Question

a. Calculate the average microscopic capture thermal cross section (σa) for Pu-239 at a neutron temperature of 353°K. b. Repeat Part (a) for the Pu-239 fission cross section.

Answer #1

We have standard values of cross-section at T=20 C=293K

We can use those values to find thermal cross section at any other time by using formula

where T0=293 K and is value of thermal cross section at that 293 K

T is the temperature at which we want to find

In our case T=353 K

Hence above eqn becomes

Now we have standard values of at 293k For Pu-239

=capture cross section for Pu-239 =269 Barn

Hence

Fission cross section at 293K for Pu-239 is 748 barn

Then

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