05000247/LER-2003-002
| Indian Point Unit 2 | |
| Event date: | 04-22-2001 |
|---|---|
| Report date: | 05-20-2003 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2472003002R00 - NRC Website | |
Note: The Energy Industry Identification System Codes are identified within the brackets {}.
DESCRIPTION OF EVENT
On March 21, 2003, at 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br />, with steady state reactor power at 100%, Indian Point Energy Center (IPEC) System Engineering determined that the both trains of the boric acid storage system (BASS) {CB} were inoperable and remained so for 102.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> from April 22 to April 26, 2001. Technical Specification (TS) 3.2.B.3 requires one flow path from the BASS to the reactor coolant system (RCS) {AB}. TS 3.2.C.2 allows this flow path to be inoperable for a period of up to 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> before going to hot shutdown so the plant was in a condition prohibited by technical specifications for 54.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. Condition Report (CR) CR-IP2-2003-01681 was written in Entergy's Corrective Action Program.
The reportable event was discovered during an extent of condition review from a February 26, 2003 event documented in CR-IP2-2003-01121. The CR identified the inability to verify a boric acid flow path to the core when using the 22 Boric Acid transfer pump (BATP) {P) aligned to the blender. TS 3.2.C.2 was entered and the 21 BATP was aligned as immediate corrective action. Subsequent investigation revealed that 2-inch manual Grinnell Saunders diaphragm valve {V} 370 had failed due to the incorrect (upside down) installation of the fingerplate in the bonnet assembly.
The valve opens and closes by respectively lifting and compressing a diaphragm against a wear in the valve body. The valve contains a finger plate which is situated above the diaphragm. The fingers match the curve of the diaphragm when the valve is in the open position and as a guide for the diaphragm compressor.
When installed upside down, the fingers cut into the diaphragm when it is opened and obstruct movement. In this event, the diaphragm was torn in the middle by the fingers. The review found that Work Order 00-13327 in March 2001 was when the diaphragm was installed erroneously. Grinnell had revised its maintenance instruction manual to indicate the fingerplate should be installed with the dome side facing into the bonnet. During this event, Maintenance Procedure VDI-B-001A and the Work Order Step List had steps to verify fingerplate installation. The second verification also had requirements for a QA signature. These steps were not followed as required. The actual time of the failure was not identified since the typical boration evolution involves injection of several gallons of borated water and low flow operation could be masked under this condition since the failed valve would allow some flow to pass. For assessment, the actual flow rate was not quantified and the valve was assumed to have failed at the time of maintenance.
An extent of condition review was done. The review identified 468 Grinnell Saunders diaphragm valves (not all the valves utilize a fingerplate for valve stem operation). The plant systems that have these diaphragm valves were reviewed for critical functions. The boration flow path of Chemical Volume Control System (CVCS) {CB} was the most critical. Five additional Grinnell Saunders diaphragm valves in the CVCS were selected for verification of fingerplate installation which was completed visually. The valves were satisfactory.
CAUSE OF EVENT
The apparent cause of the event was human error in reassembling valve 370 following Preventive Maintenance.
CORRECTIVE ACTIONS
The following corrective actions have been performed under Entergy's Corrective Action Program to address the cause and prevent recurrence:
1. Valve 370 bonnet assembly was replaced with a new bonnet assembly, which includes a new diaphragm.
2. A satisfactory visual examination was completed on 5 selected Grinnell Saunders diaphragm valves to verify correct fingerplate installation.
3. Revised Maintenance Procedure VDI-B-001-A to include steps for Grinnell Saunders diaphragm valve bonnet replacement. This eliminated the need for Work Step List and reduces the possibility of a human error.
EVENT ANALYSIS
These conditions are reportable under 10 CFR 50.73(a)(2)(i)(B),any event or condition that was prohibited by the plant Technical Specifications. The plant boric acid transfer pump train was tagged out of service. The 102.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> from April 22 to April 26, 2001 was the only period greater than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. The plant was in a condition outside Technical Specifications after 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> into this outage. The condition is not otherwise reportable since CVCS is not relied upon to perform a safety function.
PAST SIMILAR EVENTS
In the past two years, Licensee Event Reports (LER) 01-04 identified a missed TS surveillance due to human error and LER-01-05 identified a failure to meet TS requirements for low temperature overprotection due to human error.
EVENT SAFETY SIGNIFICANCE
These conditions had no significant effect on the health and safety of the public.
The CVCS had alternate means to provide borated water to the RCS from refueling water storage tank (RWST) {CP} {TK) and is not credited with any post accident function. The only function involving CVCS is the dilution event postulated during refueling, startup, and operation. In all cases, Operator action in response to plant signals is depended upon to terminate primary water dilution and subsequently reborate. The RWST remained available as a borated water source during the event.