CNMT Structure

Question 1

Purpose and design bases of CNMT ?

Answer 1

• leak tight enclosure prevent release of f.p.
• radiation shielding
• structural support for components
• shelter from outside environment
• protect against missiles
• ability to sample
• source coolant for recirc mode eccs
• refueling canal
• minimize use aluminum & zinc (H2 gen and debis gen is CS actuated)

Question 2

How is CNMT integrity and isolation ensured?

Answer 2

• penetrations have automatic isolations
• able to withstand;
  
  • 47 psig
  • 271 deg
  • neg Press - 3.5 psig
  • thermal expansion from LOCA
  • DBA + double design earthquake

Question 3

How many sumps in CNMT?

Answer 3

4, cnmt structure sump(2), cnmt recirc sump, Rx cavity sump

Question 4

During modes 1-4 what is position of HCV-111?

Why?

Answer 4

• Open, with flange removed

- this allows CS to drain from cavity to recirc sump

Question 5

CNMT liner purpose

Answer 5

• leak tight pressure boundary
• support for safety related components
• part of CNMT structure

Question 6

Purpose secondary shield wall (crane wall)

Answer 6

• secondary bio shield
• shield from possible jet streams from RCS break
• support
  
  • polar crane
  • annulus structure
  • 140 deck

Question 7

Inputs to CNMT structure sumps

Answer 7

• CFCU cooling coil drip pans
• RCP seal #3
• refueling canal leak monitor system
• equip drains & relief valves

Question 8

What kind of level indication is on CNMT structure sumps?

How does it fail?

Answer 8

LT-60 is a bubbler instrument

On loss of instrument air it fails low

Question 9

What happens to CNMT structure sump when Hi level?

Answer 9

Hi- (26”) one pump will start (alt circuit swaps pumps on next occurrence)
Hi-Hi- (32”) second pump will start
Low- any running pump will stop (13”)

Pumps to FDR in A.B.

Question 10

Describe Rx cavity sump components

Answer 10

Two pumps,….two eductors,………priming tank,…..discharged to FDR

Upon actuation priming tank fills suction lines of pumps, pumps provide motive force for eductors, eductors entrain sump liquid and deliver to pump suction, discharge to FDR (actuation similar to structure sump)

Question 11

What functions does CNMT recirc sump do during accident?

Answer 11

• prevents clogging of sump
• protects ECCS equip from foreign material
• vortex suppression
• NPSH for RHR at max flowrate

Under worst postulated conditions

Question 12

How does CNMT recirc sump perform functions of ; not clogging, FME, vortex suppression, etc?

Answer 12

Debris curb- stops big stuff on floor being swept in
Trash racks- big screens, smaller screens, inner debris curb
Vortex suppressor- two strainers, rear- lower and filled w/water=>no air entry, front-higher with flow straighteners and vortex suppression

Question 13

How are electrical CNMT penetrations maintain leaktight

Answer 13

Redundant fault protection (redundant bkrs), smaller loads use redundant fuses.

Question 14

How does Automatic leak rate monitor alarm work?

Answer 14

Measures flow required to maintain pressure between door seal o-rings

Question 15

Where can you actuate CNMT evacuation alarm?

Answer 15

CR(cc1)
CNMT personnel airlock
CNMT emergency airlock
Site emergency alarm (both CNMT’s)