RKI Instruments GD-70D Series - Page 136

GD-70D - 136 -
Safety of the radioisotope 241Am (37 KBq) used in the pyrolysis-particle type
sensor
The pyrolysis-particle type sensor installed in the gas detector uses the radioisotope 241Am radiation
source (18.5 KBq x 2 = 37 KBq).
A specified designing certification device must satisfy the specified threshold for "1 cm dose equivalent
rate at a point 10 cm away from the surface of the device" as a certificate condition, which is the
following value (tolerable amount).
Tolerable amount
1 cm dose equivalent rate at a
point 10 cm away from the
surface of the device
1μSv•h
-1
This detector which uses radioisotope
241
Am radiation source (18.5 KBq x 2 = 37 KBq) has the following 1
cm dose equivalent rate at a point 10 cm away from its surface, meaning that it completely satisfies the
certification condition.
1 cm dose equivalent rate at a point 10 cm away from the surface of
the sensor (calculated value)
cm
r
Q
D
1
2
Γ
⋅
=
(
)
019.
000524
.
0
1
.0
10
5.
18
2
2
3
=
⋅
×
×
=
−
[μSv•h
-1
]
Q
: Amount of radioisotope 2 x 18.5 x 10
-3
[MBq] =(37KBq)
cm
1
Γ
: 1 cm dose equivalent rate constant of
241
Am 0.00524 [μSv•m
2
•MBq
-1
•h
-1
]
r
: Distance from radiation source 0.1[m]
It is certified as a safety device, provided that it is used in accordance with the certification conditions
specified in the "Safety Manual".