PLYMOUTH – A fourth-quarter inspection report by the Nuclear Regulatory Commission has identified five new safety violations at the Pilgrim Nuclear Power Plant in Plymouth.
A statement from the NRC said they were all identified as of “very low safety significance.”
The latest issues include problems with a reactor coolant recirculation system, vibrations in a pump system and issues with a shutdown transformer.
Other violations included failure to take timely action to fix and remove debris from air tubing that could impact a steam isolation valve and failure to conduct maintenance on a feedwater regulating valve.
Pilgrim has been under increase federal scrutiny and is listed as one of the worst-performing nuclear plants in the country.
Plant owner Entergy previously announced it would close the facility in 2019 after one more refueling this year.
A statement from NRC spokesman Neil Sheehan said the inspection results from the fourth quarter did show that Pilgrim is making slow progress in improving performance in areas that led the plant to be listed among the worst performing.
The company shut the plant down last week in advance of a major snowstorm. Whenworkers were restoring power on Monday, they discovered another equipment problem.
Officials found a leak in a feedwater valve after reconnecting to the grid early Sunday morning. That valve has since been taken offline and other lines will be used to provide hot water to the reactor before repairs can be made.
Pilgrim was at 50% power as of Tuesday.
Before the storm-related shutdown, Pilgrim was operating at reduced power after officials discovered a separate leak in a condenser tube connected to the system that is responsible for cooling the reactor.
That issue has since been repaired.
Below is an in-depth explanation of the 5 safety violations discovered in the 4th quarter inspection as detailed by the NRC.
- Entergy did not perform an adequate evaluation of the operability of a reactor coolant recirculation system flow converter (one of two such converters) after it had failed during testing on Oct. 3, 2016. This component provides data on reactor coolant flow to the plant’s reactor protection system. That automated system can initiate a reactor scram if coolant flow is too low. We wrote that, “Entergy allowed this flow converter to remain in service, without reasonable assurance of its capability to perform its required safety function, from the time the adverse condition was discovered on Oct. 3, 2016, until the component was declared inoperable and replaced on Oct. 21, 2016.” A subsequent engineering review of previous testing of the converter identified a slow, degrading trend in performance. The converter was replaced on Oct. 13, 2016.
- Between May 2015 and November 2016, Entergy failed to complete adequate corrective actions to address vibrations on the High-Pressure Coolant Injection (HPCI) system’s main pump. This led to the HPCI system being declared inoperable on Nov. 7, 2016, when vibration levels on the pump were greater than allowable. To address the problem, plant personnel installed a stiffening plate on the pump’s support pedestal to mitigate the vibrations. It was restored to operable status on Nov. 11, 2016.
- Entergy did not properly assess and manage the increase in risk caused by performing protective relay calibration and functional testing on the plant’s shutdown transformer on five occasions between March 2008 and August 2014. Specifically, the company was not aware that the electrical system alignment during the test would prevent a 4,160-volt safety bus (electrical supply system) from being supplied by other emergency power sources during a loss-of-offsite-power event. The risk significance was low given the short time window the system was in this configuration. Entergy now requires that the plant be shut down before the tests are performed.
- Entergy did not take timely corrective actions to inspect and remove debris from air tubing that supplied air to a valve actuator after the associated Main Steam Isolation Valve (MSIV) failed a (5-second) closure time test on March 29, 2016. (Pilgrim has four pairs of MSIVs, for a total of eight. They are designed to isolate steam flow from the reactor vessel in such a manner as to prevent fuel damage by limiting the loss of reactor coolant in case of a major leak from the steam piping outside of primary containment. They are also designed to limit the release of radioactive material to the environment in the event of a loss of coolant accident by closing the primary containment barrier.) We write that, “Specifically, when the MSIV initially failed its surveillance in March 2016, Entergy did not take a conservative approach in their operability determination and immediate response to the issue.” This uncorrected condition subsequently led to a repeat failure of the valve on Aug. 16, 2016. Entergy’s eventual corrective actions included replacing the affected MSIV air pack manifold, clearing loose debris from the affected air tubing and scheduled the replacement of the affected air tubing during the next refueling outage.
- Entergy did not conduct maintenance on a feedwater regulating valve on May 10, 2015, in accordance with vendor manual guidance. Specifically, the company did not install a wire locking clip on the valve’s encoder as required. This resulted in a loose wire and the valve failing during plant operations and led to a manual reactor scram (shutdown) on Sept. 6, 2016. In response to the loose connection, Entergy added a sealant to the connecter to ensure all wires remain in place on both feedwater regulating valves.