RKI Instruments GD-70D Series - Manual (Page 78)

Detection principle
GD-70D - 78 -
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 . 0 00524 . 0
1 . 0
10 5 . 18 2
2
3
= ⋅
Ч Ч
=
−
[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".