ML24348A048
| ML24348A048 | |
| 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: ML24348A048 (1) | |
Text
Response to NuScale Topical Report Audit Question Question Number: A-NonLOCA.LTR-34 Receipt Date: 04/29/2024 Question:
Provide the methodology for performing the sensitivity study on the energy deposition factor and how is the bounding energy deposition factor is determined.
The TR state that a bounding high energy deposition factor that results in all energy being deposited in the fuel is used in the non-LOCA analyses and sensitivity studies on this parameter confirm that its effect on the system response is not significant with respect to demonstrating margin to acceptance criteria for NPM events addressed by the non-LOCA evaluation model due to the MPS design and selection of the analytical limits to actuate reactor trip. However, the TR does not include information on how to perform sensitivity studies on this parameter, nor on how the bounding factor is determined.
Please provide proposed markups to the TR.
Response
As described in Section 4.3.1.1.3 of the non-loss-of-coolant accident (non-LOCA) topical report (TR-0516-49416-P, Revision 4), the bounding high energy deposition factor results in all energy being deposited in the fuel, (emphasis added). In other words, the energy deposition factor is 1.0. ((2(a),(c) The discussion of energy deposition factor in Section 4.3.1.1.3 in the current revision of the non-LOCA topical report is identical to the discussion in Revision 3 of the non-LOCA topical report that was previously reviewed and approved by the NRC (other than an editorial change to replace reactor trip system with MPS). ((
}}2(a),(c)
NuScale Nonproprietary NuScale Nonproprietary
(( }}2(a),(c) As stated in Section 3.4.3.1 of the safety evaluation report (SER) for Revision 3 of the non-LOCA topical report: TR Section 4.3.1.1.3, Energy Deposition Factor, states that a bounding-high energy deposition factor (i.e., the portion of the energy generated in the core that is deposited in the fuel) is assumed for non-LOCA calculations and further states that sensitivity studies using the non-LOCA EM demonstrate that margins to acceptance criteria are insensitive to changes in the energy deposition factor. The NRC staff audited a sensitivity calculation that examined the effect of reducing the energy deposition factor through direct moderator heating and observed only small changes in the results, as discussed in the associated audit report (ML19039A090). The NRC staff concludes that the audited sensitivity studies adequately support the docketed information and finds the use of a bounding-high energy deposition factor for the NRELAP5 non-LOCA system transient analyses acceptable. Based on the applicability review demonstrating the similarity between the NuScale Power Module (NPM) for the US460 design (i.e., NPM-20) and the NPM for the US600 design (i.e., NPM-160), no changes were made to the energy deposition factor and sensitivity studies on the deposition factor were not repeated. Because (1) the treatment of energy deposition factor has not changed since the prior NRC approval, (2) the NRC previously audited the energy deposition factor sensitivity studies, and (3) no new sensitivity studies have been performed, there is no reason to provide further information about the topic. No markup is provided because the level of information in Revision 4 of the topical report is consistent with what was sufficient for prior NRC approval of Revision 3. No changes to the SDAA are necessary. NuScale Nonproprietary NuScale Nonproprietary}}