The U.S. Department of Energy (DOE) National Nuclear Security Administration's (NNSA) Remote Sensing Laboratory (RSL) in Las Vegas, Nevada, uses the NSCEE UNLV supercomputer to run the Monte Carlo N-Particle Transport (MCNP) program to assist in equipment design and characterization. The Los Alamos National Laboratory-developed program predicts gamma, neutron and electron transport through user-defined media with a random number generator and probability distributions based on cross-section data.

MCNP-modeled data compares well with real data

MCNP detector performance of gamma radiation is modeled by Bechtel Nevada's RSL for DOE/NNSA assets such as the Fixed-Wing and Helicopter Aerial Measuring Systems (AMS). Detector responses to gamma radiation are predicted as a function of source energy and altitude and compared to available aircraft data. Modeling includes source geometries either offset or directly under aircraft.

The large degree of air attenuation and the importance of scattered photon contributions at high altitudes create the need for a large number of randomly generated particles to give statistically valid results. RSL sends input files electronically to the UNLV supercomputer, where the necessarily long run times vary from 4-24 hours.

MCNP geometry of effects of the human body
on neutron detection

Prototype modeling using supercomputer-simulated detector response results in significant cost savings over prototype fabrication and benchmarking. Reliance on computer simulations allows designers to experiment with novel and risky configurations. Preliminary designs selected for further development can optimize individual parameters to the most cost-effective values for increasing efficiency.