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Nuclear Reactor Digitization Project

Raymond L. Murray Reactor Project Notebook

Prepared for the North Carolina State University Science and Technology Electronic Text Center

The lineation of the manuscript has been maintained and all end-of-line hyphens have been preserved.

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The 10 Kw water boiler operates continuously up to a shutdown. It is

K. Way gives the following expression for energy dissipation from fission products
by Β and γ radiation.

Β and γ = 2.66 t-1.2 Mev/sec-fission7 seconds(goodman)Solution:

The contribution to power at time t by products produced in the interval dT is:

The total is the integral:

In terms of watts:

If the reactor has been operating for say 6 months, then To in seconds is 6 x 30 x

Evaluating E at t = 10 seconds:

Conclusions:

At 100 seconds after shutdown, the maximum Β and γ power from decay of fission
products is 500 watts assuming:

Since 1/2 Kw is removed from reactor by the surroundings, the solution does not

That this estimate is reasonable may be seen by the following considerations.
(Goodman,I, p. 240) Of the 200 Mev produced by a fission, ~ 22 Mev is due to

fission product decay. "About half of this last figure is emitted as neutrino

energy." Therefore, only ~11 Mev is available as γ and Β energy from fission

products. That is, if equilibrium is nearly established between the fission

products and a 10 Kw power level, then the steady state decay contribution will be

approximately 11/200 x 10 Kw = 550 watts. This decays rapidly upon reactor shutdown

Also, the 1/2 Kw conduction by surrounds is conservative in that an increase
in fuel temperature above normal operation increases the heat removed by

ing

is, if normally the conditions are 85°-25°C removing .5 Kw of heat, then at

This is the maximum heat removal by surroundings if the boiling point is
100°C. However, the boiling point will be higher due to the involatile solute and

may be computed by an elementary method given in "

If there is some question about the closeness of the power production to
heat conduction shortly after shutdown it may be shown that if the contents of the

water boiler is assumed to be 1 ft

3 of water, then a net gain of 500 watts for
a period of almost one hour is required to raise the temperature to boiling. At