ML24326A095
| ML24326A095 | |
| Person / Time | |
|---|---|
| Site: | 05200050 |
| Issue date: | 11/21/2024 |
| From: | NuScale |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML24326A092 | List: |
| References | |
| LO-175900 | |
| Download: ML24326A095 (1) | |
Text
Response to SDAA Audit Question Question Number: A-16-13 Receipt Date: 05/06/2024 Question:
The NRC SER for Revision 5 of the NuScale US600 design certification application (DCA) discusses the resolution of selected technical issues, which the staff had identified in requests for additional information (RAIs). There are instances of such discussions that reference NuScales RAI response letter and include quoted passages from DCA Part 2 (FSAR), DCA Part 4 (generic technical specifications and bases), or from the RAI response letter itself. If the subject of the RAI is valid for the NuScale US460 standard design approval application (SDAA),
the SDAA appears to implicitly rely on or credit the DCAs RAI resolution.
The applicant is requested to include in the SDAA a justification for relying on or crediting the resolution of each DCA RAI for which the subject of the RAI is valid for the NuScale US460 standard design. The justification should address the regulatory basis for relying on the DCA RAI resolution even though the SDAA does not incorporate by reference DCA RAI response letters. The justification should also identify differences between the quoted passages of the DCA and the corresponding or equivalent passages of the SDAA and for each such difference address why it does not affect the basis of the DCAs RAI resolution.
Although this issue may apply to other Sections in DCA Part 2 and SDAA Part 2, this audit item is limited to SDAA Part 2 Chapter 16 and SDAA Part 4, and to other SDAA Part 2 passages corresponding to DCA Part 2 Sections that were revised in the DCA review to resolve issues discussed in DC FSER Chapter 16. NuScale is requested to make appropriate changes to SDAA Part 2 needed to bring the DCAs basis for resolution of each SDAA-applicable issue into conformance with the US460 design.
DC FSER § Referenced Letter, Issue and Request NuScale Nonproprietary NuScale Nonproprietary
16.4.1.2 Request NuScale point to FSAR and/or TR explanation for not including an LCO for FQ AND confirm that the quotation from the 2018 RAI response letter dated 6/12/18 (ADAMS Accession No. ML18163A417) also applies to US460 standard design (SD), or provide an updated response on the SDAA docket appropriate for the US460 SD.
16.4.1.6 Request NuScale confirm on SDAA docket that DCA justification for omission of LCO for DC-FSAR-designated PAM instrumentation in RAI response letter dated 10/18/17 (ADAMS Accession No. ML17291A482) is applicable to omission of LCO for SDAA FSAR-designated PAM instrumentation, or provide an updated response on the SDAA docket appropriate for the US460 SD.
16.4.4.1 DCA RAI response letter dated 3/20/18, ML18079B134, which edited the LCO 3.0.5 Bases paragraph taken from W-STS Revision 4 Bases third paragraph for LCO 3.0.5 as modified by TSTF 529, replaced example of RCS pressure isolation valves with the NuScale US600 example using the eight CVCSI valves in the four CVCS flow path lines of LCO 3.4.6, CVCS Isolation Valves. The CVCSI valves were chosen even though the CVCS piping is designed for full RCS pressure.
Request NuScale to confirm on SDAA docket that the justification for the DCA Bases example for LCO 3.0.5 also applies to the SDAA Bases example for LCO 3.0.5 and CVCS design.
16.4.7.5 Under Conditions for Process Variable Outside Limits, the discussion of LCO 3.4.3 Condition D, which references the DCA RAI response letter dated 5/16/19, ML19140A270, explains why Action D is an appropriate means of addressing prevention and mitigation of the postulated inadvertent actuation of the containment flood and drain system (CFDS) that floods the containment vessel when RCS temperature is above the RCS temperature limit in the PTLR.
Request NuScale to confirm on SDAA docket that the DCA letters justification for LCO 3.4.3 Action D also applies to SDAA LCO 3.4.3 Action D, or provide an updated response on the SDAA docket appropriate for the US460 SD.
NuScale Nonproprietary NuScale Nonproprietary
16.4.7.6 Under Shutdown Required Actions and Completion Times, DCA RAI response letter dated 9/14/17, ML17257A450, lists items that the DCA applicant considered in its selection of Completion Times, as described in an added paragraph in Bases for DCA LCO 3.0.3.
Request NuScale to confirm on SDAA docket that the DCA letters justification applies to SDAA or provide an updated response on the SDAA docket appropriate for the US460 SD. Also confirm that the paragraph is included in SDAA LCO 3.0.3 Bases.
16.4.8.2 Under Surveillance Frequencies Not Governed by the Surveillance Frequency Control Program, DCA RAI response letter dated 12/12/18, ML18347A619, regarding SR 3.7.1.3 and SR 3.7.2.3, the DCA applicant explained how the secondary system isolation (SSI) valve leakage acceptance criteria will be determined.
Request NuScale to confirm on SDAA docket that the DCA letters response that the IST program to be completed by a COL applicant as part of FSAR Section 3.9 according to COL Item 3.9-5 (SDAA equivalent COL Item 3.9-8) also describes how this SSI valve leakage criteria will be determined by a COL applicant referencing the SDA, or provide an updated response on the SDAA docket appropriate for the US460 SD.
16.4.8.4 Under Instrumentation Surveillances, Channel Operational Test, multiple DCA RAIs are referenced with their Accession numbers, asking for additional justification of not including channel operational test (COT) SRs in the DCA GTS (for instrumentation Functions implemented in the MPS). Also referenced are several response letters (also with with their Accession numbers) to these DCA RAIs:
RAI 156 9031, Question 16 2, Subquestion c (ML17220A038); response letter (ML17269A210);
RAI 196 9050, Question 16 16, Subquestion e (ML17237C007); response letter (ML17291A482); and NuScale Nonproprietary NuScale Nonproprietary
RAI 197 9051, Question 16 25, Subquestion a4.2 (ML17237C008); response letter (ML17291A299).
Request NuScale to confirm on SDAA docket that the DCA letters response is valid for the COT omission by the SDAA GTS Rev. 1 for MPS instrumentation Functions, and MPS supported RCS leakage detection instrumentation, or provide an updated response on the SDAA docket appropriate for the US460 SD.
16.4.10.2 Under the heading GTS Subsection 5.4.1, Procedures, reference to DCA RAI response letter dated 8/26/19, ML19238A372, about the US600 DCAs lack of a description of controls for non-safety-related SSCs, which meet none of the LCO selection criteria of 10 CFR 50.36(c)(2)(ii), to be used by a NuScale Nuclear Power Plant COL holder, including references to any regulatory basis for the controls.
Request that NuScale confirm on SDAA docket that the DCA letters response is valid for the description of the subject controls for non-safety-related SSCsestablishing an owner-controlled requirements manual.
Response
A-16.4.1.2 The response to the June 12, 2018 Design Certification Application (DCA) Request for Additional Information (RAI) stated:
FQ is not used as an initial condition for any transient or design basis accident, including loss of coolant accident. As a result, a Limiting Condition for Operation for FQ is not needed in the NuScale design.
That statement also applies to the US460 Standard Design Approval Application. NuScale revises SDAA Section 4.3.2.2.1 to insert the following statement:
NuScale Nonproprietary NuScale Nonproprietary
FQ is not used as an initial condition for any transient or design basis accident, including loss of coolant accident.
A-16.4.1.6 The justification for not including a Limiting Condition for Operation (LCO) for post accident monitoring (PAM) instrumentation provided in the response to DCA Request for Additional Information 16-22 (NuScale letter RAIO-1017-56656, dated October 18, 2017) remains valid for the NuScale Generic Standard Technical Specifications (GTS).
A-16.4.4.1 Subsequent to the March 20, 2018 DCA Request for Additional Information response letter referenced by this NRC request, a supplemental response was provided to the NRC by letter dated March 13, 2019 (NuScale Letter Number RAO-0319-64840). This supplemental response references a public meeting on November 6, 2018 where the NRC staff provided the following clarification regarding DCA Request for Additional Information 16-12:
As a part of adopting TSTF-529, the third paragraph of the Bases for LCO 3.0.5, was modified to reflect the NuScale design, which lacks RCS pressure isolation valves (PIVs). In a supplemental response (ML18079B134) to RAI 157-9033, Question 16-12, the applicant stated there are eight CVCS isolation valves, which are specified to be operable by LCO 3.4.6:
o CVC-ISV-0323 Pressurizer Spray Line Outboard Isolation Valve o CVC-ISV-0325 Pressurizer Spray Line Inboard Isolation Valve o CVC-ISV-0329 CVCS Injection Outboard Isolation Valve o CVC-ISV-0331 CVCS Injection Inboard Isolation Valve o CVC-ISV-0334 CVCS Discharge Inboard Isolation Valve o CVC-ISV-0336 CVCS Discharge Outboard Isolation Valve o CVC-ISV-0401 RPV Vent Inboard Isolation Valve o CVC-ISV-0403 RPV Vent Outboard Isolation Valve NuScale Nonproprietary NuScale Nonproprietary
The containment isolation function of these valves is also required to be operable by LCO 3.6.2. The problem with the LCO 3.0.5 Bases referencing RCPB leakage isolation is that no LCO 3.4.5 Action explicitly requires isolation of leakage by closing a valve.
Although LCO 3.4.6 does not address RCPB leakage, it does address CIV leakage for systems connected to the RCS, such as the four CVCS flowpath lines listed above.
Therefore, the LCO 3.0.5 Bases discussion ought to reference a CVCS isolation valve (CIV) inoperability requiring isolation, possibly because of valve leakage. The staff suggests the following modification of the subject LCO 3.0.5 Bases paragraph:
An example of demonstrating equipment is OPERABLE with the Required Actions not met is opening a manual valve that was closed to comply with Required Actions to isolate a CVCS flowpath with excessive Reactor Coolant System (RCS) pressure boundary leakage an inoperable CVCS isolation valve in order to perform testing to demonstrate that RCS pressure boundary leakage the isolation valve is now operable within limit.
NuScale provided the following supplemental response to DCA Request for Additional Information 16-12 in the March 12, 2019 letter:
The Bases for LCO 3.0.5 have been modified as proposed by the staff.
The third paragraph of the Bases for LCO 3.0.5 were revised as follows:
An example of demonstrating equipment is OPERABLE with the Required Actions not met is opening a manual valve that was closed to comply with Required Actions to isolate a chemical and volume control system (CVCS) flowpath with an inoperable CVCS isolation valveexcessive Reactor Coolant System (RCS) pressure boundary eakage in order to perform testing to demonstrate that RCS pressure boundary leakagethe isolation valve is now within limitOPERABLE.
The revised paragraph provided to the NRC with the March 13, 2019 RAI response has been retained in the SDAA Generic Standard Technical Specifications. The SDAA design retains two NuScale Nonproprietary NuScale Nonproprietary
chemical and volume control system isolation valves for each of the four flow path lines connected to the reactor coolant system.
16.4.7.5 The justification for DCA Limiting Condition for Operation Action D from the response to DCA Request for Additional Information 16-61 (NuScale letter RAIO-0519-65608, dated May 16, 2019) also applies to SDAA Limiting Condition for Operation 3.4.3 Action D.
16.4.7.6 NuScale confirms that justification for the DCA Limiting Condition for Operation 3.0.3 Shutdown Actions and Completion Times provided in the NuScale response to DCA Request for Additional Information 16-7 (NuScale letter number RAIO-0917-55987, dated September 14, 2017) remains valid for GTS Limiting Condition for Operation 3.0.3. The paragraph inserted into the Bases for LCO 3.0.3 by the September 14, 2017 response to DCA Request for Additional Information 16-7 is included in the GTS Bases for LCO 3.0.3.
16.4.8.2 The discussion of isolation valve leakage testing in SDAA Section 3.9.6 is consistent with the information provided in the response to DCA Request for Additional Information 16-58 (NuScale letter RAIO-1218-63828, dated December 12, 2018).
16.4.8.4 NuScale confirms that the responses to DCA Request for Additional Information 16-2 Item c, 16-16 Item e, and 16-25 Item a.4 are valid for the SDAA Generic Standard Technical Specifications omission of Channel Operational Tests for module protection system instrumentation functions, and module protection system supported reactor coolant system leakage detection instrumentation.
16.4.10-2 The description of the structures, systems, and components with respect to the establishment of an owner-controlled requirements manual, provided in the response to DCA Request for NuScale Nonproprietary NuScale Nonproprietary
Additional Information 16-27 (NuScale letter RAIO-0819-66775, dated August 26, 2019), is valid for the NuScale SDAA.
Markups of the affected changes, as described in the response, are provided below:
NuScale Nonproprietary NuScale Nonproprietary
NuScale Final Safety Analysis Report Nuclear Design NuScale US460 SDAA 4.3-6 Draft Revision 2 shown in Figure 4.3-2 and Figure 4.3-3, respectively. The equilibrium cycle does not include axial enrichment zoning in the form of axial blankets.
Table 4.3-1 and Table 4.3-2 summarize the reactor core design parameters used in the analysis. The plant operating modes are described in the technical specifications.
4.3.2.2 Power Distribution Power distribution calculations are discussed in the Nuclear Analysis Codes and Methods Qualification topical report (Reference 4.3-2). This report contains a discussion of power distribution uncertainty, including application and a means for updating the uncertainty values. Additional discussion of the power uncertainties used in thermal-hydraulic analysis is provided in Section 4.4.
4.3.2.2.1 Definitions Enthalpy Rise Hot Channel Factor, FH The maximum enthalpy rise hot channel factor, FH, is defined as the ratio of the maximum integrated fuel rod power to the average fuel rod power. The limit on FH is established to ensure the fuel design criteria are not exceeded and the accident analysis assumptions remain valid. This limit ensures the design-basis value for the CHF ratio is met for normal operation, AOOs, and infrequent events. The FH limit is representative of the coolant flow channel with the maximum enthalpy rise. This channel has the highest power input to the coolant and therefore the highest probability for CHF.
Heat Flux Hot Channel Factor, FQ Audit Question A-16-13 The heat flux hot channel factor (or total peaking factor), FQ, is the ratio of maximum local heat flux on the surface of a fuel rod to the average fuel rod heat flux. The maximum FQ value is used to calculate the peak linear heat generation rate (LHGR). The maximum value of FQ is used to ensure the SAFDLs are not exceeded. FQ is not used as an initial condition for any transient or design basis accident, including loss of coolant accident.
Axial Peaking Factor, Fz The axial peaking factor, Fz, is the maximum relative power at any axial point in a fuel rod, divided by the average power of the fuel rod.