### STP1490: Coarse-Mesh Adjoint Biasing of a Monte Carlo Dose Calculation

Pevey, R. E.

*The University of Tennessee, Knoxville, TN*

Miller, L. F.

*The University of Tennessee, Knoxville, TN*

Marshall, W. J.

*The University of Tennessee, Knoxville, TN*

Townsend, L. W.

*The University of Tennessee, Knoxville, TN*

Alvord, B.

*CTI, Inc., Knoxville, TN*

Pages: 9 Published: Jan 2007

**Abstract**

Deep penetration radiation transport calculations have been performed to determine the dose rates at a positron emission tomography (PET) facility in China. The radiation source is a cyclotron that is used for the production of the PET isotopes, with a labyrinthine concrete wall arrangement to minimize dose to operation personnel. Since directionally biased Monte Carlo calculations did not reach an acceptably low standard error after a week of CPU time, approximate adjoint fluxes were calculated for each of four detector locations using coarse-mesh adjoint discrete ordinates calculations and were used to bias the Monte Carlo calculations. This biasing resulted in improved computational efficiency of a factor of one to three orders of magnitude. This result shows the value of even approximate adjoint flux biasing to speed up Monte Carlo calculations.

**Keywords:**

isotope production, Monte Carlo, discrete ordinates, adjoint biasing

**Paper ID:** STP45451S

**Committee/Subcommittee:** E10.02

**DOI:** 10.1520/STP45451S

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