33
instrument’s end surface and by annular groove on the side surface. Switch BDOI on. Select the DER
measurement mode with the BDG1;
3) at set statistical error value of less than 10 % take five DER measurement readings at an
interval of at least 30 s when there is no radiation source. Then calculate average DER value of the
external gamma background, μSv/h, using the Formula (9.1).
4) place sequentially BDG1 onto the dosimetric assembly so that geometrical center of the
detector coincides with the reference point where reference DER value equals 0.8; 8.0 and 80.0 μSv/h;
5) at set statistical error value of less than 5 % take five gamma DER measurement readings
in every reference point at an interval of at least 10 s. Then calculate average DER value
j
H
.
using
Formula (9.2).
6) calculate relative DER measurement error Qj, % using Formula (9.3).
7) calculate confidence limits of permissible intrinsic relative error of DER measurement
DER
, %, at confidence probability 0.95 using Formula (9.4).
Verification results are considered satisfactory if values of confidence limits of intrinsic
relative DER measurement error for all verifiable points, calculated using the Formula (9.4), do not
exceed the limits of permissible intrinsic relative error calculated using the Formula
)%,
20
(
.
H
K
add
(9.8)
where
.
H
− DER value, μSv/h;
К – coefficient, equal 2,0 μSv/h.
9.8.3.4 Check ability to accumulate scintillation spectra of gamma radiation and relative
energy resolution during BDG1 operation in the scintillation spectra accumulation mode as follows:
1) connect BDG1 to BDOI;
2) switch BDOI on and set into the spectrum accumulation mode according to the chapter
11.1.5 of the Operation Manual;
3) place gamma sources
137
Cs and
57
Со (10
4
- 10
5
)
Bq from the reference spectrometric
gamma sources set of OSGI-3 type at such a distance from the scintillation detector surface against
the geometrical center so that the count rate was no more than 10000 cps;
4) press START button and carry out spectrum accumulation till a well-defined spectrum will
be displayed on LCD, or continue accumulation during 100 s at least. The LCD will display
accumulated spectrum;
5) stop spectrum accumulation by pressing the MENU button, record accumulated spectrum
into BDOI memory and send accumulated spectrum to PC as specified in Operation Manual, chapter
11.11;
6) see information on working with spectra saved in the PC in “Read Me” file of the user
program “РМ1403 spectra”;
7) calculate the relative energy resolution
1
, %, using the Formula (9.5).
Verification results are considered satisfactory if relative energy resolution
1
, %, calculated
using the Formula (9.5) doesn’t exceed 8.5 %.
9.8.3.5 Calculate permissible intrinsic relative error of photon radiation DER measurement for
BDG2 in the following way:
1) connect BDG2 detection unit to BDOI;
2) place BDG2 on the verification assembly with
137
Cs gamma source so that the instruments’
panel faces the radiation source, and the line going through the geometrical center of the detector
aligns with the irradiation flow axis. Geometrical center of the detector is marked by “+” sign on
instrument’s end surface and by annular groove on the side surface. Switch BDOI on. Select the DER
measurement mode with the BDG2;
3) at set statistical error value of less than 10 % take five DER measurement readings at an
interval of at least 30 s when there is no radiation source. Then calculate average DER value of the
