05000528/LER-2004-008
| Docket Number07 19 2004 2004 - 008 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 5282004008R00 - NRC Website | |
1. REPORTING REQUIREMENT(S):
APS is reporting this condition pursuant to 10 CFR 50.73(a)(2)(i)(B) as a violation of Technical Specification 3.6.3.
Technical Specification 3.6.3 requires that each containment isolation valve (CIV) be operable in modes 1, 2, 3 and 4 to meet the containment isolation time limits assumed in the safety analysis. From May 24, 2004 at approximately 17:22 MST (after completing maintenance on valve 1JHPBUV0004), to July 19, 2004 at 16:18 MST (entered TS action), containment isolation valve 1JHPBUV0004 did not meet the requirements of TS 3.6.3.
2. DESCRIPTION OF STRUCTURE(S), SYSTEM(S) AND COMPONENT(S):
Containment hydrogen control supply isolation valve (1JHPBUV0004) is an automatic isolation valve designed to close (in approximately 12 seconds) without operator action following an accident. Two CIVs are provided in series such that no single credible failure or malfunction will result in the loss of isolation or containment leakage that exceeds the limits assumed in the safety analysis.
Upon receiving a containment isolation actuation signal (CIAS), the CIVs in the system will isolate the hydrogen recombiner inlet and outlet to containment. The inlet valves also serve as the inlets to the hydrogen purge exhaust unit. (EIIS Code: BD, BB, JM)
3. INITIAL PLANT CONDITIONS:
On July 19, 2004, at approximately 16:18 Mountain Standard Time (MST), Unit 1 was in Mode 1 at 100 percent power.
There were no other major structures, systems, or components that were inoperable at the start of the event that contributed to the event. There were no failures that rendered a train of a safety system inoperable and no failures of components with multiple functions were involved.
4. EVENT DESCRIPTION:
On May 24, 2004, a preventive maintenance (PM) activity was performed on valve 1JHPBUV0004. During the PM, a rotor cam was reset to meet the PM's instruction criteria for the rotor's "as left condition". The valve was stroke tested using instructions from 73ST-9XI08, "HP Valves - Inservice Test" with satisfactory results. The valve was determined to be operable and returned to service.
On June 10, 2004, while performing routine status display checks, plant operators noticed the Safety Equipment Actuation Status (SEAS) was illuminated even though valve 1JHPBUV0004 was in the closed position as indicated on the valve's handswitch and the Emergency Response Facility Data Acquisition Display System (ERFDADS) computer. After verifying the valve was closed, a work order was generated to troubleshoot and correct the indication problem.
Troubleshooting began on July 19, 2004. A resistance reading on the SEAS contact determined the contact was open when the contact should be closed. Maintenance personnel identified one of the rotor cams, which actuates a bank of limit switches in the motor operator, was approximately one valve hand wheel turn outside of its design setpoint. The cam was oriented such that the limit switch in this bank would actuate opposite of the desired control logic for the SEAS. Additionally, if the valve was in the open position, the valve would not close with a CIAS. The valve was declared inoperable and Unit 1 entered Limited Condition for Operation (LCO) 3.6.3 Condition A, (Containment Isolation) and LCO 3.6.7 Condition A (Hydrogen Recombiner B) and LCO 3.3.10 Condition A (Hydrogen Analyzer B).
This condition has been documented in the corrective action program. The event did not result in the release of radioactivity to the environment and did not adversely affect the safe operation of the plant or health and safety of the public.
5. ASSESSMENT OF SAFETY CONSEQUENCES:
Containment penetrations typically have two isolation barriers. These isolation devices are either passive or active (automatic). In general, two barriers in series are provided for each penetration so that no single credible failure or malfunction of an active component can result in a loss of isolation or leakage that exceeds limits assumed in the safety analysis. Containment isolation valves form part of the containment pressure boundary and are designed to close on an automatic isolation signal. The Design Basis Accidents that result in a release of radioactive material within containment are the Loss of Coolant Accident (LOCA), a Main Steam Line Break (MSLB), a feedwater line break, and a control element assembly ejection accident. In the analysis for each of these accidents, it is assumed that CIVs are either closed or function to close within the required isolation time.
The specific equipment that is isolated by 1JHPBUV0004 is the B Train hydrogen recombiner, containment hydrogen monitor, and hydrogen purge exhaust.
This equipment is designed for post-accident conditions and returns the effluent back to containment. Therefore, there is not a concern with a potential unmonitored radioactive release pathway. The indicated position for both containment isolation valves 1JHPBV0002 and 1JHPBUV0004 was the closed position from May 24, 2004 to July 19, 2004. Although the potential existed for 1JHPBUV0004 to be opened, the inboard containment isolation valve, 1JHPBUV0002, was operable and capable of isolating the containment penetration during a CIAS condition. Therefore, the safety impact for this event was minimal in that the system design and station procedure controls were in place to isolate the system to mitigate the consequences of radioactive material release.
There were no actual safety consequences as a result of this condition, the condition would not have prevented the fulfillment of the safety function, and the condition did not result in a safety system functional failure as defined by 10 CFR50.73 (a) (2) (v).
6. CAUSE OF THE EVENT:
The cause of the event is personnel error during the setting of the limit switches on the motor operator following maintenance on May 24, 2004. Additionally, the surveillance procedure (73ST-9X108) used to determine operability only verified the closure time of valve 1JHPBUV0004 and did not verify the CIAS function required by the motor operator valve program.
No unusual characteristics of the work location (e.g., noise, heat, poor lighting) directly contributed to this event.
7. CORRECTIVE ACTIONS:
Contact configuration was corrected on July 23, 2004 (11:36 MST), and valve 1JHPBUV0004 was declared operable. Based on the preliminary results from the investigation the following corrective actions have been taken or are planned to prevent recurrence:
- PM Task will be changed to specify retest as required by 39DP-9ZZ04, "Valve Service Maintenance — Motor Operated Valves", which requires the verification of the contact configuration and light indication with the valve stroke test.
- Training will include this event during the quarterly Industry Events for Maintenance Personnel.
- Operator Requalification Training will include this event during simulator cycle 5 training.
- Engineering will evaluate moving the contact function for SEAS and CIAS from rotor 1AS3 to 1A56 to reduce the potential for configuration errors.
Any additional corrective actions taken as a result of the investigation of this event will be implemented in accordance with the APS corrective action program. If information is subsequently developed that would significantly affect a reader's understanding or perception of this event, a supplement to this LER will be submitted.
8. PREVIOUS SIMILAR EVENTS:
A similar event occurred after Unit 3's seventh refueling outage where the CIAS function of 3JHPAUV0001 was disabled due to an incorrect control wire configuration. This event is documented on LER 99-001-00.
9. ADDITIONAL INFORMATION:
None.