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

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of-50"C would be +0,004 (about 1.9 d~llars) if the entire core could be iJ
filled. Wowever, the external loops contain enough salt to fill only
about one-third of the core; thus, the actual reactivity effect would be
much smaller, and it would be inserted over a period of several seconds.
The control system could readily compensate for such a S~SW change in re-
activity. With no control response, a new power level would be gradually
approached to counteract the cooling effect of the inlet condition, and
then the continued heating effect of the higher power level would cause
a reductton in reactivity and a return to a stable condition.
3.2 Reactor Thermal Hydraulics
The purpose of the thermal-hydraulic analysis of the DMSR is to dem-
onstrate that the concept is viable and not to provide a detailed design.
Neither the funding n5r the necessary thermal-hydraulic properties of mol-
ten salt flow in a graphite core are presently available to perform the
latter. Conservative estimates of important parameters are taken wherever
possible; even if some of these should be nonconservative, simple modifi-
cations Q€ the core design apparently could lead to acceptable results.
Thermal-hydraulic behavior does not appear to be a limiting design con-
straint on the DMSR reference core.
Because of the relatively low power density of this concepts simple
core configurations that were not possible in the MSWR reference design8
may be ~~nsidered, Three simple designs were considered:
1. a core made up of spaced graphite slabs,
2. a core made up of stacked hexagonal graphite blocks with circular
3.
coolant channels,
a core consisting of a triangular array of graphite cylinders with
central coolant channels.
Constraints that must be considered in selecting a core design in-
elude maximum graphite element temperature, local salt volume fraction,
and the desired 2 3 8 ~ self-shielding effect, which imposes a minimum
limitation on the coolant channel dimensions.
The temperature rise be-
tween the coolant ~fnannel and the hot spot in the graphite ~~~~derator ele-
memt is especially important because of the strong dependence of graphite