Thorium burnup

The fuel cost items which vary with thc.se two parameters are (1) bismuth iiiM iiiiiiy, (2) fuel inventory, (3) fuel burnup, (4) thorium amortization, thorium burnup, and ((>) chemical processing. Nuclear calculations spei ilietl the fuel concentrations for both core. and blanket and breeding ratios, These I alues were then used to determine the chemical processing l yclc for the blanket and the pertinent costs. 

Thorium burnup costs. Thorium is periodically replenished in the reactor to maintain the desired concentration in the slurry. The thorium burnup cost.s may lie expressed as... 

Jackson and Walser [Jl] have given a detailed description of the operations conducted in 1970 by the Atlantic Richfield Hanford Company to separate and decontaminate and its associated thorium from aluminum-clad thorium dioxide irradiated to low burnup in the Hanford reactors. 

Kiichler and associates [K6, K7] of Farbwerke Hoechst have investigated the modifications necessary in the acid Thorex process to enable it to handle (I) the high concentration of fission products present in fuel with the burnups of up to 100,000 MWd/MT expected in fuel from the HTGR, AVR, and THTR, and (2) uranium concentrations of up to 20 percent in thorium, which may be used in these reactors when fissile uranium is diluted with U to deter its use as a nuclear explosive. They found two difficulties with the acid Thorex process flow sheets previously used at Oak Ridge [B14] and Hanford [Jl] ... 

This fuel cycle was considered as a method for achieving much longer fuel cycle lengths and extended burnup due to an expected higher conversion ratio from the thorium... 

The performance targets for thoria fuel will depend on the specific fuel cycle that is intended. The requirements for a low burnup, near-breeder type of cycle will be different from those to be met by high bumup thorium fuel. 

The plutonium-based fuel form to be used in plutonium-burning reactors is closely coupled to a particular reactor design, but there are several general criteria that apply to all circumstances. Fuel forms chosen for use in any type of plutonium burner should (a) possess a high burnup capability, (b) provide a high degree of operational safety, (c) offer the cheapest and easiest fabrication methods with minimum hazardous waste, and (d) offer the cheapest and easiest end-of-life disposal. Candidate fuel forms considered in this study for use in a plutonium burner do not include uranium or thorium as a constituent. 

The rapid increase in critical inventory of during the first year can be avoided by partial withdrawl of thorium. In Fig. 14-10 the dashed lines indicate the course of events when thorium is removed at the rate of 1/900 per day. Burnup reduces the thorium concentration by another... 

The fuel added to the reactor will have a high concentration of UF4 with respect to the process fuel,. so that additions to overcome burnup will require transfer of only a small volume similarly, thorium-bearing molten. salt may be added at any time to the fuel system. The thorium, in addition to being a design constituent of the fuel salt, may be added in amounts re( uired to serve as a nuclear poison. 

Fuel costs. The fuel costs as presented in this report include (1) bismuth inventory, (2) fuel inventory, (.3) fuel burnup, (4) thorium... 

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