This is the third in a series of commentaries about the vital role nuclear safety inspections conducted by the Nuclear Regulatory Commission (NRC) play in protecting the public. This commentary describes how NRC inspectors discovered inadequate flooding protection at the Vogtle nuclear plant near Waynesboro, Georgia despite a prior warning notice.
The first commentary described how NRC inspectors discovered that limits on the maximum allowable control room air temperature at the Columbia Generating Station in Washington had been improperly relaxed by the plant’s owner. The second commentary described how NRC inspectors uncovered an improper safety assessment of a leaking cooling water system pipe on the Unit 3 reactor at Indian Point outside New York City.
Turning Back the Clock
Last century, the NRC issued a warning to nuclear plant owners about the possible submergence of electrical cables located above the estimated flood levels. The NRC’s warning informed owners about a March 20, 1989, event in which the Clinton nuclear plant in Illinois inadvertently drained water into the drywell flooding it to a depth of four inches. Workers discovered that water got into electrical junction boxes located more than four inches above the drywell floor.
Electrical junction boxes house connections of electrical cables. Figure 1 shows water pouring from an electrical junction box at the Fort Calhoun nuclear plant in Nebraska during a flood in June 2011.
The NRC’s 1989 warning pointed out that moisture could get into electrical junction boxes various ways—from condensation of steam released from a broken pipe, actuation of overhead fire sprinklers, etc. If the junction boxes lack drain holes, water could accumulate within the boxes to submerge and disable electrical cables.
Workers at Vogtle reviewed the NRC’s warning and determined it was applicable to their plant. A work order was written to require that all electrical junction boxes containing safety-related cables had drain holes.
Stopping the Clock
The work order was closed out on January 25, 1990. Typically, closing out a work order written to correct a safety problem means that work to solve the problem has been completed. But not this time.
Setting off the Clock Alarm
In late 2017, NRC inspectors examined junction box 2BTJB0486 at Vogtle. They observed that the junction box lacked a drain hole and later determined that the cables and connections inside the box were not qualified for submergence in water. The NRC issued a Green finding for the failure to properly protect electrical equipment from the environmental conditions it could experience.
The NRC’s inspectors did not examine every junction box at Vogtle. The NRC conducts audits of a few items to gain insights about the condition of the broader universe of items. During this inspection, the NRC examined a whopping total of seven components, only one being a junction box. So, the NRC looked at one junction box and found it deficient. What does that say about the rest of the junction boxes at Vogtle?
Nothing. Maybe other boxes have holes. Maybe they don’t. Maybe is maybe adequate protection of public health and safety. Maybe not.
Workers at Vogtle wrote a work order to check on other junction boxes. In other words, they repeated the same step taken following the NRC’s 1989 warning to respond to the NRC’s 2018 finding that the 1989 response was woefully deficient.
The bad news is that the electrical junction box at Vogtle did not have even a tiny hole in it.
The worse news is that the corrective action program at Vogtle has a big hole in it.
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