SYMPOSIA PAPER Published: 01 January 1963

Fast Neutron Dosimetry for Long-Term Irradiations


The use of fast neutron threshold detectors for measuring the fast neutron (neutrons with energies greater than 1 Mev) flux in nuclear reactors takes advantage of the (n, p) and (n,α) reactions which various nuclides undergo when exposed to high-energy neutrons. In order to qualify as a good dosimeter system the reactant nucleus must have a convenient and well-known reaction cross-section and the decay characteristics of the product nucleus must be well known. Other desirable characteristics include a chemical state which facilitates handling of the dosimeter and nuclear properties which allow simple radioassay procedures. The chief consideration for a dosimeter to be used for monitoring long irradiations is the halflife of the product nuclide. It should be long enough so that a significant fraction of that activity produced early in the irradiation is present at the conclusion of irradiation. This usually leads to selection of a system in which the product nuclide's half-life is at least twice the length of irradiation, although it is possible to use the system when the irradiation time is nearly equal to the half-life provided the calendar time over which the irradiation is made and the decay time from end of irradiation to analysis are not excessive.

Author Information

Ritzman, R., L.
Battelle Memorial Inst., Columbus, Ohio
Lieberman, R.
Battelle Memorial Inst., Columbus, Ohio
Kircher, J., F.
Battelle Memorial Inst., Columbus, Ohio
Sunderman, D., N.
Battelle Memorial Inst., Columbus, Ohio
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Developed by Committee: E10
Pages: 141–150
DOI: 10.1520/STP41748S
ISBN-EB: 978-0-8031-5984-6
ISBN-13: 978-0-8031-6138-2