ML24348A014
| ML24348A014 | |
| Person / Time | |
|---|---|
| Site: | 05200050 |
| Issue date: | 12/13/2024 |
| From: | NuScale |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML24348A006 | List:
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| References | |
| LO-176318 | |
| Download: ML24348A014 (1) | |
Text
Response to NuScale Topical Report Audit Question Question Number: A-NonLOCA.LTR-5S Receipt Date: 02/23/2024 Question:
Audit question A-NonLOCA.LTR-5 was received by NuScale on April 24, 2023. NuScale provided a response on May 3, 2023. On February 23, 2024, NuScale received the following written feedback from the NRC:
The response to A-NonLOCA.LTR-5 does not describe how single rod withdrawal limits are selected to be bounding for a NPM design, fully describe the specific parameters in the rod drop and single rod withdrawal analysis limits that are being compared, or demonstrate the sufficiency of the set of parameters used to screen select rod drop cases (that do not result in an immediate reactor trip) from non-LOCA transient analysis.
To help address the original audit question, provide the staff EC-103274, Rev. 0, Rod Drop Methodology Justification, EE-0000-8185, Rev. 0, Single Rod Withdrawal Methodology Improvement Scoping, and calculations documents supporting Figures 7-3 through 7-5 of TR-0516-49416, Rev. 4 in the eRR.
Response
This response is a supplement to the May 3, 2023 response; the May 3, 2023 response remains unchanged in the electronic reading room (eRR).
The May 3, 2003 response does describe how single rod withdrawal limits are selected to be bounding for a NuScale Power Module (NPM) design: ((2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
(( }}2(a),(c) The May 3, 2023 response does fully describe the specific parameters in the rod drop and single rod withdrawal analysis limits that are being compared: (( }}2(a),(c) Note that the comparison of rod drop to single rod withdrawal is only performed for the rod drop cases that do not immediately cause a reactor trip on negative power rate (i.e., a small population of the rod drop nuclear analysis cases). The May 3, 2023 response does demonstrate the sufficiency of the set of parameters used to screen select rod drop cases: NuScale Nonproprietary NuScale Nonproprietary
(( }}2(a),(c) The February 23, 2024 NRC feedback requested EC-103274, Rev. 0, Rod Drop Methodology Justification. EC-103274 is provided in the eRR. Figures 7-3 through 7-5 of TR-0516-49416, Rev. 4, are taken directly from EC-103274 Figures 4-3, 4-13, and 4-20, respectively. The February 23, 2024 NRC feedback also requested EE-0000-8185, Rev. 0, Single Rod Withdrawal Methodology Improvement Scoping. EE-0000-8185 is provided in the eRR. Another useful reference for additional information specific to the development of the rod drop methodology is EE-0000-7916, Rev. 0, Rod Drop Methodology Improvement Scoping. EE-0000-7916 started the investigation of rod drop methodology changes that ultimately led to the changes to the method described in TR-0516-49416, Rev. 4, and supported by EC-103274. EE-0000-7916 is listed as a reference in EC-103274 (i.e., Reference 1.5.7). EE-000-7916 is provided in the eRR. Note that both EE-0000-8185 and EE-0000-7916 are scoping documents issued in 2020 that predate that development of the Standard Design Approval Application (SDAA). Finally, additional details of the nuclear analysis are provided in ER-A021-3589, Rev. 4, Nuclear Analysis Methodology. Sections 6.3.4 and A.10 discuss the single rod withdrawal event and Sections 6.3.6 and A.12 discuss the rod drop event. ER-A021-3589 was previously provided in the eRR for Chapter 4. No changes to the SDAA are necessary. NuScale Nonproprietary NuScale Nonproprietary}}