 PM
- a---
3/5/2019 5 : 57 PM
- a - - -
3/5/2019 5 : 57 PM
- a---
3/5/2019 5 : 57 PM Directory : Rev l\\Spreadsheet Mode LastWriteTime
- a - --
3/6/2019 6 : 44 PM Length Name 2974 buildup f e_5_mfp. i 26456 buildup_fe_5_mfp. o 2706 buildup_pb_l_mfp. i 23845 buildup_pb_l_mfp. o Length Name 21148 purge_ no block config2. i 1569 purge no block config2. m 1350 purge no block config2.mt 171130 purge no block config2. o 21156 purge no block config3. i 1621 purge no block config3.m 1350 purge_no_block_config3.mt 387626 purge no block config3. o 20120 vent with block. i 1569 vent with block.m 1350 vent with block.mt 164797 vent with block. a Length Name 19265 Results Appendix. xlsx Page 21 of 38
Page 22 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 22 of 38
8.0 REFERENCES
- 1. NRC Correspondence, Request for Additional Information for the Technical Review of the Application for Renewal of the Three Mile Island Unit 2 Independent Spent Fuel Storage Installation License No. SNM-2508, January 29, 2018
- 2. Transnuclear West Drawing, Dry Shielded Canister Basket Assembly Safety Analysis Report, Drawing Number 219-02-2000, Revision 2
- 3. License Renewal Application, TMI-2 Independent Spent Fuel Storage Installation Application for 10 CFR 72 Specific License Renewal, Special Nuclear Materials License Number SNM-2508 (Docket No.
72-20), Revision 1, NRC Correspondence ADAMS Accession Number ML18296A527.
- 4. Safety Analysis Report, TMI-2 Safety Analysis Report, Materials License No. SNM-2508.
- 5. Vectra Calculation, Top End Dose Rates for TMI-2 Canisters, Calculation Number 219-02.0403, Revision 0, September 1996
- 6. Engineering Design File, Impact of AmBeCm Sources on the TMI-2 ISFSI Design Basis, EDF No. 1793, March 2001
- 7.
Title 10, "Energy", Code of Federal Regulations, Part 20, Standards for Protection Against Radiation
- 8. Title 10, "Energy", Code of Federal Regulations, Part 72, Licensing Requirements for the Independent Storage of Spent Nuclear Fuel, High-Level Radioactive Waste, and Reactor-Related Greater than Class C Waste
- 9. Vectra Calculation, Design Basis Source term Calculation for the TMI-2 Debris Canisters, Calculation Number 291-02.0400, Revision 0, September 1996 l 0. Transnuclear West Drawing, Dry Shielded Canister Shell Assembly Safety Analysis Report, Drawing Number 219-02-2001, Revision 2 11. Transnuclear West Drawing, Dry Shielded Canister Basket-Shell Assembly Safety Analysis Report, Drawing Number 219-02-2002, Revision 2
- 12. Transnuclear West Drawing, Dry Shielded Canister Main Assembly Safety Analysis Report, Drawing Number 219-02-2003, Revision 2
- 13. Babcock & Wilcox Drawing, Filter Canister SAR Information, Drawing Number 1161299, Revision 1
- 14. Babcock & Wilcox Drawing, Fuel Canister SAR Information, Drawing Number 1161300, Revision 3
- 15. Babcock & Wilcox Drawing, Knockout Canister SAR Information, Drawing Number 1161301, Revision 1
- 16. LA-CP-13-00634, MCNP6' User's Manual, Los Alamos National Laboratory, Version 1.0, May 2013, RSI CC Package ID C8 l OMNYCPOO 1 7. AREY A Federal Services Calculation, CALC-30125 88, Software Dedication Report for MCNP v6.1. 00, Revision 0
- 18. U.S. Nuclear Regulatory Commission, License for Independent Storage of Spent Nuclear Fuel and High-Level Radioactive Waste, License No. SNM-2508, Amendment No. 4, June 30, 2005, Docket No. 72-20, NRC Accession Number ML051810406.
- 19. NRC Correspondence ADAMS Accession No. ML19037A066, Request for Clarification of Response to Additional Information for the Technical Review of the Application for Renewal of the Three Mile Island
Page 23 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 23 of 38 Unit 2 Independent Spent Fuel Storage Installation License No. SNM-2508, February 5, 2019, ADAMS Accession No. ML19037A066.
- 20. Transnuclear West Drawing, Dry Shielded Canister Purge Port Filter Assembly (DSCJ2T-001 thru -029 except as noted), Drawing Number 219-02-1010, Revision 2.
- 21. Transnuclear West Drawing, Dry Shielded Canister Vent Port Filter Assembly (DSC] 2T-OOJ thru -029 except as noted), Drawing Number 219-02-1011, Revision 2.
Page 24 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 24 of 38 APPENDIX A:
RAI 2-2 AND RAI 3-6 FOLLOW-UP TECHNICAL SUPPORT Request for clarification of responses for RAI 2-2 and RAJ 3-6 (Reference [ 19]) inquires about the exclusion of the DSC purge port block from the scope of the renewal review. Specifically, the RAI 2-2 and 3-6 follow-up is concerned with Assumption 2, where the DSC's vent port dose rates were assumed to bound purge port dose rates based on visual analysis of Reference [ 12]. This assumption allowed the analyst to only calculate and verify compliance of the dose rates at the vent port, instead of calculating and verifying compliance of the dose rates at both the vent and purge ports. Since visual comparison has been questioned in its sufficiency to determine which DSC port penetration has more limiting dose rates, this appendix presents MCNP models that have been developed to calculate dose rates on the filter housings for both the vent port and purge port.
ln addition, the purge port dose rates are evaluated with the TMI-2 Fuel Canisters arranged in Configuration #3.
Configuration #3 does not take credit for either the shielding contribution of the interior purge port block or the relative placement of the TMI-2 Fuel Canisters caused by the presence of the purge port. All results are verified to comply with applicable limits, specifically the Limiting Conditions for Operation (LCO) 3.2.2 included in the TMI-2 ISFSI Technical Specifications [18].
A.1 Methodology A total of three MCNP models are presented in this appendix. One vent port model and one purge port model each have the TMI-2 Fuel Canisters arranged in Configuration #2, which was determined to result in the highest vent port dose rates for the scenarios analyzed in Revision 0. In addition, a second purge port model has the TMI-2 Fuel Canisters arranged in Configuration #3, an arrangement that would result should the interior purge port block be completely removed. All models have the DSC basket removed and the Licon removed from the TMI-2 Fuel Canisters. Note that original MCNP models in Reference [5] and Revision O did not follow the DSC drawings precisely in References [ 12], [20], and [21]. As such, the new models in this appendix reflect the design-basis DSC drawing dimensions.
To summarize, this appendix documents three new MCNP models:
- 1.
Model I: Modified Vent Port Model with Internal Vent Port Block Present in Configuration #2
- 2. Model 2: Purge Port Model with Internal Purge Port Block Removed in Configuration #2
- 3.
Model 3: Purge Port Model with Internal Purge Port Block Removed in Configuration #3 Each model has either a vent port or a purge port modeled at the bottom edge of the top-end of the DSC with the TMI-2 Fuel Canisters gathered around the port. Because the vent and purge ports are modeled in separate models, dose rates are calculated in the most dose-preferential arrangement of TMI-2 Fuel Canisters for each type of port, which will produce conservative results. In reality, the vent port and the purge port will both be present on the DSC top end, with the vent port offset from the purge port by 40° per Reference [12].
Model 1: Modified Vent Port Model with Internal Vent Port Block Present in Configuration #2 has an internal vent port shield block modeled as steel. The TMI-2 Fuel Canisters are arranged in Configuration #2 around the internal block.
Model 2: Purge Port Model with Internal Purge Port Block Removed in Configuration #2 has the internal purge port block modeled as void. Credit is not taken for the shielding contribution from the purge port block, but credit is taken for the placement of the TMI-2 Fuel Canisters. The TMI-2 Fuel Canisters are arranged in Configuration
- 2 around the internal block space.
Model 3: Purge Port Model with Internal Purge Port Block Removed in Configuration #3 has the internal purge port block modeled as void and the TMI-2 Fuel Canisters arranged into Configuration #3. The TMI-2 Fuel
Page 25 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 25 of 38 Canisters occupy the space occupied by the internal purge port in Model 2. In this way, Model 3 does not take credit for the shielding contribution nor the relative placement of the TMI-2 Fuel Canisters to the purge port.
A TMI-2 Fuel Canister cannot become located directly beneath the purge port because the TMI-2 Fuel Canisters are oriented by the basket during initial loading to be on either side of the port ( see Figure 4-1 ). Because of a successful loading campaign with intact baskets and internal blocks in all DSCs, a worst-case failure of the basket and purge port block hypothesized to occur during the period of extended operations (PEO) will settle the TMI-2 Fuel Canisters into Configuration #3. It is shown in this appendix that when the TMI-2 Fuel Canisters are in closer alignment to the purge port DSC penetration, the TMI-2 Fuel Canisters' upper heads block direct radiation shine though the penetration. The upper heads shield the more significant radiation coming through the sidewalls of the TMI-2 Fuel Canister shell and prevent streaming through the purge port DSC penetration. As a result, this reduces the calculated dose rates on the HEPA filter surface when compared to the results of Model 2.
Reference [14] shows the thickness of the upper head on the TMI-2 Fuel Canisters, which is modeled in MCNP.
The TMI-2 Fuel Canister model geometry remains the same as the original Top-End Shielding Dose rate calculation in Reference [5] and Revision O of this calculation. Because of the shielding provided by the TMI-2 Fuel Canisters' upper heads, streaming through the purge port DSC penetration is reduced from the shell walls of the TMI-2 Fuel Canisters (which are modeled without Licon).
Model 1 is shown in Figure A-1. The following changes were made to the Revision O Configuration #2 without Licon model to make the Model 1 in this appendix.
Changed thickness of HEPA filter housing from 1.5" to 3.38", with a 1.5" depth reduction 9.50" in diameter per [21].
Change diameters of HEPA filter holes from 2.9" diameter to 1.88" diameter per [21].
DSC top end shield plug plates with top cover plate thickness changed from 8" to 6.25" thick per main drawing [12]. Top end shield plug plates were rec:luced from 6.5" to 4.75" thick, and the top cover plate thickness remains 1.5".
Port through DSC top cover plate changed from square penetration to round penetration 9.50" in diameter, per [12].
The transport/sample covers that cover the HEPA filter holes are only used during the transport configuration, and are not applicable during normal storage operation configuration. Therefore, they are modeled as void in each respective model.
The tallies previously set on the surface of the transport cover have been adjusted to be truly flush with the surface of HEP A filter housing.
Page 26 of 38 J
Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 26 of 38 Model 2 is shown in Figure A-2. The following changes were made to the Model 1 to make Model 2:
Removed three of the four HEPA filter holes, reoriented the fourth hole to be per drawing [20). Purge port filter housing has a thru hole with a diameter of 1.88".
Thickness of purge port filter housing is 3.38" with no reduction per [20).
Diameter of purge port filter housing is 11.50" per [20).
Port through DSC top cover plate is a round penetration 5.50" in diameter, per [12).
Port through DSC top end shield plug plates is a modeled as a 2.5" diameter thru hole. Reference [ 12]
indicates the port is a counterbored hole 2.25" in diameter, however modeling the port slightly bigger is conservative.
The tallies to collect dose on the purge port filter housing are located at approximately the same locations as on the vent HEPA filter housing.
Model 3 is shown in Figure A-3. The following changes were made to the Model 2 to make Model 3:
The internal TMI-2 Fuel Canisters are arranged closely packed around the purge port penetration as Configuration
- 3.
Page 27 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 27 of 38 Figure A-1: Model 1: Modified Vent Port Model with Internal Vent Port Block in Configuration #2
Page 28 of 38 Orano Federal Services OfQ nO
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 28 of 38 Figure A-2: Model 2: Purge Port Model with Internal Purge Port Block Removed in Configuration #2
Page 29 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 29 of 38
"""'l!ll!lli!ll;j.;;_ _ _;;~'C!'!=
Approximate location of the DSC Purge Port penetr.ition Figure A-3: Model 3: Purge Port Model with Internal Purge Port Block Removed in Configuration #3
Page 30 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 30 of 38 A.2 Calculations In Revision 0, all tallies reported to be calculating dose rates on the HEP A filter surface of the vent port models were actually calculating dose rates on the transport cover surface, which would not be installed when the DSC is in the storage configuration. However, the tallies in Revision O closely match the tallies from Reference [ 5],
which were also calculating dose on the transport cover surface, and the results of the two calculations are directly comparable. In this appendix, the transport cover is modeled as void in Model 1 and the tallies calculate dose on the true HEP A filter housing surface of the vent port. Likewise, the transport cover is modeled as void in Models 2 and 3 and the tallies calculate dose on the true HEPA filter housing surface of the purge port. Both HEPA filter surfaces would be covered by dust hoods in the storage configuration, see References [20] and [21]. The dust hoods are conservatively neglected in the models in this appendix. Because the transport cover is a 0.75" thick steel plate [21 ], modeling the transport cover as void will decrease the shielding and cause higher calculated dose rates in the appendix models when compared directly to the results from Revision 0.
Figure A-4 and Figure A-6 show the approximate location of the area tally in Model 1, which collects surface dose rate across an area enclosed by a circle of diameter 16 inches. The area tally is portrayed as a hashed blue circle, and it corresponds with the area vent dose rate values in Table A-1 for Model 1. Figure A-5 and Figure A-7 show the approximate location of the mesh tallies in Model 1, which calculate dose rates in a pair of 1 in 3 cubes (consistent with the methodology in Revision 0). The mesh tallies are portrayed as a pair of blue boxes, and the boxes correspond with the center and edge dose rate values in Table A-1 for Model 1.
Figure A-8 and Figure A-10 show the approximate location of the area tally in Models 2 and 3 that collect surface dose rate across an area enclosed by a circle of diameter 11.5 inches. The Models 2 and 3 area tally results are directly comparable to the Model 1 area tally results. The area tally is portrayed as a hashed blue circle, and it corresponds with the area purge port dose rate values in Table A-1 for Models 2 and 3. Figure A-9 and Figure A-11 show the approximate location of the mesh tallies in Models 2 and 3, which calculate dose rates in a pair of 1 in3 cubes. The mesh tallies are portrayed as a pair of blue boxes, and the boxes correspond with the center and edge dose rate values in Table A-1 for Models 2 and 3.
Page 31 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 31 of 38
+
Figure A-4: Vent HEPA Filter Surface Area Tally, xy plane, z = 409.60 cm
Page 32.of 38 Orano Federal Services OrQ nO
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 32 of 38
+
HEPA Filter - Vent Edge Tally HEPA Filter -Vent Center Tally Figure A-5: Vent HEPA Filter Surface Mesh Tallies, xy plane, z = 409.60 cm
Page 33 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 33 of 38 Figure A-6: Vent Area Tally, yz plane, x = 4 cm Figure A-7: Vent Mesh Tallies, yz plane, x = 0 cm
Page 34 of 38 Orano Federal Services OrQ nO
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 34 of 38
+
Figure A-8: Purge Port HEPA Filter Surface Area Tally, xy plane, z = 409.60 cm
Page 35 of 38 Orano Federal Services 0 rQ nO
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 35 of 38
+
HEPA Filter - Purge HEPA Filter - Purge Edge Tally Center Tally Figure A-9: Purge Port HEPA Filter Surface Mesh Tallies, xy plane, z = 409.60 cm
Page 36 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 36 of 38 Figure A-10: Purge Port Area Tally, yz plane, x = 0 cm Figure A-11: Purge Port Mesh Tallies, yz plane, x = 0 cm
Page 37 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Table A-1: Summary of Top-End Dose Rates (mrem/hr)
Model 1:
Model 2: Purge Model 3: Purge Rev 000: DSC Modified Vent Basket Port Model with Port Model with Port Model with Removed, No Internal Vent Internal Purge Internal Purge Port Block Port Block
- Licon, Port Block
- Removed, Removed, Configuration
- Present, Configuration Configuration
- 2 Configuration
- 2
- 3
- 2 Tally Result Error Result Error Result Error Result Error Location HEPA Area 58*
1.08%
121 0.62%
175 2.90%
35 2.89%
Filter Center 174*
2.67%
265 1.89%
1121 5.47%
256 5.53%
Surface Edge 88*
5.92%
314 5.27%
226 6.38%
20 4.75%
- Note that the dose rates calculated in Rev O were calculated from the surface of the transport cover, not from the surface of the HEPA filter housing.
Page 37 of 38
Page 38 of 38 Orano Federal Services orano
Title:
TMl-2 Canister Top-End Dose Rates for TMl-2 ISFSI License Renewal Doc./Rev.: CALC-3021323-001 Project:
02029.00.0000.02 -
License Renewal Support Page 38 of 38 A.3 Results and Conclusions Request for clarification of responses for RAJ 2-2 and RAJ 3-6 (Reference [ 19]) inquires about the exclusion of the DSC purge port block from the scope of the renewal review. To answer this line of questioning, three MCNP models are evaluated in this appendix:
Model 1: Modified Vent Port Model with Internal Vent Port Block Present in Configuration #2 Model 2: Purge Port Model with Internal Purge Port Block Removed in Configuration #2 Model 3: Purge Port Model with Internal Purge Port Block Removed in Configuration #3 All models have the DSC Basket removed and no Licon. Dose rates for the vent port model (Model 1) are calculated with the area tallies and mesh tallies used in Revision 0, and similar area tallies mesh tallies are created for the purge port models (Model 2 and 3). The results of these calculations are in Table A-1.
A comparison between the results of Model 1 and Model 3 confirm the original Assumption 2, with the maximum purge port dose rate being bounded by the maximum vent port dose rate. Model 3 calculates a maximum dose rate of256 rnrem/hr in the center of the purge port HEPA filter housing, and is bounded by Model 1, which calculates the maximum dose rate of 3 14 mrem/hr at the edge of the vent port HEP A filter housing. As a result of the Model 3 dose rate at the center of the HEPA filter housing being less than the LCO 3.2.2 limit of 1200 mrem/hr, the purge port block is verified not to impact shielding performance, and is out of scope for license renewal.
Model 2 analyzes the failure of the steel of the internal purge port block, but still credits the space occupied by the block. However, it should be noted that Model 2 is a hypothetical, as-modeled condition, but otherwise not physically possible. A comparison between the results of Model 2 and 3 shows that Configuration #2 remains the most bounding arrangement ofTMI-2 Fuel Canisters. The maximum dose rate in Model 2 is 1121 rnrem/hr in the center of the purge port HEPA filter housing, which bounds both Model 1 and Model 3 maximum dose rates.
These results are below the LCO 3.2.2 limit of 1200 rnrem/hr, with a margin of 79 rnrem/hr.
Model 3 analyzes the complete failure of the internal purge port block, and does not take credit for the purge port block in terms of both the shielding contribution and the relative placement of the TMI-2 Canisters to the purge port. The comparable dose rates calculated in Model 3 relative to Model 1 are due to the shielding in the individual TMI-2 Fuel Canister upper heads. The upper heads shield the more significant radiation coming through the sidewalls of the TMI-2 Fuel Canister shell and prevent streaming through the purge port DSC penetration. Should a TMI-2 Fuel Canister become completely aligned with the purge port DSC penetration, the aligned shielding in the upper head would further block the more significant radiation coming from the sidewalls, thereby causing a further drop in calculated dose rates at the HEP A filter housing.
An item worth noting is the difference in the location of maximum dose rate between the Revision 0 Configuration #2 model and the results of Model 1. The maximum dose rate in Revision O Configuration #2 is calculated to be 174 rnrem/hr at the center of the transport cover, whereas the maximum dose rate in Model 1 is calculated to be 314 rnrem/hr at the edge of the HEPA filter housing. The main reason for this increase is modification of the thickness of the DSC top end shield to more precisely follow the DSC drawings. Also, one of the modifications for the models in this appendix was the port through the DSC top cover plate changing from square penetration to a round penetration 9.50 inches in diameter, per [ 12]. Modeling a square penetration effectively adds four slivers of metal around the penetration, each of the area comprised of a chord and an arc of the circular penetration. This resizing would cause the maximum calculated dose rate to occur at the edge of the HEPA filter housing instead of the center as previously reported.