Pp. Dunphy et al., A GAMMA-RAY DETECTOR FOR IN-SITU MEASUREMENT OF CS-137 RADIOACTIVITY IN SNOWFIELDS AND GLACIERS, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 353(1-3), 1994, pp. 482-485
The rate of snow deposition at various cold regions on the earth is an
important quantity for glaciological and climatological studies. Radi
oactive debris from above-ground tests of nuclear weapons (mainly 1954
-1970) and from the Chernobyl accident (1986) have been deposited on g
laciers and snowfields, where they can be used as time and depth marke
rs to determine the subsequent accumulation of snow. We discuss a tech
nique to locate these markers that has been used just recently - in-si
tu measurement of gamma-rays from Cs-137. These gamma-rays, which are
associated with radioactive fallout, have a distinctive depth profile
and serve as markers of the historical nuclear events. The gamma-ray m
easurement involves lowering a scintillation detector down a borehole
in the snow or ice and recording the response to the Cs-137 gamma-rays
as a function of depth. The in-situ measurement can be done relativel
y quickly and can replace sample retrieval, or it can be used to decid
e which ice or snow samples should be transported for later analysis i
n the laboratory. The feasibility of in-situ gamma-ray measurement has
been demonstrated at sites in the French Alps and Greenland. We repor
t on a portable detector system that is being developed for use in Ant
arctica. It is based, as much as possible, on inexpensive, commerciall
y available detectors and electronics. The advantages and disadvantage
s of this approach are discussed. The problems involved with making th
ese measurements in a harsh environment and the steps taken to deal wi
th them are also presented.