ML18295A660
| ML18295A660 | |
| Person / Time | |
|---|---|
| Site: | PROJ0769 |
| Issue date: | 10/22/2018 |
| From: | NRC |
| To: | NRC/NRO/DLSE/LB1 |
| References | |
| Download: ML18295A660 (4) | |
Text
NuScaleTRRaisPEm Resource From: Cranston, Gregory Sent: Monday, October 22, 2018 12:06 PM To: Request for Additional Information Cc: Lee, Samuel; Karas, Rebecca; Skarda, Raymond; Bavol, Bruce; Chowdhury, Prosanta; NuScaleTRRaisPEm Resource
Subject:
Request for Additional Information Letter No. 9624 (eRAI No. 9624) Topical Report Thermal Hydraulic Stability 15.9, SRSB Attachments: Request for Additional Information No. 9624 (eRAI No. 9624).pdf Attached please find NRC staffs request for additional information (RAI) concerning review of the NuScale Topical Report.
Please submit your technically correct and complete response by December 17, 2018 to the NRC Document Control Desk.
If you have any questions, please contact me.
Thank you.
1
Hearing Identifier: NuScale_SMR_DC_TR_Public Email Number: 104 Mail Envelope Properties (BN1PR09MB02586673634A69F61E9657B390F40)
Subject:
Request for Additional Information Letter No. 9624 (eRAI No. 9624) Topical Report Thermal Hydraulic Stability 15.9, SRSB Sent Date: 10/22/2018 12:05:46 PM Received Date: 10/22/2018 12:05:53 PM From: Cranston, Gregory Created By: Gregory.Cranston@nrc.gov Recipients:
"Lee, Samuel" <Samuel.Lee@nrc.gov>
Tracking Status: None "Karas, Rebecca" <Rebecca.Karas@nrc.gov>
Tracking Status: None "Skarda, Raymond" <Raymond.Skarda@nrc.gov>
Tracking Status: None "Bavol, Bruce" <Bruce.Bavol@nrc.gov>
Tracking Status: None "Chowdhury, Prosanta" <Prosanta.Chowdhury@nrc.gov>
Tracking Status: None "NuScaleTRRaisPEm Resource" <NuScaleTRRaisPEm.Resource@nrc.gov>
Tracking Status: None "Request for Additional Information" <RAI@nuscalepower.com>
Tracking Status: None Post Office: BN1PR09MB0258.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 332 10/22/2018 12:05:53 PM Request for Additional Information No. 9624 (eRAI No. 9624).pdf 158870 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:
Recipients Received:
Request for Additional Information No. 9624 (eRAI No. 9624)
Issue Date: 10/22/2018 Application
Title:
NuScale Topical Report Operating Company: NuScale Docket No. PROJ0769 Review Section: 15.09 - A.DSRS NuScale Thermal Hydraulic Stability Application Section: 15.09 QUESTIONS 15.09-13 Title 10 of the Code of Federal Regulations (10CFR), Part 50, Appendix A, General Design Criterion (GDC) for Nuclear Power Plants - Criterion 12Suppression of reactor power oscillations requires that oscillations be either not possible or reliably detected and suppressed. The Design-Specific Review Standard (DSRS), 15.9.A, "Design-Specific Review Standard for NuScale SMR Design, Thermal Hydraulic Stability Review Responsibilities," indicates that the applicant's analyses should correctly and accurately identify all factors that could potentially cause instabilities and their consequences. The analyses should also demonstrate that design features that are implemented prevent unacceptable consequences to the fuel. The Standard Review Plan (SRP) 15.0.2 acceptance criteria with respect to accident scenario identification states that the process must include evaluation of physical phenomena to identify those that are important in determining the figure of merit for the scenario.
As part of the final response to RAI 9093 Question 01-39, the applicant provided several page changes or revisions to stability topical report (TR), TR-0516-49417-P.
In order to make an affirmative finding associated with the above regulatory requirement important to safety, NRC staff requests NuScale address the following questions related to the TR page changes or revisions proposed as part of the above cited RAI response:
- 1. In the revised page indicating the change to Section 4.1, clarify the statement "to causing reactor power oscillation." For example, if the applicant meant "to causing oscillations in the reactor coolant system that could challenge specified acceptable fuel design limits" (or similar wording), revise the TR accordingly.
- 2. In the revised page showing the importance ranking for instability in the SG tubes, the revised language states that "[d]ensity waves in the SG tubes are controlled by design via proper throttling of individual tubes as verified by experimental data." However, the SG tubes are not instrumented with flow measurement devices to experimentally confirm the limit-cycle oscillation magnitude during any test that the staff can reasonably anticipate. Therefore clarify what is meant by density waves being "controlled" by design. For example, replacing "controlled" with "limited in oscillation magnitude" (or similar wording) is acceptable to staff. If the applicant relies on analysis instead of experimental data to confirm the oscillation magnitude, revise the TR accordingly.
- 3. In the revised page showing Bullet 4 of Section 5.2, the phrase "secondary flow oscillations are controlled within acceptable limits by throttling the inlets of the SG tubes" implies active control of the SG inlet orifices, which is not possible. Revise the language to be consistent with the design.
- 4. In the revised page showing Bullet 4 of Section 5.2, the applicant states that flow oscillations in the SG tubes cannot be locked coherently in phase. If the secondary side includes dynamic controllers to adjust steam line flow through a pressure regulating value or includes dynamic control of feedwater flow with a flow regulating valve, then it is conceivable that these controllers could result in the dynamic change of the secondary side pressure drop across the tubes. Therefore, revise the page to remove the assertion that coherent oscillation is impossible.
- 5. In the revised page showing Bullet 4 of Section 5.2 the phrase "about 5 percent" is ambiguous. Revising the TR to indicate "above 5 percent," or alternatively providing significant justification for using "about 5 percent".
- 6. Explain what is meant by "to control instabilities" in the revised page showing Section 5.4.1.3.
Alternatively replace the above phase with "to limit the oscillation magnitude of instabilities" an acceptable revision. Revise the TR language accordingly.
15.09-14
Title 10 of the Code of Federal Regulations (10CFR), Part 50, Appendix A, General Design Criterion (GDC) for Nuclear Power Plants - Criterion 12Suppression of reactor power oscillations requires that oscillations be either not possible or reliably detected and suppressed. The Design-Specific Review Standard (DSRS), 15.9.A, "Design-Specific Review Standard for NuScale SMR Design, Thermal Hydraulic Stability Review Responsibilities," indicates that the applicant's analyses should correctly and accurately identify all factors that could potentially cause instabilities and their consequences. The analyses should also demonstrate that design features that are implemented prevent unacceptable consequences to the fuel. The Standard Review Plan (SRP) 15.0.2 acceptance criteria with respect to accident scenario identification states that the process must include evaluation of physical phenomena to identify those that are important in determining the figure of merit for the scenario.
The final RAI response to RAI 9093 Question 01-39 changes the current TR and Design Control Documents (DCD) requirement that "instability is precluded" to a new requirement that, "flow fluctuations are maintained within acceptable limits." The acceptable limits were not quantified in that RAI response. The staff also notes that the applicant's response to RAI 9158, states "the steam generators are conservatively designed with flow orifices at the inlet that prevent flow oscillations for a given tube of more than +/- 10% at any core power level." This statement contradicts the new requirement imposed by the applicants "final" response to RAI 9093 which allows secondary side instabilities, within some acceptable limit, to occur.
In order to make an affirmative finding associated with the above regulatory requirement important to safety, NRC staff requests NuScale to revise the response to RAI 9158 so that it is consistent with the secondary side instability requirements stated in NuScales's final response to RAI 9093 Question 01-39. Specifically, the RAI 9158 response should be revised to indicate that secondary side (SG) flow instabilities or oscillations are allowed within some acceptable limit. In addition, NuScale should provide conforming revisions and change pages for all such other instances in the NuScale DCD, stability TR, other TRs referenced by the DCD, or RAI responses that require the revision requested above.