ML20024C816

Informs That Toledo Edison Needs to Reduce Auxiliary Feedwater Setpoints for Natural Circulation.Suggestion to Resolve Impasse Provided.Further Analytical Effort Required to Confirm 10 Ft Level Setpoint Adequate

ML20024C816
Person / Time
Site:	Davis Besse, Three Mile Island
Issue date:	11/15/1978
From:	Swanson E BABCOCK & WILCOX CO.
To:	Spangler W BABCOCK & WILCOX CO.
References
TASK-*, TASK-GB GPU-0592, GPU-592, NUDOCS 8307130360
Download: ML20024C816 (3)

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/Mey y Q W. H. Spangler. :~uclear Service b.__{cfp 1

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! E. V. Swanson. Plant Integration ass ess.s

Cast. File No, I- ' '" Toledo-TSS-14

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. - . :].i Auxiliary Teodva:er Setpoints

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Novenhor 15, 1978

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1 Our recent discussicos with Toledo personnel regarding their osed'to reduce the stea= generatat level setpoint for natural circulatico, and 3&W's need to maintain a high level because of ICCS s=all break have led to an i= passe.

. f)i- ' ' Both B&V and Toledo are in a " risk" position because the Toledo s=all break topicial was based on a 32' level position; any change to that position =ay

• ' require .re-analysis a .d re-licensing. Nevertheless, a stea= ge:erator level .

value has not been reported to NRC and the ICCS Unit believes that a 10' L,,

level se: point vill bs adequate.

Toledo's needs to lover the serpoint are genuine and I offer the following

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suggestion which you should pursue with Toledo: '

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1. Alter the ec=:rol logic of the STRCS so that it vill provide evo se:pci===.

.- '71 .

Since a ec: trol function cannot be readily p!sced is an ISTai sys:es, the c.. .-? STKCS must be =rdified. In the presence of an E. STAS sigsti. the ESTAS

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sets a priority 'for operatics over any ST3C3 signal and dire::s the STICS

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to provido a high setpoint level control. In :ha abser.ce of an ISTa3 .

.- t s:gnal, bu: vith sn-STRCS generated signal, the ST7,CS con:rci se:peint

{ (, C is directed to a lev Invel. " A general sche =ati: is attached; c:h:r esthods

. . .t of implacenti=; a:e possible. but this purveys the concept.

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ESTAS could also initiate auniliary feedva:er and isolate = sin feedvater.

Turther inves:igation needs :o be e.ade as to the actual see:uence of even:s.

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' . ' 'Y.]i I believe 1: is new pcssible fc two condiriens to exis: because the II o

• systems do not initia:e A7".* by ESTAS.. These ares ,'

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Current Desirn . I

r. [ Siee co.dition Svstens Secue ee

~2,7 C.e.-trol !c ta:1.:

1. Cffsite Pcver Avsilable ISTAS .--k* ICS 2' W u. .d.ater)

2. Offsite Power Unsvallable ISTAS -cm STKCS.

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= 10' (Auz. Teedwater) .

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• If my ressening is' correct. the first condi:fon vill only previde a 2' ,

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...N contrn1 (of r. sin feedwater); r.o ST7CS sign =1 vill occur sad ths ICS will g

• control. The other condition vill e uae the STTCS to respond to a loss of Y

• Icvel (nos: likely) or to,s lost cf punp. powcr. A: any rate. STRCS will Initiate A1*J nd control to the hig!r sctpoi=t. -

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$sa$sentoSpangler Nove=ber 15. 1973 Auxiliary Teedvater Setpoints Co The first conditica =sy or c.sy not be acceptable to ICCS Analysis; If such an they

/ have not 1 vestigated s s11 breaks with KC pumps running. .

analysis were to be =.ade, the results veuld probably be unfavorable.

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" I suggest that TEco confirm that the abeve sequences are correct before a decision is r.ade to initiate ATU with ESTAS.

.... . ~.t I believe that further analytical effort vill probably be needed by Eccs .

' . .! 3. the 10' setpoint ,is acceptable even though their judge =est n to confirm that I think that some docu=entation on file vill be required to says it is.

. .~.$ substantiate their claim, but I do not recc==end analyses at this ti=e.

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4. An add).tional thouster.ight be considered for 11=1:1:3 the pressurizar ...

draining. Recent i=vestigations for the 205 plants have shove us that.

the race of additios of feeduater has a substantial effect on RC temperature

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' drop. The Toledo plant power level caly requiresYet aboutthe 500 pu=ps spsare (atcapable about

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30-40 seconds af ter trip) to remove decay heat.

'?j (at design) of about SC3 g;m each; with reduced staar. generator pressure -

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the addition sata increases by about 25: to 30%. The total flev rate possible tends to introduce subcooled water into the generator, fill to a preset level (pessibly as a subcooled inventory-I. don't kncv the effect

• 1. ! of heat pickup as the water falls th:cugh the tube nese), and the= heat up - .

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to boiling. A r. ore preferable mode would be to introduce flov at a rate +

' ' ' more equal to the decay heat load. . An i=vestigation6i=to -===hracehit li=iting

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may be a full or. partial tradeoff for level

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Further discussions with T!co about these suggestions are desirablej ve *'

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