Fuel Bundle Assembly

Question 1

What is barrier fuel?

Answer 1

A layer of iron enhanced Zirc on the inner clad. Minimizes damage from PCI

Question 2

What do water rods(water channel) do?

Answer 2

Limits magnitude of Void Coefficient. Enhance moderation in center of bundle. Non-boiling area

Question 3

Describe Gd

Answer 3

Gadolinium is a burnable poison that allows higher excess Keff.

Question 4

Describe a fuel pellet

Answer 4

Sintered UO2 with 4 – 4.5% enrichment; chamfered edges

Question 5

What do finger springs do?

Answer 5

Controls/minimizes amount of bypass flow (primary purpose) Bypass flow (10% core flow)—cools under vessel instrumentation, neutron monitoring, control rod blade mechanisms in bypass region between fuel channels Maintain bypass flow relatively constant as fuel channel creep (bowing) occurs.

Question 6

What does the Fission Gas Plenum Area do?

Answer 6

Captures fission product gases not contained within ceramic fuel pellet and allows for thermal expansion. Non Areva fuel has Zr Hydrogen Getter.

Question 7

What does the Lower Tie-Plate do?

Answer 7

• Has vortex eliminator to limit moderator turbulence. • Has 2 bypass holes to allow core bypass flow. • Directs coolant flow through assembly.

Question 8

What are 4 types of fuel damage?

Answer 8

• Debris induced fretting (DIF) caused by FME • Crud induced localized corrosion (CILC)—crud burst (SCRAM) settles out in low flow area which weakens cladding • Pellet-Clad interaction (PCI) “dog boning” • Manufacturing defects

Question 9

Coolant activity spikes during power transients, Step increases in coolant noble gas activity (Kr, Xe), Increasing SJAE readings, and Increases in Xe138/Xe133 ratio are indications of what?

Answer 9

Fuel damage

Question 10

What contributes to Pellet-clad interaction induced fuel failures?

Answer 10

-rapid power increases -increased fuel exposure increasing concentrations of Iodine and Cadmium