— section (considered constant), etc. This constant, called a calibra- tion number is evaluated by exposing a foil of the detecting media to a known neutron flux and correlating this known flux with the counting rate observed. Complete calibration data taken from 1956 to the present time by this Laboratory are presented and discussed. The calibration mmbers now considered valid for the system of detectors and counting equipment described are given. CWLR - 2299 - AN EXPERIMENTAL STUDY OF THE INDUCTION OF GAMMA~EMITTING ACTIVITIES IN SEVERAL AMERICAN SOILS BY NEUTRONS OF VARIOUS ENERGIES (U). John H. McNeilly and Eugene Eichler, September 1956. UNCLASSIFIED (u) This report describes experiments conducted at the Oak Ridge National Laboratories to determine the important gamma-emitting nuclides which are formed in soils by neutrons of various energies. Two nuclear reactors were used as sources of neutrons. The gamma rays resulting from the activity induced tin the soils were measured with a 2O-channel, differential pulse-height analyzer. The resultant spectra were then analyzed to determine the amount of activity produced by a known neutron flux. The conclusions established were: 1. The principle induced activities formed by thermal-neutron 2. The induced activities due to thermal-neutron activation irradiation in the soils studied are A128, 156 and Na24, are proportional to the amounts of the parent element in the soils studied. 3. Induced activity from Mg@7 was formed from neutrons with energies greater than 2 Mev. However, the dose rate due to MgeT is insignificant because the dose rate due to Ai28 predominates at similar times. 4k, The majority of the induced activity resulting from the detonation of a fission muclear device is due to the radioactive capture reaction, while (n, a) and (mn, p) reactions of lost neutrons produce only small quantities of activity. Dissemination —