Refueling To Cold Shutdown

Mode 6 - Mode 5

Coming from Refueling (first assy lowered into the core) to Cold Shutdown (last stud tensioned on last pass, up to 200°F)

When does Pops need to be Armed?

What does it protect from

Prior to setting the Vessel Head, POPS shall be established (or a pie-hole). With one POPS INOP, restore within 24 hrs (Mode 4 – 7 days) or depressurize and vent thru the pie hole within 8 hrs. With both INOP, depressurize and vent within 8 hrs.

This is to protect against: Brittle fracture...

a)    Starting an RCP with SG temperature greater than 50° above the loop cold leg temperature

b)    Starting and injecting an SI pump into the solid RCS

Starting and injecting a CVCS pump into the solid RCS with the PDP running

Two independent RHR Loops are OPERABLE prior to draining RCS Level in preparation of refueling cavity drain down to <23 feet above the top of the Reactor Vessel flange.

A Lower Refueling Cavity level of ≥101’ elevation provides sufficient volume to ensure the minimum required boron concentration is maintained while performing decontamination activities.

• Drain with RHR to Flange
• Raising the upper internals will facilitate the rapid drain down (>1000 gpm) and prevent drawing a void below the upper internals RHR flow ~2000 GPM, 48 amps on the RHR pump max, 41.5’ max level in RWST
• Drain with Refueling Water Purification Pump
• Drain Lower Cavity with the RCDT pumps
• Finally, drain Fuel Transfer canal thru WL221 to CAN sump

Unblock R12A and R12B

R12A Noble Gases

R12B Iodine

When DECON and draining are complete, swing the WL221 out of the way (allows for proper ECCS recirc), and put the Flange Leak Detection System in service RC2 open, RC3 closed, RC4 open to RCDT