32
8) calculate confidence limits of permissible intrinsic relative error of DER measurement
DER
, %, at confidence probability 0.95 using Formula
2
2
1
,
1
j
o
DER
Q
Q
,
(9.4)
where Q
o
− error of dosimetric assembly, %;
Q
j
− relative measurement error calculated using the Formula 9.3.
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
add
=
30
%.
9.8.3.2 Check ability to accumulate scintillation spectra of gamma radiation and relative
energy resolution during BDOI operation in the scintillation spectra accumulation mode as follows:
1) switch BDOI on and set into the spectrum accumulation mode according to the chapter
11.1.5 of the Operation Manual;
2) 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 from 150 to 900 cps;
3) press OK button and continue 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;
4) stop spectrum accumulation by pressing the MENU button and record accumulated spectrum
into BDOI memory under the selected number as specified in Operation Manual, chapter 11.11;
5) send accumulated spectrum to PC according to the chapter 11.11 of the Operation Manual;
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
100
2
1
Е
,
(9.5)
where Е − energy value of total absorption peak of low-energy line
137
Cs, keV;
2
− value of absolute energy resolution in keV, calculated using the Formula
2
=
n
К
,
(9.6)
where
n
− width value of total absorption peak of mono-energy line
137
Cs at its half-height
in channels;
К − values of the channel energy width, keV/channel, calculated using the Formula
К =
Е
Е
n
n
c
c
2
1
2
1
,
(9.7)
where Е
2
, Е
1
− energy values corresponding to total absorption peaks
137
Cs and
57
Co
correspondingly;
n
c2
, n
c1
− channels numbers corresponding to peaks’ centroids with Е
1
and Е
2
energies.
Verification results are considered satisfactory if relative energy resolution
1
, %, calculated
using the Formula (9.5) doesn’t exceed 7,5 %.
9.8.3.3 Calculate permissible intrinsic relative error of photon radiation DER measurement for
BDG1 in the following way:
1) connect BDG1 detection unit to BDOI;
2) place BDG1 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
Содержание BDG1-PM1403
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