RX Vessel Internals Flashcards
List Six major parts of the Reactor
Vessel Head Reactor vessel Upper internals assembly Core Lower internals assembly Instrument Support Assembly
How is the Core barrel attached to the vessel
the core barrel hangs from the vessel flange
What does the Lower core plate do
supports and aligns fuel assemblies
What protection does the lower core support provide
Limits the drop distance of the Core Barrel to ensure that control rods remain insertable and that the coolant flow is not blocked
Discuss the sizing of the thimble tubes
Upper section is wider to allow for rapid insertion of the control rods
Lower section is smaller to allow for hydraulic braking (Dashpot)
How many Rod Control Cluster Assemblies and what are they made of
57, 28 Shutdown and 29 Control
Made up of Silver, indium and cadmium
List advantages of using zirlo
Low Neutron absorption
Provides barrier to release of radioactivity
High strength
High Corrosion resistance
List disadvantages of using zirlo
Zirc-water reaction produces heat and Hydrogen
What are the advantages of sintering
reduces moisture content in pellet to minimize corrosion of cladding
List advantages of using a ceramic fuel
high melting point - 5080F
retain fission products
List disadvantages of using ceramic fuel
poor heat conductor
Discuss use of thimble plugs
Used in all fuel assemblies not containing a control rod or neutron source
limits core bypass flow
Describe coolant flow through core
water enters through nozzles
flows down along core barrel and thermal shields (downcomer)
Flows up through core forging and lower core plate
Flows up through the fuel assemblies and into upper plenum where it mixes and out into the hot legs
describe core bypass flow
total - 5.5% thimble tubes - 2% upper head cooling - 1.5% from inlet to outlet nozzle - 1% core baffle plates - .5% between baffle wall and periphery of the fuel - .5%
Discuss thimble cell thermal considerations
A rod in a thimble cell operates closer to its thermal limit that those in a unit cell due to less flow in the area due to the thimble plug
