Radiological Properties of Heavy Liquid Metal Targets of Accelerator Driven Systems
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regimes. The purpose of this work was to estimate the radiotoxicity of the LBC inside cylindrical targets of different sizes and under different accelerator proton beam parameters and specify the contribution of the main target components into the total radioactivity of the TC. LONG -LIVED RADIOACTIVITY AND RADIOTOXICITY The estimation of radiotoxicity of the LBC inside of two cylindrical targets of different diameter D and length L and under different accelerator proton beam energy Ep and current 1pand irradiation time T•,. (see Table I) has been carried out. Table I. Geometry sizes of targets and proton beam parameters. Target
L, cm
D, cm
E,, MeV
Ip, mA
T,r, days
#1
100
50
800
30
365
#2 60 20 800 1,25 91 In these calculation the data of Yu.N. Shubin [3,4] on spallation and fission product activity were used. For both targets #1 and #2 the radionuclide activities were calculated by Monte-Carlo 1215 Mat. Res. Soc. Symp. Proc. Vol. 556 © 1999 Materials Research Society
method using CASCADE code [10]. The cross sections were calculated using semiempirical formulas of Silbergberg and Tsao [11]. The radiotoxicity Ri of the i-th nuclide in the coolant is defined as the ratio of its activity Ai (in Bq) to its allowable concentration Ci, for population in the drink water (in Bq/m3 ):
(1) where C'' is allowable specific activity of the i-th nuclide for population. The total coolant radiotoxicity is as following::
RY =
(2) 3
The specific radiotoxicity values are expressed in the corresponding units of I m of LBC. In the whole, from [3,4] only comparatively long-lived spallation and fission products (O0,2 Ž10 days) along with polonium isotopes Po-208, Po-209, Po-210 were taken into account in our calculations. The inverse values of the allowable activities for population taken from the US Safety Standard [5], were used as the weight coefficients. The total radioactivity and radiotoxicity along with a contribution of spallation and fission products versus cooling time are presented in Fig. 1 and 2 for target #1 of 24 MW power. The values of total radioactivity and radiotoxicity for both targets #1 and #2, that is of 24 and 1 MW power were calculated
independently, using approach described in [3,4, 10 and 11 ].
Activity, Bq 11-+17
IF+145
11: f 13-
IF+14
1II13
-4----w-
pallation products fission products
iI I ý0 +l1Il'
1,+001
I1 +H)i
1V1402
Cooling time, years
Fig. I Total radioactivity of target #1.
1216
Radiotoxicity, water liters
11-+ 7I 1E101
"i 1' 1E+oo
I
I
I III III
I
]
I I
iE+01
II II !
1t"m,+2
Cooling time, years
Fig. 2 Total radiotoxicity of target #1.
It seems to be reasonable to show a principal difference between radioactivity/radiotoxicity of LBC of the ADS and reactor power units. That is why we have quantitatively analyzed the LBC radiotoxicity of the target #1 and BRUS-150 [6] reactor power unit (thermal power -500 MW). The specific coolant radiotoxicity (in cubic meters of water per cubic meter of LBC) of the target #1 and BRUS-150 reactor, along with radiotoxici
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