Page 435 - Fundamentals of Magnetic Thermonuclear Reactor Design

Safety of Fusion Reactors Chapter | 14 413

The issue of recycling some radioactive waste within the fusion reactor to
alleviate the disposal problem is currently discussed. Potentially re-usable sub-
stances include tritium, deuterium, lead-lithium eutectic alloys, lithium, vanadi-
um, beryllium, tungsten, niobium, titanium and tin. They account for 50%–80%
of all radioactive substances and materials [13–16].
An effective method for reducing the RMs radioactivity is to use low-activat-
ed materials, such as ferritic–martensitic steels with low contents of molybde-
num, nickel, niobium and vanadium. Transmutation of long-lived radionuclides
into short-lived ones by neutron irradiation is being considered. Such projects,
if implemented, could help considerably decrease the need for deep geological
burial of RMs.
The processes of reprocessing of RMs after their extraction from a fusion
reactor are being developed at the laboratory level. This work involves the fol-
lowing problems:

l Detection of unwanted impurities in tungsten alloys.
l Development of processes for the disassembly and separation of compo-
nents and materials that require special handling.
l Development of processes for the production of recyclable materials [14–16].
l Design and fabrication of complex components using RMs with the help of
remote handling technology.
l Development of processes for re-use of materials irradiated beyond levels
permitting heat treatment in smelting furnaces.
l Development of pre-recycling processes (detritiation, cleaning of surfaces,
removal of corrosion, activation, transmutation products, etc.).
The RMs and waste handling processes have a direct influence on the reactor
design. R&D works ensuring safety during reactor decommissioning must be
completed before the end of the reactor’s service life. After a decision to decom-
mission a reactor is made, a Decommissioning Programme (DP) is developed
and a SAR for decommissioning is prepared. The DP must contain a detailed
description of the site condition after the completion of decommissioning ac-
tivities. The SAR must show that after the completion of the DP activities the
safety of the population and personal is ensured, and the maximum release of
radionuclides and other hazardous substances is within the regulatory levels.
The basic principles used for ensuring radiation safety at radioactive waste
handling are the substantiation expediency principle, the limits-setting principle
and optimisation principle. Organisational and technical requirements for the
collection, storage and disposal of radioactive waste, as well as their accep-
tance by specialised entities, transportation, reprocessing, conditioning, long-
term ageing and/or burial are governed by applicable laws and regulations. In
the case of burial, human radiation protection must be ensured throughout the
whole potential exposure period. The radiation protection programme must en-
sure adequate waste isolation, with anticipated public exposure not higher than
an annual individual dose of 10 µSv.