Environmental Engineering Reference
In-Depth Information
Containment
cooling system
4
Steam line
Reactor vessel
Turbine
generator
Separation
& dryers
Feedwater
Heater
Condenser
3
Condensate
pumps
Core
1 & 2
Feed
pumps
Control
rods
Recirculation pumps
Demineralizer
Emergency water
supply systems
9.3 Graphic of the typical boiling water reactor. (Published in NUREG
-1350, Volume 23, August 2011.)
the low thermal conductivity and the resulting stresses from the very steep
temperature gradients experienced under normal operating conditions, the
resulting pieces are relatively large and most of the pores of the UO 2 fuel
act as reservoirs for fi ssion gas products and the fi ssion products themselves.
Under circumstances where the cladding leaks and coolant enters the rod,
the UO 2 fuel can further disintegrate releasing much of the soluble fi ssion
product (primarily Cs and Sr) and most of the gaseous fi ssion products. This
effect becomes more pronounced as the burnup of the fuel increases sig-
nifi cantly above the current levels of about 50 MWtd/kgU. Therefore basic
research work on fuel that is exposed to burnups >~60 MWtd/kgU is needed
and includes:
￿ ￿ ￿ ￿ ￿ ￿
￿
Structural changes in the UO
2 due to collection of solid fi ssion products
and the effect these structural changes have on the mechanical stability
of the fuel during normal and abnormal operation.
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