ORNL-5388 - the Molten Salt Energy Technologies Web Site

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Conventional
Poison Control
Control
Burnup
H20 H20
Makeup >
Tank
Charging
i
Storage of Highly
Concentrated
Boric Acid
Boron
EOC
Borated
4-24
E
.r
H20
Makeup
Tank
-
H20
/~
Storage of Highly
Concentrated
(80%) D20
Spectral Shift
Control
D20
D20 . Upgrader
ORNL-DWG 78- 15056
0,
$ n 0 OBurnup N EOC
Fig. 4.2-1. Basic Spectral Shift Control Modifications.
- Mixture
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containing boron at high concentrations. The latter stream is stored until the beginning
of the subsequent cycle where it is used to provide the boron necessary to hold down the
excess reactivity introduced by the loading of fresh fuel. The SSCR can consist of the
identical nuclear steam supply system as employed in a conventional poison-control led
PWR, except that the boron concentrator is reDlaced with a D20 upgrader. The function
of this upgrader is to separate heavy and light water, so that concentrated heavy water
is available for the next refuelina. The upgrader consists of a series of vacuum distillation
columns which utilize the differences in volatility between liqht and heavy water
to effect the separation. Although the boron concentrator and the upgrader perform
analogous functions and operate usina similar processes, the D20 upgrader is much larger
and more sophisticated, consisting of three or four towers each about 10 ft in diameter
and 190 ft tall. Although Fig. 4.2-1 illustrates the basic changes required to implement
the shift-control concept, numerous additional changes will be required to realize spectral-shift
control in practice. These include modifications to minimize and recover D20
leakage, to facilitate refueling, and to remove boron from the coolant after refueling.
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