Page 428 - Fundamentals of Magnetic Thermonuclear Reactor Design

406 Fundamentals of Magnetic Thermonuclear Reactor Design

Fundamental Safety Objectives. In its safety recommendations, the IAEA
sets out the following general, radiation and technical safety objectives:

– General purpose: protection of the population, personnel and environment
against the harmful effects of ionising radiation and other harmful and haz-
ardous factors.
– Radiation safety objectives: limitation of radiation exposure of people and
the release of radioactive substances (RSs) to the environment to levels
prescribed by regulatory documents, achievement of the lowest reasonably
achievable radiation levels and mitigation of the severity of accident conse-
quences.
– Technical objectives: prevention of accidents or, where such prevention is
ineffective, implementation of technical and organisational measures to mi-
nimise negative effects and prevent severe accidents.
The radiation safety objective is achieved by creating safety systems and
implementing effective measures to ensure the protection of human health and
food, water, air and land against exposure to harmful radiation. The objective
is considered to be achieved if a fusion system substituting non-fusion power
generating capacities poses a lower risk than the substituted capacities.
Radiation Safety Criteria. The dose limits set by nuclear regulations. Ac-
cording to the Russian Radiation Safety Standards (NRB-99/2009) and ICRP
recommendations, the following radiation exposure doses are taken to be
the maximum permissible during normal operation (see also Appendix 14.1)
[2,9]:

l For radiation workers (group A), the effective dose limit is 20 mSv/year
measured over 5 years, but ≤50 mSv in any single year.
l For a population, the effective dose limit is 1 mSv/year measured over
5 years, but ≤5 mSv in any single year.
At such doses, the individual lifetime risk of stochastic effects is 0.001 for
–5
personnel and ∼5 × 10 for the public (cf. the average annual effective dose of
naturally occurring radiation is 2 mSv/year, of which 0.3 mSv/year comes from
cosmic rays (at sea level) and 1.7 mSv/year from earth-borne sources, including
radon (∼1 mSv).
To follow the principle of enhanced safety management applicable to new
technology, tighter requirements should be placed on fusion reactors, including
the lowest reasonably achievable dose limits.
For ABDB the maximum acceptable level of emissions is the one, above
which expected doses for the population within a controlled area and outside it
require protection measures, such as sheltering, iodine prophilaxis and evacu-
ation. According to the Russian radiation safety regulation, the necessity of
population evacuation should be considered if expected whole-body avertable
absorbed doses are in the range of 50–500 mGy over the first 10 days after an
accident [9].