ML19255F141
| ML19255F141 | |
| Person / Time | |
|---|---|
| Site: | 07109325 |
| Issue date: | 09/05/2019 |
| From: | Holtec |
| To: | Office of Nuclear Material Safety and Safeguards |
| Shared Package | |
| ML19255F222 | List: |
| References | |
| 1553042-NRC, EPID: L-2019-LLA-0122 | |
| Download: ML19255F141 (3) | |
Text
Enclosure 1 to Holtec Letter 1553042-NRC HOLTEC NON-PROPRIETARY INFORMATION HOLTEC NON-PROPRIETARY INFORMATION Page 1 of 3 Response to NRC Request for Supplemental Information Holtec International Docket No. 71-9325 HI-STAR 180 Transportation Package Chapter 3 - Thermal Evaluation NRC RSI 3-1 Provide calculations and analysis results for cases when cyclic vacuum drying is used.
Section 3.3.5 of the application states that, for high burnup fuel, the cyclic drying method is used to avoid exceeding ISG-11, Revision 3 limits. This section also states that the permissible time for heat-up/cooldown cycles is a function of the cask heat loads for which a suitable methodology is prescribed to compute heat load specific cyclic drying durations.
However, the application does not include calculations or analyses to demonstrate that temperatures will remain below the criteria specified in ISG-11, Rev. 3 for cyclic vacuum drying of high burnup fuel.
The staff needs this information to determine compliance with allowable cladding temperature limits during cyclic drying operations.
This information is needed to determine compliance with 10 CFR Part 71.71.
Holtec Response to RSI 3-1:
Holtec thermal calculation package HI-2073649 Thermal Analyses of the HI-STAR 180 and HI-STAR 180 SAR Chapter 3 have been updated to include an explicit analysis of an example of cyclic vacuum drying for the most limiting thermal scenario, i.e. F-32 basket, under the design basis heat load pattern A/B, listed in Table 3.3.4 of the SAR.
The thermal methodology currently present in Section 3.3 of the SAR (Revision 7) has been adopted for this evaluation unchanged. New Table 3.3.12 of the SAR has been added to present the results of the calculation. Results demonstrate compliance with the cladding temperature criteria specified in ISG-11 Revision 3. Propose Revision 7.A of the SAR and Revision 11 of Holtec Report HI-2073649 are provided with this response.
to Holtec Letter 1553042-NRC HOLTEC NON-PROPRIETARY INFORMATION HOLTEC NON-PROPRIETARY INFORMATION Page 2 of 3 Chapter 4 - Containment Evaluation NRC RSI 4-1 Observation Provide product vendor justification for the temperature limits for the Technetics seal design with a silver sealing liner. In addition, clarify if there are any chemical, galvanic, or other reactions due to the Technetics seal jacket material change.
Proposed change PC-23 refers to a seal design featuring a silver sealing liner, instead of aluminum jacket, for the HI-STAR 180 Technetics seals. For the staff to evaluate this type of change, vendor data sheets are necessary for staff to verify any change in seal temperature limit.
Material compatibility is necessary to ensure there are no significant chemical, galvanic, or other reactions among the packaging components, or between the packaging components and the packaging contents.
This information is needed to determine compliance with 10 CFR 71.43(d), 71.51(a)(1) and (2).
Holtec Response to RSI 4-1:
Appendix 4.A of HI-STAR 180 SAR [2] gives the description of containment seal options.
Technetics seal has been considered as an option to containment boundary seals. The material specifications for the Technetics seal are given below.
Sealing lining Silver Inner lining SS 304L Spring material Alloy 90 (Nimonic)
The main environments to which the closure seals are exposed are spent fuel pool water, helium and external atmosphere.
Spent fuel pool water-From the galvanic series of metals and alloys [1], it can be seen that silver is a noble metal and higher up in the galvanic series than stainless steel. Being a noble metal, silver has a high corrosion resistance and does not corrode when the cask is immersed in spent fuel pool water. 304L stainless steel has a high chromium content (18-21 %) which makes it highly corrosion resistant. The thin chromium oxide layer present on its surface makes it passive in the ambient pool water conditions. As articulated in operations Chapter 7 [2], the cask remains in the pool for a short duration during the loading operation, thereby minimizing the potential for galvanic, chemical or other reactions to occur.
Helium-After the cask is removed from the spent fuel pool, it is dried and backfilled with helium as discussed in Chapter 7 [2]. This eliminates any moisture from the cask interior and the internal components get exposed to hot dry helium. Due to the to Holtec Letter 1553042-NRC HOLTEC NON-PROPRIETARY INFORMATION HOLTEC NON-PROPRIETARY INFORMATION Page 3 of 3 absence of an electrolyte or moisture, the possibility of any chemical, galvanic or other corrosion mechanisms is removed.
External atmosphere-The cask containment closure flange seal surfaces are covered with a protective cover during the cask closure operation. The cask impact limiters installed on the cask act as barrier for the seals. Thus, gross exposure of containment seals to external atmosphere is minimized. Since the duration of transportation of the cask is small, potential for any rain-water or moisture from atmosphere to enter the seals is minimal. Therefore, possibility of galvanic, chemical or other corrosion is minimized.
Seal datasheets are available on vendor website but do not contain temperature limits for long-term use. Temperature limits of the seal specified in the Safety Analysis Report
[2] have been verified by the seal vendor via letter from Technetics Group to Holtec International dated September 5, 2019 [3]. The letter [3] is submitted with this response as Enclosure 5 of Holtec Letter 1553042-NRC.
References
[1] M. G. Fontana, Corrosion Engineering, McGraw-Hill International Edition, 3rd ed., pp.
43-44, 1987
[2] Safety Analysis Report on the HI-STAR 180, HI-2073681, Revision 7 (Submitted with HI-STAR 180D LAR 9325-3 under Holtec Letter 1553041-NRC)
[3] Letter from Technetics Group to Holtec International dated September 5, 2019