GAO: Not all US reactors meet fire regulations

Tuesday, 1 July 2008

The US Government Accountability Office (GAO) said that some the country's nuclear power plants have yet to comply with some of the government's fire safety regulations issued in the 1970s.
 

On 22 March 1975, a candle used by a worker to test for air leaks ignited electrical cables at the Browns Ferry nuclear power plant. The fire, which damaged more than 1600 electrical cables - more than 600 of which where important to plant safety - raised awareness of the potential danger that fires pose to the ability of the USA's commercial nuclear power plants to safely shutdown. The US Nuclear Regulatory Commission (NRC) subsequently issued prescriptive fire safety rules for commercial nuclear reactors. However, nuclear units with different designs and different ages have had difficulty meeting these rules and have sought exemptions to them. In 2004, NRC began to encourage the country's reactor operators to transition to a less prescriptive, risk-informed approach that will analyze the fire risks of individual nuclear units.
 

The GAO has visited ten of the USA's 65 nuclear power plant sites, reviewed NRC reports and related documentation about fire events at nuclear units, and interviewed NRC and industry officials to examine compliance with existing fire protection rules and the transition to the new approach.

Long-standing issues

 

It has concluded that the NRC has not resolved several long-standing issues that affect the nuclear industry's compliance with existing NRC fire regulations, and the NRC lacks a comprehensive database on the status of compliance. These long-standing issues include nuclear plants relying on manual actions by plant workers to ensure fire safety (for example, a unit worker manually turns a valve to operate a water pump) rather than 'passive' measures, such as fire barriers and automatic fire detection and suppression.
 

In addition, the GAO said that workers use "interim compensatory measures" (primarily fire watches) to ensure fire safety for extended periods of time, rather than making repairs. The GAO highlighted uncertainty regarding the effectiveness of fire wraps used to protect electrical cables necessary for the safe shutdown of a nuclear unit. There is also the issue of mitigating the impacts of short circuits that can cause simultaneous, or near-simultaneous, malfunctions of safety-related equipment and hence complicate the safe shutdown of nuclear units.
 

Compounding these issues, GAO said, is that the NRC has no centralized database on the use of exemptions from regulations, manual actions, or compensatory measures used for long periods of time that would facilitate the study of compliance trends or help NRC's field inspectors in examining unit compliance.
 

Primarily to simplify units' complex licensing, the NRC is encouraging nuclear plants to transition to a risk-informed approach. As of April 2008, some 46 reactors had stated they would adopt the new approach. However, the transition effort faces significant human capital, cost, and methodological challenges. The GAO found that "a lack of people with fire modelling, risk assessment, and plant-specific expertise could slow the transition process." Four nuclear power reactors are piloting the new approach, and the NRC plans to evaluate the results of the pilot program units by March 2009. The NRC said that a further 22 units will begin submitting their licence amendment requests for the risk-informed approach by March 2009.
 

According to NRC, there were 125 fires at 54 of the USA's 65 nuclear power plant sites between January 1995 and December 2007, all of which were classified as being of limited safety significance. Many of these fires were in areas that do not affect shutdown operations or occurred during refuelling outages, when nuclear units are already shut down and usually undergo maintenance, the NRC added. The most commonly reported cause of fires was electrical followed by maintenance-related causes and the ignition of oil-based lubricants and coolants.