ML24228A212
| ML24228A212 | |
| Person / Time | |
|---|---|
| Site: | 99902049 |
| Issue date: | 08/15/2024 |
| From: | Holtec, SMR |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML24228A212 (1) | |
Text
SMR, LLC. A Holtec International Company May 22, 2024 Page 1 of 2
Subject:
Clarification Question - Applicability of 10 CFR 50.155 to RTNSS SMR, LLC (SMR) is seeking clarification on the NRC expectations for application content pertaining to Regulatory Treatment of Non-Safety Systems (RTNSS).
SMR has reviewed SRP 19.3, Regulatory Treatment of Non-Safety Systems for Passive Advanced Light Water Reactors, to inform application content and to understand the NRCs expectations for what non-safety-related SSCs are considered within the RTNSS process. It is not clear what the NRCs expectations are for non-safety-related SSCs used to meet 10 CFR 50.155, Mitigation of Beyond-Design-Basis Events within the RTNSS process.
Page 3 of SPR 19.4 states the following to define RTNSS criteria A (consistent with SECY-94-084 and SECY-95-132):
A. SSC functions relied on to meet beyond design basis deterministic NRC performance requirements such as those set forth in Title 10 of the Code of Federal Regulations (10 CFR) 50.62 for mitigating Anticipated Transients Without Scram (ATWS) and in 10 CFR 50.63 for Station Blackout (SBO).
10 CFR 50.155 states, in part:
(b) Strategies and guidelines. Each applicant or licensee shall develop, implement, and maintain:
(1) Mitigation strategies for beyond-design-basis external eventsStrategies and guidelines to mitigate beyond-design-basis external events from natural phenomena that are developed assuming a loss of all ac power concurrent with, for passive reactor designs, a loss of normal access to the normal heat sink. These strategies and guidelines must be capable of being implemented site-wide and must include the following:
(i) Maintaining or restoring core cooling, containment, and spent fuel pool cooling capabilities; and (ii) The acquisition and use of offsite assistance and resources to support the functions required by paragraph (b)(1)(i) of this section indefinitely, or until sufficient site functional capabilities can be maintained without the need for the mitigation strategies.
(2) Extensive damage mitigation guidelinesStrategies and guidelines to maintain or restore core cooling, containment, and spent fuel pool cooling capabilities under the circumstances associated with loss of large areas of the plant impacted by the event, due to explosions or fire, to include strategies and guidelines in the following areas:
(i) Firefighting; (ii) Operations to mitigate fuel damage; and (iii) Actions to minimize radiological release.
(c) Equipment.
(1) The equipment relied on for the mitigation strategies and guidelines required by paragraph (b)(1) of this section must have sufficient capacity and capability to perform the functions required by paragraph (b)(1) of this section.
(2) The equipment relied on for the mitigation strategies and guidelines required by paragraph (b)(1) of this section must be reasonably protected from the effects of natural phenomena that are
SMR, LLC. A Holtec International Company May 22, 2024 Page 2 of 2 equivalent in magnitude to the phenomena assumed for developing the design basis of the facility.
(e) Spent fuel pool monitoring. In order to support effective prioritization of event mitigation and recovery actions, each licensee shall provide reliable means to remotely monitor wide-range water level for each spent fuel pool at its site until 5 years have elapsed since all of the fuel within that spent fuel pool was last used in a reactor vessel for power generation.
SMR notes that the current revision of SRP 19.3 was issued prior to § 50.155 rulemaking.
The language in § 50.155 seems to include the beyond design basis deterministic NRC performance criteria of an assumed loss of all AC power concurrent with loss of heat sink. SMR will need to evaluate a mitigation strategy for this event, including the potential use of both portable and installed non-safety-related SSCs. SMR is seeking clarification on the NRCs expectations for how these SSCs are treated because the beyond design basis mitigation strategy could include an exhaustive list of SSCs to address contingencies.
Based on a plain language reading of RTNSS criterion A, SMR considers that non-safety-related SSCs relied upon to meet § 50.155 would be considered RTNSS A SSCs and thus be included in the Reliability Assurance Program (RAP). Because the RAP is a precursor to the maintenance rule program (§ 50.65), SMR is concerned this effectively changes the scoping criteria of the maintenance rule criteria.
§ 50.65 requires three categories of non-safety-related SSCs to be included in its scope. These are SSCs:
(i) That are relied upon to mitigate accidents or transients or are used in plant emergency operating procedures (EOPs); or (ii) Whose failure could prevent safety-related structures, systems, and components from fulfilling their safety-related function; or (iii) Whose failure could cause a reactor scram or actuation of a safety-related system.
The term accidents in item (i) has typically been understood to refer to design basis accidents.
The SSCs typically relied upon to meet § 50.155 (e.g., diesel generators and pumps stored in a dedicated location onsite) do not fall under categories (i), (ii), or (iii), and therefore would not typically fall under the maintenance rule program.
SMR is seeking clarification on the NRCs expectations for how such SSCs would be considered relative to RTNSS criterion A.