05000338/FIN-2017001-02
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Finding | |
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| Title | Chemical Addition System Outside of Technical Specification Due to Excessive Unseating Thrust on MOVs |
| Description | a. Inspection Scope The LER documented that North Anna failed to maintain the full design bases functionality of its Sodium Hydroxide (NAOH) injection for both units as required by TS 3.6.8. The inspectors reviewed the LER and the associated corrective action document (CR 1029674) to verify the accuracy and completeness of the LER and the appropriateness of the licensees corrective actions. The inspectors also reviewed the LER and CR to identify any licensee performance deficiencies associated with the issue. b. Findings Description: On March 9, 2016, with Unit 1 (U1) at 100 percent power in Mode 1 and Unit 2 (U2) in Mode 6 for a scheduled refueling outage, 2-QS-MOV-202B failed to stroke open during testing due to excess unseating thrust. An extent of condition review and engineering evaluation determined that 2-QS-MOV-202A maintained its safety function. An extent of condition review and engineering evaluation of the U1 valves determined that 1-QS-MOV-102B maintained its function but 1-QS-MOV-102A did not. While only one of the valves is needed in order for the system to perform its safety function, TS 3.6.8 requires both valves to function in order to be considered operable. A failure of these valves would result in a loss of redundant safety function and inability to perform an emergency operating procedure or to prevent mitigating the consequences of accidents that would result in potential offsite exposure in excess of 10 CFR Part 100 limits. These valves were originally installed in September 2010 (U1) and September 2011 (U2). These valves are stroked every refueling outage per the IST and monitored by the motor operated valve (MOV) program every six refueling outages. The licensees investigation determined that all appropriate testing per the MOV program and design changes have been applied. No previous failure of these valves were identified. No human errors were found during initial valve set up or maintenance and no design errors were identified. The licensees apparent cause evaluation (ACE) concluded that the cause of 2-QS-MOV-202B exhibiting excessive unseating thrust, resulting in a failure to open during functional testing, was due to mechanical binding internal to the valve body and/or actuator. This was also considered to be the cause for the excessive unseating thrust exhibited in 1-QS-MOV-102A. Valves 2-QS-MOV-202A and 1-QS-MOV-102B also exhibited mechanical binding, but not to the same degree and did not fail. The licensee implemented corrective actions to ensure the chemical addition tank isolation MOVs do not bind again, Design Changes (DC NA-16-00023 for U1 and DC NA-16-00021 for U2) were implemented to change the actuator gear set to provide more unseating capability for the valves. In addition, the valve stroke was changed to position limit switch controlled verses torque controlled seating, allowing valve seating to be adjusted to lighter loads providing even more margin. As an interim compensatory measure, these valves will be stroked every six months in addition to every cold shutdown. Stroking the valves verifies capability and reduces the pull-out-force required for the next stroke. Valve stroke frequency will be reviewed based on data collection and may support revision to the operability determination currently in place for Units 1 and 2. Based on review of the licensees ACE, the historical industry operating experiences, and previous MOV test data and IST stroke time data, the inspectors determined that there was no performance deficiency associated with this issue because the cause of failed the TS surveillance tests was not reasonably within the licensees ability to foresee and correct. Enforcement: The inspectors determined a violation of TS occurred because of failure to maintain the full design basis functionality of the Chemical Addition System. North Anna TS Limiting Condition for Operation (LCO) 3.6.8 requires the Chemical Addition System to be operable when in Modes 1, 2, 3 and 4. The associated action statement requires, in part, that with the Chemical Addition System inoperable, Restore Chemical Addition System to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and if Required Action and associated Completion Time is not met, the unit be in Hot Standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in Cold Shutdown within 84 hours9.722222e-4 days <br />0.0233 hours <br />1.388889e-4 weeks <br />3.1962e-5 months <br />. Contrary to the above, on March 9, 2016, the licensee determined that the Chemical Addition System was inoperable on U1 for more than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> while the unit was in Modes 1, 2, 3 and 4; and U1 was not placed in Hot Standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in Cold shutdown within 84 hours9.722222e-4 days <br />0.0233 hours <br />1.388889e-4 weeks <br />3.1962e-5 months <br />. Later, through an extent of condition review, the licensee concluded that the U2 Chemical Addition System was also inoperable. Although a violation of the TS occurred, the violation was not reasonably foreseeable and preventable by the licensees QA measures or management controls. Therefore, the violation of TS 3.6.8 was not associated with a licensee performance deficiency. The inspectors concluded that the violation would normally be considered at Severity Level III in accordance with Enforcement Policy section 6.1.c. However, the inspectors utilized available risk-informed tools to more accurately assess the safety significance of this issue. Since the chemical addition system is considered a part of containment system, the inspectors evaluated this issue in accordance Manual Chapter 0609.04, Initial Characterization of Findings, Table 2, dated October 7, 2016 and the finding was determined to adversely affect the Barrier Integrity Cornerstone. The inspectors screened the finding using Inspection Manual Chapter (IMC) 0609, Appendix A, Significance Determination Process (SDP) for Findings at-Power, dated June 19, 2012, and determined that the finding screened as low safety significance (Green) because it did not represent an actual open pathway in the physical integrity of reactor containment (valves, airlocks, etc.), containment isolation system (logic and instrumentation), and heat removal components; and it did not involve an actual reduction in function of hydrogen igniters in the reactor containment. This issue represented a degradation of the radiological barrier function provided for the reactor building. However, because the violation was not associated with a licensee performance deficiency and it was not avoidable by reasonable licensee QA measures or management controls, the NRC is exercising enforcement discretion (EA-17-007) in accordance with Section 3.10 of the Enforcement Policy. The violation will not be considered in the assessment process or the NRCs Action Matrix. This issue was documented in the licensees corrective action program as CR1029674. |
| Site: | North Anna  |
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| Report | IR 05000338/2017001 Section 4OA3 |
| Date counted | Mar 31, 2017 (2017Q1) |
| Type: | Violation: Green |
| cornerstone | Barrier Integrity |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | A Masters D Merzke G Croon J Munday S Cuadrado-Dejesus |
| Violation of: | Technical Specification |
| INPO aspect | |
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Finding - North Anna - IR 05000338/2017001 | |||||||||||||
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Finding List (North Anna) @ 2017Q1
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