HOW TO WRITE ABSTRACTS FOR THE PROCEEDINGS OF THE XXXIV ANNUAL

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HOW TO WRITE ABSTRACTS FOR THE PROCEEDINGS OF THE XXXIV ANNUAL Powered By Docstoc
					USEFUL CESIUM FROM CHERNOBYL

S. Kasi                             homepage: http://www.helsinki.fi/people/servo.kasi

Helsinki University of Technology
email: servo.kasi@helsinki.fi



Deposition of radioactive 137Cs (half-live 30.07 a) after the accident is in soil near sur-
face and its vertical distribution seems to be stable [1]. Its 661.7 keV gamma has a
ccnsiderable peak in scintillation gamma spectrum measured in an airplane in Finland. K

                        200
                                                 3
                                       25 dm NaI(Tl) scintillator
                        150
             Counts/s




                                             Cs
                        100
                                                       in year 2000
                         50
                                  before                      K                                               Th
                                   1986
                          0
                              0            500       1000     1500                            2000           2500         3000
                                                     Gamma photon energy, keV

                                                                                              1
                                                                                              0.9
and Th peaks above as well as the relatively
                                                                     Relative counting rate




                                                                                              0.8
weak peak of U at the energy 1764.5 keV have
halflives in Ga. These photons and those of Cs                                                0.7


can be used to determined water equivalent                                                    0.6


(mm H2O) of snow cover and they give a                                                        0.5


possibility to determine water content in the                                                 0.4
                                                                                                                     Th
surface soil layer [2]. Snow attenuates Cs-                                                   0.3

photons more efficiently than the more energe-                                                0.2

tic photons.                                                                                  0.1
                                                                                                      Cs
                                                                                              0
                                                                                                  0    100     200    300    400   500   600
Another Chernobyl isotope 134Cs (2.062 a,
1986-05-01 activity 57 % of the 137Cs activity)                    Snow cover, water mm
is a tracing nuclide of the 1986 deposition of
137
    Cs, especially long when its activity is determined by the 795.8 and 604.7 keV photons
coincidence [3]. These isotopes have been applied in erosion-deposition research earth-
widely.

[1] S.S.H. Kasi, Radiation Physics and Chemistry 61(3-6) June 2001, 673.
[2] S.S.H. Kasi, http://www.mv.helsinki.fi/home/skasi/Cs-use.pdf
[3] Chien Chung, Shen-Ming Liu, Cheng-Chang Chan, J. Radioanal. Nucl. Chem. 161(1992),
   495.