ECCS/ SI

Question 1

SI-8804A……..what is it?
Interlocks…..?
Why………?

Answer 1

RHR -> CCP suction
- cannot open unless 8701 or 8702 closed
(no eccs in norm mode)(ovrprs eccs)
- 8974A or 8974B closed
(pellets back to RWST)(SI recirc valves)
- 8982B open
(recirc sump isolation valve)(x-conn only in recirc mode)

Question 2

SI-8804B………..what is it?
Interlocks………?
Why…….?

Answer 2

RHR -> SI pump suction
- cannot be opened unless, 8701 or 8702 closed
(Not x-conn, if norm lineup)(ovrpsrz rhr w/RCS)
- 8974A or 8974B closed
(Not x-conn, w/recirc l/u)(pellets back to RWST)
- 8982B open
(X-conn only if in cnmt recirc)

Question 3

SI-8982A(B)……..what is it?
Interlocks……….?
Why……….?

Answer 3

CNMT recirc sump isolation valves
- cannot be opened unless 8700A & B closed
(don’t drain RWST to floor)(x-conn RWST->sump)

Question 4

SI-8974A(B)…….what is it?
Interlocks……..?
Why………?

Answer 4

SI pump recirc back to RWST
- cannot open unless 8804A (B) closed
(Pellets back to RWST)(SI pump recirc valves closed when in CNMT recirc mode)

Question 5

ECCS design basis (10CFR50.46)

Answer 5

2200 deg - limit peak cladding temperatures
17% - total oxidation > 17% total clad thickness
1% - max H2 generated < 1% of all cladding reacting w/H2O
Coolable geometry maintained
Long term cooling

Question 6

RWST required vol and [B]?
Outputs?
Interlocks?

Answer 6

> 455,703 gal, 2300-2500 ppm

• RW purification pump, CCP, SI, RHR, CS
• 2/3 Lrwst < 33% & cnmt recirc sump suction closed=>RHR pumps Trip

Question 7

Flow and pressure for ECCS pumps?
CCP……
SI……
RHR……

Answer 7

CCP (150-560 gpm / 2550-650 psid)

SI (425-675 gpm / 1150-675 psid)

RHR (3000-5000 gpm / 150 psi)

Question 8

Describe 8808A, B, C, D

Interlocks….?

Answer 8

Isolation valves to accumulators, norm open w/ power removed

Auto open- SI
Auto open- neutral + Prcs > P-11

Question 9

During LOCA, what happens at 33% RWST level?

Answer 9

RHR pumps Trip automatically
- manually swap to cold leg recirc (RHR gets suction from CNMT recirc sump, SI & CCP get suction from RHR, CS continues to get suction from RWST until 4% when all pumps taking suction secured

Question 10

When is hot leg recirc initiated, describe line up

Answer 10

• 7 hours after cold leg recirc established, to inhibit precipitation of boron on fuel assemblies and possibly restrict flow
• CCP continue inject to all four cL
• SI stops cL inj, and inj to all four hL
• RHR continues provide suction to CCP & SI, also injects hL 1 & 2, (stops inj cL)

Question 11

Accumulators purpose and design bases?

Answer 11

• passively inject borated water into RCS cold legs during intermediate-large LOCA (2200-2500 ppm, 600-640 psig)
• quickly reflood core following blowdown phase of LOCA (up to bottom of active fuel)(utilizing 3 of 4 accumulators, one on floor)
• after reflood, diesels should be up and loaded, eccs pumps take over to “refill” core, covering F.A.