ML19297D126
| ML19297D126 | |
| Person / Time | |
|---|---|
| Issue date: | 11/26/2019 |
| From: | Matthew Sunseri Advisory Committee on Reactor Safeguards |
| To: | Riccardella P Advisory Committee on Reactor Safeguards |
| Snodderly, M, ACRS | |
| Shared Package | |
| ML19297D008 | List: |
| References | |
| Download: ML19297D126 (3) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, DC 20555 - 0001 November 26, 2019 MEMORANDUM TO: Peter Riccardella, Chairman Advisory Committee on Reactor Safeguards FROM: Matthew Sunseri, Vice Chairman /RA/
NuScale Subcommittee Advisory Committee on Reactor Safeguards
SUBJECT:
PROPOSED RECOMMENDATION FOR ACRS REVIEW OF NUSCALE POWER, LLC, DESIGN CERTIFICATION APPLICATION - SAFETY EVALUATION WITH NO OPEN ITEMS FOR CHAPTER 10, STEAM AND POWER CONVERSION SYSTEM In response to the Committees request, I have reviewed the NRC staffs safety evaluation with no open items for Chapter 10, Steam and Power Conversion System, dated September 12, 2019 (ML19218A037). The following is my recommended course of action concerning further review of this chapter of the design certification application and the staffs associated safety evaluation.
SER Phase 4 Summary The steam and power conversion system transfers thermal energy from the reactor coolant system to the turbine generator where it is converted into electric energy. The main elements of the steam and power conversion system include the main steam, turbine generator, turbine bypass, main condensers, circulating water, condensate polishing, feedwater treatment, condensate and feedwater, and auxiliary boiler systems. In general, the steam and power conversion system is not safety-related and is not required for safe shutdown. However, the main steam and main feedwater systems have piping that penetrate the containment and components that directly interface with safety-related structures, systems, and components (SSCs). The failure of these components can have an adverse impact on plant safety and the plants ability to achieve a safe shutdown. In addition, failure of some system equipment may result in the potential for internal flooding or the creation of missiles that may have the potential to adversely impact SSCs important to safety.
Using a graded approach, the staff review of the steam and power conversion system focused on the safety-related piping and the system components that are part of the main steam and main feedwater systems that support containment isolation and the operation of the safety-related decay heat removal system. However, the staff also recognizes, as indicated above, that the failure of some portion of the steam and power conversion system may have the potential to adversely impact SSCs important to safety. Because the steam and power conversion system functions are not relied on to support the safety-related and safe-shutdown aspects of the NuScale plant, the staff reviewed the design to verify that failure of the SSCs that
are not safety-related and not risk-significant will not adversely affect the ability of the plant to achieve and maintain safe shutdown or result in excessive releases of radioactivity to the environment.
Applicable Concerns from ACRS Phase 3 Letter Report Our Phase 3 letter report addressed Chapters 9, 10, 11, 12 and 16. There are potentially risk-significant items in the NuScale design that are not yet fully developed. For these items, requirements should be included in the design certification application (DCA) to ensure that the licensed NuScale plant will perform as credited. However, none apply to Chapter 10.
We expressed concerns with turbine generator missile protection. The applicant has decided not to take credit for turbine generator overspeed protection nor provide a probabilistic analysis of the likelihood of missile generation. The applicant is providing protection of safety significant SSCs using robust structures. Because no steam and power conversion systems are involved, the staff has included their analysis of the acceptability of this approach in their Chapter 3 SER review. The Committee will align our review activities with the staff; therefore, there are no Chapter 10 concerns.
NRC Staff Response to ACRS Letter Report No staff response was necessary related to Chapter 10.
Open Items from Phase 3 Requiring Further ACRS Review None Recommendation The staff has addressed all open items from the Phase 3 review for Chapter 10 of the DCA.
Staff also addressed our Phase 3 letter report recommendation (that didnt contain any Chapter 10 elements). There are no unresolved items related to NuScale DCA Chapter 10. As lead ACRS reviewer for NuScale Chapter 10 DCA and the associated SER, I recommend that no additional Phase 5 review by the Committee is necessary.
November 26, 2019
SUBJECT:
PROPOSED RECOMMENDATION FOR ACRS REVIEW OF NUSCALE POWER, LLC, DESIGN CERTIFICATION APPLICATION - SAFETY EVALUATION WITH NO OPEN ITEMS FOR CHAPTER 10, STEAM AND POWER CONVERSION SYSTEM Package No.: ML19297D008 Accession No: ML19297D126 Publicly Available Y Sensitive N Viewing Rights: NRC Users or ACRS Only or See Restricted distribution *via email OFFICE ACRS/TSB SUNSI Review ACRS/TSB ACRS NAME MSnodderly MSnodderly LBurkhart MSunseri (KHoward for)
DATE 10/24/2019 10/24/2019 11/12/2019 11/26/2019 OFFICIAL RECORD COPY