Endress+Hauser gammapilot FTG 671, Руководство по эксплуатации

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The shielding material is lead in a welded steel housing. Fire proof source containers are
available, which ensure that the radiation source and lead shielding cannot be lost when
the housing is heated above the melting point of lead (327 °C/620 °F); e.g. in case of
fire. The position of the radiation exit channel is marked in the dimensional drawing and
on the container, and must be taken into account when planning and mounting.
The source containers are available with manual or pneumatic ON/OFF-switching. The
QG 2000 can be obtained in a version with proximity switches for remote display of the
switching status.
Additionally, QG 20 and QG 100 are available in Euro/Swedish and Chemical design for
special safety requirements.
Attenuation factor The attenuation factor F
s
and the number of half-value layers for the different source
containers with
60
Co and
137
Cs sources are summarized in the following table.
From these values one may calculate:
•
The local dose rate D at a given distance r from the source container (more preci-
sely: from the source in the interior of the container).
•
The radius r of the control area . At this radius the local dose rate is attenuated to a
given value D .
The following table summarizes some typical examples:
For
137
Cs in the QG 2000 the local dose rate at the surface of the container is below the
given value. Therefore, no control area is present in these cases.
K = 357
µ
Sv m
2
/ h GBq (= 13.200
µ
Sv m
2
/ h Ci) for
60
Co
K = 96
µ
Sv m
2
/ h GBq (= 3.550
µ
Sv m
2
/ h Ci) for
137
Cs
F
S
for
60
Co F
S
for
137
Cs
QG 020
37 (5,2 HWS) 194 (7,6 HWS)
QG 100
181 (7,5 HWS) 1448 (10,5 HWS)
QG 2000
4096 (12 HWS) 8.389.000 (23 HWS)
Table 2.2:
Attenuation factors F
S
and the number of
half value layers (HWS)
D
=
K
A
r
2
F
S
D : Local dose rate [
µ
Sv/h]
r : Distance from source (control area) [m]
A : Activity of the source [GBq]
F
S
: Attenuation factor
(s. above table)
r
= √
KA
/ D
F
S
Equation 2.1:
Calculation of the
local dose rate and the
control area
Source
container
Activity
[GBq]
60
Co
D = 7,5
µ
Sv/h
60
Co
D = 2,5
µ
Sv/h
137
Cs
D = 7,5
µ
Sv/h
137
Cs
D = 2,5
µ
Sv/h
QG 020
0,74 0,98 m 1,69 m 0,22 m 0,31 m
QG 100
3,7 0,99 m 1,71 m 0,18 m no
control area
QG 2000
11 0,36 m 0,62 m no
control area
no
control area
Table 2.3:
Control area of the
Source containers by
different activitys from
60
Co and
137
Cs
Gammapilot FTG 671 Chapter 2: Installation
13