ML19322C315
| ML19322C315 | |
| Person / Time | |
|---|---|
| Site: | Crane, Davis Besse  |
| Issue date: | 11/15/1978 |
| From: | Swanson E BABCOCK & WILCOX CO. |
| To: | Spangler W BABCOCK & WILCOX CO. |
| Shared Package | |
| ML19322C316 | List: |
| References | |
| TASK-TF, TASK-TMR NUDOCS 8001160837 | |
| Download: ML19322C315 (7) | |
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'J. E. Spangler, Nuclear !e vice Po-805 **: '
E. *J. Swanson, Plan: Integration Cast.
File No.
or Ref.
Tclede-NSS-14 Su oj.
Date Auxiliary Feedwater Se: points Nove=ber 15, 1978 ga..i...i..............................,.
Our recent discussions with Toledo personnel regarding their need to reduce the steam generator level oe: point for natural circulation, and B&W's need to maintain a high level because of ICCS small break hre led to an i= passe, l
i Both ISW and Toledo are in a " risk" position because :he Toledo small break topical was based on a 32'. level position; any change to that position cay
, require re-analysis and re-licensing.
Nevertheless, a 2:eam generator. level
, value has not been reported to NRC, and the ECCS Unit believes tha: a 10',
level se: point will be adequate.
Toledo's naeds to lower the se: point are genuine and I offer :he following suggestien which you should pursue with Zoledo:
1.
Alter the control logic of the STRCS so that it will provide two setpoints.
Since a con::cl fune:1on cannot be readily placed in an ESFAS sys:e=, the SFRCS sus be mcdified.
In the presence of an ESFAS signal, :he ES?AS sets a priority for opera: ion over any STRCS signal and direc:s the STRCS
- o provide a high se:poin: level control.
In the absence of an ES?AS signal, bu: wi:h an STRCS genera:ed signal, the SFRCS :entrol se:pcin:
is direc:ed :0 a 10w level.
A general sche =stic is a : ached; other ne hods j
of imple enting are possible, but this purveys :he concep:.
2.
ESTAS could also ini: ate auniliary feedwater and isolate =ain feedwa:er.
Further investiga: ion needs :o be made as :o :he actual sequence of events.
I believe 1: is now possible for :vo conditions Oc exis: because the TECo syste=s do not ini:iate ATJ by ISFAS.
These are:
Curren: Desi:n Site Condition Svste=s Secuen:e Control Se: cir:
1.
Offsi:e Power Available ESTAS
> ICS 2' (.v.ain Feedws.:e' O.
Offsi:e ?:ver "navailable ES?AS -r> SFRCS 10' (Aux. Feedwa:er)
If my reasoning is correc:, the firs: cond :icn will enly pr vide a 2' cen::ci (of =ain feedva:er); ne SFRCS signal will c:ur and the ICS will centrol.
The Other ::ndi:icn will cause :he 5?R S :: respond :: a loss of level (nes: likely) or :o a less Of pump p:ver.
A: any ra:c, SFRCS will ini:ia:e ATJ and control :c :he nigh se:pcin:.
ooq
-7 8001160837
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.f Sucncon to Spenglar Pago Two Auxiliary Feedwater Se: points Nove=ber 15, 197S
$Ihe first condition may or.=ay not be acceptable to ECCS Analysis; they
, ;have not investigated small breaks with RC pumps running.
If such an L analysis were to be made, the results would probably be unf avorable.
I suggest that TICo confirm tha: :he above sequences are corree: before a decision is made to ini:iate AFW with ESTAS.
- 3. l.I believe that further analytical effort will probably be needed by ICCS
- to confirm that the 10' setpoint is acceptable even though' their judgement
'says.it is.
I think that some docu=entazion on file will be required to substantiate their claim, but I do not reco= mend analyses at this time.
4.
An additional though might be considered for 11=1:ing the pressurizar draining.
Recen: investigations for the 205 plants have shown us that the ra:e of addition of feedwa:er has a substantial effect on RC :e:perature drop. : The Toledo plant power level only requires about 500 gpm (a: about 30-40 secondr after trip) to remove decay heat. Yet the: pumps are capable (at design) of about 800 gym each; with reduced steam generator pressure the addition rate increases by about 25% :o 30%.
The total flow rate possible tends to introduce subcooled water in:o the genera:or, fill to a preset level (possibly as a subcooled inven:ory--I don't kncv the effect of heat pickup as the va:er f alls through the tube nest), and : hen hea up to boiling.
A more preferable code would be to:in:roduce flow at a rate
'm7re equal to the decay heat load.
A'n investigation in:o ra:e limi:ing (valve opening restrictions, cavitating venturis) may be worthwhile.
Rate li=1:ing =ay be a full or partial tradcoff for level 11=iting.
5.
Further discussions with TECo about these suggestions are desirable; we will support efforts in this area.
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i EWS:dh Attach j
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H. A. Bailey l
L. R. Cartin l
- 3. M. Dunn 1
- 3. A. Karrasch l
D. E. Leinhart R. C. Luken F. R. Fais t
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e *9 N. H. Shah i
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-'Ld R. O. Vosburgh R. W. Winks E. A. Wonack e
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