SYSTEM FOR MONITORING OF
THE NATURAL AND
artificial
RADIOACTIVITY in the aerosols AT
BEO "MUSSALA"
The system includes an air turbine, a filter device, a press for
preparing of the samples for measuring, H.P.Ge-spectrometer and a program for analysis
of gamma spectra. All of them have been developed in the INRNE, and mounted at
BEO "MUSSALA", except H.P.Ge detector, which is in the INRNE,
Sofia.
The
air turbine allows to pass through the filter
1500-1800m3 per hour, which is relatively big volume. The air is
passing through the fibers filter, type ÔÏÏ-15-1,5, with high effectiveness,
94-99%.
The
size of the filter is 50x50cm, after sampling the filter is pressed to the pill
with a diameter 57mm, and thickness ~ 15mm.
device on the roof of
BEO MUSALA
The view of
the used samples
after pressing, for
measurements
of the radioactivity at H.P.Ge
spectrometer
The
volume passed through the filter is about ~ 15000m3
, the measurements start usually several days after sampling in the
laboratory in INRNE-BAS.
MINIMAL DETECTABLE ACTIVITY FOR SOME ISOTOPES FISSION OR ACTIVATION PRODUCTS
isotope |
energy of gamma- rays, KeV |
min. detect. concen-ration, microBq/m3 |
der.air
concentr. DAC/20 ITU-EU Bq/m3 |
NA of R. of B. Bq/m3 |
factor of sensibility R.B./min |
Cs
- 134 |
604,6 |
~
7 |
20.8 |
6.0 |
0.85x106 |
Cs
- 137 |
661,6 |
~
4 |
10.7 |
3.2 |
0.80
x106 |
I
-131 |
364.5 |
~
4 |
56.5 |
3.3 |
0.82
x106 |
I
- 133 |
529.9 |
~
5 |
760 |
29 |
5.8
x106 |
Nb
- 95 |
765.8 |
~
4 |
231 |
62 |
15
x106 |
Zr
- 95 |
756.7 |
~
6 |
70 |
19 |
3.1
x106 |
Ru
- 103 |
497.1 |
~
5 |
139 |
37 |
7
x106 |
Co
- 60 |
1173,2 |
~ 3 |
13.5 |
4.0 |
1.3
x106 |
Na
- 22 |
1274,54 |
~
3 |
320 |
72 |
24
x106 |
Factor
of the sensibility is the ratio of mean activity per year for the public places
for
The
same concentrations proposed by ITU are several times higher
.
On
reality this one means how many times the minimal measured activity for any isotope
is lower, then maximum
permissible on the public places.
The
measurements started on December, 2006, for some time they had been stopped,
because of very bad weather conditions.
The
results for Be-7 are presented on the plot, the error
is ~ 15%.
Artificial
radioactivity has not been identified since then , in the frame of above mentioned
sensibility.
A new
spectrometer with H.P.Ge-detector, cooling with "
We
have possibility, if necessary, in the frame of less then several hours to take
a sample, to start measurements and to make analysis.
An
additional, there is a NaI spectrometer with 2l volume as a reserve for fast
measurements.
For
more information and questions :
ilpen@inrne.bas.bg
Dr.Ilia
Penev,
INRNE-BAS,
boulv. Tzarigradsko shosse 72
Sofia-1784,