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NTS LOCA: An Accident Gone as Planned

January 29, 2014
three mile island
Three Mile Island power plant

On March 28th 1979, “TMI-2 Reactor Destroyed” was the topic that swept this nation. After having been online only 13 months, Unit 2 in the Three Mile Island nuclear power plant had a partial core meltdown due to a fault that initiated in the secondary side of the plant which ultimately lead to a Coolant System Failure. This was “The Accident” that went beyond the designed second tier fault tree to reach the other safety systems per their design.

 

The Nuclear Power Plant Safety Protocol has multiple planned accident scenarios (fault trees) that they have designed into their safety programs. The major accidents designed into the Emergency Core Cooling System fall into the following two categories:

  1. Criticality Accidents, Example: Chernobyl (1986) and Fukushima Daiichi (2011)
  2. Loss of Coolant Accident, Example: Three Mile Island (1979)

This Loss of Coolant Accident environment is simulated at the NTS Huntsville Facility to ensure that the surrounding equipment survives the necessary time span required for the equipment to perform its designed safety functions and ensure cooling of the reactor core. It is theorized that during a LOCA event, the initial 5 minutes are the worst condition for equipment in regards to Temperature, Humidity and Pressure, reaching maximum temperature within 10 seconds and the most critical for plant safety.

NTS has been performing these accidents runs for the last 35 years and currently the NTS Huntsville system is used to provide harsh environment needed for testing for the components that will be subjected to a High Energy Line Break (HELB) or Main Steam Line Break (MSLB). The purpose of these tests, which is conducted in accordance with IEEE Standard 323 are to subject the Equipment Under Test (EUT) to a rapid rise in temperature and pressure that may be experienced inside a Nuclear Power Plant Containment Structure or Main Steam line area should there be a catastrophic line rupture. The objective is to reach temperature of over 375°F and pressures as much as 70 PSI in less than 10 seconds then hold a lower temperature and pressure for a period of up 30 to 60 plus days.

The boiler system is designed for 350 PSIG, 800°F of superheated steam with a designed steam capacity of 11,000 Lbs/Hr. There are two test autoclaves which the (EUT) can be placed in; one rated at 300 PSIG, and the other 150 PSIG. The system also has the capacity to mimic the Core Spray System inside of the containment structure to quench the pressure and steam by providing a spray of a buffered boric acid solution. The LOCA system is monitored and test data is collected on a Custom Integrated Control and Data Recording System developed by our NTS Albuquerque Operation.

Other industries who may utilize this super-heated steam testing are: Cable Mfg, Valve & Actuator Mfg, Relay Mfg, Military Std 810 testing facilities, I&C Instrumentation Mfg, RTD/Thermistor Mfg, Pressure Transducer Mfg and Enclosures Mfg. For more information on our LOCA testing services you can contact Huntsville at 256-837-4411 or visit the webpage for more information.

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