Accelerator driven production of tritium: target and blanket design

Abstract

Tritium is an essential component of thermonuclear weapons in the US arsenal. Unfortunately, tritium is a radioactive form of hydrogen, and one-half of the inventory disappears through radioactive decay every 12 years; therefore, it must be replenished. Until a few years ago, the only way to accomplish the tritium production mission was to use fission reactors. Recently, thanks to the development of new accelerator technologies (SDI and SSC studies) and to the post cold war era (international treaties limiting the number of warheads and therefore the tritium requirements), accelerator-based production of tritium seems feasible and is being investigated. The production of tritium using accelerators is a two step process: the production of neutrons in the 'target' and the use of these neutrons in the 'blanket assembly'. The systems described in this thesis employ a linear accelerator (1 GeV protons, I 00 mA beam current), lead targets for the production of neutrons via spallation reactions, and tritium breeding regions (blankets containing '6Li in various mixtures). The high energy interactions and the particle transport were modeled with the LAHET computer code system. Heterogeneous and homogeneous spallation target/blanket systems were investigated. The target designs in the heterogeneous systems were 1 / liquid lead, and 2/ layers of solid lead plates cooled by heavy water. The tritium breeding blanket assemblies contained either lithium oxide or molten fluorine salt with or without UF4' The tritium production rates achieved were-1 5 tritium atoms per incident proton for the L'20 blanket,-1 6 tritium atoms per incident proton for the LiF BeF2ZrF4blanket, and-215 tritium atoms per incident proton for the LiF BeF2ZrF4UF4blanket. An homogeneous target/blanket system consisting of molten lithium lead eutectic (L',7Pb83) was also considered. This design was the most promising with-24 to-29 tritium atoms per incident proton, upgradable to-32 tritium atoms per incident proton.