ML24348A024
| ML24348A024 | |
| Person / Time | |
|---|---|
| Site: | 05200050 |
| Issue date: | 12/13/2024 |
| From: | NuScale |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML24348A006 | List:
|
| References | |
| LO-176318 | |
| Download: ML24348A024 (1) | |
Text
Response to NuScale Topical Report Audit Question Question Number: A-NonLOCA.LTR-22 Receipt Date: 04/01/2024 Question:
Explain why the pressure in the primary system is not listed in the PIRT table as part of the Non-LOCA transient parameters in Non-LOCA. The system response and major parameters such as heat transfer coefficient vary as the pressure changes in the primary side during Non-LOCA transients. Section 4.3.5 of the TR clearly indicates that the effect of pressure on critical heat flux (CHF) must be established to determine the appropriate direction for biasing. However, Table 5-3 does not include primary side pressure. Please provide proposed markups to the TR.
Response
The non-loss-of-coolant accident (non-LOCA) topical report (TR-0516-49416-P Revision 4)
Table 5-3 summarizes the high-ranked phenomena for non-LOCA events as part of the phenomena identification and ranking table (PIRT). Primary system pressure is not listed in the non-LOCA PIRT because pressure is not a stand-alone phenomenon. Instead, primary pressure is a characteristic of the system, and it is a figure of merit in Phase 1 and Phase 2 of the non-LOCA transients, as identified in Section 5.1.3 of the non-LOCA topical report. The phenomena in the PIRT impact the primary pressure. Primary pressure is also considered in the range of conditions to demonstrate non-LOCA evaluation model (EM) applicability.
As described in Section 2.1 of the non-LOCA topical report, the high-ranked non-LOCA phenomena were evaluated with respect to the high-ranked phenomena identified as part of the NuScale LOCA evaluation model development. ((2(a),(c) The non-LOCA EM validation basis and applicability assessment focuses on phenomena associated with the steam generator and NuScale Nonproprietary NuScale Nonproprietary
decay heat removal system that are more important for non-LOCA transients, compared to large LOCA pipe breaks. For prediction of conditions in the primary system, including primary pressure, the non-LOCA EM uses the NRELAP5 validation basis and applicability assessment presented in the LOCA topical report (TR-0516-49422-P Revision 3) as well as the validation basis presented in the non-LOCA EM. ((
}}2(a),(c)
In addition, as described in the response to audit question A-NonLOCA.LTR-16, the PIRT developed for the NuScale Power Module (NPM)-160 associated with the US600 design was not required to be updated for the NPM-20 associated with the US460 design. Therefore, the list of high-ranked phenomena in Table 5-3 of the non-LOCA topical report has not changed from the list included in the previous version of the non-LOCA topical report that was reviewed and approved by the NRC (TR-0516-49416-P-A Revision 3). Primary pressure is not included in Table 5-3 in TR-0516-49416-P-A Revision 3. For the reasons provided above, it is not necessary to include primary system pressure in Table 5-3 of the non-LOCA topical report. Primary system pressure is appropriately modeled, calculated, and addressed in non-LOCA analyses. No changes to the SDAA are necessary. NuScale Nonproprietary NuScale Nonproprietary}}