ML23108A219
| ML23108A219 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 04/13/2023 |
| From: | Vistra Operating Co. (VistraOpCo) |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML23108A246 | List: |
| References | |
| Download: ML23108A219 (1) | |
Text
WEB-BASED PROPOSED ALTERNATIVE SUBMISSION 10 CFR 50.55a(z)(2)
Submission Date: April 13, 2023 Submitted By:
Document Sensitivity: Non-Sensitive Licensee: Vistra Operations Company LLC (Vistra OpCo)
Plant Unit(s) and Docket No(s):
Licensee
Contact:
Jim Barnette James.barnette@luminant.com (254) 897-5866
- 1. Project
Title:
RELIEF REQUEST RV Extension Request for Thermal Relief Valves
- 11. Proposed Alternative Number or Identifier:
RV-1
- 6. Request Type:
Inservice Testing (IST)
- 10. Requested Completion Date:
May 04, 2023
- 12. Brief Description of Proposed Alternative Since suitable replacement parts or valves to support rework or replacement cannot be procured by 2RF20 or 1RF23, Vistra OpCo proposes to replace the Unit 2 and Unit 1 relief valves no later than 2RF21 (in the Fall of 2024) and 1RF24 (in the Spring of 2025), respectively.
In the interim, Vistra OpCo proposes to control the service water system in a manner that eliminates the chances of overpressure due to thermal transients by requiring the applicable vent valve to be opened upon isolation of the heat exchanger or cooler and remain open until the heat exchanger or cooler is no longer isolated from the safe shutdown impoundment.
- 13. Proposed Duration of Alternative (in terms of ISI/IST Program Interval with Start and End Dates):
This proposed alternative, upon approval, will be applied until 2RF21 in the Fall of 2024 for valves in Unit 2 and 1RF24 in the Spring of 2025 for valves in Unit 1. This duration proceeds beyond the current third interval end date of August 2, 2023, until the first refueling outage for each respective unit in the fourth IST program interval, which starts on August 3, 2023.
- 14. Applicable ASME Code Requirements I-1390 Test Frequency, Classes 2 and 3 Pressure Relief Devices That Are Used for Thermal Relief Application. Tests shall be performed on all Classes 2 and 3 relief devices used in thermal relief application every 10 years, unless performance data indicate more frequent testing is necessary. In lieu of tests the Owner may replace the relief devices at a frequency of every 10 years, unless performance data indicate more frequent replacements are necessary.
The only differences between OM-2004/2006 and OM-2017 are that the words years have been abbreviated to yr. Both editions are described because the relief request will begin in the Third Interval when OM-2004/2006 is applicable and end in the Fourth Interval when OM-2017 will be applicable.
- 15. Applicable American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPV Code), or ASME Operation and Maintenance of Nuclear Power Plants (OM Code), Edition and Addenda American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code), 2004 Edition, 2006 Addenda until August 2, 2023, and 2017 Edition beginning August 3, 2023.
- 16. Current ISI or IST Program Interval Number and Start/End Dates IST Program Third Interval Start Date: August 3, 2013 End Date: August 2, 2023
- 17. Applicable ASME Code Components and/or System Description Select thermal relief valves in the Station Service Water (SSW) system which provide overpressure protection for the SSW side of the Component Cooling Water Heat Exchangers and the SSW side of various ECCS pump lube oil coolers:
1SW-0442,1SW-0451,1SW-0444, 2SW-0436,1SW-0452,1SW-0443,1SW-0450,1SW-0445, 2SW-0438,1SW-0453, 2SW-0422, 2SW-0435, 1SW-0446, 2SW-0439 2SW-0440, 2SW-0423, 2SW-0434, 1SW-0447, 2SW-0441 More details on these valves are provided in the attached Table 1: RV-1 Relief Valve Descriptions
- 18. Reason for Request Pursuant to 10 CFR 50.55a, Codes and standards, paragraph (z), Alternatives to codes and standards requirements, item (2), VISTRA Operations Co. LLC (Vistra OpCo) is providing this proposed alternative to testing the selected relief valves due to a hardship without a compensating increase in quality and safety.
- 19. Full Description of Proposed Alternative Since suitable replacement parts or valves to support rework or replacement cannot be procured by 2RF20 or 1RF23, Vistra OpCo proposes to rework/replace the 19 relief valves no later than 2RF21 (in the Fall of 2024 for Unit 2 valves) and 1RF24 (in the Spring of 2025 for Unit 1 valves). Until valve rework/replacement, Vistra OpCo proposes to place Shift Manager Caution Tags on the heat exchanger isolation valves and vent valves requiring the heat exchangers to be vented upon isolation and to remain vented until the heat exchanger is no longer isolated from the safe shutdown impoundment.
- 20. Description of Basis for Use During preparation of the CPNPP IST Program Interval update, it was discovered that multiple ASME Code Class 3 relief valves that protect systems or portions
of systems that are required to perform a specific function in shutting down a reactor to the safe shutdown condition, in maintaining the safe shutdown condition, or in mitigating the consequences of an accident were incorrectly excluded from the IST Program. The extent of condition review determined that the error occurred in 1996 based on a liberal interpretation of the skid-mounted components exclusion (now found in ASME OM Code section ISTC-1200(b)). In total, 54 relief valves were found to have been incorrectly excluded from the IST Program. Many of the valves have been tested or replaced within the OM Code required 10-year interval under the Preventative Maintenance Program. However, as of April 10, 2022, twenty-two valves are not in compliance with the OM Code interval or will become non-compliant before replacement parts or valves are available. Three of the non-compliant valves, for which sufficient parts are available, have been scheduled to be tested no later than the next refueling outage (2RF20 in the Spring of 2023 and 1RF23 in the Fall of 2023). This discussion is focused on 19 of the relief valves that require testing/replacement and which have insufficient parts or replacement valves available in the event that replacements are necessary. Some spare parts (base, gasket, spring) for these valves are on hand, but the more critical parts (disc, guide, spindle) are not available. Since four of these relief valves have been in service for the licensed life of the plant without record of testing or maintenance and the remaining fifteen valves have been in service for several years, replacements/repair parts are anticipated to be needed to support installation of valves that meet set pressure and/or seat leakage performance requirements. At minimum, it is expected that the valves will require rework to restore a leak tight condition. Some critical parts are extremely likely to require replacement due to the potential for corrosion or buildup of mineral deposits from exposure to the lake water chemistry circulating in the SSW system. Corrosion or mineral deposits could impair disassembly without damage to the critical components for which there are no available replacements. The potential for these issues has been confirmed during recent testing of sister relief valves in the same service conditions. Since Vistra OpCo does not have sufficient parts to support anticipated rework, and no suitable replacements are available for 6 - 9 months, implementing the OM Code requirement to test the valves has the potential to cause an extended outage of the service water system or ECCS pump and result in a hardship without a compensating increase in the level of quality and safety. Suitable replacement valves are long lead time items. Emerson (the company with Lonergan intellectual property design expertise and the supplier of Crosby replacement parts and valves) has been contacted and is currently working to quote replacement valves to the full design requirements and specifications of Vistra OpCo. The timing for a quote and procurement has been communicated as 10-12 weeks for document review and 30 weeks for delivery after receipt of a purchase order which will not support either our Unit 2 refueling outage in the spring 2023 or Unit 1 refueling outage in the fall 2023.
The earliest expected delivery date is January 2024. Licensee procurement engineers with Paragon have been searching RAPIDS and other avenues to find replacements for the four Lonergan relief valves available on the shelf in the industry. Few (less than four) valves that meet at least some of the specifications have been found. The valves closest to meeting our requirements are at DC Cook, but the valves were procured to the requirements of ASME B&PV Code Section III without the N stamp - which our design specification requires. In addition, the set pressures of the DC Cook valves are 125#, whereas
CPNPPs valves are set to 150#. Since two of the Lonergan valves in each Unit require replacement, two valves are needed in May 2023 (a total of four preceding our Unit 1 fall outage). Three of the DC Cook valves do not have a design report (including the record of seismic testing and qualification);
Emerson is in progress of determining whether they can make the design report, which is applicable to the one valve, also applicable to the other three valves, but this is not expected to be achievable in time to support having replacement valves on hand during the Spring 2023 or Fall 2023 outages. Critical replacement parts for the fifteen Crosby JMAK model relief valves are not in stock and are not available prior to 2RF20. On April 6, 2023, during disassembly of a JMAK relief valve which had been in service in the SSW system for ~20 years, the valve did not pass final seat tightness testing. Upon disassembly, the spindle was found stuck in the disc due to corrosion. While this did not impair the open or close function of the valve in service, the corrosion prevented the disk from articulating and forming a leak tight seal with the nozzle seat. An RFQ for replacement spindles was submitted on March 14, 2023, and Emerson has responded that the spindles have a 24-week lead time after order. Due to a vendor upgrade to their operating system, the earliest order date for these spindles is May 1, 2023. Therefore, these spindles may not be available prior to 1RF23 which starts on October 15, 2023. None of the subject station service water relief valves have an open safety function because the SSW system is an open system which cannot be over-pressurized unless the system is isolated. System isolation is only required when the system is out of service for maintenance and not credited to perform a nuclear safety function. When the SSW system is in service and required to be operable, the only safety function of the relief valves is to be closed to maintain the system pressure boundary. The overpressure design function of the relief valves is only required when the heat exchangers or coolers are isolated for maintenance or in response to a condition requiring the heat exchanger/cooler to be taken out of service (i.e. Alarm Procedure ALM-011A/B requires isolation of the CCW/SSW Heat Exchanger in the event of an alarm indicating a potential tube leak). Operation of the SSW relief valves is not required to support the function of the CCW system or ECCS pump lube oil systems. There are no indications that the valves leak or that the lack of testing has adversely affected their close function. The SSW system does not have a history of pressure transients that cause the valves to open during pump start transients or system valve manipulations. In the history of licensed plant operation, there has been only one instance of relief valve leakage at these locations (CR-2010-001359). In the unlikely event of a transient that resulted in a stuck open relief valve, the full open relief rate of a valve over the full mission time of the SSW system would be insignificant compared to the available margin in Safe Shutdown Impoundment (SSI) inventory and less than half the capacity of the Auxiliary Building or Safeguards building sump pumps. Since the relief valves only have an open function when the heat exchanger is isolated, Vistra OpCo proposes to place Shift Manager Clearances (in the form of Caution Tags) on the affected heat exchanger/cooler isolation valves and vent valves.
The Caution Tags will provide directions to open the respective vent valve upon isolation of the heat exchanger from the safe shutdown impoundment. The open vent valve will eliminate the chances of overpressure due to thermal expansion.
A caution tag is preferred over a danger tag because a danger tag would unnecessarily delay operators from responding appropriately to alarms and/or system leakage. The position of components that are danger tagged cannot be
changed without a time-consuming process to remove the tags. Caution tags can be written to provide appropriate guidance whether the heat exchanger is in service or isolated, and caution tags are superior to operating procedures or specific maintenance clearances because these caution tags would be referenced in all scenarios prior to isolation of the heat exchanger/cooler.
- 21. Include Any Additional Information None
22. Precedents
L-2020-LLR-0062 Comanche Peak Relief Valve Test Interval Extension Verbal Authorization 2020-04-09. L-2020-LLR-0096 Comanche Peak Unit 1 COVID IST Interval Extension Verbal Authorization 2020-08-11.
- 24. Attachments
- 2. Table 1 RV-1 Relief Valve Descriptions.pdf