TFTR Radiation Contour and Shielding Efficiency Measurements During D-D Operations

Abstract

Extensive neutron and gamma radiation contour, shielding efficiency, and spectral measurements were performed during high power TFI'R D-D operations at the tokamak Test Cell inner walls, ceiling, roof, and outer walls, in nearby control rooms, work areas, and personnel pathways, outdoors along the site fence at 125 m, and out to the nearest property lines at 180 m. The results confirmed that the efficiency of the basic radiation shieIding was sufficient to allow the TFI'R D-T experimental p h , and provide empirical guidance for simulating the radiation fields of fume fusion reactors.

Measurements of TFTR D-T radiation shielding efficiency

“…A value of the gamma dose per D-D neutron is unavailable for this east wall location. However, measurements at 2 midplane locations at the opposite west wall gave an average of 3.5x10-'5 mrem per D-D neutron [4]. Using this value gives a gamma D-T to D-D dose ratio of 0.91 which is of order the simulation result at the inner walls [5].…”

“…The Table 1 also lists the neutron and gamma dose-equivalents per D-D neutron measured prior to the start of D-T operations [4]. It is seen that the ratio of the neutron D-T dose-equivalent to the neutron D-D dose-equivalent varies in the range from about 2 to 37 depending on the local material densities and shielding wall efficiencies.…”

“…Since, the total concrete shielding in the northeastward direction is 1.8 m and in the southeastward direction is 2.7 m, these comparable property line intensities imply that the direct contribution through the walls is negligible and that the residual fields at the property lines are dominated by skyshine and upper building reflections. Table 2 also lists the neutron and gamma dose-equivalents per D-D neutron measurements prior to the start of D-T operations [4]. It is seen that the ratio of the neutron D-T dose-equivalent to the neutron D-D dose-equivalent varies in the range from about 1 to 5 depending on the local material densities and shielding wall efficiencies.…”