05000321/LER-2006-003
| Docket Number(S) | |
| Event date: | 10-12-2006 |
|---|---|
| Report date: | 12-06-2006 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| Initial Reporting | |
| 3212006003R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor Energy Industry Identification System codes appear in the text as (EIIS Code XX).
DESCRIPTION OF EVENT
The 11 Safety Relief Valves (SRVs) (EIIS Code SB), which are located on the four main steam lines within the drywell between the reactor vessel and the inboard main steam isolation valves (MSIV EIIS Code SB), are required during Modes 1, 2, and 3 to prevent over pressurization of the reactor vessel. Per Technical Specification (TS) SR 3.4.3.1, the valves are tested in accordance with the In-service Testing Program to verify the safety function lift setpoints are within the specified limits.
outage, the eleven SRVs were removed and bench-tested. Test results revealed that three of the eleven Unit 1 SRVs removed during the spring 2004 outage actuated at pressures greater than 34.5 psig above the setpoint. Four of the eleven Unit 2 SRVs removed during the spring 2005 outage actuated at pressures greater than 34.5 psig above the setpoint according to test results. (An additional Unit 1 valve that had been removed during a mid-cycle shutdown was tested in conjunction with the Unit 2 valves in 2005 and actuated at pressures greater than 34.5 psig above the setpoint.) Finally, three of eleven Unit 1 SRVs removed during the spring 2006 outage actuated at pressures greater than 34.5 psig above the setpoint according to test results.
These events should have been reported as a condition prohibited by Technical Specifications based on guidance in NUREG-1022 revision 2, issued in 2000, section 3.2.2 example 3. However, in 1993, a determination had been made that Licensee Event Reports (LERs) on SRV setpoint drift due to corrosion-induced bonding were not required.
During an NRC Baseline Inspection, NRC inspectors identified the multiple SRV setpoint drift as a condition prohibited by TS per 10 CFR 50.73 (a)(2)(i)(B). Because an LER had not been written to formally notify the NRC of this condition, the NRC issued a non-cited violation (NCV) in the NRC Integrated Inspection Report for Plant Hatch dated October 30, 2006.
The basis for Plant Hatch not reporting multiple SRV setpoint drift events developed as follows.
SRV setpoint drift had been an issue due to corrosion-induced bonding of the pilot disc to the seat.
The Boiling Water Reactor Owners' Group (BWROG) had been involved with this issue since 1983. Following a BWROG recommendation in May 1990, Plant Hatch designed and obtained NRC concurrence on a pressure switch actuation system as a non-credited defense-in-depth approach to addressing SRV setpoint drift (reference NRC SER dated July 24, 1992). This system provides a redundant, independent method (i.e., electrical signal) to open the SRVs. The system was procured to Class lE environmental and seismic standards. This system was installed on both Units 1 and 2 between 1992 and 1993.
On April 1, 1993, the as-found test results for five of the Unit 1 SRVs revealed setpoint drift in excess of the 3 percent tolerance specified in the TS. According to the general rules of usage for TS, unless there is sufficient evidence to suspect otherwise, a problem such as a failed surveillance that results in TS inoperability is assumed to occur at the time of discovery; in other words, the failure is not typically assumed to have existed prior to that time. Therefore, the SRV setpoint drift in excess of the 3 percent tolerance specified in the TS did not represent a condition prohibited by Technical Specifications. NUREG-1022, Revision 0, "Licensee Event Report System," dated September 1983, was utilized as guidance at that time to understand reportability requirements.
Though the multiple setpoint drift of SRVs (or similar condition) was not addressed in NUREG- 1022, Revision 0 as a reportable event, a voluntary LER was written (ref: LER 1-1993-002, dated April 21, 1993). The voluntary submittal represented an effort to communicate information to assist in the ongoing BWROG efforts to address the SRV setpoint drift issue. Following the safety assessment, the analysis concluded that there was no adverse impact on nuclear safety. As a result of the installation of the electronic actuation system for the SRVs, and the finding of no safety impact, it was stated in the LER that the submittal of further voluntary reports regarding SRV setpoint drift in the future was not anticipated.
Subsequent to the referenced 1993 LER, NUREG-1022, Revision 1, dated January 1998, was issued. This revision cites a specific example of multiple occurrences of SRV setpoint drift in Section 3.2.2, Example 5, "Multiple Test Failures." This discussion concludes that, "...the existence of similar discrepancies in multiple valves is an indication that the discrepancies arose over a period of time. Therefore, the condition existed during plant operation and the event is reportable under 10 CFR 50.73(a)(2)(i)(B)." Revision 2 to NUREG-1022 (October 2000) also includes this example. This interpretation differs from the previous position that the discrepancies should be assumed to occur at the time of discovery. Therefore, reporting of multiple occurrences of SRV setpoint drift should have ensued following the issuance of NUREG-1022, Revision 1 in 1998.
CAUSE OF EVENT
This event was caused by personnel error in the organizations responsible for determining event reportability. Determination of reportability for condition reports (CRs) involving multiple occurrences of SRV setpoint drift that were generated after January 1998 (NUREG-1022 Rev. 1 issuance) failed to identify that an LER was required. Reliance on the 1993 determination resulted in failure to adequately research applicable regulatory guidance, specifically NUREG-1022.
RC FORM 366A (1-2001) L A contributing cause is as follows. Upon issuance of NUREG-1022, Rev. 1 (January 1998) and Rev. 2 (October 2000) inadequate SNC review failed to identify changes, specifically the new example on "Multiple Test Failures," that had potential impact on the reporting of SRV setpoint drift events.
REPORTABILITY ANALYSIS AND SAFETY ASSESSMENT
This event is reportable per 50.73(a)(2)(i)(B) because an event occurred which is prohibited by Technical Specifications. Specifically, multiple test failures of SRVs is defined as reportable in NUREG 1022, Revision 2 dated October 2000, in section 3.2.2 example 3 titled "Multiple Test Failures.
The function of the SRVs is to limit the peak pressure in the nuclear system such that it will not exceed the reactor coolant system pressure safety limit, reference Technical Specification 2.1.2, and the applicable ASME code overpressure limit for the reactor coolant pressure boundary (RCPB). The most severe pressurization transient is closure of all MSIVs, followed by a reactor scram on high neutron flux. Analysis of this event, using the referenced test results for SRV actuation pressures in 2004 through 2006, has demonstrated that the peak pressure results meet the referenced applicable regulatory acceptance criteria.
Based on this analysis, it is concluded that this event had no adverse impact on nuclear safety.
CORRECTIVE ACTIONS
1. Personnel involved in reportability determinations have been re-instructed on the issues surrounding this event. The need to use correct up-to-date references was stressed.
Additionally, the need to verify historical justifications was discussed. This corrective action is complete.
2. The change management aspect discussed in the cause analysis section relates to the issuance of NUREG-1022, Revision 1 in 1998. Since that time, organizational changes have resulted in a broader, fleet-wide approach to regulatory issues. In addition, the NRC now uses the Regulatory Issue Summary (RIS) vehicle to disseminate information to licensees. Future changes to NUREG-1022 will likely be issued to licensees via a RIS. SNC has administrative controls to assure the information in a RIS is evaluated for any impacts on SNC activities.
Finally, SNC has established a fleet Operating Experience program that would also target changes to NUREG-1022 for review and evaluation. Based on these factors, corrective action for the change management aspect of this event is complete.
366A (1-2001 NRC FORM 366A� U.S. NUCLEAR REGULATORY COMMISSION (1-2001) �
ADDITIONAL INFORMATION
Other Systems Affected: No systems other than those already mentioned in this report were affected by this event.
Commitment Information: This report does not create any new permanent licensing commitments.
Previous Similar Events:
There are no other similar events in the past two years in which a failure to report has been identified.