Notes on the photographic film-dosimetry of fast neutrons

Abstract

Kodak Fast Neutron Monitoring Films of different ages were irradiated for calibration with fast neutrons of the reaetions (D + D) and (D + T). The energy distributions of the neutrons were also measured using Ilford K2 nuclear plates irradiated simultaneously.Aecording to the resuhs the density of the "traeks" eontaining less than five grains is independent of the dosis on a wide range; the track-counting was performed with ah aeeuracy of • under a realistic scanning time; ageing tendeney was not observed.The fast n e u t r o n personal d o s i m e t r y of those working with n e u t r o n generators is m a i n l y based on nuclear t r a c k counting, and even t o d a y ir is performed with the aid of a nuclear emulsion. Several comprehensive works have been published as to the description of the m e t h o d e.g. [1,2]. The K o d a k Personal N e u t r o n Monitoring Films of t y p e A ate m o s t widely used. I t is the above t y p e of film t h a t has been used in this I n s t i t u t e since 1964.A n u m b e r of papers h a v e been published relating to the calibration of the K o d a k F a s t N e u t r o n Monitoring Films [3 --10]. W i t h i n the scope of the present article no systematic s t u d y of the factors determining the calibration of the films is given. Here, we only a t t e m p t to draw a t t e n t i o n to a few phen o m e n a and conditions t h a t were observed during the s t u d y of the films used for the calibration. I t should also be added t h a t our investigations, in m a n y aspects, c a n n o t be regarded as complete.A s a rule, in every series calibration exposures were m a d e with b o t h neutrons originating from the D -4-T and D -k D nuclear reactions of known yield. The films to be irradiated were placed at 90 ~ to the direction of the deuteron beato a n d a t 0 ~ in other cases. I n each case the badges were irradiated on a n o r m a l front.The t i m e -i n t e g r a t e d neutron flux received was m e a s u r e d with a long aounter, which was calibrated b y using P o --B e of R a --B e neutron sources. The conditions of irradiation were chosen in such a w a y t h a t the error of distance m e a s u r e m e n t could be regarded as negligible. The films were always irradiated simultaneously at different distances. * Dedieated to Prof. A. SZALXY on his 60th birthday.

Progress in Solid-State Fast Neutron Personnel Dosimetry.

“…There are various more or less well-known contributing factors, which make the occasions where reasonably accurate results can be obtained with this method very rare indeed. For example, many of the earlier calculations on the low-energy response limit of track films have been based on the assumption that short recoil proton tracks consisting of three or four grains can be counted; it has, however, been shown [3] that there is no relationship whatsoever between the count of such "tracks" and the neutron dose.…”