On Nov. 1, the public conference to discuss the safety significance level in regard to the incident that took place on April 16, in Nine Mile Point Nuclear Station (NMPNS) in Scriba, N.Y. took place in the U.S. Nuclear Regulatory Commission (NRC) office Region 1, located in King of Prussia, Pa.
NMPNS Unit 1’s loss of shutdown cooling during the planned refueling outage led to the reactor vessel temperature rise. Final ruling of safety significance on the incident was not made in the conference last Friday. It will take another month for the NRC’s determination.
“We committed to them at the meeting that we would have something early December,” said Neil Sheehan, the public affairs officer of NRC office Region 1.
“Greater Than Green”
After completing the inspection of units 1 and 2 from April 1 to June 30 at NMPNS, the Aug. 13 NRC inspection report identified the April 16 case as the apparent safety violation following the NRC’s Enforcement Policy, which was due to NMPNS Unit 1’s experiencing loss of shutdown cooling on April 16.
According to the Aug. 13 report, along with the apparent safety violation, the NRC spotted two more NRC-identified findings and two more self-revealing findings. The other four were treated as non-cited violations, which affects little in determining the safety significance level.
After the NRC’s reactor risk analysts’ classification, the Sept. 23 NRC inspection report has given a preliminary safety rating of “greater than green” to NMPNS. This means the apparent safety violation found in Aug. 13 was graver than very low safety significance.
The safety rating of the NRC follows its manual named “Significance Determination Process” and is indicated by their color. From the lowest significance to highest, it is classified in four groups: green, white, yellow and red.
If rated “greater than green,” the facility would be required to abide by additional NRC inspection and undergo the escalated enforcement process. Also, it is required to establish administrative policies and submit written procedures. If rated higher than white, more NRC enforcement would follow based on the significance and the facility may receive civil penalties.
According to the NRC official website, the manner in which it processes a violation is intended to reflect the significance of the violation and the circumstances involved. The NRC website also said the NRC first assesses the significance of a violation by considering actual safety consequences, potential safety consequences, potential for impacting the NRC’s ability to perform its regulatory function and any willful aspects of the violation.
How the conference was held
The conference was held following the request of Constellation Energy Nuclear Group (CENG), the owner of NMPNS.
After Aug. 13, the NRC inspection report was issued and the NRC made its final significance determination within 90 days of the issuance. Before the due date, Sept. 23 the NRC report provided CENG with an opportunity to discuss before the final ruling is made. Before Oct. 3, CENG could pick one of the two choices: to attend a regulatory conference to present the perspective of CENG or to submit a written response stating its position.
CENG decided to hold a public conference and notified it to the NRG on Sept. 30, according to Sheehan.
In the conference on Nov. 1, Chris Costanzo, vice president of NMPNS, told the NRC that the company has already made corrective actions and implemented new procedures in response to the April incident, according to the Post-Standard.
Aug. 13, the NRC inspection report found out that “the violation does not represent an immediate safety concern because Constellation (CENG) has conducted a prompt human performance event review, entered the issue into their corrective action program, and conducted a root cause analysis.”
Also, David Lochbaum, director of the Nuclear Power Project at the Union of Concerned Scientists, said to the Post-Standard that the incident was “a relatively low-stress event.”
However, Lochbaum also said the incident revealed operator errors that would be significant during a more serious event.
CENG argued in the conference that the April 16 event was less serious than NRC inspectors had asserted since the incident occurred and was resolved during the refueling outage.
This conflict was an expected procedure, as NMPNS and the NRC view the April 16 incident from different standpoints on the following fact: approximately 80 minutes after the cooling system restarted, the fuel rods started to boil.
Explaining the same fact, the Post-Standard reported that “the problem was fixed ‘at least 80 minutes before’ water surrounding the fuel rods started to boil … Nevertheless, the NRC said the episode revealed weaknesses,” stressing the insignificance of 80 minutes.
In contrast to this, the Sept. 23 NRC inspection report of NRC said that “inadequate CENG procedures resulted in an unplanned loss of all shutdown cooling when time to boil was ‘less than two hours.’
What happened on April 16?
Nuclear power plant practices call for a refueling outage to replace the depleted fuel in the reactor.
“During a refueling outage, plant workers have greater access to many areas of the plant that are sometimes difficult to access during normal operations,” said Marcus Nichol, Nuclear Energy Institute’s senior project manager. “This lends itself to being a great opportunity to conduct routine inspections and maintenance and perform any necessary repairs.”
Based on Lochbaum’s presentation slides on Nov. 1, during the ongoing planned refueling outage, a team of workers the next day were conducting maintenance on electromatic relief valves, which is used to protect the reactor pressure vessel from excessive pressure.
A contractor in the team opened the breaker cabinet to make sure their maintenance work could be performed safely when the electric power is off. However, he opened the wrong breaker cabinet at 2:44 p.m.
This led to DC electrical power loss in the only shutdown cooling pump out of three operating that day, not reducing the reactor coolant system temperature to maintain at refueling temperature for an extended period, as needed.
Signals to turn off the shutdown cooling pump did not reach at first, with the signal arriving after momentary re-energization at 3:46 p.m., causing the shutdown cooling pump to be turned off.
Because the cooling pump was off, the temperature inside the reactor started to rise from 118 degrees Fahrenheit, reaching up to 145 degrees Fahrenheit at 4:17 p.m.
The operators of the reactor worked on this and succeeded to have two other shutdown cooling pumps operate 31 minutes after all the power was gone.
CENG officials pointed out in a statement to the Post-Standard that the event presented “no actual health or safety consequences to the plant, our employees or the public, but we have learned from the issue and are incorporating appropriate corrective actions to prevent recurrence.’’
What is Nuclear Regulatory Commission?
The NRC is an independent agency of the U.S., established following the Energy Reorganization Act of 1974. This made the United States Atomic Energy Commission in 1975 separate into two organizations based on their disparate functions: Energy Research and Development Administration (ERDA), which is currently the United States Department of Energy, and NRC, which focuses on overseeing nuclear reactors, materials and waste.
There have been constant critics on the NRC. John Byrne and Steven M. Hoffman said in their book named “Governing the Atom: The Politeness of Risk,” that the NRC committed a practice of regulatory capture, by favoring the interest of nuclear industry.
However, since the Fukushima Daiichi nuclear disaster case broke out in 2011, Gregory Jaczco, former NRC chairman, stated that he would strengthen regulations of U.S. nuclear power plants.
“I cannot support issuing this license as if Fukushima never happened,” Jaczko said to Reuters in 2012. “I believe it requires some type of binding commitment that the Fukushima enhancements that are currently projected and currently planned to be made would be made before the operation of the facility.”