05.08.2013 Views

ORNL-TM-7207 - the Molten Salt Energy Technologies Web Site

ORNL-TM-7207 - the Molten Salt Energy Technologies Web Site

ORNL-TM-7207 - the Molten Salt Energy Technologies Web Site

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

98<br />

All <strong>the</strong> MSR options from <strong>the</strong> breeder through <strong>the</strong> simplest c~rtvertef<br />

WQUM take advantage of <strong>the</strong> fact that <strong>the</strong> noble-gas fission products<br />

Q including <strong>the</strong> very important wuc~ear poison b 4%e) are very sparingly<br />

soluble in <strong>the</strong> molten fluoride fuel. I~?~PIS, <strong>the</strong>y would all use simple<br />

stripping with gaseous helium to remove krypton and xenon from <strong>the</strong> pri-<br />

mary system. In addition, <strong>the</strong>y would all take advantage of <strong>the</strong> fact that<br />

<strong>the</strong> noble-metal and seminoble-metal fission products do not fom stable<br />

fluorides in <strong>the</strong> fuel and would precipitate as elemental species, pri-<br />

marily on metal surfaces outside <strong>the</strong> reactor core.<br />

4, E. 1 Breakeven breeding<br />

The presence of 238U in a DMSR, combined with <strong>the</strong> effects of flux<br />

flattenfng, sufficiently reduces <strong>the</strong> nuclear pe~fo~~~nce so that a net<br />

breedfng ratio substantially greater than 1.0 probably could not be<br />

achieved even with full-scale fission-product processing (A positive<br />

breeding gain pres~maibly would be undesirable ita a pPoliferation-resfstant<br />

system because Pt would require <strong>the</strong> periodic 'qexport.n' of excess fissile<br />

rnaterfal_.) However, <strong>the</strong> studies that have been carried out indicate that<br />

bseak-even breeding is within <strong>the</strong> uncertainty limits of <strong>the</strong> neutronic caP-<br />

cralations for a flux-flattened DMSR core with a 30-year moderator life ex-<br />

pectancy. Extended operation at break-even would requite a carefully op-<br />

tinized COPE? design as well as continuous fuel-salt processing on a rela-<br />

tively short time cycle (-20 d) to remove fission products and retain ( ~ r<br />

returd all fissfle anel higher-actinide n~clides.<br />

The reference fuel processing concept proposed for <strong>the</strong> MSBR could not<br />

be directly applied to a DMSR for several reasonse<br />

I. Isolation of 23% W Q ~ I . not ~ be acceptable in a DMSR because its decay<br />

would lead to 8 supply of diversiom-sensitive, high-purity 233ue<br />

2,<br />

Isolation of protactinium would be accompanied by removal and loss of<br />

plutonim f~om <strong>the</strong> aperating system. This would not only degrade sys-<br />

tern performance brit also provide a source of plutonium that would have<br />

to be safeguarded and/or disposed of.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!