Measurement of Prompt Fission Neutron Spectrum Using a Gamma Tagging Method

Since its discovery 75 years ago fission has been at the forefront of nuclear science and engineering research. Although the fission process is being used worldwide to generate safe reliable power, there are several aspects of the fission process which are still not well known. One such parameter of the fission process is the prompt fission neutron spectrum (PFNS). Although the average number of neutrons per fission nu-bar is a well-known quantity, the energy of those neutrons is not as well known. Furthermore uncertainties in these values can have significant impact on the uncertainty associated with reactor criticality and criticality safety measurements [1]. Criticality measurements of keff are directly sensitive to the prompt fission neutron spectrum [1]. The current uncertainties in the prompt fission neutron spectrum can correspond to up to a 4% uncertainty on keff for various systems including both fast and light water systems as well as for UO2 and MOX fuel [1]. This demonstrates a need for more accurate measurement of the prompt fission neutron spectrum.