Nuclear Safety Testing Advancement: Test Chamber Exceeds Peak Temperature and Pressure Requirements for the AP1000® Harsh Environment Design Basis Accident Profile

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Fauske & Associates, LLC, (FAI) the world leader in nuclear and chemical process safety, achieved a significant nuclear safety breakthrough recently when its test chamber exceeded the peak temperature and pressure requirement for the AP1000® nuclear plant Harsh Environment Design Basis Accident (DBA) profile.

FAI LOCA Chamber - open with cables

FAI LOCA Chamber - open with cables

“At FAI, we can simulate all aspects of the DBA profile,” Raines noted.

Fauske & Associates, LLC, (FAI) the world leader in nuclear and chemical process safety, achieved a significant nuclear safety breakthrough recently when its test chamber exceeded the peak temperature and pressure requirement for the AP1000® nuclear plant Harsh Environment Design Basis Accident (DBA) profile.

All safety-related equipment that is in a currently operating nuclear power plant or is planned to be installed in a future nuclear power plant, such as the Westinghouse AP1000 plants being constructed in China and in the southeastern United States, needs to be qualified for the environment in which the equipment will reside.

The formal qualification process, called Equipment Qualification (EQ), ensures that the equipment will function if called upon, even if an accident occurs at the nuclear power plant. If the equipment to be used is already qualified to plant requirements, it can be used in a safety-related capacity without any additional actions. However, if the equipment to be used is new and/or not qualified, it must undergo a formal qualification process before use.

For AP1000 plants, guidelines for the EQ process are specified in Institute of Electrical and Electronics Engineers (IEEE) Standard 323-1974, “IEEE Standard for Qualifying Class 1E Equipment for Nuclear Power Generating Stations” (1974). This standard specifies several methods for performing the EQ process, including: type testing, operating experience, qualification by analysis, combined qualification and on-going qualification. It states that, “Type testing of actual equipment using simulated service conditions is the preferred method. This method should be used for qualifying the greater portion of equipment.”

According to James C. Raines, Manager, Equipment Qualification at FAI, “The type testing qualification process involves exposing the equipment to a ‘normal’ lifetime of normal service conditions (temperature, pressure, radiation, etc.). In addition to that exposure, the equipment needs to experience a representative Design Basis Accident (DBA) that coincides with the equipment’s location. A DBA is an accident condition that the plant experiences which can result, for example, from a break in the primary system pressure boundary. Following the DBA, the equipment must also be able to operate for a post-DBA, if appropriate.”

Raines explained that a DBA results in high: temperatures, pressures, radiation and steam environments. Three typical types of DBAs are: Main Steam Line Breaks (MSLB), Loss of Coolant Accidents (LOCA) and High Energy Line Breaks (HELB). Since the actual DBA the equipment may see is unknown, a representative DBA accident profile is followed. The representative DBA profile is a combination of each of the DBA accident types that could occur in the location where the equipment resides.

For AP1000 plants, the most severe location in which equipment can reside is called the harsh environment. The AP1000 harsh environment profile requires a rapid exposure of the equipment to a temperature of 437°F (225°C) and a pressure of 63 psig (434.4 kPa) within 19 seconds of the start of the transient. “At FAI, we can simulate all aspects of the DBA profile,” Raines noted. Within the first hour following the initial transient for the AP1000 harsh environment, chemical sprays expose the equipment under qualification to a liquid or steam shower for 24 hours.

The Westinghouse AP1000 In-Core Instrumentation System (IIS) Cable and Connector Assemblies require EQ for the AP1000 harsh environment. The IIS cable and connectors connect to in-core thermocouples and detectors. In early 2012, Westinghouse awarded FAI the contract to qualify the IIS cable and connector assemblies for the AP1000 harsh environment DBA.

The IIS system is a large piece of equipment made predominately of stainless steel and insulation. The IIS System Equipment Under Test (EUT) weighs approximately 200 lbs. and, as configured for the DBA test, had a width of four feet, height of three feet and a length of eight feet, which fits comfortably in the FAI DBA chamber. The burden imposed by the large thermal mass and heat transfer area of the IIS EUT was not a challenge for the FAI DBA chamber. On June 7, 2012, in the process of qualification testing of the IIS cable and connector assemblies, FAI exceeded the peak temperature and pressure requirement for the AP1000 harsh environment DBA profile. Raines stated, “The IIS EUT is currently undergoing accelerated aging for post-DBA conditions. The IIS EQ campaign will be completed in July 2012.”

The FAI DBA chamber is a state-of-the-art, stainless steel pressure vessel that is four feet by six feet with the ability to accommodate components up to eight feet in length. Because it is a stainless steel vessel, the chance of particle contamination of the EUT from, for example, rust generated from a steel DBA chamber, is eliminated.

The FAI DBA chamber is capable of exceeding the AP1000, Evolutionary Power Reactor (EPR), current- and next-generation nuclear plant DBA profiles. It is one of only a few DBA chambers that has met the AP1000 harsh environment profile. Along with EQ, the unique configuration of the DBA chamber’s, Super Heater heating system and controls provide the needed capability to perform: high temperature/pressure steam and super-heated steam tests and experiments, qualification of mechanical equipment (QME-1), rapid air blow down tests, valve testing and qualification and other related functions that use combinations of these unique capabilities.

Fauske & Associates, LLC is an affiliate of Westinghouse Electric Company, LLC. FAI is recognized in the nuclear industry for its expertise in modeling severe accident phenomena and conducting comprehensive plant evaluations. FAI’s Nuclear Systems Group helps its customers enhance the availability and reliability of their operating plants while maintaining regulatory compliance, extending plant life, and reducing operation and maintenance costs.

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AnnMarie Fauske
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