05000456/LER-2002-003
| Ii) Docket (2) Ler Number Od Page C4 | |
| Event date: | 09-11-2002 |
|---|---|
| Report date: | 11-26-2003 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) |
| Initial Reporting | |
| 4562002003R01 - NRC Website | |
14. SUPPLEMENTAL REPORT EXPECTED
X NO
15. EXPECTED
SUBMISSION
DATE
DAY
N/A
B. Description of Event:
There were no structures, systems, or components inoperable at the start of the event that contributed to the event.
The surveillance requirement (SR) for verifying that the isolated loop boron concentration is greater than or equal to the required shutdown margin (SDM) boron concentration of the unisolated portion of the reactor coolant system (RCS) within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> prior to opening the hot or cold leg loop stop isolation valve (LSIV) in the isolated loop (SR 3.4.18.2) has not been complied with during refueling outages at Braidwood since approximately 1995. A specific surveillance procedure has not existed to ensure the requirements of SR 3.4.18.2 are followed. Instead, the operating procedure for restoring a RCS loop to service (SWOP RC-8, "Restoring a Reactor-Coolant Loop tp Service7Lhas_been relied upon as the implementing procedure to ensure Compliance with SR 3.4.18.2. The key procedure step (P.3) states, "Betermiiie that the Boron Concentration in the Isolated RCS Loop is greater than or equal to the Required Shutdown Margin boron concentration of the unisolated portion of the RCS. (This must be determined within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> prior to opening the Loop Stop Valves.)" A note preceding this step states "Loop Boron Concentration can be inferred from samples of fill source during loop fill. As long as no actions to dilute the isolated loop occur between loop fill and opening of stop valves, these results equate to Loop Boron Concentration.
This note was added to BwoP RC-8 in 1995. Before the note was added to the procedure, the RCS loop boron concentration was controlled by a chemistry procedure and was required to be determined within the TS SR time requirement prior to opening the RCS loop isolation valves. The RCS loop boron samples were locally obtained from a pressure tap on the loop flow transmitters. The chemistry procedure was referenced in SWOP RC-8, but this reference was removed in the 1995 procedure revision.
The accompanying 10 CFR 50.59 screening for the procedure change determined that an evaluation in accordance with 10 CFR 50.59 was not required. A Station On-Site Review (OSR) of the change and the accompanying note was not performed. This note was essentially a TS interpretation inserted into the procedure. A 10 CFR 50.59 evaluation and an OSR should have been performed for the TS interpretation to ensure the appropriate reviews were performed before implementing the change. Station administrative procedures required a TS interpretation to have an Independent Technical Review, a Plant Operations Review Committee (PORC) review, NRC notification, and Station Manager approval.
NRCFORhI3456A (1-001) US. NUCLEAR REGULATORY COMMISSION ,.' � .
FACILITY NAME II) DOCKET (2) LER NUMBER OD PAGE C4 Braidwood, Unit 1 STN 05000456 Y fAlt namr.R susaNTIAL Konstu NusinERN 2002 - 003 - � 01 Operating procedure BwOP RC-8 was changed for several reasons.
Since the loop could not be circulated to mix the contents of the loop, the sample results were not accurate or representative of actual boron concentration.
The time from when the sample was collected from the local RCS loop drain tap until it was analyzed often challenged the TS time requirement. The sample had to be drawn locally from the isolated RCS loop, transported to the Chemistry lab, and then analyzed. A RCS sample also had to be collected and analyzed for boron concentration for comparison.
The boron concentration of the loop fill source was sampled during the loop fill to ensure the boron concentration was greater than or equal to the required SDM boron concentration. The only other sources of water into the isolated RCS loop are RCS seat leakage past the LSIVs and RCP seal injection. The boron concentration of both of these water sources is greater than or equal to the required SDM boron concentration. As long as no RCS dilutions had been performed since the RCS loop was filled, the valid conclusion is that the isolated RCS loop boron concentration is the same or greater than RCS loop fill boron concentration measured during the loop fill.
The common practice at Braidwood was to fill the isolated RCS loop and record the boron concentration of the fill source for each loop. Before opening the RCS LSIVs, the boron concentration of the unisolated portion of the RCS was determined. Within 30 minutes of opening the RCS LSIVs, the RCS loop temperatures were checked to be within the TS limit and the boron concentration of the unisolated portion of the RCS was compared to the fill source boron concentration. If the temperatures and boron concentrations were within the TS limits, the RCS LSIVs were opened. Comparing the fill source boron concentration to the TS required boron concentration within 30 - iranutes; regardless of whenfhai-b6i-On"eoncentration was actually determined: crag' believed to meet the TS SR time requirement.
C. Cause of Event
The root cause of the TS SR noncompliance was the misapplication of a note that was added to the procedure that directs RCS loop restoration. The note was not properly reviewed in accordance with 10 CFR 50.59 to ensure literal compliance with the TS SR.
This procedure was relied upon as the implementing procedure to ensure the requirements of SR 3.4.18.2 were met. The sample frequency was interpreted, in the context of the note, as being met by comparing the RCS loop fill boron concentration to the required SDM boron concentration within the SR time requirements before opening the isolated loop isolation valves.
D. Safety Consequences:
The isolated RCS loops are filled with borated water of a known concentration. The concentration is maintained greater than the required SDM boron concentration. The only sources of water into the isolated RCS Loop are from the loop fill system, leakage past the LSIVs, and RCP seal injection. Any leakage past the LSIVs would be the same concentration as the unisolated RCS system (i.e. greater than the required SDM boron concentration). The RCP seal injection water boron concentration is the same as the RCS loop fill boron concentration or the unisolated RCS boron concentration.