35
2) place verified BDN on the calibration bench of the reference assembly gage carriage so that
the position of neutron field point for which the reference value of measured DER was calculated,
oj
H
.
, coincides with the direction of detection unit geometric center. Geometric center of BDN
neutron detector must coincide with symmetry axis of neutrons collimated beam. At that longitudinal
axis of the detector must be perpendicular to the symmetry axis of neutrons collimated beam;
3) successively place the gage carriage with BDN on the reference assembly so that the
detector’s geometric center coincides with the reference points where the reference value
oj
H
.
, equals
3.0; 30.0; 300.0; 1500 and 4000 μSv/h. When statistical error is less than 5 %, read five neutron
radiation DER values in every reference point with the interval no less than 30 s. Then calculate
average DER value
j
H
.
for every verifiable point, using the Formula (9.2).
4) calculate the instrument readings caused by direct radiation, using the Formula
R
ij
ijB
B
H
H
.
.
,
(9.12)
where В
R
– coefficient taking into account the effect of scattered neutron radiation on the
instrument readings (the coefficient is calculated during the assembly verification);
5) calculate the measurement error Q
j
, %, using the Formula
oj
oj
ijB
j
H
H
H
Q
.
.
.
;
(9.13)
6) calculate permissible limits of intrinsic relative measurement error at confidence
probability 0,95, using the Formula
2
max
2
max
2
3
j
j
o
s
S
Q
Q
K
,
(9.14)
where К
s
– coefficient depending on random errors equal to 2;
Q
o
− error of reference dosimetric assembly, %;
S
jmax
– value of the relative average deviation of measurements result S
j
, % calculated
using Formula
%
100
)
1
(
)
(
1
5
1
2
.
.
.
n
n
H
H
H
S
jB
ijB
jB
j
.
(9.15)
Verification results are considered satisfactory, if values of confidence limits of intrinsic
relative DER measurement error for all reference points, calculated using Formula (9.14), do not
exceed the limits of permissible intrinsic relative error
add
calculated using Formula
)%
30
(
.
H
K
add
,
(9.16)
where
H
– DER value, μSv/h;
К – coefficient = 10.0 μSv/h.
9.8.3.8 Calculate permissible intrinsic relative error of
- radiation flux density measurement
for BDAB in the following way:
1) connect BDAB to BDOI, switch BDOI on and select
- radiation flux density
measurement mode;
2) open β- filter. Place the detector successively very close to the reference sources,
239
Pu,
second category, 4P9, 5P9 or 6P9 type so that the detector surface is parallel to the source surface. At
that detector geometrical center must be perpendicular to geometric center of detector sensitive
surface with
2 mm accuracy. Press the START button. Read measured values of
- radiation flux
density when statistical error is less than 5 %;
Содержание BDG1-PM1403
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