ML13050A320
| ML13050A320 | |
| Person / Time | |
|---|---|
| Site: | 07201007, Palisades |
| Issue date: | 02/14/2013 |
| From: | Sisley S EnergySolutions |
| To: | Document Control Desk, NRC/NMSS/SFST |
| References | |
| TAC L24694, SFD/NRC 13-003 | |
| Download: ML13050A320 (22) | |
Text
ENERGYSOLUTIONS Spent Fuel Division February 14, 2013 SFD/NRC 13-003 Docket No. 72-1007 ATTN: Document Control Desk Director, Division of Spent Fuel Storage and Transportation Office of Nuclear Material Safety and Safeguards U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Response to Request for Supplemental Information - VSC-24 Ventilated Storage Cask Certificate of Compliance Renewal Application (TAC No.
L24694)
References:
- 1. Letter from S. Sisley (EnergySolutions Spent Fuel Division, Inc.) to U.S.
Nuclear Regulatory Commission, "VSC-24 Ventilated Storage Cask Certificate of Compliance Renewal Application," SFD/NRC 12-004, October 12, 2012, ADAMS Accession Number ML12290A139.
- 2. Letter from P. Longmire, Ph.D. (NRC) to S. Sisley (EnergySolutions),
"Acceptance Review of Renewal Application to Certificate of Compliance No. 1007 for the Ventilated Dry Storage Cask (VSC-24) - Supplemental Information Needed (TAC No. L24694)," January 15, 2013, ADAMS Accession Number ML12355A816.
- 3. Letter from S. Sisley (EnergySolutions Spent Fuel Division, Inc.) to U.S.
Nuclear Regulatory Commission, "Extension of RSI Response Submittal Date for VSC-24 CoC Renewal Application (TAC No. L24694),"
SFD/NRC 13-002, January 28, 2013, ADAMS Accession Number ML13030A307.
By letter dated October 12, 2012 (Reference 1), EnergySolutions Spent Fuel Division (ES-SFD) submitted the Certificate of Compliance Renewal Application for VSC-24 Ventilated Storage Cask, LAR 1007-007, Revision 0, requesting that Certificate of Compliance (CoC) No. 1007 be renewed for a term of 40 years. By letter dated January 15, 2013 (Reference 2), NRC staff requested that ES-SFD provide supplemental information needed for NRC staff to continue their review of the application. The Request for Supplemental Information (RSI) also included observations. In the Reference 2 letter, NRC requested that ES-SFD provide the supplemental information by February 1, 2013. By letter dated January 28, 2013 (Reference 3), ES-SFD informed NRC that additional time was required to prepare and submit the RSI response and requested an RSI response due date of February 15, 2013.
2105 South Bascom Ave., Suite 316
- Campbell, California 95008
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408.558.3500 ° Fax: 408.558.3518
- www.energysolutions.com cQ11; e_, 0V.-S OJe;C '!2 R-4 I,
SFD/NRC 13-003 February 14, 2013 Page 2 ES-SFD hereby provides the information requested by NRC in the Reference 2 letter, as described in Enclosure 1, Responses to Request for Supplemental Information. Enclosure 1 also includes responses to the observations included in the Reference 2 letter. Six copies of Revision 1 of LAR 1007-007, which has been revised to respond to the RSI, are provided in. None of the information provided in Enclosures 1 and 2 is requested to be withheld from public disclosure.
Should you or any member of your staff have questions, please contact the undersigned at (408) 558-3509.
Sincerely, Steven E. Sisley Licensing/Regulatory Compliance Manager EnergySolutions Spent Fuel Division, Inc.
Enclosures:
- 1) Responses to Request for Supplemental Information
- 2) Certificate of Compliance Renewal Application for the VSC-24 Ventilated Storage Cask System (Docket No. 72-1007), Document No. LAR 1007-007, Revision 1.
cc w/ enclosure Pamela Longmire, PhD, U.S. NRC, NMSS, SFST Dan Shrum, EnergySolutions
SFD/NRC 13-003 February 14, 2013 Responses to Request for Supplemental Information (19 pages, excluding attachments)
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information The responses to the NRC Request for Supplemental Information (RSI) and Observations associated with the EnergySolutions Spent Fuel Division (ES-SFD) request to renew the Certificate of Compliance (CoC) for the VSC-24 Ventilated Dry Cask Storage System for an additional 40 years are provided herein. The NRC RSI and Observation questions, which are shown in italics, are followed by the ES-SFD response and a summary of the resulting changes to the VSC-24 CoC renewal application.
GENERAL RSI-1.
Provide justification for the acceptability of the storage of high burnup (HBU)fiuel by providing a time-limited aging analyses (TLAA) and aging management program (AMP) to demonstrate that HBUfiel is protected against possible degradation that may lead to gross ruptures for storage periods beyond 20 years and potential operation safety problems during removal from storage. Alternatively, propose a certificate condition that would limit HBUfluel storage in the VSC-24 canisters to no more than 20 years.
The TLAA should address reasonable and known physical or degradation phenomena associated with storage periods from 20 to 60 years, such as embrittlement of cladding from the ductile to brittle transition from hydride reorientation in the radial direction in HBUfiiel. The TLAA should systematically address, in part, potential storage conditions and failure modes (e.g., pinching of embrittled cladding) during normal conditions of storage that may potentially strain cladding and lead to gross rupture.
The AMP should define specific confirmatony inspection or monitoring of storage HBU fuel to address conflicting information, uncertainties or indications of presence of a specific potential aging affect of the fuel. The program may specify inspection and monitoring of HBUjfuel within the cask system after 20 years of storage and at periodic intervals (e.g., every 10-20 years) during the renewal period; and mnay define an alternative, optional program to periodically review and use surrogate confirmatory information from other confirmation programs in the U.S. with similar types of HBU fuel. The applicant may also consider proposing licensing conditions to limit the scope of storage time of HBUfiuel during the renewal period to address uncertainties and lack of confirmatory data. This question is applicable to the initial CoC and Amendments 1 through 3, which allow storage of HBUfuel.
This information is needed to determine compliance with 10 CFR 72.240(b)(2).
Response to RSI-1:
The VSC-24 CoC renewal application has been revised to include a proposed certificate condition that would limit the storage of HBU fuel in VSC-24 casks to 20 years. In addition, Section 2.2.1.1 has been revised to better describe the changes to the fuel types and fuel parameters included in each CoC amendment.
Page 1 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information Summary of LAR changes:
" Section 1, It paragraph, 1st bullet: Added a proposed certificate condition to limit the storage of HBU fuel in VSC-24 casks to 20 years.
- Section 1.1.2, 1st paragraph, last sentence: Revised to clarify the maximum allowable SNF assembly average burnup specified in the initial CoC and subsequent CoC amendments.
- Section 2.2.1.1: Revised to expand discussion of fuel types and fuel parameters included in each CoC amendment.
" Appendix B: Revised to include a condition in the Fuel Specification for the initial CoC and Amendments 1, 2, and 3 that limits the storage period for casks containing fuel assemblies with burnups exceeding 45,000 MWd/MTU to 20 years.
RSI-2.
Justify why systems under the initial CoC and Amendment 1 call continue to be fabricated. Alternatively, condition the CoC renewal such that new systems cannot be constructed using the initial CoC and Amendment 1.
Amendment 2 was submitted in response to design and fabrication flaws with the cask design in the initial CoC and Amendment 1. Significant, detailed justification may be required to permit construction of new casks under the initial CoC and Amendment 1.
Otherwise the CoC will be conditioned to prohibit construction of new systems under the initial CoC and Amendment 1 in accordance with 10 CFR 72.240(e).
This information is needed to determine compliance with 10 CFR 72.236(d) and 72.236(h).
Response to RSI-2:
The VSC-24 CoC renewal application has been revised to include a proposed license condition for the initial CoC and Amendment 1, 2 and 3 that requires that all new VSC-24 cask Structures, Systems, and Components (SSCs) be constructed under CoC Amendment 4 or subsequent CoC amendments. The proposed condition further states that subcomponents required for maintenance and repair of the existing loaded VSC 24 cask SSCs may continue to be constructed in accordance with the CoC under which they were originally constructed, and that any VSC 24 cask SSCs constructed under the initial issue and Amendments 1, 2, and 3 of the VSC 24 Storage System CoC that have not been loaded, may be used, provided that they are loaded to Amendment 4 or later.
Summary of LAR changes:
Section 1, It paragraph, 2 nd bullet: Added proposed condition for construction of new VSC-24 cask SSCs.
Page 2 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information Section 1, 2nd paragraph, Item (2): Editorial revision to use SSC acronym since it already defined in the section.
RSI-3.
Provide the results of the remote visual inspection of the lead canister to facilitate the safety evaluation of the renewal application.
The lead canister inspection results were summarized in the CoC renewal application.
Additional documentation should be provided to the staf This information is needed to determine compliance with 10 CFR 72.240(d) and conformance to Appendix E of NUREG-1927.
Response to RSI-3:
A copy of the Palisades Lead Cask Inspection Report, which includes the results of the remote visual inspection, is included in Attachment 1 of the RSI response.
Summary of LAR changes:
e None.
RSI-4.
Provide further information on the choice of the lead canister.
a) Section 3.2.2.4 "Lead Cask Inspection" indicates that the lead canister inspection was petformed on a canister loaded in June 1999. This canister was fabricated after fabrication/qualiýy control lessons were learned as a result of Confirmator, Action Letter (CAL) 97-7-001 (ML060620420). Prior to the CAL, there were a number of multi-assembly sealed baskets (MSBs) with indentified cracks, as described throughout the application (e.g., Section 3.4.3.2, 3.4.3.3, etc.). These canister(s), which have know cracks/flaws, would tend to warrant further examination under a lead canister inspection (and future, periodic inspections).
For example, were the cracks/flaws from initial radiographic and ultrasonic testing examinations, performed years earlier, unchanged? An explanation of why canisters with known fabrication/flaw issues were not considered as a lead canister and an explanation of why the submitted lead canister inspection results apply to these canisters should be provided.
b) Only one lead canister from one site was chosen for detailed observation to justify the conditions of the VSC-24s. Provide supporting documentation demonstrating that each site environment is similar enough that the use of only lead cask fromn one site is justified.
This information is needed to determine compliance with 10 CFR 72.236(d) and (e) and conformance to Appendix E of NUREG-1927.
Page 3 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information Response to RSI-4:
a) As discussed in Sections 3.4.3.2 and 3.4.3.3 of the VSC-24 CoC renewal application, the corrective actions taken for all MSB assemblies with weld indications or flaws were determined to be sufficient to provide reasonable assurance that the MSB assemblies would continue to perform their intended functions during the initial and extended storage periods. Specific weld flaws that were discovered by NDE during the MSB loading process were either removed by grinding and repaired to restore the MSB closure weld to its intended design condition or evaluated to demonstrate that the MSB would continued to perform its intended functions. Corrective actions taken in response to the events associated with these weld indications or flaws are considered to be effective in preventing recurrence of the conditions. Furthermore, evaluations and NDE of known or suspect weld flaws in loaded MSB assemblies, as discussed in Sections 3.4.3.2 and 3.4.3.3, demonstrate that they will not propagate and will not prevent the MSB assemblies from performing their intended functions during the initial and extended storage periods, as discussed below. Therefore, MSB weld indications and flaws were not included in the selection criteria for the VSC-24 lead cask.
Specifically, as discussed in Section 3.4.3.2, "Lamellar Tearing in MSB Shell," the evaluation of potential adverse effects of undocumented weld repairs in the region of the closure welds shows that these potential defects are smaller than the threshold for crack propagation due to cyclic loading for all normal, off-normal, and accident condition stresses. Furthermore, as discussed in Section 3.4.3.2, "Hydrogen-Induced Weld Cracking," UT examinations of the welded closures of all previously loaded MSB assemblies were performed in the Summer of 1998 to check for potential DHC-induced weld failure that theoretically could have occurred shortly after the MSB weld inspection during the loading process. All flaw indications identified by the UT examinations were initially dispositioned using conservative screening criteria developed using Linear Elastic Fracture Mechanics (LEFM) methods. Flaw indications that did not satisfy the initial screening criteria were further evaluated using LEFM or Elastic-Plastic Fracture Mechanics, and were shown to satisfy the allowable flaw size criteria of ASME Section XI and the primary stress limits of ASME Section III. The evaluations of the flaw indications show that: (1) All MSB closure weld indications identified by the UT examinations satisfy the applicable fracture mechanics acceptance criteria, and therefore will not propagate, and (2) The MSB closure welds with flaw indications satisfy the applicable primary stress limits of ASME Section III for the limiting load conditions.
Finally, as discussed in Section 3.4.3.3, the fatigue crack-growth evaluation of a bounding subsurface flaw size demonstrates that the known flaws in the seam weld of Palisades MSB-04 will not grow significantly under cyclic loading for all normal, off-normal, and accident condition stresses during the initial storage period, and that the flaw stability factors of safety are greater than those required by the ASME Code for normal and faulted conditions. As discussed in Section 3.3.3.6, the Page 4 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information Palisades MSB-04 crack growth evaluation TLAA demonstrates that these results remain valid for the extended storage period.
In addition to the evaluations and NDE discussed above, period radiological surveys were performed on the first four VSC-24 casks loaded at Palisades on a routine basis, and Palisades MSB-04 was surveyed for an extended period of time.
The results of the radiological surveys did not identify any unusual dose rates or contamination levels, thereby providing further evidence that the MSB confinement function is satisfied.
b) Since none of the existing VSC-24 ISFSI sites are located in a marine environment, the primary environmental condition that could affect cask degradation rates is the range of temperature extremes (e.g., freeze-thaw cycles). Both Palisades and Point Beach are located on the shores of Lake Michigan and experience average monthly temperatures ranging from approximately 20'F to 70'F, whereas ANO is located in Arkansas, experiences average monthly temperatures ranging from 30'F to 93°F.
This data shows that the VSC-24 casks at Palisades and Point Beach will experience slightly more freeze-thaw cycles than those at ANO. Therefore, selection of a lead cask at Palisades, and not at Point Beach or ANO, is justified based on site environmental conditions.
Summary of LAR changes:
Section 3.2.2.4, 2nd paragraph: Revised to expand discussion of the environmental conditions at the three VSC-24 ISFSI sites to support the selection of Palisades Cask Number VSC-15 for the VSC-24 lead cask inspection.
RSI-5.
Clarify if corrosion on the lead canister was mitigated after inspection.
If the effects of corrosion on the lead canister were iuitigated then future lead canister inspections will not be typical of VSC-24s where no corrective actions were taken to mitigate corrosion.
This information is needed to detennine compliance with 10 CFR 72.240(d) and conformance with Appendix E of NUREG-1927.
Response to RSI-5:
As discussed in Section 3.2.2.4 of the VSC-24 CoC renewal application, the coating on the MSB structural lid of the lead canister was found to be in good condition when the VCC lid was initially removed. However, after completing the inspection activities of the MSB structural lid, a small area of coating adjacent to the closure weld was inadvertently scraped off when temporary shielding was removed. The steel surface that was exposed, which did not show any signs of corrosion, was cleaned and recoated for corrosion protection using the General Licensee's (GL's) approved procedures, in Page 5 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information accordance with the requirements of the Lead Cask Inspection, as discussed in Section 3.4.4.
The initial condition of the MSB structural lid on the lead canister is believed to be typical of the other VSC-24 casks. The coating repair was required to address damage that occurred as a result of the lead cask inspection, not coating degradation that occurred during the initial storage period. The coating repairs restored the condition of the lead MSB to the pre-inspection condition. Thus, the lead canister remains representative of the other loaded VSC-24 casks. Future lead cask inspections will provide additional data that, when compared to the baseline from the initial lead cask inspection, can be used to identify potential degradation occurring during the extended storage period.
Summary of LAR changes:
- None.
RSI-6.
Provide a table and description of the changes made to the VSC-24 system by means other than certificate amendment (e.g., via 10 CFR 72.48). The information should include a brief description of the change, the licensee or CoC holder making the change, and the FSAR revision to which the change was made.
The application discusses some changes made under 10 CFR 72.48; however, it is not clear that all changes made to the storage system by means other than amendment applications (such as changes made under 10 CFR 72.48) have been described. A brief description of the change in a table that includes the requested information will assist the staffs understanding of the system configurations that are in use and subject to the CoC renewal.
This information is needed to determine compliance with 10 CFR 72.240.
Response to RSI-6:
A copy of the VSC-24 Storage System Aging Management Review (AMR), which includes the requested information, is provided in Attachment 2. Descriptions of the changes to the VSC-24 Storage System that were made by the GLs and Certificate Holder (CH) in accordance with 10 CFR 72.48 and the FSAR revisions to which they were made are discussed in Sections 6.2.2.1.1 and 6.2.2.1.2 of the AMR.
Summary of LAR changes:
0 None.
RSI-7.
Clarify Section 3.4.3, to address any issues that occurred during fabrication or use that affect the storage sleeves and MSB basket assembly and the impacts on aging effects.
Page 6 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information The application describes in Section 3.4.3 some issues that occurred during fabrication and use of some VSC-24 systems. It is not clear if there were issues (e.g., welding) that affected the storage sleeves and the basket assembly. The application should describe any such issues, including how they were resolved and the impacts on aging effects, as was done for those issues currently described in the application.
This information is needed to determine compliance with 10 CFR 72.240(d).
Response to RSI-7:
Although fabrication nonconformances were identified during the fabrication of the MSB storage sleeve assemblies, most were associated with dimensional nonconformances (e.g., a slightly under-sized storage sleeve tube opening) and none were associated with significant events. Furthermore, all storage sleeve assembly fabrication nonconformances were resolved in accordance with the applicable QA program. The most significant fabrication issue identified for the MSB storage sleeve assembly was stress-cracking at the comer of storage sleeve tubes. All stress-cracks in the MSB storage sleeve tubes were identified through shop inspection and repaired by welding. Furthermore, a fracture mechanics analysis was performed to show that any undetected cracks in the storage sleeve tubes will not propagate under the maximum stresses present during normal, off-normal, and accident conditions. A discussion of the MSB storage sleeve tube stress cracking issue has been added to Section 3.4.3.4 of the application.
Summary of LAR changes:
- Section 3.4.3.5 "MSB Storage Sleeve Tube Cracks": Added section to address stress-cracks that occurred during the fabrication of the MSB storage sleeve tubes and their impact on aging.
RSI-8.
For each of the amendments listed in 10 CFR 72.214, revise the renewal application by providing a drawing list similar to that of Section 1.5, "Supplemental Data," of the latest final safety analysis report (FSAR). For applicable drawings, also identify the important-to-safety structures, systems, and components (SSCs) or subcomponents that were added or removed from the storage system through certificate amendment and/or 10 CFR 72.48 change process.
Section 2.2.1, "Description of SSC," of the renewal application notes that the VSC-24 storage system components are provided in Chapter I of the FSAR, Revision 8, dated April 2009. Given that when the NRC renews a CoC, all amendments to that CoC are renewed (response to Question W, 8878 Federal Register/Vol. 76, No. 32), it is imperative for the applicant to submit lists of drawings for all approved amendments to facilitate staff review of the completeness of the SSCs and subcomponents considered by the applicant for the scoping review.
This information is needed to determine compliance with 10 CFR 72.240.
Page 7 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information Response to RSI-8:
A new table, which lists the drawing numbers and drawing revisions that were included in the initial SAR, associated with the CoC initial issue, and all subsequent FSAR revisions that were issued following CoC amendments, has been added to the application. Sections 2.2.1.2, 2.2.1.3, 2.2.1.4, and 2.2.1.5 have also been revised to discuss the addition and removal of components from the VSC-24 storage system, either through amendments or 10 CFR 72.48, and their use in the previously fabricated VSC-24 storage system SSCs.
Summary of LAR changes:
Section 1.3: Added references [1.2] through [1.9] for the different revisions of the VSC-24 SAR and FSARs, and renumbered references [1.10] and [1.11]
accordingly.
Section 1, 1st paragraph: Added last sentence before bullet list to clarify scope of the CoC renewal application.
Section 1, 2 nd paragraph, Item (1): Revised reference number of FSAR.
Section 2.2: Added general discussion of general arrangement drawings.
Added new Table 3 (and renumbered all subsequent tables) that lists the general arrangement drawing numbers and revisions included in each of the different revisions of the VSC-24 SAR and FSARs.
Section 2.2.1, last sentence: Revised to reference all revisions of the VSC-24 Storage System SAR and FSARs.
Section 2.2.1.2, 1st paragraph, 1 st sentence: Revised to reference all revisions of the VSC-24 Storage System SAR and FSARs.
Section 2.2.1.2: Revised to describe the different lengths of the MSB assemblies and to include a footnote to clarify when the long MSB configuration was added.
Section 2.2.1.2, 3rd paragraph, 1st sentence: Deleted reference to the general arrangement drawings in Section 1.5 of the VSC-24 Storage System FSAR.
Section 2.2.1.3, 1st paragraph, 1st sentence: Revised to reference all revisions of the VSC-24 Storage System SAR and FSARs.
Section 2.2.1.3, 2nd paragraph, 2 nd sentence: Revised to include a footnote to clarify when the long VCC configuration was added.
- Section 2.2.1.3, 2 d paragraph: Added discussion at the end of the paragraph about the alternative ceramic tile configurations in the VCC assembly.
Page 8 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information
" Section 2.2.1.4, 1st paragraph, Is' sentence: Revised to reference all revisions of the VSC-24 Storage System SAR and FSARs.
" Section 2.2.1.4, 2"d paragraph: Revised to discuss the adoption of GL 10 CFR 72.48 changes to the MTC design, including changes associated with the light MTC assembly configuration, removal of the MTC middle shell, and replacement of the shielded lifting trunnion body design with a solid steel lifting trunnion body design.
" Section 2.2.1.5: Revised to include a footnote to clarify the reason for, and timing of, the removal of the general arrangement drawings of the hydraulic roller skid and lifting yoke from the FSAR.
- Section 2.2.1.6, 1st paragraph: Revised to reference all revisions of the VSC-24 Storage System SAR and FSARs.
- Section 2.2.1.7, 1st paragraph: Revised to reference all revisions of the VSC-24 Storage System SAR and FSARs.
" Section 2.2.3, "Fuel Transfer and Auxiliary Equipment": Revised to reference all revisions of the VSC-24 Storage System SAR and FSARs.
" Section 2.3: Added references [2.2] through [2.9] for the different revisions of the VSC-24 SAR and FSARs, and renumbered references [2.10] through [2.17]
accordingly.
- Table 7: Revised to include the subcomponents of the MTC assembly that were deleted in later drawing revisions and added Note 3 to clarify that none of the existing MTC assemblies have been fabricated with these deleted subcomponents.
Table 7: Editorial correction of referenced drawing number for Coating subcomponent.
" Section 3.1, 1st paragraph: Revised to reference all revisions of the VSC-24 Storage System SAR and FSARs.
Page 9 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information
- Section 3.6: Added references [3.2] through [3.9] for the different revisions of the VSC-24 SAR and FSARs, and renumbered references [3.10] through [3.33]
accordingly.
RSI-9.
Provide a clear description of the certification basis for the initial CoC and each amendment to the CoC.
CoC renewals include the initial CoC and each CoC amendment. All are treated as separate approved systems though theey are listed under the same CoC and docket number. Thus, each has a separate basis for certification. The certification basis for the initial CoC and for each CoC amendment includes the version of the FSAR (including the revision(s) of the drawings) associated with the initial, or amended CoC.
Also, as indicated by the guidance in Section 1.3 of NUREG-1927, the certification basis for each amendment (and the initial CoC) is the edition of 10 CFR Part 72 that was in effect at the time of approval. The applicant should provide a clear description of the certification basis for the initial CoC and each CoC amendment to be included in the CoC renewal. The description should address the FSAR version and any supplements and the edition of 10 CFR Part 72 in effect at the time of approval. The description should identify differences between the FSAR and the effective edition of Part 72for each CoC amendment and the FSAR and the effective edition of Part 72for the initial CoC or preceding CoC amendment(s). The revision(s) of the drawings for the initial CoC and for each amendment should also be provided. The description should also discuss the potential impacts of these differences on the TLAAs and AMPs.
The TLAAs and AMPs shoidd address the components of the in-scope SSCs that appear in any of the revised drawings, as appropriate.
This information is needed to determine compliance with 10 CFR 72.240.
Response to RSI-9:
Section 1.1.1 of the VSC-24 CoC renewal application has been revised to more clearly describe the certification basis for the initial CoC and each CoC amendment. The description includes the dates of the applications and associated supplements, as well as the CoC amendment number and effective date, and the revision number of the FSAR in which the amendment changes were incorporated. In addition, Section 1.1.1 has been revised to identify the edition of 10 CFR Part 72 in effect at the time of approval of each amendment and any changes in the respective CoC amendment that resulted from differences in 10 CFR Part 72. The information provided will allow the NRC reviewer to consult the edition of 10 CFR Part 72 that was in effect at the time of CoC issuance, as discussed in Section 1.3 of NUREG-1927.
Summary of LAR changes:
- Section 1.1.1: Revised to more clearly describe the certification basis for the initial CoC and each CoC amendment. In addition, the List of Acronyms and Abbreviations has been revised to include those added in Section 1.1.1.
Page 10 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information 0 Section 1.3: Added reference [1.12].
AGING MANAGEMENT RSI-I0. Provide the data for the dose rate surveys described in Section 3.2.2.3 of the application.
The application provides a general description of the surveys that have been performed and some conclusions drawn by the applicant from those surveys. The applicant should provide the data in a form appropriate for the staff to do an independent evaluation of the surveys and the applicant's conclusions (e.g., a table and graph for each general licensee). The data should include the survey results for both near the systems and at the controlled area/site boundary and list results for gamma and neutron measurements.
This information is needed to determine compliance with 10 CFR 72.240.
Response to RSI-10:
The Aging Management Review (AMR) includes a plot showing inlet duct dose rate versus time for the Palisades plant, and a plot showing ISFSI area fence dose rates (vs.
time) for the Point Beach plant. The AMR also includes, as attachments, all of the raw dose rate survey data provided by the GLs. The discussion of the dose rate survey data is provided in Section 6.2.2.4 of the AMR. A copy of the AMR is included in.
Summary of LAR changes:
0 None.
RSI-11. Provide a helium leakage evaluation that justifies the VSC-24 storage canister will have a 60 year lifetime.
Table A-] provides a summary of FSAR changes that often indicate an increase in design lifetime to 60 years (i.e., satisfy 10 CFR Part 72 requirements). The MSB Helium Leakage Evaluation described in Section 3.3.3.1 of the application should be provided.
This information is needed to determine compliance with 10 CFR 72.236(g).
Response to RSI-11:
A copy of the helium leakage (TLAA) analysis is included in Attachment 3.
Page 11 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information Summary of LAR changes:
0 None.
RSI-12. Confirm that all loaded canisters currently meet 10 CFR Part 72 confinement, fuel integrity and subcritical requirements.
Section 3.4.3.2 and Section 3.4.3.3 indicate that multiple VSC-24 canisters had cracks/flaws. According to Section 3.4.3.3, MSB-04 canister, for example, currently has a known flaw(s) in the seam weld but that crack-growth analyses have indicated that "cracks in the longitudinal seal weld of MSB-04 will not prevent it from performing its intended finctions (primarily confinement) during the extended storage period." Considering the delayed period offinding the flaw in MSB-04 (as discussed further in OBS-4 below), the application should confirm that all loaded canisters currently satisfy, and are projected to satisfy, the 10 CFR Part 72 confinement, fuel integrity and subcritical (i.e., prevent water intrusion) requirements.
This information is needed to determine compliance with 10 CFR 72.236(c), (d), (e) and (g).
Response to RSI-12:
As discussed in Sections 3.4.3.2 and 3.4.3.3, all conditions related to indications or flaws in welds that are included in the confinement boundary of certain MSB assemblies were adequately addressed through corrective actions that provide reasonable assurance that all MSBs currently satisfy, and will continue to satisfy, the confinement, fuel integrity, and subcritical requirements of 10 CFR Part 72 for the initial and extended storage periods.
As discussed in Section 3.4.3.2, "Hydrogen-Induced Weld Cracking," UT examinations were performed for all previously loaded MSB assemblies to check for possible DHC-induced flaws in the MSB closure welds. The results of the UT examinations were shown to satisfy the allowable flaw evaluation criteria developed in accordance with the requirements of ASME Section XI. Furthermore, the crack growth analysis of the flaws in the MSB closure weld shows that they will not propagate under normal, off-normal, and accident loads, and therefore, they will continued to perform their intended functions, including confinement, fuel integrity, and criticality control, during the initial and extended storage periods. Section 3.4.3.2, "Hydrogen-Induced Weld Cracking," has been revised to discuss the UT examinations performed on the closure welds of all previously loaded MSB assemblies and the corresponding fracture mechanics analyses used to disposition the resulting weld flaw indications.
Prior to loading Palisades MSB-04, independent reviews of MSB shell seam weld radiographs were performed, but did not require a fabrication hold-point. The GL's Level III inspector did not identify flaws in the shell seam welds of Palisades MSB-01,
-02, and -03. Thus, there is reasonable assurance that the shell seam welds of Palisades Page 12 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information MSB-01, -02, and -03 did not include flaws and, therefore, they will satisfy the confinement requirements of 10 CFR Part 72 for the initial storage period. However, the flaws in Palisades MSB-04 longitudinal seam weld were identified by the GL's Level III inspectors shortly after loading Palisades MSB-04. The corrective actions taken to assure continued safe storage of Palisades MSB-04 are discussed in the following paragraph. As discussed in Section 3.4.3.3, the fabrication process was subsequently changed to require a hold point for an independent review of radiographs in order to prevent recurrence of this condition. Thus, since all MSBs loaded after Palisades MSB-04 (which include all VSC-24 casks loaded at both Point Beach and ANO) received an independent review of MSB shell seam weld radiographs prior to loading, there is reasonable assurance their seam welds did not include flaws and, therefore, they will satisfy the confinement requirements of 10 CFR Part 72 for the initial storage period.
As discussed in Section 3.4.3.3, the flaws identified in the radiographs of the longitudinal seam weld of Palisades MSB-04 were also evaluated using fracture mechanics analysis to demonstrate that the flaws would not propagate under the full range of normal, off-normal, and accident loads. Specifically for Palisades MSB-04, the fatigue crack growth analysis of Palisades MSB-04 shows that the flaw sizes will remain essentially unchanged during the initial storage period for the full range of normal, off-normal, and accident load conditions. The same conclusion is also reached for the extended storage period by TLAA, as discussed in Section 3.3.3.6.
As an addition measure, period radiological surveys were performed on the first four VSC-24 casks loaded at Palisades on a routine basis, and Palisades MSB-04 was surveyed for an extended period of time. The results of the radiological surveys did not identify any unusual dose rates or contamination levels, thereby providing further evidence of the MSBs confinement boundary integrity.
Summary of LAR changes:
" Section 3.4.3: Revised to state that there is reasonable assurance that all VSC-24 storage systems that are currently loaded satisfy the confinement, fuel integrity, and subcriticality requirements of 10 CFR Part 72.
- Section 3.4.3.2, "Hydrogen-Induced Weld Cracking," 4 th paragraph: Added to discuss the UT examinations performed on the closure welds of all previously loaded MSB assemblies and the corresponding fracture mechanics analyses used to disposition the resulting weld flaw indications. In addition, the List of Acronyms and Abbreviations has been revised to include those added in Section 3.4.3.2, "Hydrogen-Induced Weld Cracking."
- Section 3.4.3.3, last paragraph, 1" sentence: Editorial correction Section 3.3.3.6 cross reference.
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SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information OBSERVATIONS OBS-1. Address the potential for spent ftel cladding degradation by zinc fumes inside the multi-assembly sealed basket (MSB) VSC-24.
NUREG/CR-6732, "Zinc-Zircaloy Interaction in Dry Storage Casks" discusses the potential for cladding degradation due to zinc fumes.
This information is needed to determine compliance with 10 CFR 72.240(d).
Response to OBS-1:
A discussion has been added to Section 6.2.1.1 of the Aging Management Review, which addresses the issue of zinc vapor inside the MSB. A copy of the Aging Management Review is included in Attachment 2. The evaluation concludes that zinc-Zircaloy interaction is not an issue for the extended storage period, because peak cladding (and zinc-bearing coating) temperatures are well under 300TC.
Summary of LAR changes:
9 None.
OBS-2. Clarify how additional concrete degradation mechanisms besides defects wider than
'/2-inch or 1/4-inch deep (as described in the Technical Specification 1.3.2) will be addressed under the aging management program such as an industry consensus standard (e.g., American Concrete Institute Code Requirements 349).
Other concrete degradation mechanisms should be evaluated such as alkali-silica reactions or alkali-carbonate reactions which exhibit map-cracking.
This information is needed to determine compliance with 10 CFR 72.240(c)(3).
Response to OBS-2:
Concrete degradation mechanisms other than those described in Technical Specification 1.3.2 are addressed in Section 3.4.2.2 and Table 15 of the VSC-24 CoC renewal application (Reference 2). As discussed in Section 3.4.2.2, the exposed surfaces on the sides and top of the VCC assembly are visually examined in accordance with ACI 201.1R-08, or an equivalent industry consensus standard, for evidence of ASR or leaching of CaOH that may indicate loss of strength. Per Table 15, "Method or Technique," personnel performing the visual inspection of the VCC concrete surfaces are required to be qualified in accordance with industry guidelines for implementing the requirements of the Maintenance Rule (10 CFR 50.56), such as ASME Code,Section XI, Subsection IWL or ACI 349.3R. Per Table 15, "Monitoring and Trending,"
monitoring and trending of data collected from the examinations (e.g., crack maps) is Page 14 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information required to identify progressive growth of defects that may indicate degradation due to ASR-induced expansion or corrosion of rebar. Per Table 15, "Acceptance Criteria,"
any evidence of degradation mechanisms that may result in loss of concrete strength (e.g., ASR-induced expansion, leaching, or corrosion of rebar) is considered unacceptable. Per Table 15, "Corrective Actions," concrete that shows evidence of degradation mechanisms that may result in loss of concrete strength shall be evaluated for continued storage.
Summary of LAR changes:
- Section 3.4.2.2, 1st, 2 nd, and 3 rd paragraphs: Editorial corrections to clarify that the inspection and monitoring requirements in the AMP are credited with managing aging mechanisms that may cause loss of strength, such as aggregate reactions.
- Section 3.4.2.2, 3rd paragraph: Added sentence requiring visual examination of the VCC concrete exterior surfaces to be performed in accordance with ACI 201.1 R-08, or an equivalent industry consensus standard.
- Section 3.6: Added references [3.34] thru [3.36].
" Table 15, "Method or Technique": Revised to require that visual examination of the VCC concrete exterior surfaces to be performed in accordance with ACI 201.1 R-08, or an equivalent industry consensus standard.
- Table 15, "Method or Technique": Editorial correction of reference numbers for ASME Section XI, Subsection IWL and ACI 349.3R.
" Table 15, "Acceptance Criteria": Editorial corrections.
- Table 15, "Corrective Actions": Revised to clarify that defects in the concrete exterior shall be evaluated in accordance with the GL's corrective action program and clarify the required corrective actions for defects identified.
- Table 17, "Method or Technique": Editorial correction of reference numbers for IWE-2330.
OBS-3. Justify why crevice corrosion at the bottom of the MSB was not considered in the lead cask inspection.
Crevice corrosion is an accelerated form of corrosion which should be considered if there is a credible way for water to enter the Ventilated Concrete Cask (VCC).
This information is needed to determine compliance with 10 CFR 72.240(d).
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SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information Response to OBS-3:
The potential for crevice corrosion of the carbon steel subcomponents of the MSB and VCC is addressed in Section 3.2.1.1 of the application. Crevice corrosion can occur when two metal surfaces are in contact and exposed to a wet environment. Crevice corrosion at the bottom of the MSB is not considered to be a credible degradation mechanism since the conditions under which it occurs are not present at the bottom of the MSB.
The VCC liner bottom plate includes ceramic tiles that support the MSB assembly and prevent it from contacting the VCC liner bottom during normal storage. The separation provided by the ceramic tiles also permits any moisture at the bottom of the VCC cavity to drain and dry. However, the environment at the bottom of the MSB is not expected to be wet since the VCC assembly includes a sealed lid and ventilation duct geometry that provides a torturous path for water ingress. This conclusion is supported by the results of the 5-year cask inspections performed by all GLs and the initial lead cask inspection performed at Palisades, all of which show no evidence of a wet environment or corrosion products at the bottom of the VCC cavity. Had corrosion of the MSB bottom plate occurred prior to these inspections, it is expected that corrosion products would be visible on the VCC bottom plate at the bottom of the annulus, which they were not.
Finally, even though the VSC-24 storage system is designed to prevent corrosion at the bottom of the MSB and no evidence of corrosion has been observed, a conservative corrosion allowance of 0.18-inches is assumed at the bottom of the MSB over a 60-year storage period, as discussed in Section 3.3.3.3 of the application. Thus, the scope of the lead cask inspection did not include visual examination of the MSB bottom plate for crevice corrosion.
Summary of LAR changes:
0 None.
OBS-4. Provide discussions for differences in explanations of crack/flaw formation found in Section 3.4.3.2 and Section 3.4.3.3.
Section 3.4.3.2 "MSB Closure Weld Cracks" states that "... the delay time for the onset of hydrogen-induced cracking (deemed the only credible type of delayed cracking) is only a matter of hours; shorter than the time period between placement of the weld and weld inspections. No other (longer-term) mechanisms for delayed cracking or crack growth were identified." However, Section 3.4.3.3 "Palisades MSB-04 Shell Seam Weld RT Indications" describes the situation where multiple cracks/flaws were found in MSB-04 after a much longer period of time. Confirm that the timing and methodology of MSB inspections can detect cracks/flaws, whether due to hydrogen-induced cracking or by other mechanisms. The reasons for the inconsistent explanations found in Section 3.4.3.2 and Section 3.4.3.3 should be provided.
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SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information This information is needed to determine compliance with 10 CFR 72.236(d) and (e).
Response to OBS-4:
Section 3.4.3.2 discusses several conditions related with weld flaw indications that were identified while performing MSB closure field-weld operations at the sites; whereas, Section 3.4.3.3 discusses flaws in the longitudinal seam shop-weld of Palisades MSB-04 that were identified during an independent review of radiograph records from the inspection performed by the fabricator. Although both sections discuss weld flaw indications in the MSB confinement boundary welds, they differ not only in the location of the weld flaw indications (shell longitudinal seam weld vs.
structural lid-to-shell weld), but also in the corrective actions taken to repair the weld flaws. As discussed in Section 3.4.3.2, the weld flaw indications identified during the MSB closure operations were all removed by grinding and repaired in accordance with approved welding procedures. However, as discussed in Section 3.4.3.3, the flaw indications in the longitudinal seam weld of Palisades MSB-04 were not able to be repaired since it had been loaded shortly before the condition was identified by the GL's level III inspector.
In all cases, corrective actions were taken to: (1) Assure that the affected MSB assemblies would continue to perform their intended functions during the initial storage period, and (2) Prevent recurrence of these conditions. These corrective actions included changes to the methods and timing of weld examinations in order to prevent recurrence. For instance, as discussed in Section 3.4.3.2, "Lamellar Tearing in MSB Shell," a requirement was added for acid etching and/or UT inspections of the top 4-inches of the MSB shell to identify any flaws or defects in the region of the MSB closure weld. Also, as discussed in Section 3.4.3.2, "Hydrogen-Induced Weld Cracking," the MSB loading operations were changed to require a minimum 2-hour waiting period after completing the MSB closure weld to perform the weld inspection to allow the onset of DHC, should it occur. Finally, as discussed in Section 3.4.3.3, the MSB assembly fabrication process was changed to require a hold-point for an independent review of radiographs. The changes were made to provide additional assurance that any flaws in the MSB confinement boundary welds will be detected by the weld examinations.
Summary of LAR changes:
- Section 3.4.3.2, "Lamellar Tearing in MSB Shell," 3 rP paragraph: Revised to clarify the changes made to the weld inspection methods and timing as a result of the corrective actions, and to identify the CoC Amendment and FSAR revision in which these changes were included.
- Section 3.4.3.2, "Hydrogen-Induced Weld Cracking," last paragraph: Revised to clarify the changes made to the MSB closure weld inspection requirements as a result of the corrective actions, and to identify the CoC Amendment and Page 17 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information FSAR revision in which these changes were included. In addition, the 4 'h paragraph in the section has been added to discuss the UT examinations and fracture mechanics evaluations performed for the closure welds of all MSBs that were loaded prior to implementing the corrective actions.
OBS-5. Include the following SSC components in Tables 4 through 6 of the application, or justify why they do not need to be scoped in:
a) bolts described in Drawing No. MSB-24-002, Sheet 1, top view and Note 9.
b) coating described in:
- Drawing No. VCC-24-008, Note 2;
- Drawing No. VCC-24-001, Note 2; and
- Drawing No. VCC-24-002, Note 2 c) lead plug in Drawing No. MTC-24-009 (Item No. 3) d) items in Drawing No. MTC-24-010 This information is needed to determine compliance with 10 CFR 72.240.
Response to OBS-5:
With the exception of the Item (a) above, Tables 6 and 7 of the application (formerly Tables 5 and 6) have been revised to include the missing VCC and MTC assembly subcomponents, as described below. In reference to Item (a), the thread specification called out in the "Top View" of the MSB shell shown on Drawing No. MSB-24-002, Sheet 1, Revisions 4, 5, and 6 and in Note 9 of Drawing No. MSB-24-002, Sheet 1, Revision 6 refers to the threaded holes in the MSB structural lid that are used for MSB lifting operations, not to bolts.
Summary of LAR changes:
- Table 6, "Coating" subcomponent: Revised to include coating specified on all general arrangement drawings.
- Table 7: Revised to include the light MTC shield door lead plug shown in Drawing No. MTC-24-009, Item 3 and Hydraulic Cylinder Assembly subcomponents shown in Drawing No. MTC-24-010.
OBS-6. Update TLAAs offatigue cracking based upon identified cracks in the VSC-24 systems.
Confirm the adequacy of the provided TLAAs and provide significant justification for why the crack growth evaluation listed in Section 3.3.3.6 is bounding.
The CoC Renewal Application cites a fatigue analysis of a bounding 1-inch long by 1/2-inch deep subsurface flaw at the Palisades nuclear generating station (Section Page 18 of 19
SFD/NRC 13-003, Enclosure 1 Docket No. 72-1007 Responses to Request for Supplemental Information 3.3.3.6). Confirmatory Action Letter 97-7-001 (ML060620420) notes significantly longer cracks in VSC-24 systems at different sites.
This information is needed to determine compliance with 10 CFR 72.236(d).
Response to OBS-6:
The TLAA discussed in Section 3.3.3.6 is specific to the weld flaw indications identified in the shell longitudinal seam weld of Palisades MSB-04, and it is not intended to be a bounding analysis for the weld flaws identified in CAL 97-7-001 (which are discussed in Section 3.4.3.2). The subsurface flaw size evaluated in the TLAA bounds those identified in the shell longitudinal seam weld of Palisades MSB-04.
The longer cracks identified in CAL 97-7-001 are discussed in Section 3.4.3.2, "Lamellar Tearing in MSB Shell" and "Hydrogen-Induced Weld Cracking." These are different than those discussed in Section 3.4.3.3, as discussed in the response to OBS-4.
As discussed in Section 3.4.3.2, these longer flaws were all ground out and repaired by welding, but a fracture mechanics analysis of a bounding hypothetical flaw in the MSB shell was performed to evaluate the possible effects of undocumented weld repairs.
The results of the fracture mechanics analysis show that the bounding weld flaw size is smaller than the allowable crack size for normal and faulted conditions. The results also show that the bounding weld flaw size is lower than the threshold for crack propagation due to cyclic loading, and therefore not susceptible to fatigue failure.
Therefore, it is concluded that any potentially undiscovered flaws from undocumented weld repairs would not prevent the MSB from performing its intended functions during the initial or extended storage period.
Summary of LAR changes:
" Section 3.4.3.2, "Lamellar Tearing in MSB Shell," 1st paragraph: Revised to describe the size of the defect cavity associated with the Palisades MSB-05 shield lid-to-shell weld failure.
" Section 3.4.3.2, "Lamellar Tearing in MSB Shell," 4th paragraph: Revised clarify the discussion of the fracture mechanics analysis performed to evaluate potentially undiscovered weld flaws.
- Section 3.4.3.2, "Hydrogen-Induced Weld Cracking," 1S paragraph: Revised to describe the size of the defect cavity associated with the ANO shield lid-to-shell weld failures and refer to the bounding fracture mechanics analysis described previously in "Lamellar Tearing in MSB Shell."
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