ML24311A222
| ML24311A222 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 11/13/2024 |
| From: | Robert Kuntz Plant Licensing Branch III |
| To: | Rhoades D Constellation Energy Generation |
| Wiebe J | |
| References | |
| EPID L-2024-LLR-0042 | |
| Download: ML24311A222 (1) | |
Text
November 13, 2024 David P. Rhoades Senior Vice President Constellation Energy Generation, LLC President and Chief Nuclear Officer Constellation Nuclear 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
BYRON STATION, UNIT NO. 2 - ALTERNATIVE REQUEST TO EXTEND INSERVICE TESTING INTERVAL FOR ESSENTIAL SERVICE WATER VALVES FOURTH 10-YEAR INSERVICE TESTING PROGRAM INTERVAL (EPID-L-2024-LLR- 0042)
Dear David Rhoades:
By letter dated June 25, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24177A213), Constellation Energy Generation, LLC (Constellation or the licensee) submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for an alternative to specific inservice testing (IST) requirements in the 2004 Edition through 2006 Addenda of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) for certain essential service water system (SX) valves at Byron Station (Byron), Unit No. 2.
Specifically, Constellation proposed to delay the IST of three specific air-operated SX valves at Byron, Unit No. 2, until after the 2A containment chiller was returned to operable status. Testing these valves would take the 2B containment chiller out of service. For reasons discussed in the licensees letter, taking the 2B containment chiller out of service while the 2A containment chiller is out of service has adverse impacts on other plant equipment and would increase the chances of a plant shutdown at a time when there were grid alert conditions. Therefore, the licensee asked for a one-time extension of the testing under the provisions of Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(z)(2).
On June 26, 2024, the NRC staff issued verbal authorization (ML24306A007) of the proposed alternative for a one-time extension to the IST programs 3-month intervals. The authorization was granted only for testing of the three specified SX air-operated valves at Byron, Unit No. 2, in accordance with 10 CFR 50.55a(z)(2) until the 2A containment chiller was returned to operable status, but no later than July 19, 2024. LIC-102, Revision 3, states that that the NRC staff should issue its written safety evaluation (SE) within 150 calendar days after giving verbal authorization. The NRC staffs written SE is enclosed.
The NRC staff has reviewed the subject request and concluded, as set forth in the enclosed SE, that Constellation provided adequate justification that compliance with the applicable ASME OM
Code test requirements for the subject SX valves at Byron, Unit No. 2 would have resulted in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The NRC staff also found that the testing and performance experience of the subject SX valves described in the licensees request provided reasonable assurance that the SX valves would be operationally ready to perform their safety functions for the duration of the request. Accordingly, the NRC staff concluded that the licensee had adequately addressed all regulatory requirements set forth in 10CFR50.55a(z)(2). Therefore, the NRC staff authorized a one-time extension of the IST interval for the three specific SX valves until restoration of the 2A containment chiller to operable status but no later than July 19, 2024. The NRC staff notes that the one-time extension of the IST interval for the subject SX valves does not extend the end date of the fourth 10-year IST program interval at Byron, Unit No. 2, beyond June 30, 2026.
All other ASME OM Code requirements as incorporated by reference in 10 CFR 50.55a for which relief or an alternative was not specifically requested and granted or authorized (as appropriate), in the subject request remain applicable.
If you have any questions, please contact the Senior Project Manager, Joel Wiebe at 301-415-6606 or via e-mail at Joel.Wiebe@NRC.gov.
Sincerely, Robert Kuntz, Acting Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-455
Enclosure:
Safety Evaluation cc: Listserv ROBERT KUNTZ Digitally signed by ROBERT KUNTZ Date: 2024.11.13 16:31:32 -05'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ALTERNATIVE REQUEST TO EXTEND INSERVICE TESTING INTERVAL FOR ESSENTIAL SERVICE WATER VALVES FOURTH 10-YEAR INSERVICE TESTING PROGRAM INTERVAL CONSTELLATION ENERGY GENERATION, LLC BYRON STATION, UNIT NO. 2 DOCKET NO. 50-455 EPID L-2024-LLR-0042
1.0 INTRODUCTION
By letter dated June 25, 2024 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML24177A213), Constellation Energy Generation, LLC (Constellation or the licensee) submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for an alternative to specific inservice testing (IST) requirements in the 2004 Edition through 2006 Addenda of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) for certain essential service water (SX) system valves at Byron Station (Byron), Unit No. 2.
Specifically, pursuant to subparagraph (2) in paragraph (z), Alternatives to codes and standards requirements, of section 55a, Codes and standards, in part 50, Domestic Licensing of Production and Utilization Facilities, to Title 10, Energy, of the Code of Federal Regulations (10 CFR), the licensee requested a one-time extension of the IST interval for specific SX valves at Byron, Unit No. 2, on the basis that compliance with certain ASME OM Code requirements, at that time, would present an undue hardship without a compensating increase in the level of quality or safety.
On June 26, 2024, the NRC staff communicated a verbal authorization (ML24306A007) for the proposed one-time extension of the 3-month interval for the IST of the three specified SX valves at Byron, Unit No. 2, in accordance with 10 CFR 50.55a(z)(2) until the 2A containment chiller would be returned to operable status but no later than July 19, 2024. The verbal authorization documentation provided a summary of the NRC staff evaluation for the proposed alternative.
This safety evaluation documents the NRC staff review of the licensees alternative request for the specific SX valves at Byron, Unit No. 2.
2.0 REGULATORY EVALUATION
The NRC regulations in 10 CFR 50.55a(f)(4), Inservice testing standards requirement for operating plants, state, in part, that throughout the service life of a boiling or pressurized water-cooled nuclear power facility, pumps and valves that are within the scope of the ASME OM Code must meet the IST requirements (except design and access provisions) set forth in the ASME OM Code and addenda that become effective subsequent to editions and addenda specified in 10 CFR 50.55a(f)(2) and (3) and that are incorporated by reference in 10 CFR 50.55a(a)(1)(iv), to the extent practical within the limitations of design, geometry, and materials of construction of the components.
The NRC regulations in 10 CFR 50.55a(z), Alternatives to codes and standards requirements, state that alternatives to the requirements of 10 CFR 50.55a(b) through (h) or portions thereof may be used when authorized by the Director, Office of Nuclear Reactor Regulation. A proposed alternative must be submitted and authorized prior to implementation.
The applicant or licensee must demonstrate that:
(1) Acceptable level of quality and safety. The proposed alternative would provide an acceptable level of quality and safety; or (2) Hardship without a compensating increase in quality and safety. Compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
3.0 TECHNICAL EVALUATION
3.1 Licensees Alternative Request Applicable Code Edition The applicable Code of Record for the fourth 10-year IST program interval at Byron, Unit No. 2, is the 2004 Edition through 2006 Addenda of ASME OM Code as incorporated by reference in 10 CFR 50.55a. The fourth 10-year IST program interval at Byron, Unit No. 2, began on July 1, 2016, and is currently scheduled to end on June 30, 2026.
ASME Code Components Affected Table 1 lists the air-operated valves at Byron, Unit No. 2, for which this alternative is being requested.
Table 1 Component Description Code Class OM Category 2SX112B CONTAINMENT CHILLER SX SUPPLY VALVE 3
B 2SX114B CONTAINMENT CHILLER SX RETURN VALVE 3
B 2SX147B ESW RCFC RETURN PRESSURE CONTROL VALVE 3
B
=
Applicable Code Requirement===
The IST requirements in the ASME OM Code, as incorporated by reference in 10 CFR 50.55a, related to this alternative request are as follows:
ASME OM Code, subsection ISTC, Inservice Testing of Valves in Light-Water Reactor Nuclear Power Plants, paragraph ISTC-3500, Valve Testing Requirements, states that active and passive valves in paragraph ISTC-1300, Valve Categories, shall be tested in accordance with the paragraphs specified in table ISTC-3500-1, Inservice Test Requirements, and the applicable requirements of paragraphs ISTC-5100 and ISTC-5200.
ASME OM Code, subsection ISTC, paragraph ISTC-3510, Exercising Test Frequency, states, in part, that Active Category A, Category B, and Category C check valves shall be exercised nominally every 3 months, except as provided by paragraphs ISTC-3520, ISTC-3540, ISTC-3550, ISTC-3570, ISTC-5221, and ISTC-5222.
ASME OM Code, subsection ISTC, paragraph ISTC-3560, Fail-Safe Valves, states that valves with fail-safe actuators shall by tested by observing the operation of the actuator upon loss of valve actuating power in accordance with the exercising frequency of paragraph ISTC-3510.
ASME OM Code, subsection ISTC, paragraph ISTC-5130, Pneumatically Operated Valves, subparagraph ISTC-5131, Valve Stroke Testing, states in subparagraph (a) that active valves shall have their stroke times measured when exercised in accordance with paragraph ISTC-3500.
Licensees Proposed Alternative In its submittal dated June 25, 2024, the licensee proposed a one-time extension to the 3-month intervals for the IST of the subject SX valves at Byron, Unit No. 2. The licensee submitted the proposed alternative associated with performing the IST of the subject SX valves in accordance with 10 CFR 50.55a(z)(2) on the basis that compliance with the specified ASME OM Code requirements would result in hardship or unusual difficulty without a compensating increase in level of quality or safety during the short duration of restoring Byron 2A containment chiller to operable status.
Licensees Basis for Use The SX system at Byron, Unit No. 2, provides cooling water to the containment chillers, which provide cooling to the chiller water system for maintaining containment cooling during non-emergency conditions. Performing valve testing on the SX system requires shutting down the associated train's chiller to prevent the chiller from tripping on loss of cooling flow. On March 31, 2024, the licensee removed the Byron 2A containment chiller from service for scheduled preventative maintenance. During the initial return of that chiller to service, the licensee identified additional work needed to be performed, including leak repairs, seal replacements, and a stator replacement. The licensee stated troubleshooting and maintenance of the Byron 2A containment chiller were being performed and would continue until the chiller was returned to an operable status. The licensee requested an extension of the IST interval for the specified SX valves such that the 2B containment chiller would not be required to be shut down while the 2A containment chiller was inoperable.
The licensee noted that the required IST activities consisting of exercise, fail-safe, and valve stroke testing, are satisfied by performing a valve stroke-time test. The licensee described the history of the IST performance for the SX valves in its submittal dated June 25, 2024.
The licensee considered that the testing history provided reasonable assurance that the SX valves were operable and ready to perform their safety functions if needed. The data in the Constellations submittal showed that for each valve the stroke-time testing was completed satisfactorily over the past 2 years. Based on the test history, the licensee asserted that the proposed alternative to extend the interval for IST of the subject SX valves would not result in an adverse consequence to safety at Byron, Unit No. 2.
Licensees Reason for Request In its request, Constellation proposed a one-time extension of the IST interval for the specified SX valves at Byron, Unit No. 2. To perform the surveillance and testing for the specified SX valves, the 2B containment chiller would need to be shut down. However, with the 2A containment chiller undergoing maintenance at that time, the B-train chiller was being relied upon for containment cooling. The licensee noted that the required IST window for these valves would have expired at 11:59 p.m. on Wednesday, June 26, 2024. This was the latest date, including the allowed 25-percent grace period, to maintain compliance with the ASME OM Code and Code Case OMN-20, Inservice Test Frequency.
With the 2A containment chiller unavailable due to emergent work, the licensee stated that shutting down the 2B containment chiller would have caused Byron, Unit No. 2, to lose atmospheric cooling. Therefore, the licensee proposed a one-time extension of the IST interval for the SX valves until after the 2A containment chiller was available, but no later than July 19, 2024. Accordingly, the licensee requested authorization of its alternative on an expedited basis for the IST program at Byron, Unit No. 2, to maintain compliance with the ASME OM Code as incorporated by reference in 10 CFR 50.55a.
The licensee proposed the alternative as a result of the hardship associated with the potential need for an unnecessary plant shutdown of Byron, Unit No. 2. With the loss of atmospheric cooling within the containment to perform the testing, there was an increased risk to all systems inside the containment and increased potential for a unit shutdown. With a loss of containment cooling combined with the hot weather at the time of the request, the fourth reactor containment fan cooler would have required an unnecessary start and would have increased the potential to exceed the limit in Technical Specification 3.6.5, Containment Air Temperature.
The licensee proposed this alternative under 10 CFR 50.55a(z)(2) that with the then-current plant configuration of the 2A containment chiller being unavailable, the required IST of the subject SX valves posed a hardship or unusual difficulty without compensating increase in level of quality or safety.
3.2
NRC Staff Evaluation
In its alternative request dated June 25, 2024, the licensee proposed a one-time extension of the 3-month interval for IST of three specific valves in the essential SX system at Byron, Unit No. 2, until the 2A containment chiller could be returned to operable status. The performance of the IST of these valves would have removed the 2B containment chiller from service. In the alternative request, the licensee described how taking the 2B containment chiller out of service, while the 2A containment chiller was out of service, would have adversely impacted other plant equipment and increased the potential for a plant shutdown of Byron, Unit No. 2, at a time when there were grid alert conditions from the summer hot weather. Based on these factors, the licensee submitted the proposed alternative under the hardship provisions of 10 CFR 50.55a(z)(2).
The licensees OM Code of Record for the IST program requires the SX valves at Byron, Unit No. 2, to be tested every 3 months. The licensee reported that the next test was due on June 25, 2024. In its request, the licensee proposed to delay the IST of these three valves until after the 2A containment chiller was returned to operable status but no later than July 19, 2024.
The licensees submittal summarized the history of the test results for the subject SX valves. In particular, the stroke-time testing of subject SX valves had been completed satisfactorily over the past 2 years and the first quarter of 2024. No deficiencies or adverse trends had been identified that might have reflected degraded performance of the subject SX valves. Further, no maintenance work orders were open for the subject SX valves. On this basis, the NRC staff determined that there was reasonable assurance that the subject SX valves would continue to be capable of performing their design function during the requested IST interval extension.
Based on its review, the NRC staff found that compliance with the specified IST requirements for the subject SX valves during the short duration of the requested alternative would have resulted in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Removing the 2B containment chiller from service while the 2A containment chiller was out of service could have resulted in an adverse impact on other plant equipment and increased the potential for a plant shutdown of Byron, Unit No. 2, during grid alert conditions.
Also, the test and performance history for the specified valves provided reasonable assurance of their operational readiness during the time period of the alternative request. Therefore, the NRC staff concluded that the proposed alternative met the requirements of 10 CFR 50.55a(z)(2). As indicated in the verbal authorization on June 26, 2024, the NRC staff authorized a one-time extension of IST interval for the three specific SX valves until restoration of the 2A containment chiller to operable status but no later than July 19, 2024.
4.0 CONCLUSION
As set forth above, the NRC staff determined that the licensees submittal dated June 25, 2024, provided adequate justification that compliance with the applicable ASME OM Code test requirements for the subject SX valves at Byron, Unit No. 2, would have resulted in hardship or unusual difficulty without a compensating increase in the level of quality and safety. The NRC staff also found that the testing and performance experience of the subject SX valves described by the licensee in its request provided reasonable assurance that the SX valves would be operationally ready to perform their safety functions for the duration of the request. Accordingly, the NRC staff concluded that the licensee had adequately addressed all regulatory requirements set forth in 10CFR50.55a(z)(2). Therefore, the NRC staff authorized a one-time extension of the IST interval for the three specific SX valves until restoration of the 2A containment chiller to operable status but no later than July 19, 2024. The NRC staff notes that the one-time extension of the IST interval for the subject SX valves does not extend the end date of the fourth 10-year IST program interval at Byron, Unit No. 2, beyond June 30, 2026.
All other ASME OM Code requirements as incorporated by reference in 10 CFR 50.55a for which relief or an alternative was not specifically requested, and granted or authorized (as appropriate), in the subject request remain applicable.
Principal Contributors: Gurjendra Bedi, NRR Thomas Scarbrough, NRR Date: November 13, 2024
ML24311A222 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DORL/LPL3/PM NRR/DEX/EMIB/BC NAME BWetzel SRohrer JWiebe (SArora for)
SBailey DATE 11/5/2024 11/7/2024 11/8/2024 11/8/2024 OFFICE NRR/DORL/LPL3/BC(A)
NAME RKuntz DATE 11/13/2024