ML101810148
| ML101810148 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 07/02/2010 |
| From: | Markley M Plant Licensing Branch IV |
| To: | Parrish J Energy Northwest |
| Lyon C Fred, NRR/DORL/LPL4, 301-415-2296 | |
| References | |
| TAC ME4046 | |
| Download: ML101810148 (9) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 July 2, 2010 Mr. J. V. Parrish Chief Executive Officer Energy Northwest P.O. Box 968 (Mail Drop 1023)
Richland, WA 99352-0968
SUBJECT:
COLUMBIA GENERATING STATION - REQUEST FOR RELIEF NO. RV-06 TO EXTEND THE TEST INTERVAL ON A ONE-TIME BASIS FOR A CLASS 2 PRESSURE RELIEF VALVE (TAC NO. ME4046)
Dear Mr. Parrish:
By letter dated June 9, 2010, as supplemented by letter dated June 18, 2010, Energy Northwest (the licensee) submitted request for relief No. RV-06 for the third 10-year inservice testing (1ST) program interval at the Columbia Generating Station (CGS). The licensee requested an alternative test plan in lieu of certain 1ST requirements of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code).
The applicable ASME OM Code for CGS for the third 10-year 1ST interval is the 2001 Edition with 2002 and 2003 Addenda. The CGS third 10-year 1ST interval began on December 13, 2005.
Energy Northwest requested expedited NRC review of the request for relief because the licensee incorrectly scheduled the testing for valve CSP-RV-52. The licensee stated in its letter dated June 9, 2010, that the discrepancy was entered into the corrective action program and an extent of condition review was performed that revealed no similar discrepancies.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(a)(3)(ii),
the licensee requested to extend the test interval for Class 2 pressure relief valve CSP-RV-52 on a one-time basis until restart after refueling outage R20, which is currently scheduled for June 2011, as a proposed alternative to the ASME OM Code requirements. The licensee stated in its relief request that complying with the requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Based on the information provided by the licensee in request for relief No. RV-06, the U.S. Nuclear Regulatory Commission (NRC) staff has determined that the proposed alternative provides reasonable assurance that valve CSP-RV-52 is operationally ready; therefore, the proposed alternative is authorized in accordance with 10 CFR 50.55a(a)(3)(ii) until restart after refueling outage R20, which is currently scheduled for June 2011.
All other ASME OM Code requirements for which relief was not specifically requested and approved in this relief request remain applicable.
J. Parrish
- 2 The detailed results of the NRC staff review are provided in the enclosed safety evaluation. If you have any questions concerning this matter, please contact Mr. F. Lyon of my staff at (301) 415-2296 or by electronic mail at fred.lyon@nrc.qov.
Sincerely, Michael T. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-397
Enclosure:
As stated cc w/encl: Distribution via Listserv
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CLASS 2 PRESSURE RELIEF VALVE CSP-RV-52 REQUEST FOR RELIEF NO. RV-06 ENERGY NORTHWEST COLUMBIA GENERATING STATION DOCKET NO. 50-397
1.0 INTRODUCTION
By letter dated June 9, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML101740075), as supplemented by letter dated June 18, 2010 (ADAMS Accession No. ML101800150), Energy Northwest (the licensee) submitted request for relief No. RV-06 for the third 1O-year inservice testing (1ST) program interval at the Columbia Generating Station (CGS). The licensee requested an alternative test plan in lieu of certain 1ST requirements of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code). The applicable ASME OM Code for CGS for the third 10-year 1ST interval is the 2001 Edition with 2002 and 2003 Addenda. The CGS third 1O-year 1ST interval began on December 13, 2005.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR), paragraph 50.55a(a)(3)(ii), the licensee requested to extend the test interval for Class 2 pressure relief valve CSP-RV-52 on a one-time basis until restart after refueling outage R20, which is currently scheduled for June 2011, as a proposed alternative to the ASME OM Code requirements. The licensee stated in its relief request that complying with the requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
2.0 REGULATORY EVALUATION
The regulations in 10 CFR 50.55a(f), "Inservice testing requirements," require, in part, that ASME Class 1, 2, and 3 components must meet the requirements of the ASME OM Code and applicable addenda, except where alternatives have been authorized pursuant to paragraphs 50.55a(a)(3)(i) or (a)(3)(ii).
In proposing alternatives, a licensee must demonstrate that the proposed alternative provides an acceptable level of quality and safety, or compliance would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Section 50.55a of Enclosure
- 2 10 CFR allows the U.S. Nuclear Regulatory Commission (NRC) to authorize alternatives to ASME OM Code requirements upon making necessary findings. NRC guidance contained in NUREG-1482, Revision 1, "Guidance for Inservice Testing at Nuclear Power Plants," provides alternatives to ASME OM Code requirements which are acceptable.
The NRC's findings with respect to authorizing the alternative to the ASME OM Code are provided in section 3.0 below.
3.0 TECHNICAL EVALUATION
3.1 Relief Request RV-06 3.1.1 ASME Components Affected Containment Supply and Purge (CSP) Relief Valve (RV) CSP-RV-52, Class 2, a 3/4-inch by 1-inch relief valve for tank CSP-TK-51.
3.1.2 ASME OM Code Requirements ASME OM Code, Subsection ISTC, "Inservice Testing of Valves in Light-Water Reactor Nuclear Power Plants," ISTC-5240, "Safety and Relief Valves," states that, Safety and relief valves shall meet the inservice test requirements of Mandatory Appendix I.
ASME OM Code, Mandatory Appendix I, "Inservice Testing of Pressure Relief Devices in Light Water Reactor Nuclear Power Plants," 1-1350, "Test Frequency, Class 2 and 3 Pressure Relief Valves," states, in part, that, (a) to-year Test Interval. Class 2 and 3 pressure relief valves, with the exception of PWR [pressurized-water reactor] main steam safety valves, shall be tested every 10 years, starting with initial electric power generation. No maximum limit is specified for the number of valves to be tested during any single plant operating cycle; however, a minimum of 20% of the valves from each valve group shall be tested within any 48-month interval. This 20% shall consist of valves that have not been tested during the current 1O-year test interval, if they exist.
The test interval for any individual valve shall not exceed 10 years. PWR main steam safety valves shall be tested in accordance with 1-1320.
3.1.3 Licensee's Basis for Requesting Alternative Testing In its letter dated June 1, 2009, and supplemented by letter dated June 18, 2010, the licensee stated, in part, that, During an internal review to verify compliance of testing frequencies for ASME Class 2 and 3 safety relief valves, a scheduling discrepancy was discovered.
- 3 The scheduling for CSP-RV-52 was incorrectly scheduled 48 months after installation instead of 48 months after testing. As a result, the subject valve is required to be tested on or before July 11, 2010, 9 months prior to the next refueling outage (R20). Energy Northwest documented the scheduling discrepancy in the [CGS] corrective action program and performed an extent of condition review that revealed no other relief valve in a similar condition....
Removal and testing of CSP-RV-52 results in 3 inboard vacuum breakers failing open when nitrogen is removed from the valves. This testing is normally performed when CGS is shut down in a mode in which the vacuum breakers are not required to be operable (Mode 4 or 5). At power, the plant would be reliant upon a single valve, the outboard vacuum breakers next to each failed open inboard vacuum breaker, for containment isolation which is considered to be an unnecessary risk to plant personnel and to the health and safety of the public.
Additionally, this action would place the plant in a 72-hour action statement for 3 open vacuum breakers (LCO [limiting condition for operation] 3.6.1.6, Condition A), a time frame that would challenge completing the testing while at power. Based on this, the testing of CSP-RV-52 at power would present an adverse impact on plant operation and may require a plant shutdown to perform testing.
In May 1996 and May 2003, [the valve] was removed from service and bench tested. On both occasions, it passed the as-found test requirement and the valve was re-installed without any repairs. In June 2007, the relief valve was again removed and tested. The valve passed the visual inspection and the set point test, but failed the as-found leakage test (60 bubbles/min vs 20 bubbles/min). It was disassembled for repair and the disc dimensions were found to be undersized. At that point, the relief valve was replaced with the Crosby OMNI Model 9511817D rather than perform repair to the Lonergan Model LCT-13 relief valve.
When removed in May 1996, May 2003, and June 2007, the Lonergan valve was found in good condition both externally and internally. There was no accumulation of corrosion materials within the valve cavity.
The [Crosby OMNI 900 series] relief valve has the same relief set point as the Lonergan [relief valve]. The design flow of the Crosby relief valve is in excess of the requirement for CSP-RV-52 and comparable to the Lonergan [relief valve].
CGS has similar Crosby OMNI 900 Series valves (Model 9511882A) in use (RHR-RV-25 AlB/C). These valves are used in a water application, have been tested since October 2004, and have been installed since May 2005 with no issues. Additionally, Crosby OMNI 900 Series types relief valves are used in various applications throughout the industry. A review of the Equipment Performance and Information Exchange (EPIX) database has not indicated a history of chronic failure with this series of [relief] valves.
- 4 CSP-RV-52 provides overpressure protection for CSP-TK-1, the backup air tank with the nitrogen pressure system for operation of the 3 inboard reactor building to wetwell vacuum breakers.
The valve is located in an area considered a "harsh environment" area for design purposes since the ambient conditions will experience energy changes due to a postulated Loss of Coolant Accident (LOCA) Design Basis Event (DBE) or High Energy Line Break (HELB) DBE.
The relief valve has not experienced a "harsh environment" during its service. It has been installed for 36 months and operated in a controlled, mild environment with small swings in temperature and humidity. The relief valve has been exposed to minimal radiation. The relief valve internals are exposed to air from the Control Air System (CAS) with nitrogen backup. The CAS system is sampled quarterly for air quality and results have met the air quality acceptance criteria of 40 micron maximum particulates, 1.0 ppm [parts per million] maximum hydrocarbons, and _4° F [degrees Fahrenheit] at 100 psig [pounds per square inch gauge] dewpoint. The environment has not accelerated degradation of the relief valve and the environmental conditions have been well below the design qualifications of the relief valve.
The probability that an over-pressure event would challenge the relief valve is very low. The CAS system is regulated with several other relief valves. The likelihood of an over-pressurization of the CAS system simultaneously with all relief valves failing to lift is low. The backup nitrogen tanks also have an additional relief valve. The likelihood of an over-pressurization of the backup nitrogen tanks simultaneously with their relief valve failing to lift is low. In the event of an over-pressurization of significance, piping may rupture and the CAS air or nitrogen within the CSP system would disperse into the reactor building.
Under such conditions..., the inboard reactor building to wetwell vacuum breakers would lose pressure and open. The event would have no effect on the outboard reactor building to wetwell vacuum breakers (CSP-V-7/8/1 0) and they would remain closed.
Based on the low probability and the medium level consequence, the overall risk is low.
3.1.4 Licensee's Proposed Alternative Testing (as stated)
Energy Northwest proposes to extend the 48-month test interval [on a one-time basis] for [relief valve] CSP-RV-52 by approximately 11 months to allow for testing during the next scheduled refueling outage.
3.2
NRC Staff Evaluation
The licensee is in its third 10-year 1ST program interval which commenced on December 13, 2005. The licensee has proposed an alternative in lieu of the requirements found in the 2001 Edition through 2003 Addenda of the ASME OM Code, ISTC-5240 and Mandatory Appendix I,
- 5 1-1350(a), for relief valve CSP-RV-52. ASME OM Code, Appendix I, 1-1350(a) requires Class 2 and 3 pressure relief valves to be tested every 10 years, with a minimum of 20 percent of the valves from each group tested within any 48-month interval. CSP-RV-52 is the only relief valve within its respective valve group and, therefore, must be tested every 48 months. Specifically, the licensee proposes to extend the 48-month test interval on a one-time basis for CSP-RV-52 by approximately 11 months to allow for testing during the next scheduled refueling outage.
The NRC staff has reviewed the information provided by the licensee to determine if it is acceptable to extend the test interval for relief valve CSP-RV-52. In its request for relief, the licensee stated that relief valve CSP-RV-52 has maintained a good in-service performance level. Previous ASME OM Code tests found the valve to be in good condition with no adjustments required. The latest test completed in June 2007 found the valve to be in good condition and it lifted at the required set point. However, the valve did not pass the strict leakage test. Subsequent maintenance identified undersized disc dimensions. The relief valve was replaced rather than repaired due to valve obsolescence. The replacement relief valve was a Crosby OMNI 900 Series relief valve. The replacement relief valve was determined to be a one-for-one replacement.
Relief valve CSP-RV-52 is located in a harsh-duty design area w~lich, under normal conditions, is considered a mild environment with minimal radiation exposure. The relief valve has never experienced a harsh environment. The location is not conducive to accelerating degradation.
This assessment is supported by the excellent maintenance history record of the previously installed Lonergan relief valve Model LCT-13. Additionally, the Lonergan valve was found to be in good condition both externally and internally when removed from service for testing and no accumulation of corrosion materials was found within the valve cavity.
An industry performance history check of the Crosby OMNI 900 Series relief valve was completed by the licensee by searching the Institute of Nuclear Power Operations (INPO) EPIX database. The licensee found no significant failures of this type of relief valve. The NRC staff confirmed that there were no significant failures of Crosby OMNI 900 Series relief valves mentioned in the EPIX database. The licensee also noted that it has installed similar model Crosby OMNI 900 series relief valves in a water application. Although the similar model valves are being used in water applications in lieu of gas, the similar model valves have not had any issues since their May 2005 installation.
The licensee performed a risk evaluation and determined that the overall risk that an overpressure event would challenge relief valve CSP-RV-52 is low. The valve has a low probability of failure with medium-level consequences. This evaluation, coupled with the industry historical performance check of the Crosby OMNI 900 Series relief valve and its installation in a relative mild environment, gives reasonable assurance that the valve will maintain operational readiness over the requested 11-month extension period. Testing the valve online at the required 48-month interval places the plant in a challenging 72-hour LCO.
The plant system would be reliant upon a single valve for containment isolation, which is considered to be an unnecessary risk to plant personnel and to the health and safety of the public. This represents a hardship or unusual difficulty without a compensating increase in the level of quality and safety.
- 6
4.0 CONCLUSION
The NRC staff concludes that the alternative proposed by the licensee in request for relief No RV-06 provides reasonable assurance that valve CSP-RV-52 is operationally ready.
Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(a)(3)(ii), and is in compliance with the ASME OM Code's requirements. Therefore, the proposed alternative is authorized in accordance with 10 CFR 50.55a(a)(3)(ii) until restart after refueling outage R20, which is currently scheduled for June 2011.
All other ASIVIE OM Code requirements for which relief was not specifically requested and approved in the subject request for relief remain applicable.
Principal Contributor: M. Farnan Date: July 2, 2010
J. Parrish
- 2 The detailed results of the NRC staff review are provided in the enclosed safety evaluation. If you have any questions concerning this matter, please contact Mr. F. Lyon of my staff at (301) 415-2296 or by electronic mail at fred.lyon@nrc.gov.
Sincerely,
/RA!
Michael T. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-397
Enclosure:
As stated cc w/encl: Distribution via Listserv DISTRIBUTION:
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