05000454/LER-2001-002
| Byron Station, Unit 1 | |
| Event date: | 09-26-2001 |
|---|---|
| Report date: | 11-26-2001 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(b) |
| 4542001002R00 - NRC Website | |
licensing process and fed back to industry. Forward comments regarding burden LICENSEE EVENT REPORT (LER) estimate to the information and Records Management Branch (t-6 f33), U.S.
Paperwork Reduction Project (3150-0104), Office Of Management And Budget, Washington, DC 20503.1f an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Byron Station, Unit 1 STN 05000454 NUMBER NUMBER (If more space is required, use additional copies of NRC Form 366A)(17)
A. Plant Conditions Prior to Event:
Event Date / Time: September 26, 2001 / 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> Unit 1 — Mode 1 — Power Operations, Reactor Power — 100% Reactor Coolant System [AB]: Normal operating temperature and pressure No structures, systems or components were inoperable at the start of the event that contributed to the event.
B. Description of Event:
Prior to the implementation of Improved Technical Specifications (ITS) at Byron Station the methodology and the implementing procedures for Main Steam [SB] Isolation Valve (MSIV) stroke testing had allowed the stroke testing to be performed in Modes 3, 4, or 5. Prior to implementing ITS, the Surveillance Requirement (SR) allowed entry into Mode 3 to perform the surveillance, but did not require the SR to be performed in Mode 3. The Bases for the TS provided no guidance on when the surveillance was to be performed. Therefore, Station procedures were written to allow testing in Modes 3, 4, or 5.
In the conversion to ITS, the Bases documents were also converted using NUREG 1431, "Standard Technical Specifications Westinghouse Plants." Any deviation from the NUREG Bases documents was identified and documented. In this case, Byron Station did not identify a deviation from the words provided in the NUREG. The following sentence was contained in the new Bases for SR 3.7.2.1: "This test is conducted in MODE 3 with the unit at operating temperature and pressure." This sentence created an unrecognized more restrictive requirement than the Current Technical Specification.
On July 28 and 30, 1997, a non-licensed contract individual initiated Revision 1 to Units 1 and 2, Byron Station Engineering Surveillance Requirements Procedures (1/2 BVSR) 7.2.1-1, "Main Steam Isolation Valve Operability Tests," and 7.2.1-2, "Main Steam Isolation Valve Partial Stroke Test," (henceforward, referred to as ITS procedures). The procedure change request form indicated the procedures were being changed for ITS implementation. The request form also stated the procedure and referenced Limiting Condition for Operations Action Requirement had been renumbered to be consistent with ITS and editorial changes had been made. The procedure revision did not change the required operational mode for testing to Mode 3 as required by the new ITS Bases for SRs 3.7.2.1 and 3.72.2.
(p:01Iers1454-2001-002-00.doc) licensing process and fed back to industry. Forward comments regarding burden LICENSEE EVENT REPORT (LER) estimate to the information and Records Management Branch (t-6 f33), U.S.
Paperwork Reduction Project (3150-0104), Office Of Management And Budget, Washington, DC 20503. If an intonation collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Byron Station, Unit 1 STN 05000454 NUMBER NUMBER (If more space is required, use additional copies of NRC Form 366A)(17) B. � Description of Event (continued):
Between September 22, 1998, and October 15, 1998, the System Engineer performed a technical review of the four ITS procedures. His review did not identify the discrepancy between the ITS procedures and the SR Bases mode requirement for completing the surveillance. Procedures 1/2 BVSR 7.2.1-1 allow testing in modes 2 through 6 and indicates the test is normally done in Mode 4 or 5.
Whereas, procedures 1/2 BVSR 7.2.1-2 allow testing in any mode with no reference to a Mode the surveillance is normally performed in.
Between October 1, 1998, and October 15, 1998, the In-Service Test (1ST) Engineer also performed a technical review of the ITS procedures. This review was for IST requirements only. The American Society of Mechanical Engineers (ASME) Code °Ma-1998, Part 10, Inservice Testing of Valves in Light Water Reactors Power Plants," allows testing of valves in cold shutdown (i.e., Mode 5) if not practicable during plant operations; however, TS requirements take precedence over the ASME Code.
Between October 8, 1998, and October 19, 1998, the System Engineering Department's Thermal Group Leader approved the ITS procedures for use. On February 5, 1999, ITS was implemented at Byron Station. Beginning on this date, the ITS procedures were not in exact compliance with the TS Bases since they allowed testing in modes other than Mode 3.
On March 7, 2001, procedures 2BVSR 7.2.1-1 and 7.2.1-2 were converted to Unit 2 Byron Operating Surveillance Requirement (2BOSR) 7.2.1-1 and 7.2.1-2. There were no technical changes to the procedures for this conversion. The Unit 1 procedures were scheduled to be converted at a later date.
On September 26, 2001, during a review of the SR section of the Bases in support of outage activities, a Byron Station person working at Braidwood Station for their refuel outage found the current Operating Department surveillance procedures were inconsistent with the TS Bases. Byron Station was notified immediately of the concern.
At 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br />, September 26, 2001, Byron Station entered SR 3.0.3 due to a missed TS SR, allowing 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to perform the surveillance or take other remedial measures, such as requesting a Notice of Enforcement Discretion (NOED) from the NRC.
On September 27, 2001, the NOED was verbally requested and granted by the NRC.
On October 1, 2001, after Nuclear Safety Review Board (NSRB) approval of the Licensing Amendment Request (LAR), the NOED and exigent LAR were submitted to the NRC for review and approval. The NRC subsequently approved the exigent LAR.
(p:01Iers1454-2001-002-00.doc) APPROVED BY OMB NO. 3150-0104 EXPIRES 031/2004 collection request 50 hrs. Reported lessons learned are incorporated into the licensing process and fed back to industry. Forward comments regarding burden estimate to the information and Records Management Branch (t-6 f33), U.S.
Nuclear Regulatory Commission, Washington, DC 20555.0001, and to the Paperwork Reduction Project (3150.0104), Office Of Management And Budget, Washington, DC 20503. If an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person Is not required to respond to, the information collection.
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Byron Station, Unit 1 STN 05000454 (If more space is required, use additional copies of NRC Form 366A)(17)
C. Cause of Event:
The contract individual responsible for incorporating the requirements of ITS into site procedures failed to properly capture this new mode restriction for testing the MSIVs. This individual was unavailable to be interviewed, consequently, the root cause of this failure is unknown.
A contributing cause to this error was that inadequate guidance was provided to procedure reviewers by the ITS project management in the Regulatory Assurance Department. The guidance provided was to focus on the ITS SR wording to ensure it was implemented in the procedure correctly.
D. Safety Analysis:
The consequence of operating for a timeframe without demonstrating the ability to isolate the MSIVs within the required time under the Mode 3 limiting test conditions has been conservatively assessed.
This was done by postulating that the valve stroke time could have been greater than previously measured. The likelihood and magnitude of such a postulated increase, and the margin available to accommodate it, were evaluated and determined to be acceptable as discussed below. Failure of the MSIVs to close was not postulated due to the successful past history of fast exercise tests.
The MSIVs are required to stroke closed within 5 seconds with the unit at operating temperature and pressure. The most recent stroke time data for Byron Station indicates a maximum stroke time of 2.9 seconds for Unit 1 MSIVs and 2.94 seconds for Unit 2.
According to the valve's manufacturer, a few tenths of a second would be added to the valve stroke times under maximum design steamline pressure (i.e., steamline pressure in Mode 3) versus a stroke time without steamline pressure. A review was conducted of the surveillance history for stroke time testing the MSIVs. The stroke time testing has generally been performed in Modes 4 and 5 with two instances of being tested in Mode 2. The stroke times achieved range from 1.1 to 3.2 seconds. The Unit 1 "D" MSIV was stroke timed at 2.63 seconds on April 24, 1999, in Mode 2 under operating temperature and pressure after an emergent valve packing problem was corrected. Eight days prior, the valve was timed under cold conditions at 2.34 seconds.
Based on the above data, it was concluded that the ability of the MSIVs to close within the required time at operating temperature and pressure was not adversely affected.
(p:011ers1454-2001-002-00.doc) licensing process and fed back to industry. Forward comments regarding burden LICENSEE EVENT REPORT (LER) estimate to the information and Records Management Branch (t-6 f33), U.S.
Paperwork Reduction Project (3150-0104), Office Of Management And Budget, Washington, DC 20503. If an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Byron Station, Unit 1 STN 05000454 NUMBER NUMBER (If more space is required, use additional copies of NRC Form 366A)(17) D. Safety Analysis (continued):
Sufficient justification exists to conclude that the MSIVs were fully capable of achieving the 5-second closure criteria at normal operating pressure and temperature. Performing the SR under less limiting test conditions did not affect the failure frequency assumed for the MSIVs. Therefore, since the failure frequency is unaffected, the results of the probabilistic risk assessment are unaffected by this situation.
The event did not result in a Safety System Functional Failure.
E. Corrective Actions:
Byron Station requested a NOED and exigent TS amendment to defer performing the MSIV surveillance requirements until the first unit startup after September 27, 2001. Enforcement discretion was granted by the NRC on September 27, 2001, and the subsequent exigent license amendment was approved on November 1, 2001.
The outage work control schedule has been revised to ensure MSIV surveillance testing is conducted in Mode 3.
The procedures utilized for satisfying the SRs are in the process of being revised to ensure the procedures are performed in Mode 3.
The Engineering Department will provide continuing training to Engineering personnel on their roles and responsibilities in conducting technical reviews.
A review was conducted of other TS SR Bases that contain modifying notes similar to the SRs for the MSIVs to ensure they are being implemented correctly. No additional concerns were identified.
The current process to change the TS Bases is the TS Bases Control Program. The program requires the requestor to identify the affected sections and include a marked up copy of the Bases change. In addition, it also requires a review of implementation requirements that includes any possible procedure changes.
F. Previous Occurrences:
Inadequate Procedures" (p:01 lers 454-2001 -002-00.doc)