L-19-009, Independent Spent Fuel Storage Installation Remaining Responses to NRC Letter Dated April 30, 2019, Request for Additional Information for the Technical Review of the Application for Renewal of the Humboldt Bay Independent Spent Fuel

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Independent Spent Fuel Storage Installation Remaining Responses to NRC Letter Dated April 30, 2019, Request for Additional Information for the Technical Review of the Application for Renewal of the Humboldt Bay Independent Spent Fuel
ML19221B564
Person / Time
Site: Humboldt Bay
Issue date: 07/25/2019
From: Welsch J
Pacific Gas & Electric Co
To:
Document Control Desk, Division of Spent Fuel Management
Shared Package
ML19221B575 List:
References
HIL-19-009
Download: ML19221B564 (22)
v • d • e


Text

Enclosure 3 to this letter contains Confidential Information - Withhold Under 1 O CFR 2.390

  • .. Pacific Gas and

~~. Electric Company~

James M. Welsch Senior Vice President Diablo Canyon Power Plant P.O. Box 56

  • Generation and
  • Chief Nuclear Officer Avila Beach, CA 93424 805.545.3242
  • E-Mail: James.Welsch@pge.com July 25, 2019 PG&E Letter HIL-19-009 ATTN: Document Control Desk Director, Division of Spent Fuel Management Office of Nuclear Material Safety and Safeguards\\

U.S.. Nuclear Regulatory Commission 10 CFR 72.42 Washington, DC 20555-0001

. Docket No. 72-27, Materials License No. SNM-2514

  • Humboldt Bay Independent Spent Fuel Storage Installation*

Remaining Responses to NRC Letter dated April 30, 2019, "Request for Additional Information for the Technical Review of the Application for Renewal of the Humboldt Bay Independent Spent Fuel Storage Installation License No. SNM-2514 (CAC No.001028)"

References:

1. PG&E L,etter HIL-18-006, License Renewal Application for the Humboldt Bay Independent Spent Fuel Storage Installation, dated July 10, 2018 (ML18215A180 and ML18215A213)
2. PG&E Letter HIL-18-008, Response to NRC Letter dated September 20, 2018, "Request for Supplemental In.formation for the Technical Review of the Application for Renewal of the Humboldt Bay Independent Spent FLiel Storage Installation License No. SNM-2514 (CAC No. 001028)," dated October 22, 2018 (ML18330A050)
3. NRC Letter, "Request for Additional Information for the Technical
  • Review of the Application for Rene~al of the Humboldt Bay

. Independent.Spent Fuel Storage Installation License No. SNM-2514 (CAG No. 001028)," dated April 30, 2019 (ML19122A231 and ML19122A230)

4. PG&E Letter HIL-19-008, Partial Response to NRC Letter dated April 30, 2019, "Request for Additional Information for the Technical Review of the Application for:Renewal of the Humboldt Bay Independent Spent Fuel Storage Installation License No. SNM-2514

. (CAC No. 001_028)," dated July 1, 2019

  • ( contains Confidential inform~tion - Withhold Und.er 1 O CFR 2.390 When separated from Enclosure 3: this document is d~controlled
  • to this letter contains Confidential Information -Withhold Under 10 CFR 2.390 Document Control Desk July 25, 2019 Page2

Dear Commissioners and Staff:

PG&E Letter HIL-19-009 By Pacific Gas and Electric Company (PG&E) letters dated July 10, 2018 and October 22, 2018 (References 1 and 2), PG&E submitted a License Renewal Application (LRA) to the U.S. Nuclear Regulatory Commission (NRC) for the renewal of Materials License SNM-2514, for the Humboldt Bay (HB) Independent Spent Fuel Storage Installation (ISFSI).

By NRC letter dated April 30, 2019 (CAC/EPID No. 001028/L-2018-RNW-0016, Reference 3), the NRC Staff requested additional information to support their review of the HB ISFSI LRA. By PG&E letter dated July 1, 2019 (Reference 4 ), PG&E provided responses to a portion of the requests for additional information (RAls) and committed to providing the remaining RAI responses by July 31, 2019. PG&E also committed to notify the NRC of the completed shielding analysis update and evaluation findings in response to RAI 2-1 Part 13, by July 31, 2019. This letter satisfies these commitments. contains PG&E's responses to RAI 2-1 Part 9, RAI 3-4 Part 1, RAI A-6, and RAI A-7 and the results of the completed shielding analysis update and evaluation findings in response to RAI 2-1 Part 13. contains Revision 3 of the LRA, resulting from the RAI responses included in Enclosure 1, with the changes designated by change bars in the left margin. The LRA is being provided on one disk labeled, "Humboldt Bay Independent Spent Fuel Storage Installation Site Specific License Renewal Application, Revision 3, July 2019." provides Holtec's Holtite-A Development History and Thermal Performance Data, as r~ferenced in response to RAI A-7. Enclosure 3 contains confidential information that should be withheld from public disclosure in accordance with 10 CFR 2.390. contains an Affidavit pursuant to 10 CFR 2.390. The Affidavit sets forth the basis for which specific information included in Enclosure 3 may be withheld from public disclosure by the Commission and addresses the considerations listed in 10 CFR 2.390(b)(4). All documents within the scope of this affidavit are marked as "Confidential Information -Withhold Under 10 CFR 2.390."

PG&E makes no new or revised regulatory commitments (as defined by NEI 99-04) in this letter. contains Confidential information -Withhold Under 10 CFR 2.390 When separated from Enclosure 3, this document is decontrolled to this letter contains Confidential Information -Withhold Under 10 CFR 2.390 **

Document Control Desk July 25, 2019 Page3 PG&E Letter HIL-19-009 If you have any questions regarding this response, please contact Mr. Philippe Soenen at (805) 459-3701.

I state under penalty of perjury that the foregoing is true and correct.

Executed on July 25, 2019.

Sincerely,

,if_ -- A)u)~'

~Welsch*

Senior Vice President Generation and Chief NuclearOfficer Enclosures cc:

Humboldt Distribution cc/enc:

William C. Allen, NMSS Project Manager Christopher Markley, NMSS Project Manager Scott A. Morris, Region IV Administrator Gonzalo L. Perez, California Department of Public Health (without Enclosures 3 and 4) contains Confidential information -Withhold Under 10 CFR 2.390 When separated from Enclosure 3, this document is decontrolled

Holtec Confidential Information Affidavit PG&E Letter HIL-19-009

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Document ID 3015002-AFF Non-Proprietary Attachment 1 AFFIDA VJT PURSUANT TO 10 CFR:2.390 I, Kimberly Manzione, being duly sworn, depose and state as follows:

\\..

(1)

I have reviewed the information described in paragraph (2) which is sought to be withheld, and am authorized to apply for its withp.olding.

I*~

1...-

(2)

The information sought to be withheld is informat1on provided in reference documents listed below as noted in'the responses to the NRC's Request for Additional Information for the Technical Review of the Humboldt Bay Independent Spent Fuel Storage Installation License No. SNM~2514. These following references contain Holtec Proprietary information:

Holtite A: Development History and Thermal Performance Data,*

Holtec Report HI-2002396, Rev. 5.

American Seal Certificate of Conformance# 34048-CE for HI-STAR Overpack Closure Plate Seals.

(3). In making this application for withholding of proprietary information of which it is the owner, *Holtec International relies upon the exemption from disclosure set forth in the Freedom of Information Act ("FOIA"), 5 USC Sec. 552(b)(4) and the Trade Secrets Act, 18 USC Sec. 1905, and NRC regulations 10CFR Part 9.l 7(a)(4), 2.390(a)(4), and 2.390(b)(l) for "trade ~ecrets,and commercial or

  • financial information obtained from a person and privileged or confidential" (Exemption 4). The material for which exemption from disclosure is here sought is* all "confidential commercial information", and some portions also qualify under the narrower definition of "trade-secret", within the meanings assigned to those terms for purposes of FOIA Exemption 4 in, respectively, Critical Mass Energy Project v. Nuclear Regulatory Commission, 975F2d871 (DC Cir. 1992),

and Public titizen Health Research Group v. FDA, 704F2dl280 (DC Cir.

1983).

  • 1 of5

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk.

Document ID 3015002-AFF Non-Proprietary Attachment 1

Some examples of categories of information which fit into the definition of

  • proprietary information are:

. a.

Information that discloses a process, method, or apparatus, including supporting data and analyses, where prevention of its use by Holtec's competitors without license* from Holtec International constitutes a competitive economic advantage over other companies;

b.

Information which, if used by a competitor, would reduce his expenditure of resources or improve his competitive *-position in the design, manufacture, shipment, installation, assurance *of quality, or licensing of a similar product.

c.

Information which reveals cost or price information, production, capacities, budget levels, or commercial strategies ofHoltec International, its customers, or hs suppliers;

d.

Information which reveals aspects of past, present, or future Holtec International customer-funded development plans and programs of potential commercial value to Holtec Intern3:tional;

e. *.
  • Information which discloses patentable subject matter for which it may be desirable to obtain patent protection.

The information sought to be withheld is considered to be proprietary for the reasons set forth in paragraphs 4.a and 4.b above.

(5)

The information sought to be withheld is being; submitted to the NRC in confidence. The information (including that compika,,p. from many sources) is of a sort customarily held in confidence by Holtec International, and is in fact so held. The information sought to.be withheld has; to the best ofmy knowledge and belief, consistently been held in confidence by Holtec International. No **

public disclosure has been made, and it is not available in public sources. All

  • disclosures to third parties, including any required transmittals to the NRC, hav~

2 of S

U.S. Nuclear Regul2.tory Commission ATTN: Document Control Desk Document ID 3015002-AFF Non-Proprietary Attachment 1 AFFIDAVIT PURSUANT TO 10 CFR.2.390 been made, or must be made, pursuant to regulatory provisions or proprietary agreements which provide for maintenance of the information in confidence. Its:

initial designation as proprietary information, and the subsequent steps taken to

  • prevent its unauthorized disclosure, are as set fort1:t in paragraphs ( 6) and (7) following.

( 6)

Initial approval of proprietary treatment of a document is made by the manager of the originating component, the person most likely to be acquainted with the value and sensitivity of the information in relation to industry knowledge.

Access to such documents within Holtec International is limited on a "need to know'1 basis.

(7)

The procedure for approval of external release of -such a document typically requires review by the staff manager, project manager, principal scientist or other equivalent authority, by the manager of the cognizant marketing function

( or his designee ), and by the Legal Operation, for technical content, competitive effect, and determination of the accuracy of the proprietary designation.

Disclosures outside Holtec International are limited to regulatory bodies, customers, and potential customers, and their agents, suppliers, and licensees, and others with a legitimate need for the inforniation, and then only in accordance with appropriate regulatory provisions b,r proprietary agreements.

(8)

The information classified as proprieta1y was developed and compiled by Holtec International at a significant cost to Holtec Intemat.ional. This information is classified as proprietary because it contains detailed.. descriptions of analytical approaches and methodologies not available elsewhere. This information would provide other parties1 including competitors, with infonnation from Holtec Intemational's technical database and the results of.evaluations performed by Holtec International. A substantial effort has been expended by Holtec International to develop this information. Release_.of this information would improve a competitor's position because it would enable Holtec' s competitor to copy our technology and offe;r it for sale in competition "with our company, causing us financial injury.

  • 3 of5

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Document ID 3015002-AFF

  • Non-Proprietary Attachment 1 AFFIDAVIT PURSUANT TO 10 CFR *_2.390 (9)
  • Public disclosure of the information sought to be *.withheld is likely to cause substantial harm to Holtec Intemational's competifrv:e position and foreclose or reduce the availability of profit-making opportunitie~... The information is part of Holtec International's comprehensive spent fuel storage technology base, and its commercial value extends beyond the original development cost. The value of the technology base goes beyond the extensive physical database and analytical methodology and includes development of the expertise to determine and apply the appropriate evaluation process.

The research, development, engineering, and analytical costs comprise a substantial investment of time and money by Hohec-"Intemational.

The precise value of the expertise to devise an evaluation process and apply the correct analytical methodology is difficult to quantify, but it clearly is substantial.

Holtec International's competitive advantage will be.lost if its competitors are able to use the results of the Holtec International experience to normalize or verify their own process or if they are able to claim an1 equivalent understanding by demonstrating that they can arrive at the same o:-. similar conclusions.

The value of this information to Holtec International would be lost if the information were disclosed to the public. Making such information available to competitors without there having been required'.. to undertake a similar expenditure* of resources would unfairly provide competitors with a windfall and deprive Holtec International of the opportunity to exercise its competitive advantage to seek an adequate return on its large inve~tment in developing these ve~ valuable,analytical tools.'

\\.

4of5

U.S. Nuclear Regulatory Commission ATTN:'Document Control Desk Document ID 3015002-AFF Non-Proprietary Attachment 1 AFFIDAVIT PURSUANT TO 10 CFR 2.390 STATEOFNEWJERSEY

)

)

ss:

COUNTY OF BURLINGTON )

Kimberly Manzione, being duly sworn, deposes and; says:.

That she has read the foregoing affidavit and the matters stated therein are true and correct to the best of her knowledge, information, and belief.

Executed at Camden, New Jersey, this 22 day ofMay 2019.

5 of5 Kimberly Manzione Holtec International Erika Grandrimo NOTARY PUBLIC

. STATE OF NEW JERSEY MY ~OMMISSION liXPIRES January 17, 2022 I

ii

'i

' J PG&E Letter HIL-19-009 PG&E Response to NRC Letter dated April 30, 2019, "Request for Additional Information for the Technical Review of the Application for Renewal of the Humboldt Bay Independent Spent Fuel Storage Installation License No. SNM-2514 (CAC No. 001028)"

/

PG&E Lefter HIL-19-009 Page 1 of 10 PG&E Response to NRC Letter dated April 30, 2019, "Request for Additional Information for the Technical Review of the Application for Renewal of the Humboldt Bay Independent Spent Fuel Storage Installation License No. SNM-2514 (CAC No. 001028)".

RA/ 2-1. Parts 9 and 13 Clarify the Scoping Evaluation with regard to the following items and their safety functions, modifying that evaluation and the aging management review as necessary.

9. Inclusion of a shielding function for port plugs, base plugs, and similar subcomponents of the overpacks. These items are relied on to prevent radiation streaming from the openings in the overpacks and minimize occupational exposures from these streaming paths. Thus,. these subcomponents should have a shielding safety function.
13. Confirmation that there is no lid for the GWC's inner shell. The referenced GWC drawings do not include an inner shelf lid; however, the shielding analysis for the GTCC waste is based on that waste remaining within the GWC's inner shell. Thus, a lid may be needed for that inner shell to erisure the waste remains within it, which also means that this lid would scope in, and have a shielding safety function This information is needed to confirm compliance with 10 CFR 72.42(b), 72.24(d) and (e), 72.104, 72.106, 72.124, and 72.126.

PG&E Response to RAI 2-1. Parts 9 and 13 The Scoping Evaluations are clarified as follows:

9.

In response to this RAI, the Humboldt Bay Independent Spent Fuel Storage Installation (HB ISFSI) shielding analysis was revised. Within the constraints of the shielding model geometry, the analysis was revised to evaluate the equivalent dose effect by removing an approximate annular volume of metal shielding material representing the overpack base plug, flange top plug, and closure plate plug, and other sjmilar subcomponents. The revised shielding analysis conclusions demonstrate these plugs have negligible impact to the dose. Therefore, these plugs do not hav~ a shielding safety function. The port plugs are relied upon in the shielding model. Enclosure 2 provides revised License Renewal Application (LRA) Tables 2-5 and 3.5-1, which have been updated to reflect a shielding safety function for the overpack port plugs.

13. As discussed in response to RAI 2-1, Part 13, in Pacific Gas and Electric Company (PG&E) letter dated July 1, 2019; there is no lid for the Greater

PG&E Letter HIL-19-009 Page 2 of 10 Than Class C (GTCC) Waste Container's (GWC) inner shell. There is a

  • space between the top of the inner shell and the bottom of the GWC lid bottom which stores GTCC waste components. The sizes and shapes of the GTCC waste pieces preclude movement out of the inner shell (see drawings referenced in LRA Table 2-12). However, because the GTCC waste pieces protrude above the top of the inner shell inconsistent with the GTCC waste shielding analysis, the shielding analysis was updated to reflect this configuration. The revised shielding analysis demonstrates the shielding calculation conclusions regarding doses from the HI-STAR HB GTCC remain, valid and are consistent with the offsite dose analysis.

RAJ 3-4,

  • Part 1 Clarify the following items, modifying the renewal application and analyses as necessary.
1. The fraction of boron-10 in the Holtite-A shielding material that is estimated to be depleted over the 60 years of storage (20-year initial license period plus the 40.:.year period ofextended operations). The renewal application indicates this fraction will be Jess than 5x10-10; however, the original evaluation on which this is
  • based, the 10 CFR Part 71 safety analysis for the HI-STAR 100 transportation package, indicates the fraction for 50 years is 4. Ox10-8. Thus, it is not clear how the 5x10-10 fraction was derived.

This information is needed to confirm compliance with 10 CFR 72.42(a).

  • PG&E Response to RAI 3-4, Part 1 The 5x10-10 value provided in the HB ISFSI LRA contained an incorrect exponent. HB ISFSI LRA Sections 4.4.1 and 4.6, and Appendix D, Section 9.4.3.4 have been updated to reflect the total depletion of Boron-10 over a 60-year period remains negligible (less than 5x10~8 of total Boron-10 atoms depleted). As described inHB ISFSI LRA Section 4.4.1, this fraction is derived by conservatively scaling up the original evaluation value by a factor of 6/f> (60 years/50 years). Enclosure 2 provides the revised LRA sections.

. RAJ A-6 Provide an evaluation of the public and occupational doses for operations for overpacks and the /SFSI vault that:

1. accounts for the combined effects of potential degradation of the carbon steel, Ho/fife-A neutron shielding, and the concrete sub-components PG&E Letter HIL-19..:QQ9 Page 3 of 10
2. demonstrates that the proposed aging*management programs ensure the shielding function will be maintained when considering the combined degradation effects
3. demonstrates that the doses will remain within the design basis limits described in Chapter 7 of the FSAR and the regulatory limits in 10 CFR Part 72 and
4. addresses all relevant operations configurations within the design basis. -

The renewal application includes discussion of aging effects and mechanisms for the carbon steel subcomponents of the overpacks and the ISFSI vault as well as the vault concrete and the Ho/tite-A neutron shielding for the overpacks containing spen_t fuel.

These components are included in the shielding analysis for determining overpack dose rates, demonstrating compliance with regulatory dose limits (e.g., 10 CFR 72.104(a) and 10 CFR 72.106(b)), and determining occupational dose estimates. In the renewal application, the licensee addresses each the effects of aging for each subcomponent separately and only for the configuration of the overpac_k in its /SFSI vault cell. Since these subcomponents all contribute to the shielding function, the licensee should

, evaluate the combined. effect of their degradation, as evaluated in the proposed analyses and allowed in the acceptance criteria of the proposed aging management progr?ms. Additionally, the license design basis includes operations with configurations in addition to the configuration, of the overpacks being in their respective vault cells with the cell lid in place. At least some of these operations may be encountered during operation of the /SFSI (e.g., operations with the vaulf. cell /id removed, operations with the overpack out of the vault cell for preparation for transport). Thus, the licensee's evaluation should address configurations of the subcomponents for the relevant operations allowed by the license. The following discussion provides additional detail regarding items the requested evaluation should address.

The proposed aging management of the concrete subcomponents uses the AC/ 349.3R

,, evaluation criteria.

  • These criteria are intended for ensuring structural performance of the concrete, not ensuring the shielding function. So, the evaluation should address the degradation that use of these criteria would allow before the degradation would be entered into the licensee's corrective action program. The licensee has performed some analysis for Joss of material for carbon steel subcomponents; however,. the staff cannot determine that the analysis is adequate to account for the amount of corrosion of carbon steel subcomponents that is discussed in the renewal application! (e.g., the estimated annual corrosion rates discussed in the application). The scope of this analysis is limited to the overpack being in its vault cell with no consideration for the impacts on shielding from degradation of the Holtite-A and the concrete subcomponents.

The design bases in Chapter 7 of the FSAR include evaluations of the dose rates and doses and evaluation of compliance with regulatory limits that address the configurations and operations included in the design basis and described in the FSAR.

PG&E Letter HIL-19-009 Page 4 of 10 The evaluation in the renewal applicatiOn'should demonstrate that the actions and evaluation criteria in the proposed aging management programs are sufficient to ensure the shielding function is maintained for these configurations and operations, notjust the configuration with the overpacks in their vault cells with the vault cell /ids in place.

The evaluation should consider relevant transfer operations, periodic maintenance activities and activities required by technical specifications, if any, and should consider that operations may be for multiple overpacks within a given year period. In instances where the evaluation may indicate that design bases or compliance with regulatory limits may be challenged (e.g., 10 CFR Part 20 occupational dose limits), the evaluation should describe the* actions that would be taken, controls that would be imposed, or conditions that would assure compliance is maintained. Guidance such as is provided in Section 11.4.3.1 of NUREG-1567, particularly the bulleted list at the end of the section, should be considered, as needed.

72.122(h)(5), 72.104, 72.106, 72.124, 72.126, and 72.42(a).

PG&E Response to RAI A-6 The HB ISFSI shielding analysis (Hl-2033047) was revised to evaluate the dose impact from the combined effects of hypothetical conservative potential degradation of the carbon steel and concrete sub-components.* Degradation of Holtite-A was not considered in this analysis consistent with PG&E's response to RAI A-7 which concludes there are no credible aging mechanisms for Holtite-A in the HI-STAR 100 HB during the license renewal period. The density of all carbon steel components of HI-STAR HB and the vault was reduced by 20 percent and the density of the vault's concrete was decreased by 10 percent to reflect hypothetical conservative potential degradation during the period of extended operation. As presented below, PG&E completed the revised analysis to address the NRC's RAI; however, it is PG&E's opinion that the analysis represents a very conservative degradation scenario that is unlikely to occur given inspection findings thus far. In addition, as described below, PG&E will conduct ongoing inspections on one and five-year frequencies to identify any

  • trends in degradation.

In 2017, after 11.years in service, a pre-application inspection of the HB ISFSI (LRA, Appendix E, Section E.7) was conducted to support proposed LRA aging management.

Except for an isolated localized pit in the vault lid 0.0625 inches in depth, the carbon steel components were found to have minor coating damage, but no base metal degradation. The aging management programs proposed by PG&E conduct inspections on one and five-year frequencies, and therefore, will identify age-related.

degradation prior to the potential conservative degradation assumed in the referenced shielding analysis. Consist~nt with the proposed aging management programs, when PG&E identifies any degradation that does riot meet acceptance criteria, it will be entered in the corrective action program and evaluated for a timely resolution..

PG&E Letter HIL-19-009 Page 5 of 10 Expected, or even conservatively aggressive, corrosion will be detected before any design function would be impacted.

  • The assumptions in the revised shielding analysis are consistent with the beginning of the license renewal period inspections (i.e., includes 19 years of fuel coo'ling since initial
  • loading to the HB ISFSI). The following bounding operational configurations were evaluated:

1

1. All six casks in the normal long-term storage configuration in the vault with vault lids installed.
2. One vault lid removed to facilitate maintenance/inspections to the cask in situ:

From a shielding perspective, this configuration bounds normal long-term storage with the vault lids installed (configuration 1 above) because the vault lid provides additional shielding.

3. One cask rem0ved from the vault to facilitate maintenance/inspections: This configuration assumes there is no shielding from the vault for the removed cask. The remaining five casks are in the normal long-term storage configuration with the vault lids installed.

The table below presents the maximum annual doses for hypothetical conservative potential dry cask system degradation in the revised shielding analysis (Hl-2033047, Tables J.3 and K.2). PG&E will implement administrative controls to ensure compliance with regul~tory limits.

Ann ID ua f

H th f IC ose or 1ypo e1ca f

P t f I b C k S 't onserva 1ve o en 1a

,ry as iysem D d tion egra a Maximum Hourly Annual Dose Annual Dose at Site at Nearest Configuration Dose Rate Boundaryl1>

Residencel2>

(mrem/hour)

(mrem)

(mrem)

1. Normal Operations

- All Casks in Vault 0.0073 15.19 4.0 with Vault Lids

2. All Casks in Vault 0.00559 for cask with with One Vault Lid no vault lid 25<4).

6.6 Removed(3l 0.0073 for six casks in vault(5l

3. Five Casks in Vault 0.186 for cask aboveQround With One Cask 0.0073 for six casks
  • 25(4) 6.6 Aboveground(3l in vault(5l Notes:

mrem - millirem

1. 2080 hours0.0241 days <br />0.578 hours <br />0.00344 weeks <br />7.9144e-4 months <br /> per year; approximately 50 feet from ISFSI *
2. 8760 hours0.101 days <br />2.433 hours <br />0.0145 weeks <br />0.00333 months <br /> per year; approximately 800 feet from ISFSI PG&E Letter HIL-19-009 Page 6 of 10
3. A cask will not be in this configuration for a year. It could potentially be in the configuration on the order of days instead. The annual dose values are provided for comparative purposes only.
4. Twenty five mrem is the regulatory limit. As discussed below, administrative controls will be established to ensure compliance with regulatory limits.
5. This dose rate is conservative because, for the period of time cask(s) are-not in the normal long-term storage configuration, it double counts the dose from that cask.

From the above information, all configurations meet the dose rate limits in 10 CFR 20.1201 and 20.1502. As qescribed in HB ISFSI FSAR Update Section 7.5, there is a public trail at the site boundary 53 feet from the edge of the ISFSI. In addition, the following conclusions are applicable to regulatory dose compliance for each of the configurations:

)

Configuration 1 meets the design basis limit of 17 mrem/year per HB ISFSI FSAR Update, Table 7.5-1, the 10 CFR 72.104 limit of 25 mreril/year for site boundary dose, and the 10 CFR 20.1301 limits for individual members of the public. HB ISFSI LRA Appendix A, Tables A-1 and A-2, Elements 7 and 9, and Appendix 0, Section 0.2 have been updated to reflect the analysis results for this configuration Configuration 2 meets the 10 CFR 20.1301 limits for individual members of the public and the 10 CFR 72.104 limit of 25 mrem/year for site boundary dose for up to 73 days per year. In other words, vault lids may be removed for a combined total of up to 73 days per year (if actual dose rates are consistent with those calculated dose rates in the above table) to comply with regulatory dose requirements. HB ISFSI LRA Appendix-A, Tables A-1 and A-2, Elements 7 and 9, and Appendix D, Section 0.2 have been updated to reflect the limiting time this configuration is allowed per year and the administrative controls required during the period of extended operation.

Configuration 3 meets the 10 CFR 20.1301 limits for individual members of the public for up to 19 days per year and the 10 CFR 72.104 limit of 25 mrem/year for site. boundary dose for up to 2.1 days per year. In other words, casks may be removed from the vault for a combined total of up to _

2.1 days per year (if actual, dose rates are consistent with those calculated dose rates in the above table) to comply with regulatory dose requirements.

HB ISFSI LRA Appendix A, Tables A-1 and A-2, Elements 7 and 9, and Appendix 0, Section 0.2 have been updated to reflect the limiting time this configuration is allowed per year and the adm"ir1istrative controls required

  • during the period of extended operation.

Furthermore, as discussed in HB ISFSI FSAR Update Section 8.2, the only HB ISFSI

-design basis accident that could result in an increased dose is a fire that results in. loss-PG&E Letter HI L-19-009 Page 7 of 10 of Holtite-A. The revised shielding analysis demonstrates that calculated annual doses at the site boundary for configurations 1 through 3 are less than those in the original calculation (comparison of Hl-2033047, Tables 2, J.1, and K.1 ). Thus, the existing evaluation of dose for a fire accident as described in HB ISFSI FSAR Update Section 8.2.5.3 bounds the configurations discussed above and remains valid. Therefore, the HI-STAR HB System fulfills the 5 rem dose requirement of 10 CFR 72.106 during the period of extended operation with the assumed carbon steel and concrete degradation.

RA/ A-7 Provide justification that the proposed aging management progr.am for managing degradation of the.Holtite-A shielding material is adequate to ensure the shielding function of this material is maintained for the period of extended operation for each spent fuel overpack.

The proposed aging management of the Holtite-:-A shielding material includes quarterly radiation surveys of the ISFS/'s vault cells' lids and general area, quarterly evaluation of TLD dose data, and dose rate measurements on the vault cells' lids every 5 years along with dose rate measurements on the closure plates (the lid area) of the* overpack in the vault cell which is opened for more detailed inspections of the vault cell interior. While surveys of the /SFSl's general area or the dose data from the TLDs will provide an indication of the overall /SFSI dose rates and doses, the licensee should justify how these data will enable identification of degradation of an individual overpack's Holtite-A material that requires further 'action to ensure the shielding function is maintained. All overpacks will contribute to the measurements (survey and TLD) and, depending on the area of the Holtite-A that is degraded, the surveys and TLDs may be at locations that will not detect the effects of the degraded Holtite-A. Additionally, the measurements on the vault cell /id and the overpack closure plates are in areas where there is no.Holtite-A or in locations where the Holtite:..A does not have any expected impact on dose rates.

The Holtite-A is on the. radial side of the overpacks, whereas all of the dose rate measurements are on the top of the o'verpack or directly above the overpack (on the vault cell lid).

Thus, the staff currently finds that the proposed measurements are not sufficient to detect degradation of Holtite-A on an individual overpack that would require corrective.

action. The justification should include discussion of sensitivity of the measurement techniques and how that is sufficient to identify an issue with the Holtite-A. The justification should also include discussion of the locations at which dose rates will be measured on the vault lids and overpack lid, including whether the measurements will be taken at multiple lid locations, and the basis for the measurement location selection, including the number of locations and the appropriateness and adequacy to detect Holtite-A degradation on an individual overpack that requires corrective action. The discussion should also explain the adequacy of the proposed acceptance criteria to ensure the measurements are sufficient to detect Ho/tite-A degradation on an individual PG&E Letter HIL-19-009.

Page 8 of 10 overpack that requires corrective action. The justification should demonstrate that the actions and evaluation crite_ria are sufficient to ensure the Ho/fife-A shielding function is maintained for the configurations and operations which are part of the license design

  • basis.

This information is needed to determine compliance with 10 CFR 72.24(e),

72.122(h)(5), 72.104, 72: 106, 72.124, 72.126, and 72.42(a).

PG&E Response to RAI A-7 As outlined in Draft NUREG-2214, Managing Aging Processes in Storage, Table 4-9, there are three potential aging mechanisms and effects for Holtite-A: (1) cracking due*

  • to radiation embrittlement, (2) loss of fracture toughness and loss of ductility due to thermal aging, and (3) loss of shielding due to boron depletion.

HB ISFSI LRA Section 4.4.1 demonstrates through analysis that boron depletion is valid for the period of extended operation. As evaluated in Holtec's Holtite-A Development History and Thermal Performance Data ("Sourcebook" provided as Enclosure 3), the principal degradation mechanisms are thermal aging and radiation damage, including swelling, shrinkage, or cracking. Using the Sourcebook test data, the exposure of Holtite-A under long term storage in HI-STAR 100 HB for the license renewal period is evaluated below, demonstrated to remain well within Holtite-A qualification limits, and, therefore, thermal aging and radiation embrittlement are shown to not be credible for the HI-STAR 100 HB during the license renewal period. Because boron depletion is valid for the period of extended operation and therma_l aging and radiation embrittlement are not credible for the HI-STAR 100 HB, no aging management program for the Holtite-A shielding material is required to ensure the shielding function of this material is maintained for the period of extended operation.

Thermal Aging The principal effect of thermal aging is weight loss of Holtite-A under elevated temperatures as evaluated in the Holtite-A Sourcebook. Holtite-A fracture toughness and ductility are strength properties which do.not apply to the HI-STAR 100 overpack safety evaluation as these are not relied upon in the structural qualification of the overpack.

To ensure suitability of Holtite-A for spent fuel storage applications the cumulative weight loss must not exceed the 4 weight percent qualification criteria (Enclosure 3, Section 3.1 ). To this end, a conservatively articulated weight loss correlation is defined in the Sourcebook. The correlation excerpted below (Enclosure 3, Section 3.2) facilitates calculation of cumulative weight loss W (percent) as a function of exposure temperature T (°F) and storage time D (days).

W(T,D) = (A ln(D)+B)*2(T-325l141 *3

/

I

Where: A= 0.549 & B = 0.19 PG&E Letter HIL-19-009 Page 9 of 10 To conservatively maximize W, the maximum Holtite-A temperature under lt>ng term storage at the HB ISFSI is adopted with no credit for decay heat attenuation for the entire duration of 20 years of initial storage and 40-year license renewal period. The weight loss is computed as follows:

T = 195°F (HB ISFSI FSAR, Table 4.2-10)

D = (20+40)*365 = 21,900 Days

,W(T,D) = 0.641 percent I

The cumulative weight loss computed above is well within the Holtite-A qualification criteria of 4 weight percent. Therefore, thermal aging of Holtite-A is not credible for the HI-STAR 100 HB during the license renewal period.

Radiation Testing As evaluated in the $ourcebook, radiation testihg has qualified Holtite-A under the following exposure levels (Enclosure 3, Section 4.1.1 ):

Neutron Fluence: 1.28x1015 neutrons per centimeter squared (n/cm2)

Gamma Dose: 1.7x106 rad In addition to the above, radiation testing has also qualified thermally-aged Holtite-A under the following exposure levels (Enclosure 3, Section 4.2.1):

Neutron Fluence: 1.50x1015 n/cm2 Gamma Dose: 1.97x106 rad The qualification testing concluded Holtite-A is unaffected by exposure to neutron and gamma radiation, does not swell or shrink and that"... it is an acceptable material for long-term use in casks designed to hold spent nuclear fuel" (Enclosur~_3, Section 4.2).

While the Holtite-A qualification test exposures listed above exceed Holtite-A exposure under 50-year storage of hot fuel (47.5 gigawatts days per metric ton of uranium burnup, fuel cooled for five years) in the generic HI-STAR 100 cask, these parameters substantially bound the HB ISFSI fuel (per HB ISFSI FSAR, Section 7.2.1, 23 gigawatts

. days per metric ton of uranium burnup, fuel cooled for 29 years at loading) to support a conclusion of no degradation under exposure during the license renewal period.

Nevertheless, an exercise is undertaken below to quantify the qualification margins specific to HI-STAR 100 HB:

Neutron Flux: 2.023x107 n/cm2/hour Gamma Dose Rate: 3.88x10-2 rad/hour

J 60-Year Exposure Time: 60

  • 365
  • 24 = 525,600 hours0.00694 days <br />0.167 hours <br />9.920635e-4 weeks <br />2.283e-4 months <br /> PG&E Letter HIL-19-009 Page 10 of 10 Neutron Fluence: 2.023x107
  • 525,600 = 1.063x1013 n/cm2 Gamma Dose: 3.88x10-2
  • 525,600 = 2.037x104 rad Qualification Margin (i.e., radiation exposure under qualification testing divided by HI-STAR 100 HB 60-Year Exposure):

I Radiation Testing -

Neutron FILience: 1.28x1015 / 1.063x1013 = 120 Gamma Dose: 1. 7x106 / 2.037x104 = 83 Combined Thermal Aging and Radiation Testing -

Neutron Fluence: 1.50x1015 / 1.063x1013 = 141 Gamma Dose: 1.97x106 / 2.037x104 = 97 The margins computed above support the conclusion that Holtite-A is unaffected under neutron and gamma exposure in the HI-STAR 100 HB casks for the license renewal period. Therefore, radiation embrittlement of Holtite-A is not credible, even if combined with thermally-aged materials.

In conclusion, because boron depletion is valid for the period of extended operation and thermal aging and radiation embrittlement are not credible for the HI-STAR 100 HB, no aging management program for the Holtite-A shielding material is required to ensure the shielding function of this material is maintained for the period of e:xtehded operation.

HB ISFSI LRA Section 3.5.4.3, Table 3.5-1, Table A-2, Table A-4, Appendix D, Sections 9.4.3.3.2 and Table 9.4-1, and Appendix F, Section F4.1 are revised ac*cordingly. provides the revised LRA sections and tables.

PG&E Letter HIL-19-009 License Renewal Application (LRA) Revision 3,.

Affected LRA Sections and Tables

  • LRA Section/Table Reason for Chanae Table 2-5 RAI 2-1, Part 9 Section 3.5.4.3, RAI A-7, Table 3.5-1 RAI 2-1, Part 9 RAI A-7 Section 4.4.1 RAI 3-4, Part 1 Section 4.6 RAI 3-4, Part 1 Appendix A, Table A-1 RAI A-6 Appendix A, Table A-2 RAI A-6 RAI A-7 Appendix A, Table A-4 RAI A-7 Appendix D, Section D.2

\\

RAI A-6 Appendix D, Section D.3 RAI 3-4, Part 1 RAI A-7 Appendix F, Section F4.1 RAI A-7 PG&E Letter HIL-19-009 License Renewal Application (LRA) Revision 3 Affected LRA Sections and Tables

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