ML25069A628
| ML25069A628 | |
| Person / Time | |
|---|---|
| Site: | 05200050 |
| Issue date: | 03/10/2025 |
| From: | NuScale |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML25069A609 | List: |
| References | |
| LO-180139 | |
| Download: ML25069A628 (1) | |
Text
Response to NuScale Topical Report Audit Question Question Number: A-FSR.LTR-37 Receipt Date: 10/14/2024 Question:
Section 6.5.1.3 states in part, [
] This is contrary to the current PWR operating fleet. What is unique about the NuScale FSR design, NuScale fuel design, and/or NuScale Rx operation that leads to this result?
Response
The detailed criticality analysis includes an investigation of the reactivity effect of flat versus distributed profiles in a single storage cell configuration with reflecting boundary conditions, simulating an infinite array. These calculations confirm the generally understood trend that a flat profile is conservative at low burnups ([
]) and a distributed profile is conservative at higher burnups. The conclusion of this investigation confirms that neither the flat nor distributed profile always produces a conservative reactivity, and therefore calculations [
] are performed with both profiles.
The ((2(a),(c) allows for the modeling of the nominal fuel loading map (mix of fresh and spent fuel) shown in Figure 6-6, along with various postulated eccentric positioning scenarios as described in Section 6.5.4. Because the nominal fuel loading map includes a mix of fresh and spent fuel that have significantly different reactivities, (( [
] }}2(a),(c)
NuScale Nonproprietary NuScale Nonproprietary
Additional factors that contribute to (( [ ] [ ]
}}2(a),(c)
NuScale Axial Burnup Profiles ((
}}2(a),(c) The axial burnup profiles contained in YAEC-1937, Axial Burnup Profile Database for Pressurized Water Reactors, includes a number of axial burnup profiles for fuel assemblies that experienced operation with the control rods inserted a significant portion into the fuel assembly. The axial burnup profiles for a large commercial light water reactor typically includes profiles where the control rods are inserted into the top couple of inches of the fuel assembly (i.e., the bite position). ((
}}2(a),(c) The limiting (( }}2(a),(c) includes eccentric positioning (Scenario 3, shown in Figure 6-7). (( [ ] }}2(a),(c) NuScale Nonproprietary NuScale Nonproprietary
(( }}2(a),(c) No changes to the LTR are necessary. NuScale Nonproprietary NuScale Nonproprietary}}