Calibrating Passive Neutron Multiplicity and Waste Counters Using Calibrated Cf Sources: Estimating aPu-Values Without Pu

Cf sources are especially interesting for calibrating passive multiplicity counters without the need for Pu because: they are genuinely point-like and being lightly encapsulated offer a nearly isotropic unperturbed fission spectrum of neutrons for all practical purposes they can be considered as a pure source of spontaneous fission neutrons which considerably simplifies interpolation. That is the leakage self multiplication, ML, can be taken as unity and the ratio α of (α, n)-to-(SF, n) neutrons can be taken as zero. it is a well studied multiplicity system with the factorial moments νi of the distribution P(ν) being well established. the energy spectrum is similar to that of the spontaneous spectra of the Pu isotopes it is readily available with well known outputs , Y, determined absolutely by reference to Mn-baths operated by National Standards Laboratories In this work we exploit these features in the framework of the point-model interpretational equations discussed in ASTM C 1500 ‘Standard Test Method for Nondestructive Assay of Plutonium by Passive Neutron Multiplicity Counting’. In particular we: extend the equations to include the delayed neutron contribution showing how to extract the gate utilization factors (GUFs) accurately from the data available; extend the solutions given in the Appendices to cases where the Triples GUF is not equal to the square of the Doubles GUF; and, illustrate how to project Pueff performance from measured Cf.