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Energy Deposition and Shielding Requirements for All Concepts of the Blanket Comparison and Selection Study

Yousry Gohar, Shi-Tien Yang

Fusion Science and Technology

Volume 8 / Number 2P1 / September 1985 / Pages 2010-2020


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The Blanket Comparison and Selection Study (BCSS) carried out 16 blanket concepts [7 tokamaks and 9 tandem mirror reactors (TMRs)] for the final evaluation process. This process requires all the blanket design parameters, including the energy multiplication factors, the atomic displacement rate in the first wall, and the shielding definition for the reactor. A shielding assessment is performed to determine shielding materials, compositions, arrangements, and thicknesses for each concept. Two shielding criteria are adopted for this assessment: (a) workers are permitted in the reactor hall 1 day after shutdown, and (b) superconductor coils are required to function for a 150 MW·yr/m2 deuterium-tritium neutron exposure at the first wall without a change in their performances. For the design purpose, the occupational exposure is 0.5 mrem/h, based on working 8 h/day and 40 h/week. This dose level is used to concur with current practice in the nuclear industry and the exposure policy of the U.S. Department of Energy, which limits the on-site personnel exposure level to less than one-fifth of the maximum permissible dose equivalent limits. The personnel exposure criterion is used to size the outboard bulk shield for tokamak reactors and the shield thickness between the central cell coils for TMRs. In the fusion power environment the insulator materials are the most sensitive components in the superconductor coils from the radiation damage point of view. A maximum insulator dose of 1010 rad in the thermal insulator is used to size the bulk shield in the inboard section of the tokamak reactors and the central cell sections under the coils for TMRs. As a result of this criterion, all other nuclear responses do not exceed any design limit for the superconductor materials or the copper stabilizer. Also, the nuclear heating in the winding materials is ∼0.1 mW/cm3, which is very close to the optimum design conditions for TMRs and quite satisfactory for the design of the toroidal field coils in tokamak reactors. An analysis for the energy multiplication factors, the energy loss to the shield, the atomic displacement rate in the first wall, and the shield definition for the 16 blanket concepts of the BCSS is provided.

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