Civil Engineering Reference
In-Depth Information
Table 4.5
Exposure limit for the annual effective radiation dose from nuclear installations to the
population permissible on top of the natural background radiation
Effective dose
ICRP 60 (1991)
EU (1996)
US NRC (10 CFR 20)
Limit (population) per annum
1 mSv/year
1 mSv/year
1 mSv/year
Table 4.6
Limits for persons occupationally exposed to radiation
ICRP
60 (1991)
German Radiation Prot.
Ord. 2008
EU (1996)
20 mSv/year 20 mSv
a
/year 20 mSv/year
Limit for persons occupationally exposed
to radiation
a
100 mSv in 5 consecutive years, but not more than 50 mS/year in 1 year
4.6.5 Life Time Occupational Exposure Limit
According to §56 of the German Radiation Protection Ordinance [
14
] an occupa-
tionally exposed person can receive a maximum of 400 mSv during its professional
life. This limit can only be exceeded by 10 mSv/year if both, medical authorities
and the person having reached the professional
lifetime limit of 400 mSv,
agree [
14
].
4.6.6 The ALARA Principle
Above and beyond these standards defined by ICRP and national regulations, the
“as low as reasonably achievable” (ALARA) principle must be applied to all
emissions of nuclear plants. This means that practically all facilities of the fuel
cycle must keep below those standards [
5
,
7
,
12
,
19
,
20
].
4.7 Nuclear Power Plants
Most of the radioactive inventory in Bq of a nuclear power plant is made up of
fission products. Gaseous fission products, such as noble gases (especially krypton
and xenon) and tritium, can enter the coolant through leaks in the claddings of fuel
rods. They are passed through the primary coolant purification system and the
exhaust air system into carbon filter lines and into the exhaust air stack from
where they are released into the environment. Emissions of shortlived isotopes,
such as Kr-88 (half-life 2.8 h), can be minimized by adequate holdup of gaseous
effluents in storage and decay tanks before release.
