Environmental Engineering Reference
In-Depth Information
The effect of oxide level and hydride content on the mechanical behav-
ior of zirconium alloys.
The effect of rapid stress levels on the mechanical behavior of zirconium
alloys.
Effects of long-term wet and dry storage as well as environmental condi-
tions in any potential disposal site on the integrity of the zirconium alloy
cladding.
Effect of mechanical stresses induced by fl ow vibration on the fuel rod
cladding as well as the grid support structures.
Effect of fl ow rate on corrosion and erosion of both the fuel and the fuel
structure.
Modeling of these effects to allow performance prediction in extended
burnup and in transient operating conditions.
9.2.3 Development of advanced claddings
and accident tolerant fuel
Recent (Fukushima) and not so recent events (Three Mile Island 2), have
accelerated the quest for new cladding materials that will be much more
resistant, if not totally tolerant, to current LOCA conditions (~1200°C for
400 s) as well as more extreme beyond-design basis accident conditions
such as a long-term full station blackout where there is little or no sup-
ply of coolant to the fuel. The most notable of these materials is the use
of SiC composites. As little as is known about the behavior of zirconium
alloys on a phenomenological basis under normal or accident conditions,
much less is known about SiC composites or any other ceramic materi-
als that could potentially replace metal alloys as fuel cladding materials.
SiC cladding along with higher density or higher enrichment fuel could
provide:
Resistance to accidents and departure from nucleate boiling (DNB) or
dry-out incidents because of higher operating temperature (~2000°C)
capability.
Minimal hydrogen production due to a much lower rate of reaction with
water.
Ability to operate in much longer cycles due to the very low corrosion
rate of SiC in water.
Enrichment savings due to ~75% lower thermal neutron absorption.
Uprate capability of ~30% due to the ability to operate at DNB or
dry-out conditions.
Immunity to debris or fretting failures.
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