**Part 2**

**Radioisotopes in Environment** 

172 Radioisotopes – Applications in Physical Sciences

[15] C. Nicole Foley, Thanasis E. Economou and Robert N. Clayton, Final Chemical Results

[21] V. Radchenko, B. Andreichikov, H. Wanke, V. Gavrilov, B. Korchuganov, R. Rieder, M

[22] Economou, T.E, The Chemical Composition of an Asteroid Surface by the Alpha X-Ray

108, No 12, doi:10.1029/2003JE002019, 2003.

[18] Klingelhoefer, G., J. Geophys. Res., 108, p. 8067, 2003 [19] Clark,B.C., et al., J. Geophys. Res., 87, p.10059, 1982

[17] http://www.esa.int/esaMI/Rosetta

XXXI, 2000, 1861.pdf

[16] Rieder, R., et al., *J. Geophys. Res., 108(E12), doi:10.1029/2003JE 002150, 2003*

[20] Beagle 2 mission to Mars in 2003, http://www.beagle2.com/index.htm

Applied Radiation and Isotopes, 2000 Oct., 53(4-5):821-824.

from the Mars Pathfinder Alpha Proton X-ray Spectrometer, J. Geoph. Res. Vol.

Ryabinin, and T. Economou, Curium-244 alpha-sources for space applications,

Spectrometer on the MUSES-C Mission Lander, In Lunar and Planetary Science

**10** 

Mats Isaksson

*Sweden* 

*University of Gothenburg* 

**Environmental Dosimetry –** 

**Measurements and Calculations** 

*Department of Radiation Physics, Institute of Clinical Sciences, The Sahlgrenska Academy,* 

According to UNSCEAR (2008) the largest contribution to external exposure comes from naturally occurring, gamma-emitting, radioactive elements in the ground. Apart from 40K, these elements are members of the decay chains starting with 238U and 232Th, respectively. Both of these radionuclides have half-lives comparable to the age of the earth and have been present in the earth's crust since its formation. The half-life of 40K is of the same order of magnitude. However, nuclear weapons fallout and debris from accidents at nuclear facilities

Calculation of the external dose rate from field gamma spectrometric measurements requires knowledge of how the primary fluence rate, *i.e.* the number of unscattered photons per unit area and time, from different distributions of radioactive elements, at or in the ground, affects the detector response. Likewise, determination of external dose rate based on gamma spectrometry of soil samples must include a calculation of the primary fluence

The main topic of this chapter is to describe, and compare, some of the methods that can be used to estimate external dose rate from environmental sources of ionizing radiation from radioactive elements. The external dose rate from radioactive sources at or below ground may be estimated in several ways. One method is to simply measure the dose rate with a properly calibrated intensimeter or other type of dose meter (*e.g.* ionization chamber or thermoluminescent dosimeter, TLD). Another method is to calculate the dose rate based on gamma spectrometric measurements, *e.g.* field gamma spectrometry or soil sampling. However, due to assumptions of the relation between primary and scattered radiation, as well as calibration requirements, the dose rate estimations from these methods seldom agree in practical situations. The topics mentioned above will be exemplified with reference to actual measurements by field gamma spectrometry and intensimeter, as well as model

The quantity fluence has been defined by the International Commission on Radiation Units

area. According to the definition, d*N* is the number of particles (here photons) incident on

= d*N*/d*a*, *i.e.* the number of particles per unit

Φ

may at some sites contribute even more to the exposure.

calculations of fluence rates from different environmental geometries.

**2. Primary fluence rate from different source geometries** 

and Measurements, ICRU, (ICRU, 1998) as

rate from the actual soil inventory.

**1. Introduction** 
