Environmental Engineering Reference
In-Depth Information
These SiC characteristics allow simplifi cation of safety systems, higher energy
density (to reduce capital costs) and longer operating cycles with higher
density or enrichment advanced fuels to reduce fuel and reactor operating
costs. However, they do come at a cost - the need to develop whole new
areas of understanding in behavior and manufacturing including:
Modeling and design of a SiC composite that will be acceptable for use
in reactors, that will not shatter, and can withstand normal handling
and operations as well as transients and accidents. However, many dif-
fi culties remain before these composite structures are understood well
enough to model, including:
The behavior of ceramic composites in a radiation fi eld is not well
◦
known.
The interaction between the monolithic SiC tube and the composite
◦
layer is especially diffi cult to model.
The interaction between pellet and ceramic cladding will require exten-
sive tests and modeling.
The impact of manufacturing variations on the ultimate performance of
the ceramic structure under operating and accident conditions will need
to be understood.
Joining an end plug to the tube to form a hermetic seal in a cost effective
way is an extremely challenging task.
Methods to produce about 15 million feet of reactor cladding per year
to very exacting specifi cations at acceptable costs will require signifi cant
manufacturing development.
Ultimately, the understanding of all these effects for this relatively new
material must be integrated into a licensable fuel performance code. The
data that is needed can be gained empirically and fi tted into phenomeno-
logical models with empirical verifi cation. At a minimum, the following is
needed under irradiation and coolant conditions (Lahoda, 2011):
Property standards for SiC/SiC-composite matrix ceramic (CMC) mate-
rials as applied to LWR's.
Mechanical properties as a function of time, temperature and irradiation
and use.
Corrosion properties at high temperatures in oxidizing (steam/air)
atmospheres.
Thermohydraulic response under design basis (LOCA, RIA) and severe
accident scenarios.
Core melt progression and relocation during beyond-design basis
accidents.
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