ML24309A216
| ML24309A216 | |
| Person / Time | |
|---|---|
| Site: | Technical Specifications Task Force |
| Issue date: | 11/04/2024 |
| From: | Michelle Honcharik NRC/NRR/DSS/STSB |
| To: | Technical Specifications Task Force |
| References | |
| EPID L-2024-PMP-0007 | |
| Download: ML24309A216 (7) | |
Text
November 4, 2024 Technical Specifications Task Force 11921 Rockville Pike, Suite 100 Rockville, MD 20852
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION RE: TRAVELER TSTF 601, REVISION 0, EXTEND SHIELD BUILDING COMPLETION TIME AFTER REFUELING" (EPID: L-2024-PMP-0007)
Dear Members of the Technical Specifications Task Force:
By letter dated May 31, 2024 (Agencywide Documents Access and Management System Accession No. ML24152A200), you submitted a request to the U.S. Nuclear Regulatory Commission (NRC) to incorporate Traveler TSTF 601, Revision 0, Extend Shield Building Completion Time After Refueling," into the standard technical specifications.
Upon review of the information provided, the NRC staff has determined that additional information is needed to complete the review. Mr. Brian Mann, Vice President of Licensing, EXCEL Services Corporation, agreed that the NRC staff will receive your response to the enclosed request for additional information questions within 90 calendar days of the date of this letter.
The review schedule that was provided in the acceptance letter dated July 25, 2024 (ADAMS ML24207A182), has not changed.
MILESTONE SCHEDULE DATE Issue Draft Safety Evaluation July 25, 2025 Issue Final Safety Evaluation December 19, 2025 If you have any questions, please contact me at (301) 415-1774 or via email to Michelle.Honcharik@nrc.gov.
Sincerely,
/RA/
Michelle C. Honcharik, Senior Project Manager Technical Specifications Branch Division of Safety Systems Office of Nuclear Reactor Regulation Project No. 753
Enclosure:
Request for Additional Information cc: See next page cc:
Technical Specifications Task Force c/o EXCEL Services Corporation 11921 Rockville Pike, Suite 100 Rockville, MD 20852 Attention: Brian D. Mann Email: brian.mann@excelservices.com Drew Richards STP Nuclear Operating Company 12090 FM 521 Mail Code: N5016 Wadsworth, TX 77483 Email: amrichards@stpegs.com Kevin Lueshen Constellation Energy Generation 4300 Winfield Road Warrenville IL 60555 Email: kevin.lueshen@constellation.com Jordan L. Vaughan Duke Energy EC07C / P.O. Box 1006 Charlotte, NC 28202 Email: jordan.vaughan@duke-energy.com Shane Jurek 2818 Provin Oaks Ct NE Grand Rapids, MI 49525 Email: Shane.Jurek@pseg.com Wesley Sparkman Southern Nuclear Operating Company 3535 Colonnade Parkway / Bin N-226-EC Birmingham, AL 35242 Email: wasparkm@southernco.com
- via email NRR-106 OFFICE NRR/DRA/ARCB/BC* NRR/DSS/SNSB/BC* NRR/DSS/STSB/BC* NRR/DSS/STSB/PM*
NAME KHsueh PSahd SMehta MHoncharik DATE 10/15/24 10/2/24 10/7/24 11/4/24
REQUEST FOR ADDITIONAL INFORMATION TECHNICAL SPECIFICATIONS TASK FORCE TRAVELER TSTF-601, REVISION 0, "EXTEND SHIELD BUILDING COMPLETION TIME AFTER REFUELING" (EPID: L-2024-PMP-0007)
INTRODUCTION By letter dated May 31, 2024 (Agencywide Documents Access and Management System Accession No. ML24152A200), the Technical Specifications Task Force (TSTF) submitted Traveler TSTF 601, Revision 0, Extend Shield Building Completion Time After Refueling, to the U.S. Nuclear Regulatory Commission (NRC). Traveler TSTF 601 proposed changes to the Standard Technical Specifications (STSs)1 for pressurized water reactors (PWRs) of the Westinghouse and Combustion Engineering designs that have a shield building. The proposed change would revise the Westinghouse and Combustion Engineering shield building STS to extend the Completion Time (CT) following a refueling outage and prior to criticality.
REGULATORY BASIS FOR REQUEST Section 182(a) of the Atomic Energy Act requires nuclear power plant operating licenses to include TS. The provisions in 10 CFR 50.36, Technical specifications, establishes the NRC regulatory requirements related to the content of the TS.
10 CFR 50.36(a)(1) states in part: A summary statement of the bases or reasons for such specification shall also be included in the application but shall not become part of the technical specifications.
10 CFR 50.36(c)(2) states: Limiting conditions for operation are the lowest functional capability or performance levels of equipment required for safe operation of the facility. When a limiting condition for operation (LCO) of a nuclear reactor is not met, the licensee shall shut down the reactor or follow any remedial action permitted by the technical specifications until the condition can be met.
REQUESTS FOR ADDITIONAL INFORMATION STSB RAIs:
- 1. The STS Bases for the shield building state that 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (in Modes 1-4) is a reasonable CT because of the low leakage design of the containment building and the low probability of an event. The proposed STS Bases for Action A.1 for the shield building specification do not maintain the premise that the containment building has a low leakage design. There is no discussion of why the low leakage aspect is no longer important, especially considering 1-NRC NUREG-1431, Standard Technical Specifications, Westinghouse Plants, Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21259A155 and ML21259A159, respectively).
-NRC NUREG-1432, Standard Technical Specifications, Combustion Engineering Plants, Volume 1, Specifications, and Volume 2, Bases, Revision 5, September 2021 (ML21258A421 and ML21258A424, respectively).
that the primary containment pressure could be relatively high following a loss of coolant accident (LOCA) in Mode 3. Alternatively, the STS Bases could recognize the low leakage design of the primary containment for Action A.1. The NRC staff requests that the STS Bases be reviewed and updated as needed.
- 2. LCO 3.0.4 prohibits entering the Applicability of an LCO with the LCO not met unless one of three conditions (i.e., a, b, or c) is satisfied. TSTF-601 proposed shield building STS markups included a new Condition A that states, Shield building inoperable in Mode 3 or 4 following refueling as modified by a Note that states Only applicable if Mode 2 has not been entered following refueling. In addition, new Required Action A.1 states, Restore shield building to OPERABLE status, as modified by a Note that states LCO 3.0.4.c is applicable. The addition of the LCO 3.0.4.c Note would permit a licensee to enter Modes 4 and 3 following a refueling outage and prior to criticality before completion of the surveillance requirements needed to establish the operability of the shield building.
Section 3.1 of TSTF-601, details multiple STS containment systems specifications (e.g.,
Spray and Cooling Systems), with LCO Applicability in Modes 1-4, that must be operable prior to entry into Mode 4. The STS Actions Bases for Spray and Cooling describe that there is no restriction on the use of LCO 3.0.4.b because LCO 3.0.4.b requires performance of a risk assessment addressing inoperable systems and components, consideration of the results, determination of the acceptability of entering MODE 4, and establishment of risk management actions, if appropriate. The NRC staff did not identify any STS related to containment systems that specifies LCO 3.0.4.c is applicable. According to the STS Bases for LCO 3.0.4.c, the risk assessments performed to justify the use of LCO 3.0.4.b usually only consider systems and components. For this reason, LCO 3.0.4.c is typically applied to Specifications which describe values and parameters (e.g., reactor coolant system (RCS) Specific Activity), and may be applied to other Specifications based on NRC plant-specific approval.
LCO 3.0.4.b applies if a risk assessment determines the acceptability of entering the Applicability while relying on the Action. The risk assessment, for the purposes of LCO 3.0.4.b, must take into account all inoperable technical specification equipment.
Section 3.3 of TSTF-601, describes applying LCO 3.0.4 to an inoperable shield building and concluded that LCO 3.0.4.b is not a practical option to enable entering Mode 4 (Applicability of LCO). According to the STS Bases cited above, it appears that use of LCO 3.0.4.b for entering Mode 4 would be permitted for containment systems such as spray and cooling. As such, it appears to the NRC staff that STS LCO 3.0.4.b would be applicable to the shield building for entering Mode 4 for the same reasons that STS LCO 3.0.4.b is applicable to other containment systems for entering Mode 4. In addition, if the status of systems related to containment integrity may be changing during startup, it is appropriate to assess the risk of shield building inoperability considering the overall plant status instead of just allowing entry into the Applicability without consideration of the overall plant status.
Therefore, based on the discussion above, the NRC staff determined that the use of LCO 3.0.4.b should be considered a practical option for the shield building and the Note that states LCO 3.0.4.c is applicable should be removed.
- 3. The current STS requires the shield building to be operable in Modes 1, 2, 3, and 4. If the shield building is inoperable, for example while in Mode 1 (or other Mode of Applicability) it must be returned to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The reason for the TSTF-601 proposed
change is that during a refueling outage, sections of the shield building are removed to allow access to the containment equipment hatch. At the end of the outage after the equipment hatch is installed, restoring the shield building boundary, including cure time for sealants, and performing necessary surveillance tests to verify the shield buildings integrity, are among the last activities performed prior to entering Mode 4. This places restoration of the shield building on or near the outage critical path. The TSTF-601 proposed approach, it appears, would allow reinstalling the removed sections of the shield building after entering Mode 4 or Mode 3.
The shield building was designed and constructed in accordance with NRC and industry code requirements to fulfill certain safety functions. Some of the requirements include the ability to maintain structural integrity during seismic events and to provide environmental protection of the containment vessel from adverse weather conditions including flying objects generated by tornados.
The potential for reinstalling sections of the shield building during Modes 4 and 3, would unnecessarily expose the limited leakage containment to external hazards. Based on this understanding, the NRC staff conclude that entering Mode 4 after an outage should not be permitted unless all shield building sections are installed and secured in place. As such, reinstallation of shield building sections should occur prior to entering a Mode of Applicability. Therefore, the TSTF-601 proposed change which permits entry into Mode 4 and 3 with an inoperable shield building following a refueling outage and prior to criticality, should include additional constraints that require all access openings to be operable and all shield building sections to be installed and secured in place with inoperability of the shield building limited to the application and curing of sealants necessary to support the performance of surveillance requirements that demonstrate the shield buildings integrity.
SNSB RAI:
- 4. STS Table 1.1-1. MODES, specifies RCS temperature in Mode 4 as [350] > Tavg > [200]°F and in Mode 3 [350]°F. In Mode 3, with temperature [350]°F and pressure equal to full operating pressure, the RCS will be in a higher subcooled state compared to its state during Mode 1 plant operation at normal temperature and pressure. Therefore, a large break LOCA in Mode 3 could result in comparable (or higher due to higher mass release resulting from a higher density of subcooled RCS) blowdown pressure and subsequent pressure transient in containment as compared to the blowdown pressure and pressure transient during a Mode 1 large break LOCA. Therefore, given the Mode 3 scenario discussed above, the NRC staff requests the TSTF assess whether the TSTF-601 claims of reduced likelihood of containment pressurization and significant leakage into the shield building remain valid.
ARCB RAI:
- 5. In traveler TSTF-601, it is noted that reductions in source term inventory would occur due to two factors: removal of 1/3 of the irradiated fuel and time for radioactive decay, thereby reducing the radiological consequences associated with a LOCA following refueling and prior to criticality. Please provide further qualitative evaluation to support the premise that the radiological consequences of an accident during the proposed new Action A are significantly lower than what would be expected during the currently allowed Actions
associated with Mode 1 operations. Please include in the response the status of other safety systems (e.g. Control Room envelope) during the proposed LCO.