Nuclear Regulatory Commission Programs

Los Alamos National Laboratory has been working for the NRC in a wide variety of programs and providing technical support since the early 1970's. The NRC first came to the Laboratory in the early 1970's because of our computational capabilities in the weapons program to see if we could develop a new, advanced three-dimensional thermal-hydraulics computer code from first principles to analyze large-break loss-of-coolant accidents (LOCAs) in Pressurized Water Reactors (PWRs). The NRC needed a code such as this to verify, validate and independently check code calculations produced by vendors such as Westinghouse. The Laboratory accepted the challenge from the NRC and developed the Transient Reactor Analysis Code (TRAC) over the next several years. TRAC became the "flagship" code for analyzing LOCAs (both large break and small break) in PWRs and later in Boiling Water Reactors (BWRs). In 1979 the accident at Three Mile Island (TMI) occurred and TRAC was used as the main workhorse to analyze what happened during the accident and to determine how much the reactor core was damaged. The results formed the basis of the findings by the Presidential Commission (Kemeny Commission) on TMI.

Over the years TRAC has been used to analyze and design a variety of test facilities and to analyze a variety of reactor postulated accidents for the NRC. These have included:

• Semiscale and LOFT test facilities (used to validate TRAC pre-test predictions of experiments)
• 2D/3D test facilities in Japan and Germany (TRAC was used to first support the design of the facilities and later for pre-test predictions of experiments)
• Pressurized Thermal Shock predictions of the reactor vessels in PWRs
• Steam Generator Tube Rupture postulated accidents in PWRs
• Various large and small break LOCA calculations in many US PWRs

TRAC is still being used today by the NRC and many other organizations in the world.

Other major support the Laboratory has provided (and to some extent still provides) to the NRC includes:

• Risk Analysis on a variety of NRC programs
• Nuclear Facility Vulnerability Assessments
• Resolution of PWR sump clogging issues
• Seismic analysis
• Technical assistance and support to Reactor Systems and Plant Systems branches of the NRC
• High Temperature Gas Cooled reactor safety code development and analysis
• Fast Reactor safety code development and analysis

Currently the Laboratory is planning to use its capabilities to support NRC in a number of areas in the anticipation of new advanced reactor orders.

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