05000333/LER-2009-008
| James A. Fitzpatrick Nuclear Power Plant (Jaf) | |
| Event date: | 1-7-2009 |
|---|---|
| Report date: | 01-11-2010 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| Initial Reporting | |
| 3332009008R00 - NRC Website | |
BACKGROUND
The High Pressure Coolant Injection (HPCI) System [EllS System Identifier: BJ] is comprised of various components which include pumps, valves, piping, and instrumentation. The function of the HPCI system is to ensure that the reactor is adequately cooled to limit fuel clad temperature in the event of a small break loss of coolant accident (LOCA) which does not result in rapid depressurization of the reactor vessel. The HPCI system permits the plant to be shutdown while maintaining sufficient reactor vessel water inventory until the reactor vessel pressure is low enough to allow the Low Pressure Coolant Injection (LPCI) System [EMS System Identifier: BO] or Core Spray (CS) System [EllS System Identifier: BM] to maintain core cooling.
The HPCI TURBINE STEAM SUPPLY STOP VALVE (23H0V-1) [EllS Component Identifier: V] is a hydraulically operated valve that is either fully closed (following turbine trip and in the standby condition) or full open (during turbine operation). Its safety function is to open once sufficient hydraulic pressure is developed, thus allowing steam to supply the HPCI turbine. 23H0V-1 is also designed to close automatically and trip the HPCI turbine in the event of a turbine overspeed, high turbine exhaust pressure, low pump suction pressure, or low steam supply pressure.
EVENT DESCRIPTION
On September 17, 2009, a root cause analysis (RCA) was performed as a result of the 23H0V-1 failure to meet the In-service Testing (IST) opening stroke time during a maintenance activity performed earlier in the year in January. The RCA discovered that a change performed on August 10, 2005, raised the opening stroke time reference value from 19.45 seconds to 22.12 seconds. This resulted in the upper time limit being increased from 24.3 seconds to 27.6 seconds. In order to change reference values, the ASME OM code requires that the cause of the deviation be understood and documented. In this case, the change did not contain the technical justification that is required in accordance with the ASME OM Code. As such, subsequent testing of 23HOV-1 stroke times that were within the new (incorrect) values, but outside the old (correct) values was not identified as causing 23HOV-1 and the HCPI System inoperable.
The first HPCI surveillance test using the new stroke time acceptance criteria was performed in November, 2005. From November 1, 2005, until January 31, 2009, the Turbine Steam Supply Stop Valve stroke times were tested fourteen times. In four of those tests, the opening stroke time was above the original upper time limit. The failure of 23H0V-1 to meet the IST acceptance criteria should have resulted in declaring the HPCI system inoperable as required by ASME OM code. JAF Technical Specifications (TS) require the plant to be in MODE 3 within 14.5 days if HPCI is inoperable as long as the low pressure Emergency Core Cooling (ECCS) injection/spray system is operable or within 84 hours9.722222e-4 days <br />0.0233 hours <br />1.388889e-4 weeks <br />3.1962e-5 months <br /> if one subsystem of ECCS injection/spray is also inoperable. The failure to meet ASME code acceptance criteria for the stroke time was not previously identified since the valve met the revised IST acceptance criteria and it had not yet been discovered that the change was performed in error.
The event is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B), "Any operation or condition which was prohibited by the plant's Technical Specifications..." because during the time period described, the HPCI system was inoperable longer than allowed by the TS completion times.
EVENT ANALYSIS
Following a scheduled HPCI outage during the month of January 2009, post maintenance testing was being performed to ensure that the HPCI system was operable prior to returning it to service. To verify operability, Operations personnel performed the HPCI Quick Start Procedure (ST-4N) which requires stroking of 23H0V-1 and verifying the stroke times meet acceptance criteria as established by the IST program. The first attempt at performing this procedure on January 23, 2009, was unsuccessful. As a result, personnel began troubleshooting the HPCI system for likely causes. Troubleshooting and repair lasted several days until January 31, 2009, when testing was able to verify that the HPCI system was repaired. On January 31, 2009, at approximately 12:40 pm, the HPCI system was returned to service.
As a result of the failure to stroke within the required time, an RCA focusing on the mechanistic failure of the turbine stop valve was performed. The analysis discovered that the IST opening stroke time had been incorrectly changed on August 10, 2005. The reference value change (IST-2005-001) documented that the change to the opening stroke time reference value was performed in accordance with AMSE 0M-10, Section 4.2.1.8 (Paragraph 3.5). Paragraph 3.5 is intended to allow the owner to establish an additional set of reference values when a particular test can have different sets of test conditions. Paragraph 3.5 was misapplied to the reference value change because an additional set of reference values was not being established. Instead, the existing reference value was improperly raised from 19.45 seconds to 22.12 seconds based on trend data that showed the stroke time was trending towards the upper Code acceptance limit. The change in reference value corresponded to a change in the opening stroke time upper limit from 24.3 seconds to 27.6 seconds.
The HPCI Turbine Stop Valve opening stroke time exceeded the pre-2005 Code acceptance criterion on four occasions between the date IST-2005-001 was implemented and January 2009. Per ASME OM Code Article ISTC-5143(a) "If a valve fails to exhibit the required change of obturator position or exceeds the limiting values of full stroke time [see ISTC-5141(b)], the valve shall be immediately declared inoperable.
The ASME OM Code allows for establishing Limiting Values that are greater than acceptance criteria, however, in the case of 23H0V-1 no such values were previously established. When no Limiting Values are established, the stroke time becomes the Limiting Value for the purposes of OM Code Compliance. Since the stroke times measured between 2005 and 2009 exceeded the pre-change upper time limit, the valve should have been declared inoperable.
Between February 2009 and November 2009, additional review of the IST stroke time change was performed to include consultation with an industry subject matter expert on the IST program. It was originally believed that the TS start time of 60 seconds could be considered the limiting time for IST purposes. This conclusion was determined to be in error and it was subsequently determined this condition was reportable per 10 CFR 50.73.
CAUSE OF EVENT
The cause of this event is attributed to personnel error in the implementation of the IST program. Specifically, a section of the ASME OM code which allows establishing a new set of reference values under a different set of test conditions was mis-applied to allow changing an existing reference value.
The reference value change masked an overall degrading trend in the valve opening stroke time because it adjusted the reference opening time to account for valve stroke within the previous 2-1/2 years without determining the cause of the increasing stroke time trend. This change was technically inaccurate in that it was performed as a re-baseline without determining the reason for the change in stroke time as required by the ASME OM code.
EXTENT OF CONDITION
An extent of condition review was performed by the Engineering department to identify any other potentially degrading components that acceptance criteria had been changed in order to accept a degrading trend. This review did not find any other instances of improper changes to IST acceptance criteria.
FAILED COMPONENT IDENTIFICATION
Manufacturer:� AMETEK Model No.: M67-05774-V NPRDS Manufacturer Code:� A365 NPRDS Component Code: V FitzPatrick Component Id:� 23H0V-1 CORRECTIVE ACTIONS (All Complete) 1. An extent of condition review was performed to identify any other potential degrading components within the purview of the IST program. See Extent of Condition section.
2. The. IST program supervisor and program owner have been coached and understand the nature of the cause of this event.
3. A technical basis for 23H0V-1 was developed to include adequate stroke time limitations. This was accomplished by engineering evaluation 1ST-2009-017 which established Limiting Values for 23H0V-1.
ASSESSMENT OF SAFETY CONSEQUENCES
Actual Consequences There were no actual industrial, radiological, or nuclear safety consequences during or as a result of the described period of HPCI inoperability. However, the improper changes to the IST reference stroke time masked a degrading trend in opening stroke times that eventually resulted in the failure of 23H0V-1 to open during testing.
During the period between 2005 and 2009, the HPCI System was routinely tested under the Surveillance Test Program to confirm its OPERABILITY. Those tests were completed satisfactory or the system was declared INOPERABLE and the deficiency was corrected.
The surveillance tests demonstrated that the HPCI system was capable of starting on demand, supplying cooling water to the core at rated pressure and flow rates, and was capable of stopping and restarting. Based on that information, Engineering has determined, that prior to the maintenance activities conducted in January 2009, the HPCI system would have started and injected to the core, if required, within the required system initiation time of 60 seconds and would have been able to perform its safety function during the eight hour mission time assumed in the JAF accident analyses. Therefore, this condition did not constitute a safety system functional failure.
SIMILAR EVENTS
A review of operating experience at JAF was performed to identify any similar events involving personnel errors in the implementation or interpretation of the ASME OM code. While there have been human performance errors, there have been no other instances of inappropriate changes based on misunderstanding the ASME OM Code.
REFERENCES
1. JAF Condition Reports: CR-JAF-2009-00350, CR-JAF-2009-03964, CR-JAF-2009-00284, CR-JAF-2009-00286 2. Root Cause Analysis Report: 23H0V-1 Failed To Open (CR-JAF-2009-00350) 3. JAF Updated Final Safety Analysis Report: Section 6.4.1, High Pressure Coolant Injection System 4. JAF Technical Specifications 3.5.1, Emergency Core Cooling Systems — Operating 5. JAF Procedure: SEP-IST-007, Pump and Valve 1n-service Testing Program 6. JAF Procedure: ST-4N, HPCI QUICK-START, INSERVICE, AND TRANSIENT MONITORING TEST (1ST) FOIA/Privacy Service Branch (T-5 F52), U.S. Nuclear Regulatory Commission,LICENSEE EVENT REPORT (LER) Washington, DC 20555-0001, or by internet e-mail to infocollects@nrc.gov, and to
- the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150- 0104), Office of Management and Budget, Washington, DC 20503. If a means used number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
4. TITLE
High Pressure Coolant Injection System Inoperable Longer Than Allowed By Technical Specifications 5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVED FACILITY NAME . DOCKET NUMBER
MONTH DAY YEAR YEAR MONTH DAY YEARSEQUENTIAL REV NUMBER NO N/A
FACILITY NAME DOCKET NUMBER09 17 2009 2010 - 001�- 00 01 11 2010 N/A 9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 10 CFR : (Check all that apply) 20.2201(b) - 20.2203(a)(3)(i) - 50.73(a)(2)(i)(C) = 50.73(a)(2)(vii) - _ 20.2201(d) _ 20.2203(a)(3)(ii) _ 50.73(a)(2)(ii)(A) _�50.73(a)(2)(viii)(A) 01 20.2203(a)(1) 20.2203(a)(4) = 50.73(a)(2)(ii)(B) = 50.73(a)(2)(viii)(B) - 20.2203(a)(2)(i) - 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) - 50.73(a)(2)(ix)(A) - -� 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 10. POWER LEVEL - -� - -20.2203(a)(2)(iii) _ 50.36(c)(2) _ 50.73(a)(2)(v)(A) _ 73.71(a)(4) _ 20.2203(a)(2)(iv) 50.46(a)(3)(ii) _ 50.73(a)(2)(v)(B) - 73.71(a)(5) _ - 100 _1 20.2203(a)(2)(v) _ 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C) _ OTHER - _ 2 0.2203(a)(2)(vi) 50.73(a)(2)(i)(B) _ 50.73(a)(2)(v)(D) Specify in Abstract below or in MANU- REPORTABLE MANU- REPORTABLECAUSE SYSTEM COMPONENT CAUSE SYSTEM COMPONENTFACTURER TO EPIX FACTURER TO EPIX 14. SUPPLEMENTAL REPORT EXPECTED 15. EXPECTED MONTH DAY YEAR
SUBMISSION
- ,Yes�(If yes, complete 15. EXPECTED SUBMISSION DATE)� 14 NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) On September 17, 2009, a root cause analysis of the High Pressure Coolant Injection (HPCI) TURBINE STEAM SUPPLY STOP VALVE (23HOV-1) failure in January 2009 discovered that a previous change to the In-service Testing (1ST) opening stroke time reference value had been incorrectly raised from 19.45 seconds to 22.12 seconds. The change, which was made on August 10, 2005, was not properly evaluated and did not contain adequate technical justification in accordance with the ASME OM Code. The cause of this event is attributed to personnel error in the implementation of the IST Program. Specifically, the opening stroke time reference value was revised without the appropriate technical justification. The change masked a degrading trend in the 23H0V-1 opening stroke time and resulted in the inoperability of the HPCI system.
The condition is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B), "Any operation or condition which was prohibited by the plant's Technical Specifications..." because during the time period described, the HPCI system was inoperable longer than allowed by the TS completion times. Although the HPCI system was technically inoperable prior to the maintenance activity, the HPCI system would have started and injected to the core, if required, within the required system initiation time of 60 seconds, and would have been able to perform its safety function during the eight hour mission time assumed in the JAF accident analyses.