| The Transient Reactor Test (TREAT) Facility at the Idaho National Laboratory (INL) has
been revitalized from a 23-year standdown to study fuel behavior of nuclear fuels and materials.
Testing of light water reactor (LWR) reactivity insertion accidents (RIA) has created a need for
TREAT to generate pulses with a full width at half max (FWHM) in the 45 to 75 millisecond range
as compared to the current 93 millisecond pulse width. A helium-3 clipping system is being
evaluated for its effectiveness in reducing the pulse width of the TREAT core. A Monte-Carlo-N-
Particle (MCNP) transport code, using a conceptual module design, it was determined that a
system that included 4 modules, placed within the modular TREAT core, filled with an initial
pressure of 500 psig was sufficient to reach the desired clipping rate to reduce the pulse width of
the TREAT core within the desired range. The results will help guide final design of the system.
Key Words: Transient Reactor, Pulse Width, RIA, TREAT, MCNP, Helium-3 Clipping |