One-Dimensional Gamma-Ray and Photoneutron Shielding Calculations for the Elmo Bumpy Torus Proof of Principle Device

One-dimensional radiation transport calculations have been performed to obtain estimates of the nuclear heat loads and biological dose rates due to bremsstrahlung gamma rays and photoneutrons in the ELMO Bumpy Torus proof of principle device. The bremsstrahlung gamma rays arise because of electron impingement on the magnetic coil assemblies, and these gamma rays in turn produce photoneutrons through interactions in the high-Z shielding materials. For a 1-MW electron power loss, ₂₃₈U and tungsten coil shield thicknesses of ∼22.5 and 27.3 mm, respectively, were found sufficient to limit the nuclear heat load on a single superconducting coil to 10 W. The estimated lead and concrete primary shield thicknesses required to reduce the biological dose rate due to bremsstrahlung gamma rays to 2.5 mrem/h were calculated to be 0.318 and 1.92 m, respectively. Because of photoneutron production, however, lead by itself was not found to be an acceptable biological shield.