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The FuTure oF nuclear Fuel cycle - MIT Energy Initiative

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Figure 3b.1 Cumulative probability distribution Function for θ<br />

cumulative PdF<br />

1<br />

0.9<br />

0.8<br />

0.7<br />

0.6<br />

0.5<br />

0.4<br />

0.3<br />

0.2<br />

0.1<br />

0<br />

–0.2 –0.1 0 0.1 0.2 0.3 0.4 0.5<br />

theta<br />

Discussion<br />

<strong>The</strong> overall model in its present form is admittedly crude. However, it provides a framework<br />

for incorporation of future improvements. In particular, better (than uniform) frequency<br />

distribution functions for n, s, and f could be specified, given greater insight into uranium<br />

geochemistry and mining experience. Allowing n = 1 and f = 100% merely to accommodate<br />

past oversimplification is open to question. Following the practice adopted in the recent<br />

AFCI review (3), a triangular PDF, zero at the low and high values of the range, and peaked<br />

at the nominal value, may be warranted.<br />

Separative WorK (SWu) requirementS<br />

This subject is of interest because SWU can be traded off for natural uranium feed requirements,<br />

by reducing the enrichment facility tails composition. Per kg of product, P, at enrichment<br />

X p , given in weight percent (w/o), F, the U NAT feed required is:<br />

where X N = 0.711 w/o, natural uranium enrichment<br />

X W = specified tails enrichment<br />

Curve fits to data from the exact expression for kg of SWU per kg of product (S/P) in the<br />

range of interest (2.5 < X P < 7 w/o) give the following linear approximations:<br />

x W , W/o S/p ~<br />

0.10 3.00 X P – 3.03<br />

0.15 2.57 X P – 2.72<br />

0.20 2.27 X P – 2.51<br />

0.25 2.06 X P – 2.36<br />

0.30 1.89 X P – 2.24<br />

0.35 1.75 X P – 2.14<br />

152 <strong>MIT</strong> STudy on <strong>The</strong> <strong>FuTure</strong> <strong>oF</strong> <strong>nuclear</strong> <strong>Fuel</strong> <strong>cycle</strong>

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