In the NRC’s quarterly inspection report for the months of May, June and July released on August 12, the NRC cited Dominion for three violations of its federal licensing conditions. The NRC imposed no penalties. The cited violations:
(1) Dominion’s radiation protection personnel overseeing contract workers told them respiratory protection was not needed for work they were assigned to do to replace a valve, a job known to involve exposure to airborne radiation requiring use of a respirator. One of the workers set off the radiation alarm as he left the assignment and was found to have been exposed to a measurable internal dose of radiation. Such an exposure is a cancer risk. The NRC declined to impose a penalty on Dominion, finding the violation was not a deliberate one.
(2) During Millstone Unit 2’s refueling outage (April 5 – May 19), Dominion violated federal regulations when it was found to have failed to maintain “emergency action level schemes” for assessing a loss of forced flow cooling during the outage. The violation had potential to compromise emergency preparedness by impairing Dominion’s ability to classify an Unusual Event or an Alert for an uncontrolled reactor coolant system (RCS) heat-up event because of the lack of site specific criteria to assess the RCS temperature. The NRC declined to impose a penalty for the violation.
(3) Also during Millstone Unit 2’s refueling outage, Dominion operated without an adequate procedure for reactor filling and draining, posing a risk to the reactor coolant system’s decay heat removal capability. The NRC inspectors found that pressurizer and head vents were open when they should have been closed, causing control room instrumentation to display inaccurate water level drop. The NRC declined to impose a penalty for the violation.
The inspection report also noted these issues:
(1) The inspectors investigated underground bunkers/manholes subject to flooding which contain cables whose failure could affect safety equipment. They observed a cable vault which contains power cables for the service water system to verify that cables were not submerged in water. The inspectors discovered some cables submerged in water. The NRC declined to cite Dominion for this condition.
(2) In the course of the three-month inspection period, Millstone Units 2 and 3 both shut down due to a loss of offsite power, according to the NRC. Both units suffered a loss of condenser vacuum and other complications. The shutdown damaged the Unit 3 pressurizer relief tank rupture disk, containment, excessive relief valve leakage, loss of instrument air, low pressure turbine rupture disk and the reactor head vent pipe hangar.
The NRC identified numerous operational issues in the Unit 3 reactor trip:
“Additional complications at Unit 3 included a main steam isolation signal due to a steam leak in the turbine building and an unexpected loss of instrument air pressure. The loss of instrument air pressure led to the inability to maintain a normal [reactor coolant system] letdown flow path, which resulted in the necessary diversion of letdown through the reactor head vent into the pressurizer relief tank (PRT). After the PRT exceeded rated pressure, the PRT rupture disk opened as planned and reactor coolant drained into the containment building basement and collected in the structure’s sump system. During the restoration of instrument air pressure, a relief valve on the unit’s volume control tank lifted as the normal drainage flow path was being restored causing the primary drains transfer tank to overflow inside the auxiliary building.”
The NRC ordered a “Special Inspection” but has not yet released the results. The NRC allowed Dominion to restart Unit 3 on June 2.
The August 12 NRC inspection report is available here: Millstone Power Station – NRC Integrated Inspection Report 05000336/2014003 and 05000423/2014003 ADAMS Accession No. ML14224A098