SURVEY METHODS FOR NEUTRON FIELDS

Abstract

To one whose responsibility it is to make evaluations of the degree of hazard existing in the radiation field of a nuclear accelerator or a nuclear reactor, the valid estimate of the contribution of neutrons to such a field is of considerable importance. The degree of difficulty of such a measurement depends strongly upon the information desired - whether (1) simply the presence of 'slow' and 'fast' neutrons in significant numbers is in question, or (2) a measure of flux densities within known energy intervals is required, or (3) a direct estimate of the specific rate of energy absorption due to neutron-produced effects in a given medium is desired. The importance of securing trustworthy estimates of the neutron field can be appreciated by recalling that the biological damage due to a given amount of ionization produced in biological tissue by effects due to neutrons is estimated to be several times the damage due to a similar amount of ionization produced by X-rays or gamma rays. This 'relative biological effectiveness' must be evaluated by carefully controlled animal experiments. Its value appears to range from about 2.5 for slow neutrons to abount 10 for fast and high energy neutrons. Of course themore » value obtained may also be a function of the particular biological variable under observations, and from some experiments a value as high as 20 for fast neutrons may be indicated.« less