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

8
DMSR, the shutd~wn residual-heat-remova1 (RHR) probPem would be Less se-
vere than in the MSBR. Consequently, a less elaborate RHR system than
would be needed for an MSBR might be acceptable for a DMSR. However, for
purposes of characterizing the DMSK, the assumption was that the balance-
of-plant would be the same as that for an EISBW,
2.4 Fuel Randline and Processing
The performance of an MSBR wouEd be strongly dependent the avail-
ability of an on-site continuous chemical-processing facility for removal
of fission products and isolation of protactinium on relatively short time
cycles, These treatments would make possible the achievement of a posi-
tive 233U breeding gain in a system with a low specific fissile inven-
tory. Because a DPfSR on a 30-year fuel cycle would not require even nomi-
nal break-even breeding and because a significantly higher fissile inven-
tory could be tolerated, the processing requirements for a DMSR would be
much less stringent than for an MSBR. Isolation of protactinium would be
avoided for proliferation reasons, and chemical processing to remove €is-
sion products could be avoided without severe performance penalties.
Despite these concessions, some fission-product removal would take
glace in any PISR. Most of the rare gases (and some other volatile fis-
sion products) would be removed by the gas-sparging system in the primary
circuit. ~n addition, a substantial fraction of the noble-metal" fission
products would be expected to plate out on metal surfaces where they
would not affect the neutronic performance. However, the reference-design
reductive-extraction/me~~~-t~~~s€~~
process would not be involved.
Although there would be no chemical processing for fission-product
removaih, the DMSR likely would require a hydrofEuorination system for
occasional (presumably batchwise) treatment of the salt to rem~ve oxygen
contaminatione Ira addition, because a BMSR would requfre routine additions
of fissile fuel, as well as additions of other materials necessary
to keep the fuel-salt chemical composition in proper balance, a chemical
Nobility is defined here in relation to the U4+/lJ3+ redox potential
*
(see Sect. 3.3.2).