ML23017A159
| ML23017A159 | |
| Person / Time | |
|---|---|
| Site: | Hermes |
| Issue date: | 01/10/2023 |
| From: | Benjamin Beasley NRC/NRR/DANU/UAL1 |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| Download: ML23017A159 (1) | |
Text
14 TECHNICAL SPECIFICATIONS THIS NRC STAFF DRAFT SE HAS BEEN PREPARED AND IS BEING RELEASED TO SUPPORT INTERACTIONS WITH THE ACRS. THIS DRAFT SE HAS NOT BEEN SUBJECT TO FULL NRC MANAGEMENT AND LEGAL REVIEWS AND APPROVALS, AND ITS CONTENTS SHOULD NOT BE INTERPRETED AS OFFICIAL AGENCY POSITIONS.
The principal purpose of technical specifications (TSs) is to maintain system performance and ensure safe reactor operation. This is accomplished by including in the TSs limiting or enveloping conditions of design and operation, ensuring that emphasis is placed on the safety of the public, the facility staff, and the environment. TSs are typically derived from the facility descriptions and safety considerations contained in the facility safety analysis report (SAR).
This chapter of the Kairos Power LLC (Kairos) Hermes construction permit safety evaluation report describes the U.S. Nuclear Regulatory Commission (NRC) staffs (the staffs) technical review and evaluation of the probable subjects of TSs for the Hermes facility as presented in preliminary safety analysis report (PSAR), Revision XX, Chapter 14, Technical Specifications.
14.1 Introduction Hermes PSAR Chapter 14 provides preliminary information on Hermes facility TSs that will be applicable for various operating modes during Hermes operation. In PSAR Section 14.1, Introduction, Kairos discusses the general format and content of the TSs as well as variables and conditions that are expected to be the subjects of TSs. Kairos also discusses some probable subjects of TSs in other PSAR chapters. Kairos does not provide actual TSs in the PSAR; PSAR Section 14.1 states that the Hermes TSs will be provided in an operating license application. In PSAR Section 14.2, Operating Modes, Kairos summarizes the five different Hermes operating modes for the Hermes TSs.
14.2 Regulatory Evaluation The applicable regulatory requirements for the evaluation of the Hermes TSs are as follows:
- Title 10, Code of Federal Regulations (10 CFR) 50.34, Contents of applications; technical information, paragraph (a), Preliminary safety analysis report, including 10 CFR 50.34(a)(5),
which requires that the PSAR include [a]n identification and justification for the selection of those variables, conditions, or other items which are determined as the result of preliminary safety analysis and evaluation to be probable subjects of technical specifications for the facility, with special attention given to those items which may significantly influence the final design.
- 10 CFR 50.35, Issuance of construction permits.
- 10 CFR 50.40, Common standards.
The applicable guidance for the evaluation of the Hermes TSs is as follows:
- NUREG-1537, Guidelines for Preparing and Reviewing Applications for the Licensing of Non-Power Reactors, Part 1, Format and Content, and Part 2, Standard Review Plan and Acceptance Criteria, Chapter 14, Technical Specifications.
- ANSI/ANS-15.1-2007, The Development of Technical Specifications for Research Reactors.
14.3 Technical Evaluation PSAR Section 14.1 states that the format and content of the Hermes TSs, which will be submitted with a Hermes operating license application:
- 1. will address the requirements in 10 CFR 50.36 (consistent with the 10 CFR 50.34(b)(6)(vi) requirement that TSs be included in an operating license application),
- 2. will be consistent with the guidance provided in ANSI/ANS-15.1-2007, and
- 3. will include safety limits (SLs), limiting safety system settings (LSSSs), limiting conditions for operation (LCOs), surveillance requirements (SRs), design features, and administrative controls.
In PSAR Table 14.1-1, Kairos provides variables and conditions that it expects to be subject to TSs, based on its preliminary safety analysis described in other PSAR chapters. PSAR Table 14.1-1 also summarizes Kairos basis for each listed TS variable or condition.
PSAR Table 14.1-1 indicates that SLs will be placed on certain process variables, specifically fuel temperature and reactor vessel surface temperature, to ensure fuel and vessel integrity are maintained consistent with the safety analyses. LSSSs will be established for core exit reactor coolant temperature(s), coolant level, neutron flux (i.e., reactor power), and rate of change of neutron flux (i.e.,
reactor period), to ensure that the SLs are not exceeded and that the reactor will trip prior to reaching a SL.
During the general audit, Kairos confirmed that the exact number of separate LSSSs (i.e., one or more) for core exit reactor coolant temperature, as well as the specific location(s) of associated monitors and their setpoints, will be provided in an operating license application and will be based a final thermal-hydraulic analysis that will also be provided in an operating license application. Kairos also confirmed that these details of LSSSs for core exit reactor coolant temperature in an operating license will also consider that the defueling chute, rather than the outlet plenum, could have the highest coolant temperatures. In addition, Kairos confirmed that in an operating license application it will demonstrate by a final thermal-hydraulic analysis that its proposed LSSSs are comprehensive and, specifically, that LSSS(s) for vessel temperature are not necessary to ensure that the SLs will not be exceeded.
PSAR Table 14.1-1 indicates that LCOs, which are the lowest functional capability or performance level required for safe operation of the Hermes facility, will be provided in the TSs, will be derived from the safety analyses, and will be implemented administratively or by control and monitoring systems to ensure safe operation of the facility. Proposed subjects of LCOs listed in PSAR Table 14.1-1 include:
- reactor core parameters (pebble wear and reactor power).
- reactor control and safety systems (reactivity coefficients that ensure the severity of reactivity transients is limited, and reactor protection system operability);
- coolant systems (reactor coolant chemical composition, coolant radionuclide inventory, primary heat transport system (PHTS) pressure and flow rate, inert gas system pressure, cover gas purity, PHTS gas space materials at risk (i.e., gas space radionuclide inventory available for release),
and quantity of air in the reactor system);
- engineered safety features (decay heat removal system (DHRS) operability); and
- radiation monitoring systems and effluents.
Other PSAR chapters discuss additional probable subjects of TSs (which could include LCOs, but also design features) including shutdown margin, moderator pebble to fuel pebble ratio, and fuel enrichment (PSAR Section 4.5.2.4), and pebble burnup limits (PSAR Section 9.3.4).
PSAR Table 14.1-1 indicates that SRs relating to test, calibration, or inspection to ensure the necessary quality of systems and components is maintained; design features, which if altered or modified, could have a significant effect on safety; and administrative controls necessary to ensure safe Hermes facility operation, will be provided in the TSs included in an application for an operating license.
PSAR Section 14.2 and PSAR Table 14.2-1 describe five operational modes for the Hermes TSs, which are defined in terms of combinations of core reactivity, reactor power, and nominal reactor coolant outlet temperature.
The staff evaluated the sufficiency of the preliminary information on Hermes TSs, as described in PSAR Chapter 14, using the guidance and acceptance criteria from Chapter 14 of NUREG-1537, Parts 1 and
- 2. In its evaluation, the staff also considered the preliminary safety analysis information and discussions of the probable subjects of TSs in other PSAR chapters. The staff finds that Kairos probable subjects of TSs are consistent with important parameters determined as a result of the preliminary safety analyses in the PSAR, with special attention given to items (e.g., SLs, LSSSs, and LCOs) that may significantly influence the final design, and that the probable subjects of TSs are supported by appropriate bases.
Regarding Kairos probable LSSS for rate of change of neutron flux, the staff finds that such an LSSS would provide a defense in depth to limit the temperature difference between the kernel and pebble surface limiting the fission gas pressure increase (even if SL temperatures are not reached), consistent with limitations in Kairos fuel qualification topical report, Fuel Qualification Methodology for the Kairos Power Fluoride Salt-Cooled, High Temperature Reactor (KP-FHR), Revision 2 (see Section 4.2.1 of this safety evaluation report). The staff expects that additional subjects of TSs, including additional LCOs on reactor core parameters (e.g., excess reactivity and core reactivity) and reactor control and safety systems (e.g., control elements) will likely be needed, but finds that other probable subjects of TSs beyond those specifically listed in PSAR Chapter 14 are, in general, less likely to significantly influence the final design. Therefore, based on the information in PSAR Chapter 14 and other PSAR chapters, the staff finds that Kairos identification and justification of the preliminary subjects of TSs meets the applicable acceptance criteria in NUREG-1537 and is sufficient for the issuance of a construction permit in accordance with 10 CFR 50. The staff will perform a detailed evaluation of the complete and finalized TSs for Hermes, including SLs, LSSSs, LCOs, SRs, design features, and administrative controls, during its review of a Hermes operating license application.
14.4 Conclusion Based on its findings above, the staff concludes the information in PSAR Chapter 14 is sufficient and meets the applicable guidance and regulatory requirements for the issuance of a construction permit in accordance with 10 CFR Part 50. Further information, including a complete set of Hermes TSs and associated bases, as may be required to complete the review of a Hermes operating license application can reasonably be left for later consideration in a final safety analysis report since this information is not necessary for the review of a construction permit application.
14.5 References American National Standards Institute/American Nuclear Society (ANSI/ANS)-15.1-2007, The Development of Technical Specifications for Research Reactors, American Nuclear Society, La Grange Park, Illinois.
Kairos Power LLC. Hermes Non-Power Reactor Preliminary Safety Analysis Report, Revision 0.
September 2021. ADAMS ML21272A375 or XXXXX Kairos Power LLC, Fuel Qualification Methodology for the Kairos Power Fluoride Salt-Cooled, High Temperature Reactor (KP-FHR), Revision 2. July 5, 2022. ADAMS Accession No. ML22186A212.
U.S. Nuclear Regulatory Commission (NRC). NUREG-1537, Guidelines for Preparing and Reviewing Applications for the Licensing of Non-Power Reactors, Part 1, Format and Content, and Part 2, Standard Review Plan and Acceptance Criteria. NRC: Washington, D.C. February 1996. ADAMS Accession Nos. ML042430055 and ML042430048.
U.S. Nuclear Regulatory Commission . Report on General Regulatory Audit for the Hermes Construction Permit Application Review, dated XX, 202X. ADAMS Accession No. MLXXXXXXXXX.