Consider a reactor being held sub-critical, Keff < 1, by control rods. The reactor has heavy water reflector and has been operatored for some time prior to the current state (we got Photo Neutrons). Keff is then bought to//<![CDATA[ aax_getad_mpb({ "slot_uuid":"f485bc30-20f5-4c34-b261-5f2d6f6142cb" }); //]]>

1.

It seems to me, for Keff = 1 the neutron population should be increasing even if we have allowed enough time for Delayed and Photo N's to reach equalibrium. We have a source of neutrons from spontaneous fission in the fuel mix, 238 235, that would cause this to be the case. If my understanding of the point kinetics equations is right, then, with a constant source term there would be an increasing neutron population and the increase would be linear(???). The rate of increase would be imperceptable to an operator.

For constant neutron population, constant power, at any operating power level, Keff < 1. Granted, very very close, but still less than one.

Is my thinking correct?

Can any provide an analytical solution (1 average delayed group with only thermal neutrons) with constant source term?

Kind Regards

PW

**Physics Forums - The Fusion of Science and Community**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Point Kinetics

Have something to add?

**Physics Forums - The Fusion of Science and Community**