ML20318A323
| ML20318A323 | |
| Person / Time | |
|---|---|
| Site: | 07201008, Holtec |
| Issue date: | 11/13/2020 |
| From: | Holtec |
| To: | Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML20318A321 | List: |
| References | |
| 5014913 | |
| Download: ML20318A323 (5) | |
Text
Attachment 1 to Holtec Letter 5014913 Responses to NRC Clarification Questions on HISTAR 100 License Renewal Application RAI 2-3 and RAI 2-4 Follow-up Revise the scoping and aging management review (AMR) tables in the renewal application to clarify the responses to an NRC Observation and RAIs with respect to the subcomponents that were determined to be within scope of renewal.
The responses to NRC Observation 3 (Holtec, 2019) and RAIs 2-3 and 2-4 (Holtec, 2020) were provided to clarify which subcomponents were concluded to be within the scope of the renewal review and subject to an AMR. This clarity was sought to allow the staff to complete its review of the application and to ensure that the scoping and AMR tables (which are referenced in the aging management programs and in the proposed changes to the HI-STAR 100 Final Safety Analysis Report (FSAR) in Appendix D of the renewal application) provided an accurate description of the aging management activities in the period of extended operation.
The staff identified apparent discrepancies in the response to the Observation, responses to RAIs, and the scoping and AMR tables in the renewal application. As a result, revise the renewal application to clarify the following:
- 1. Revise Table 2.1-3 of the renewal application, MPC Basket Subcomponents, to provide a conclusion as to whether the Optional Heat Conduction Elements are within scope of the renewal. If these elements are concluded to not be within the scope (as stated in the response to RAI 2-3), remove them from Table 3.3-2, Aging Management Review of MPC Basket Subcomponents.
- 2. As appropriate, revise the scoping and AMR tables to ensure they accurately state the scoping conclusions of the following items for which the responses to Observation 3 and RAI 2-4 appear to differ MPC Plugs for Drilled Holes MPC Upper Fuel Spacer Bolt MPC Basket Shim MPC Basket Support (Flat Plate)
Overpack Thermal Expansion Foam This information is needed to confirm compliance with 10 CFR 72.240(c).
References Holtec, 2019. Attachment 1 to Holtec Letter 5014876, Submittal of Responses to NRCs RSIs on the Renewal of the HI-STAR 100 Storage CoC, Holtec International, ADAMS Accession No. ML19184A232. June 28, 2019.
Holtec, 2020. Attachment 1 to Holtec Letter 5014898, Submittal of Responses to NRCs RIs on the Renewal of the HI-STAR 100 Storage CoC, Holtec International, ADAMS Accession No. ML20153A768. June 1, 2020.
Page 1 of 5
Attachment 1 to Holtec Letter 5014913 Responses to NRC Clarification Questions on HISTAR 100 License Renewal Application Holtec Response:
- 1. The optional heat conduction elements have been added to Table 2.1-3 to provide a conclusion whether they are in the scope of renewal. As stated in the response to RAI 2-3, the heat conduction elements are not credited with any design basis safety function since crediting the convection mechanism inside the MPC was approved by NRC staff. Thus, the intended function for the subcomponent in Table 2.1-3 is given the designation of N/A and the subcomponent has been removed from Table 3.3-2.
- 2. The MPC Plugs for Drilled Holes, MPC Upper Fuel Spacer Bolt, MPC Basket Shim, and MPC Basket Support subcomponents are NITS components as well, but their failure could prevent fulfillment of a function that is ITS during the period of extended operation (the function differs depending on the subcomponent, and is listed in Table 2.1-2). Hence, the scoping conclusions for these subcomponents are accurate and they continue to be included in the aging management review in Chapter 3.
For the Overpack Thermal Expansion Foam, the scoping conclusion has been revised to designate the intended function as N/A during the period of extended operation and the subcomponent has been removed from the aging management review. See response to RAI 3-3 below for further justification.
RAI 2-5 Revise the renewal application to include the changes to the design bases in the HI-STAR 100 FSAR, Revision 4, which is associated with Amendment No. 3 to the HI-STAR 100 CoC.
By letter dated March 11, 2020, the applicant submitted Revision 4 of the FSAR that includes the changes made in CoC Amendment No. 3 (ADAMS Accession No. ML20071D992).
However, some changes were not addressed in the renewal application. Revise the renewal application to:
- 1. Include the evaluation of subcomponents added in Amendment 3 of the HI-STAR 100 Storage System CoC, updating the scoping and AMR tables accordingly. These SSCs include, but may not necessarily be limited to:
MPC Vent and Drain Tube, Optional MPC Threaded Disc, Plug Adjustment MPC Vent and Drain Plug MPC Thread Shield Cap MPC Retaining Ring
- 2. Update Table 1.3-1 of the renewal application to reference the revision of HI-2012610, the HI-STAR 100 FSAR, that defines the design bases for CoC Amendment No. 3.
Table 1.3-1 of the renewal application lists the FSAR revisions that apply to each amendment of the CoC. However, that table does not include a reference to the FSAR revision that serves as the design-basis FSAR for CoC Amendment No. 3.
This information is needed to confirm compliance with 10 CFR 72.240(c).
Page 2 of 5
Attachment 1 to Holtec Letter 5014913 Responses to NRC Clarification Questions on HISTAR 100 License Renewal Application Holtec Response:
- 1. The subcomponents listed in (1) have been included in the scoping evaluation with the intended function designated as Retrievability since the subcomponents serve this function during potential system unloading operations in the period of extended operation and have been included in the aging management review. Additionally, as based on lessons learned during the HI-STORM 100 renewal process, the vent/drain tube, the vent/drain port cap, the vent/drain cap seal washer and the vent/drain cap seal washer bolt have their intended functions modified to Retrievability since the subcomponents serve this function during potential system unloading operations in the period of extended operation and have been included back into the aging management review. Furthermore, since some of these subcomponents are required to be constructed from aluminum, Subsection 3.1.2.2 has been modified to indicate that the heat conduction elements are not the only subcomponents constructed from aluminum.
- 2. Table 1.3-1 has been updated to specify that revision 4 of the HI-STAR 100 FSAR serves as the design-basis FSAR for CoC Amendment No. 3. Additionally, the CoC Amendment No. 3 approval date was added to this table.
RAI 3-3 If the thermal expansion foam is in the scope of renewal (based on the response to RAI 2-3 and RAI 2-4 Follow-up), provide the technical basis that supports the conclusion that the foam does not have any credible aging effects due to radiation exposure that could challenge an important- to-safety function in the period of extended operation.
The silicone thermal expansion foam in the HI-STAR 100 Overpack is identified as a not-important-to-safety (NITS) item in the renewal application scoping tables. However, the foam was included in the scope of the aging management review in Chapter 3 of the renewal application, although the application did not identify the basis for including it within scope.
Further, the application concluded that the foam does not have any aging effects requiring management. If the thermal expansion foam is considered to be in the scope of renewal (based on the response to RAI 2-4a), clarify the bases for the results of the scoping and aging management review, as follows:
- 1. Clarify how an important-to-safety function is affected by potential degradation of the thermal expansion foam. HI-STAR 100 FSAR Section 1.2.1.2 states that the foam may be required to alleviate thermal stresses from differential thermal expansion. It is not clear to the staff how a change in the foam properties may prevent it from fulfilling that role (i.e., how an important-to-safety function is (or is not) impacted if the thermal stresses are not alleviated).
- 2. Provide the technical basis for the conclusion that the gamma and neutron exposure throughout the period of extended operation will not challenge the structural integrity function of the foam. As described in NUREG-2214 Section 3.3.1.3, radiation can embrittle polymeric materials, and studies on the effects of gamma and neutron radiation on silicone foams have observed a loss of ductility (Liu, 2017). HI-STAR 100 FSAR Appendix 1.C states that silicone is highly resistant to the radiation exposure levels present in the storage system; however, no support for that statement was provided.
This information is needed to confirm compliance with 10 CFR 72.240(c).
Page 3 of 5
Attachment 1 to Holtec Letter 5014913 Responses to NRC Clarification Questions on HISTAR 100 License Renewal Application Reference B. Lie, et al., Effects of Combined Neutron and Gamma Irradiation Upon Silicone Foam, Radiation Physics and Chemistry, Vol. 133, pp. 31-36, 2017.
Holtec Response:
As seen in the response to the RAI 2-3 and RAI 2-4 Follow-up above, the scoping conclusion for this subcomponent has been revised to designate the intended function as N/A during the period of extended operation and the subcomponent has been removed from the aging management review. The purpose of the foam is to mitigate pressure on the enclosure shell due to radial thermal expansion of the neutron absorber material at high temperatures. As seen in Subsection 3.4.4.3.2.6 of the HI-STAR 100 FSAR, a stress analysis of the enclosure shell was performed to demonstrate that the absence of the foam material does not cause excessive stress levels in the enclosure shell and concludes that the maximum stress in the radial channel under the worst-case thermal loading is significantly less than the ultimate stress of the material.
Therefore, a failure of the thermal expansion foam, such as radiation embrittlement and loss of ductility due to gamma and neutron radiation specified in (2) above, does not prevent fulfillment of a function of an ITS component during the period of extended operation and this subcomponent has been removed from the aging management review.
RAI D-1 Follow-up Provide the updated proposed changes to the HI-STAR 100 FSAR in Appendix D of the renewal application (FSAR supplement), including any referenced tables, as revised through the response to this request for clarification, and to incorporate the following clarifications.
Update the FSAR supplement to clarify the following renewal application references:
Table 9.2.3 of the FSAR supplement (Independent Spent Fuel Storage Installation (ISFSI)
Pad AMP) references Table 3.3.5, which is likely a reference to Table 3.3-5 (with hyphen) of the renewal application that contains the AMR table for the ISFSI pad.
When incorporating by reference the renewal application Tables 3.3-3 and 3.3-5 in the proposed FSAR Tables 9.2.2 and 9.2.3, respectively, provide a clear reference to the specific revision of the renewal application (e.g., Table 3.3-3 of Revision 1C of the HI-STAR 100 CoC Renewal Application).
Clarify these references or fully incorporate the final AMR tables into the FSAR supplement to ensure that the aging management activities are appropriately included in the FSARs for each renewed CoC amendment.
In addition, in Table 3.3-3 of the renewal application, which is referenced in the FSAR supplement, the staff noted an editorial error where the Embedded (in concrete) environment for the overpack bottom plate was placed under the Aging Effects Requiring Management column. Revise the table to clarify the aging effects being managed by the Overpack AMP for this line item.
Appendix D of the renewal application provides the proposed FSAR supplement to document Page 4 of 5
Attachment 1 to Holtec Letter 5014913 Responses to NRC Clarification Questions on HISTAR 100 License Renewal Application the aging management information associated with the CoC renewal, per 10 CFR 72.240(c).
The CoC renewal will include a condition for the CoC holder to update the FSAR to reflect the changes and commitments resulting from the review and approval of the CoC renewal. The FSAR must clearly reflect the approved design bases, including aging management information in the period of extended operation if the renewal is approved. Therefore, the FSAR supplement in Appendix D of the renewal application must include all FSAR changes related to the renewal of the CoC.
This information is required to demonstrate compliance with 10 CFR 72.240(c).
Holtec Response:
Table 9.2.3 of the FSAR supplement has been updated to correct the reference to Table 3.3-5 of the renewal application.
The HI-STAR license renewal application has been added as reference [9.2.1] to Section 9.4 of the FSAR supplement and is used as a reference in Tables 9.2.2 and 9.2.3 of the FSAR supplement when referring to the tables from the renewal application. The revision of the referenced HI-STAR license renewal application is specified as Latest Revision to ensure the latest revision of the document is used for reference. This is consistent with other reports referenced throughout the HI-STAR 100 FSAR such as the reference to the HI-STORM 100 FSAR (see reference [5.3.1] and [6.0.1] of the HI-STAR 100 FSAR) and the HI-STORM FW FSAR (see reference [7.0.5] of the HI-STAR 100 FSAR).
Table 3.3-3 of the renewal application has been updated to include Embedded (in concrete) in the Environment column and Loss of Material in the Aging Effects Requiring Management column for the overpack bottom plate.
Page 5 of 5