Environmental Engineering Reference
In-Depth Information
plants would require an investment of over $500 billion, there is a huge eco-
nomic driver for this work.
Much work remains to be done in this area including:
￿
Understanding of the effects of chemistry on the development of cor-
rosion and especially SCC in piping, equipment, fasteners (bolts) and
welds both inside and outside the core area. The likely result of better
understanding of the chemistry will be the development of new addi-
tives for use in the primary and secondary systems of LWRs to prevent
corrosion and cracking, the build-up of radioactive materials, and the
maintenance of clean heat transfer surfaces.
Long-term effects of radiation, temperature and pressure cycling, and
￿
chemistry on the integrity of the reactor vessel and its component mate-
rials. This also applies to the other components in the primary system,
though radiation effects will be much less important.
In-place maintenance methods (for instance, in-place annealing) that
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can be used to reverse the effect of irradiation on materials
Maintenance methods for remote repair of components such as under-
￿
water welding and robotics
Development of new alloys (for instance alloy 690 for steam generator
￿
tubes) or new materials (such as SiC composites) that can be used to
eliminate potential issues due to radiation and chemistry
Development of new materials for pump seals capable of withstanding
￿
high pressure drops, high wear, and primary system water chemistry
Development of modeling tools to more accurately predict the stresses
￿
that components undergo during operation, and to design components
that perform as well or better than the current components. Part of this
effort should be on developing the phenomenological models required
to predict the performance of current materials after having been in ser-
vice for 40 or more years. This capability will be required for license
renewals of current plants.
Development of monitoring tools for in-use components that will pro-
￿ ￿ ￿ ￿ ￿ ￿
￿
vide suffi cient warning to plant operators of impending maintenance
and repair issues so that appropriate steps can be taken during sched-
uled outages, minimizing the potential for failure generated accidents
and disruptions of the electrical supply.
9.4 The containment structure - the final
fission barrier
The containment structure of an LWR acts as both a barrier to the spread
of fi ssion products from the reactor into the environment and as a shield to
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