Neutron activation is used to analyse the silicon and aluminium content of samples of material, such as bauxite ore and coal. The analysis can be performed on bulk samples, on material on a moving conveyor belt, or on the walls of a borehole. The method involves high energy neutron irradiation of the sample, measurement of the thermal neutron flux in the sample, and monitoring the gamma radiation from the sample at energies of (a) 1.78 MeV and (b) 0.844 MeV and/or 1.015 MeV. Such gamma radiation is produced on decay of (a) 28 Al and (b) 27 Mg isotopes, produced by the reactions 28 Si(n,p) 28 Al and 27 Al(n,p) 27 Mg. A single gamma ray detector is used. The analysis preferably utilizes equations which include terms to compensate for (a) the production of radiation at 1.78 MeV as a result of the production of the isotope 28 Al from 27 Al by the thermal neutron reaction 27 Al(n,γ) 28 Al, and (b) the Compton scattering of 1.78 MeV gamma radiation and background.

Neutron activation analysis

137Cs and 210Pb dating of sediments from soft-water lakes in New England (U.S.A.) and Scandinavia, a failure of 137Cs dating

Accumulation of heavy metals and selenium in three seabird species from the United Kingdom

A primary health concern among residents and evacuees in affected areas immediately after a nuclear accident is the internal exposure of the thyroid to radioiodine, particularly I-131, and subsequent thyroid cancer risk In Japan, the natural disasters of the earthquake and tsunami in March 2011 destroyed an important function of the Fukushima Daiichi Nuclear Power Plant (F1-NPP) and a large amount of radioactive material was released to the environment Here we report for the first time extensive measurements of the exposure to I-131 revealing I-131 activity in the thyroid of 46 out of the 62 residents and evacuees measured The median thyroid equivalent dose was estimated to be 42 mSv and 35 mSv for children and adults, respectively, much smaller than the mean thyroid dose in the Chernobyl accident (490 mSv in evacuees) Maximum thyroid doses for children and adults were 23 mSv and 33 mSv, respectively

http://large.stanford.edu/courses/2015/ph241/english1/docs/srep00507.pdf

D. F. Covell

Papers

Determination of Gamma-Ray Abundance Directly from Total Absorption Peak