Combustion Engineering Reactors

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Older CE with 1250 psi HPSI yes.

System 80 CE with 1850 psi HPSI no.

Not always true.  I know SONGS used to credit charging, but that was only because their HPSI pumps were essentially undersized.  The analysis needed the extra flow (not the extra pressure) from charging.  Their more recent analyses (since late 90s) do not credit charging.

The largest small breaks can also result in safety injection tank actuation, as the pressure plateau is below the SIT injection pressure.

[M1Ark]

Not always true.  I know SONGS used to credit charging, but that was only because their HPSI pumps were essentially undersized.  The analysis needed the extra flow (not the extra pressure) from charging.  Their more recent analyses (since late 90s) do not credit charging.

The largest small breaks can also result in safety injection tank actuation, as the pressure plateau is below the SIT injection pressure.

SBLOCA is not the only reason for crediting charging pumps.  It is also for SDM concern during an uncontrolled cooldown.  When an ESD drives RCS pressure to SI setpoint then boration is required at CE plants at >40 gpm.  Plants with high head HPSI credit HPSI.  Those with low head HPSI will cause charging pumps to auto start and emergency boration valves to open. 

As far as SONGS... sounds like a plant specific problem with inadequate sized HPSI pumps. Does SONGS have high head HPSI pumps?

[tr]

The SONGS HPSI pumps are low head (~1300 gpm).  HPSI is credited for boration during steam line break events.  Boration via charging is implicitly credited in the post-accident cooldown evaluations (assumption is that the operators maintain required shutdown margin, which in turn requires boration via charging).

[Fermi2]

Thanks M1Ark!

[thenuttyneutron]

I am amazed at how these "Charging" pumps seem so undersized compared to what I am used to seeing.  At my plant we call the "Charging Pumps", Makeup Pumps.  These babies can both each give me 170 gpm if I have them piggybacked to my LPI pumps at 2750#.  I can get about 150 GPM if I have them sucking off my makeup tank.  My HPI pumps kick in at 1600# if they are straight off of my Borated Water Storage Tank, 1850# if they are piggy backed as well on the LPI.  These HPI pumps are good for about 800 gpm each.

[dirac]

FOr CE plant: 3 Positive displacement pumps @ 44 gpm each. Total of 132 gpm up to 2500 psi. Thats it.