THE S³² (n,p) P³² REACTION AS A FAST-NEUTRON FLUX MONITOR

Abstract

An extensive study is made of the use of sulphur as a monitor for neutrons with energies from 2 to 20 1CIev. Irradiated disks of pressed sulphur are burnt before counting to increase the efficiency and reproducibility of determining the P32 activity. I t was established that on burning irradiated sulphur 95.51t0.57~ of the P32 activity is retained with a reproducibility of = !~l . O 7~. iLIeasuretnents of relative cross sections for the S3' ( n , p ) P39eactioll have been extended to 20.3 NIev using the T (d,n) He4 and D (d,n) He3 reactions to produce monoenergetic neutrons. Neutron production using Zr-T targets is examined as is the effect of extraneous ' CVe have been using sulphur as a rnonitor in measuring excitation curves for fastneutron reactions ( G ) , and in this paper describe a study of this convenient method for fast-neutron monitoring. The procedures for sample preparation and activity measurements are given. fn addition, we have extended the measurements of the S32 (n,p) cross section to 20.3 Mev. EXPERIMENTAL A X D RESULTS A. &Ionitor MaterialFor the monitor we have chosen elemental sulphur in the form "flowers of sulphur". I t is readily available, inexpensive, and relatively pure. Any impurities which may be present appear to have low activation cross sections. Powdered sulphur has been pressed into disks of known and reproducible area mith diameters of 3/16 in. to 1 1/8 in. using a briquettingz or disk3 press. Disks of a desired thickness can be rapidly produced b y packing powdered sulphur into a short hollow tube of a predetermined volume, then tapping it out into the press. Under pressure sulphur packs into firm disks and requires no extraneous binding agent. Disks thicker than 0.015 in. do not powder or crack under normal handling and irradiation conditions. \Ye use a pressure of 25 tons/inz and produce 0.040-in. disks 3/16 in. in diameter, which weigh about 34 mg. The relatively small size of the disks enables one to determitle a flux more accurately in a position where flux gradients exist. B. IrradiationsSulphur was irradiated mith neutrons produced with an accelerator using the ( D + D) and (D + T ) reactions. The spread in energy of neutrons produced in this manner depends on the angle the sample subtends at the neutron source. By using sainples with a small diameter and irradiating a t a distance, the angle 'Issued as A.E.C.L. No. 1648. =Applied Research Lab (Glendale, Calif.). 3Research & Industrial Inst. Co. (London, England).Canadian Journal of Chemistry. Volume 41 (1963) Can. J. Chem. Downloaded from www.nrcresearchpress.com by 54.191.190.102 on 05/12/18For personal use only.

Cross sections for the 93Nb(n,2n)92mNb reaction

“…The experimental conditions used are those described in detail in previous publications (7)(8)(9). Monoenergetic neutrons with energies from 6.7 to 19.8 MeV were obtained from the reactions ~(d,n)"e and T(d,r~)~He.…”

“…The efficiency for measuring 3 2~ was 49.2 4~ 1 .O% and for 2 4~a was 29.7 f 0.6%. Corrections were applied as before (7,8) for (i) P-ray absorption, (ii) activation by neutrons produced by reactions other than in the target or by scattering, and (iii) by D(d,np) breakup neutrons.…”

A thermoluminescent fast-neutron dosemeter based on pellets of CaSO4:Dy mixed with sulphur

“…These pellets were exposed (along with a pure sulphur pellet) in the APSARA reactor in a mixed field of neutrons and gamma rays. The fast neutron and gamma doses were estimated from the 32P activity induced in the pure sulphur pellet (Santry and Butler 1963), and from the TL of CaSO, : Dy powder respectively.…”