05000250/LER-2013-004
| Turkey Point Unit 3 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2502013004R00 - NRC Website | |
DESCRIPTION OF THE EVENT
On February 27, 2013 at approximately 1750, with the Unit 3 reactor [AC, RCT] in Mode 5, power was restored to Reactor Coolant System (RCS) [AB] hot leg safety injection valve MOV-3-866A [BQ, INV] in preparation for inservice testing (IST). On February 28, 2013 at approximately 0047 normally closed MOV- 3-866A was stroked open for IST. During the IST Pressurizer [AB, PZR] level increased approximately 0.6 %. This was consistent with an observed decrease in Refueling Water Storage Tank (RWST) [BQ, TK] level of approximately 80 gallons. Volume Control Tank (VCT) [CB, TK] level was stable. All levels stabilized after MOV-3-866A was closed.
After discussion regarding possible contingencies for inventory control and known flow paths, Operations personnel resumed the 1ST. The parallel RCS hot leg injection valve MOV-3-866B was then stroked and an approximate 0.3% Pressurizer level increase was observed during the test. VCT level remained constant.
Revalidation of the valve lineup commenced.
On February 28, 2013 at approximately 0230, MOV-3-866A and MOV-3-866B were verified closed and de- energized with their breakers locked in the off position. The hot leg safety injection flow path to the RCS was now isolated in compliance with Technical Specification (TS) Limiting Condition for Operation (LCO) 3.4.9.3.
In order to support the IST and comply with TS requirements for flow path isolation, valve MOV-3-869 [BQ, INV] and remote manual valve 3-990 [BQ, INV] were verified to be closed. Investigation revealed that while the remote position indicator [BQ, V, ZI] for valve 3-990 indicated closed the actual position was open. TS Surveillance Requirement 4.4.9.3.3 requires the flow path to be isolated by closed valves with power removed or by locked closed manual valves. As a result, with valve 3-990 open and power restored to MOV-3-866A, the high pressure safety injection flow path was not isolated as required for a period of approximately 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> and 40 minutes, which exceeds the allowance of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> in TS 3.4.9.3, Action a, to restore an unisolated flow path.
Because the high pressure safety injection flow path to the RCS was not isolated as required by the TS for a period of time greater than allowed by the TS, this event is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by TS.
CAUSE OF THE EVENT
The direct cause is that the position of valve 3-990 was not verified locally after operation as required by Operations procedures.
Other causes include:
1. The design control process does not require a level of detail sufficient to identify missing roll pins during post-implementation walk downs.
2. Work planning did not provide for adequate verification of critical installation steps.
ANALYSIS OF THE EVENT
A modification package for the hot leg injection flow path provided the design, basis, installation instructions and functional testing requirements for the installation of valve 3-990, with a manual operator and reach rod.
The reach rod has seven universal joints, one splined joint, one shielded floor penetration assembly, a male drive operating station, wall terminal operating station and a 90° gear box for a total of seventeen connection points which are either pinned or keyed. Each universal joint can be connected to the adjacent components by means of a Woodruff Key or an "S" hole for insertion of a roll pin. If the roll pin option is used vendor documents identify that the "S" hole is to be located, drilled and mated at assembly by the customer in the field. No record, or a requirement for a record, was found indicating pin or key connection points on the reach rod assembly were tracked for completion by the work crew, crew supervisor or installation engineer. The installation of the reach rod was completed on July 5, 2012. The turnover walk down phase of the design process was completed on July 12, 2012.
On July 24, 2012 a post-modification test was performed by cycling valve 3-990 open and closed using the reach rod. The test was recorded as satisfactory. Following completion of testing valve 3-990 remained in the closed and locked position until February 25, 2013.
On February 23, 2013 work began to modify the male driver tab lock on the valve 3-990 reach rod and lubricate reach rod operators. This work and a post maintenance test (PMT) were completed on February 25, 2013 at approximately 1543. For the PMT, an operator cycled the valve open using the remote valve operator on the Auxiliary Building roof while a second operator stationed locally in the pipe and valve room observed valve motion. After the valve was opened, the operator stationed locally commenced closing the valve. The operator at the remote station observed the remote hand wheel rotating. At this point, the operator on the Auxiliary Building roof using the remote hand wheel assumed control and continued closing valve 3-990. The operator in the pipe and valve room relocated to the remote station. With valve 3-990 indicating closed at the remote hand wheel station the operators reported satisfactory completion of the PMT. The valve was not verified closed locally.
On February 27, 2013 at approximately 1750, as previously discussed, power was restored to RCS hot leg injection valve MOV-3-866A in preparation for IST. Compliance with TS LCO 3.4.9.3 was not met, because valve 3-990 was not closed.
On February 28, 2013 at approximately 0230, MOV-3-866A and MOV-3-866B were verified closed and de- energized with their breakers locked in the off position, restoring compliance with TS LCO 3.4.9.3.
When the incorrect valve position was investigated, it was discovered that two universal joints in the reach rod system still had their temporary assembly set screws installed and one of those had failed. Temporary set screws are used to facilitate assembly and set up, but then the set screws are to be replaced with more robust roll pins. As a result, the reach rod was not engaged to the remote operator and could be rotated without affecting the local hand wheel. The local hand wheel was used to close valve 3-990. Both universal joint connections were repaired by installing the missing roll pins.
ANALYSIS OF SAFETY SIGNIFICANCE
While TS LCO 3.4.9.3 was not met when power was restored to MOV-3-866A at approximately 1750 on February 27, 2013, the RCS hot leg injection flow path was effectively isolated except for the brief periods during which MOV-3-866A and MOV-3-866B were stroked at approximately 0048 and 0100, respectively, on February 28, 2013. Upon recognition that flow path isolation had not been maintained as required, TS 3.4.9.3 Action a, was entered. At approximately 0230 on February 28, 2013, MOV-3-866A and MOV-3- 866B were verified closed and de-energized with their breakers locked in the off position and TS LCO 3.4.9.3, Action a, was exited.
The hot leg injection flow path did not meet TS requirements for approximately 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> and 40 minutes which exceeded the allowed time of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The probability for a low temperature overpressure event occurring during this time is judged to be low. Parallel RCS hot leg injection valves MOV-3-866A and MOV-3-866B are normally closed, do not receive a safety injection initiation signal, and are manually opened in accordance with procedures during the later phases of a loss of coolant accident. As a result, the safety significance of this event is very low.
CORRECTIVE ACTIONS
Corrective actions are documented in AR 1852222 and include the following:
1. The similar valve in Unit 4, 4-990, was verified locally to be closed.
2. The reach rod assemblies for the three other recently installed valves with reach rod systems will be inspected to ensure all roll pins are installed.
3. Revise the Operations Department Instruction for valve manipulation and the Conduct of Operations procedure to provide guidelines to verify reach rod operation. Guidance will include stationing operators at both remote operator and local valve communicating with each other, to monitor reach rod operation during the entire valve travel cycle.
4. Establish a means to better control work in the field that ensures critical installation steps are verified complete.
FAILED COMPONENTS IDENTIFIED: None PREVIOUS SIMILAR EVENTS: None