.AR Rx Vessel & Internals (...part of RC-RCS) (Welch's Highlighted Notes)

Question 1

Core Bypass flows

• Explain…
• …
• Lower vessel…
• Vessel head…
• Hot leg…
• Cold leg…

Answer 1

Core Bypass flows

• Outlet nozzle clearances (1%)
• Instrumented center guide tubes, center/outer guide tubes (.6%)
• Shroud barrel annulus (.3%)
• Alignment keyways (0.4%)
• Lower vessel – 61 instrument penetrations (53 have NIs)
• Vessel head – 98 penetrations
  
  • 89 (CEDMs)
  • 1 (head vent)
  • 2 (RVLMS)
• Hot leg (42” nozzles)
• Cold leg (30” nozzles)

Question 2

Closure Head Flange Sealing system

• What type of O-Rings are used?
• Leak detection?
• Where does HV-403 vent pressure to?
• MCR psia indications? Alarms at what psia?

Answer 2

Closure Head Flange Sealing system

• Two self-energizing metal O-rings. (inner and outer)
  
  • Inner surface of the O-ring is drilled, allows RCS to pressurize the O-ring and improve the seal.
• Leak detection installed between the O-rings.
• HV-403 operated to vent off pressure to RDT
• 0-3000 psia MCR indication. Alarm at 1500 psia

Question 3

[…Not highlighted in Welch’s Notes…]

Fuel Assemblies (FAs):

• How many FAs?
• Guide tubes… explain…
• Fuel rods? What gas is used to pressurize them?

Answer 3

[…Not highlighted in Welch’s Notes…]

Fuel Assemblies (FAs):

• 241 F/As
• 150” active length
• Guide tubes:
  
  • CEA path / Incore path
• Sit on lower support structure
• Restrained from upward movement by the UGS tubes.
• Fuel rods pressurized with helium
  
  • Preclude clad collapse
  • Improve thermal conductivity (pellet to clad gap)
  • Over core life, more FPs in rod, reduces heat transfer

Question 4

• Core support barrel:
  
  • Suspended from where?…
  • Supports what?…
• Flow skirt: Installed where? For what reason?
• Lower support structure: Does what? .
• Core shroud: Welded to what? Does what?…
• Core bypass flow: minimize thermal stresses and prevent stagnation
• UGS: Explain…

Answer 4

• Core support barrel:
  
  • Suspended from a ledge on the inside surface of the vessel closure flange. Aligned through four alignment keys.
  • Supports the vessel internals and allows for expansion of the core.
• Flow skirt: Installed in the lower portion of the vessel to equalize flow distribution before coolant passes into the lower plenum
• Lower support structure: aligns F/As, guide path for the incore instrumentation, and directs coolant into the F/As.
• Core shroud: Welded to lower support structure. Envelope for the core perimeter, directs coolant flow, and limits bypass flow.
• Core bypass flow: minimize thermal stresses and prevent stagnation
• UGS: aligns and supports the upper ends of the F/As. Prevent movement during pressure transients or a severe accident condition and protects CEAs from the effects of coolant cross flow in the outlet nozzle region.