For Ionizing Radiation, we test to a dose of :
10 Krad for CMOS
50 Krad for Bipolar
For Neutrons, we need to test to a dose of:
5 x 1012 n/cm2 for CMOS
7.5 x 1012n/cm2 for Bipolar
For a Californium252 exposure of:
7.5 x 1012n/cm2 we get an exposure of about 9 Krad from photons.
Looks OK , we can use the Californium source for the neutron tests. The photon exposure is not excessive.