ML19322B936
| ML19322B936 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck, Millstone File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 11/30/1979 |
| From: | Counsil W NORTHEAST UTILITIES |
| To: | Hendrie J NRC COMMISSION (OCM) |
| References | |
| TASK-10, TASK-RR NUDOCS 7912190261 | |
| Download: ML19322B936 (6) | |
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References:
(1) TKI-2 Lessoas Learned hak Force Report (51mrt-Term) k N 578.
k (2)
D. G. Eiseekst letter to All Operating helaar Power
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F1 mate dated September 13, 1979.
(3)
W. G. Counsil letter to D. G. Eisenhut dated October 18, 1979.
l (4)
- 5. Dentos letter to All Operating helear Power h]
Flaats dated cetober 30, 1979.
(5)
W. C. Casos11 letter to u. Denton deced mvenher 21, 1979.
(6)
W. C. Coussil letter to B. H. Criar dated April 24, 1979, e
h.
Docket No. 50-213.
(7)
W. c. Coussil letter to Dr. Demvood Boss dated May 31, 1979 Wy' Docket No. 50-213.
71 (S)
W. C. Couasil letter to B. R. Grier dated April 24, 1979, 4N Dock.c us. 50-336.
(9)
W. G. Coussil letter' to Dr. Deevood moss dated May 31, 1979, d
Doebet No. 50-336.
M (10)
R. Reid letter to W. G. Cowamil dated June 7,1979.
$3 (11) it. C. Couneil letter to 5. R. Grier deced June 29, 1979.
73 (12)
W. G. Comme 11 letter to R. Reid dated February 12, 1979.
ff{j (13)
D. G. Eisenhet letter to D. C. Switzer dated October 11, 1979.
N (14)
D. C. Eisenhut letter to W. C. Coonell deced Onteber 23, 1979.
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(15) 15m30-75/087, sec sesaderd Review Plan, Revisico 1.
(16)
W. G. Caumail letter to D. L. 21emana dated September 22. 1978.
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(17)
W. G. Cosasil letter to D. L. Ziemean dated October 20, 1973.
%'s (18)
D. L. Zimanum letter to W. C. Couasil dated Detober 24, 1978.
$1 (19)
W. c. Couns11 letter to R. Reid dated February 12, 1979.
ji 12, 1979 G p ]D W
(20)
R. Reid letter to W. G. Comanit dated May de T~l (21)
W. c. Couns11 letter to R. Reid dated March 21, i
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Baddam Neck Flant l
Milletone maclear Power station, Unit No. 2 y
h Automatic Initiatico of Auxiliary Feeduster We are addressing this correspondence to your office, and requent that you give 7
it your pereenal ettention, as recent communications with your staff have i
indicated the arguments presented below require Commise1oner-level attention k
to be recognised.
In Referemme (1), the Inc Staff initiated promulgation of the recommseadation for Tl all operettas WWB's to be equipped with automatic initiation of susiliary feed-
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we:er via mmEG-0578, item 2.1.7.a.
Comaecticut Tankee Atomic Power Company 4
(CTAPCO) and Marthemse maclear Energy Company (unern) were first requestewt to
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cannit to implement this rac--iation in Reference (2). In Reference Q),
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CTAFC0 and IMECO indicated that this rachation was considered to be 9
'--ey, that it was not credible to assume that==wiliary feedwater would k<
mot he naamally initiated when required. The IEtc Staff request was reiterated in Beforence (4), wherois CTAPCO and IEECO were advised to reconsider improvhs Et the implementatica schedule to comply with the Staff requests. CYAPCO and PGECO
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M in Reference (5), osatiuming to disagree with the Staff on Item 2.1.7.a.
F cand indiented that addittomal correspondence would be forthetsins. The purpose
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of this letter is to fulfill that commitment, and comprehensively address the f
various -id=estione supporties CTAPCO's and NNRCO's conclusion that automatic p
faitiattom edb ausiliary feeduster need not be implemented to ensure continued
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anfo operatico of the saddam Neck Plant and Millstone Unit no. 2, respectively.
y Fturther, it is em purpose to assemble all relevant considerations in one document E
to facilitate achieving the proper perspective on this issue.
It has been g
addressed in asumaroue documents on the CTAPCO and 30EECO dockets na well as in f
3mesthy telephone conversations.
It is imperative that the synergistic
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impaat of the factors upon which our conclusion is based be recognized and evalested, h
CTAFCO's and IEWCO's review of the 1MI-2 occident has concluded that automatte initiation of===111ary feeduster is not a " lesson learned".
It is noted that
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1N1-2's ammiliary feedwater wee estoestie=tly initiated. One may speculate 3'
that had see of the plaat operators been required to physically manipulate the 3
eestrela, hImek valve cleeure would have besse identified earlime in the t
accident. This point is certainly subjective and is noted here primartiv i
becamme of a related consideration which will be identified later in thia letter. More importantly, the eight-minute absence of feedwater at TMf-Z in i
not judged to have had a esbatantive impact om either the nature or consequences of the accident.
Thus, it appears that undue emphasis has been placed on this synten by the MC. Staff /Leseens-Learned Task Force.
The uniqueness of the 3
36v mas with respect to its limited secondpry water inventory in the at=am 3
generators could elevate the importance of estataintag an uninterrupted flow of "l
"l Emeduster im R&W plante, but this is not applicable to the anddam Neck Plant or M111stees Unit No. 2.
An ovaluation of GDC-20 indicates that the auxillary feeduster system is not a candidate for automatic lattiation, in the context cf the term " appropriate" la CDC-20. Manual initiation has been desmoneersted g
"2 ta prevent anticipated operational occurrences from 'resulting in the speciflad
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t acceptable feel design limits (SAFDL's) being exceeded for approximately twelve years at Enddam Neck and over four years at Millstone Unit No. 2.
Not only has it been demonstrated that the SAFDL's have not been exceeded with the cearrent design. but amaziliary feedwater has always been established at these tuo fee 111 time well before steen generator dry-out has been approached.
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moted that this has been achieved with systems which are currently being upgraded s
in other respects to improve reliability.
CTAPCO end m first documented objections to the staff requirements regarding
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amerniary feeduster amadated in the I&E Bulletin No. 79-06 series in References (0) med (4). The adequacy of unemmi initiation wee further reinforced by the i
control reen eneming requirements described in References (7) and (9).
These discussions led to the interim resolution, which is currently in effect.
head in Reference (10) and confirmed in Reference (11). A licensed operster who has direct responsibility for control and operation of all main
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and sex 111ary feedwater systems will be in the main control room at all times.
5 A becamp is provided in the event the licensed operator is not available at 1
any time. The operator seeigned to this function will, at the time of a transient p
requiring such action, take immediate centrol of the main and auxiliary feedwater g
i systems, with no other concurrent responsibilities, until the steam generatnr 1
levels return to a stable condition. When considering transiente of an extended
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and esoples nature such as 1M1-2, it can be argued that the above describ=1 measures constitute an alternative comparable to that proposed by the Staff with respect to achieving plant sqfety.
s Am integral facter supporttag CTAPCO's and ISISCO's position is the lengthy
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period of time associated with steam generator dry-out, in light of the
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ehort time necessary for the plant operators to recognize the need for
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corrective action and to take that action.
Typically, the operators have K
responded in approminately thirty seconde, and these data were compiled from L
plaat trenoients which proceeded the TNI-2 accident. Considering all the f
attention given to auxiliary feedwater since that time, it is difficult to p
envisima operater response declining in this respect.
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As previously stated in Reference (2), the minimum time to steen generator F
Cry-out at Milletone Unit No. 2 following a total loss of fsedwater to in excess of fifteen minutes. The details of this conservative calculation vere
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provided in Reference (12).
Neglecting other analyticp1 conservatiges, the use
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of the ANS decay heat curve without the 203 conservatism would result in a i
miaisum dry-out time in excess of twenty minutes.
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Fce the case of Meddam Neck, evbetantially longer time is available.
The calculations supporting this statement are peqvided in Attachment 1. CaIculation p
cf Steen Generator Dry-Out Times. As shown in Table 1 of the Attachment. even P.
assuming AM + 20E for decay best, a min 1===
of 27 minutes before dry-out le 7
available. Depending upon the availability of offsite power, either 33 or 43 IL mientee would be available using AN5 + 01 for decay heat.
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Prerious Staff analysee, se documented in Referonee (13) and (14). have aeated thae the deniaast failure mode for the AFUS is the failure of the operator to monumily f[.
actuate the systen.
For the purposes of this letter. CYAFCO and NNT.C0 believe it appropriate to recognise the attention being focused on the auxiliary f**d-e unter system since the 1MI-2 accident.
- Typical" operator performance or tussen fl
. reliability facters are not judged to be applicable to this circianstance, fc This consideration further dilutes the need to automate this system in order y
to justify safe plant operation.
m CTAPCO and IEECO recognise that factors discussed to this point have not, t r>
date, been mucaessful in alterlag the Staff _ position.
For that reason, efforts
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have contimmed to engineer, design, and procure the necessary components to
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J l k JL d 7 a.te. ate a-ili.ry fe.dw.ter at noen f.ciliti.e. riree,likenortkehat conceptually the systam merely consiste of an sutomatte atart of ehe aux 111ary feeduster pumpe.
The valves would be pse-positioned to provide the appropriate flew rates.
In order to comply with the January L,1980 implementation diete, o more appropriate, emphisticated design incorporating automatic isolation in the seent of a steem or feedline break cannot be completed. CYAPCO and NNECO are apaite familiar with the complexity of this feature through the MIL 1=tona Unit No. 3 project.
In early 1978 Westinghouse Electric Corporation first identified the deofga respairement to couple automatic initiation with a provision to recognize the poteertal for steam or feedline breaks, such se flow restrictive orif ice plates or automatic isolatsee, ta order to eneure that mialmum RCS cooldown rctes usmid be achieved. The autoestic toplation feature of the Millstone Unit Es. 3 design has been under investigatica for many months and to date, the design is not complete.
It is noted that a hastily desianeuf mutamatic 1=otation echase has the potentimi to la fact decrease the reliability of the auxiliary feedenter systen, due to landvertent isolation of an intact loop. CYAPCO mod i
M soggest that reliability studies of a depth comparable to that recently conducted by the Esc Staff are appropriate before an automatic initfation i
and isolation is implemented. This position le further reinforced by the regulatory guidsace of Item I.14 of Section 10.4.9 of Reference (15). Therefore, CYAPCO and MCO have reviewed the systes that is feasible to implement by January 1, 1980, ammaly automatic pump start without automatic isolation, pursuant to the requirements of 10CFR,50.59, and have determined that lastallation of such a system cometitutes as moreviewed eefety spaastion. Without prejudgina the Staff etaluation of the argumente presented in the first portion of thie letter, it.
1J moted that implementation is prohibited without doce===ted Staff approval of the esecept weder consideration.
The basis for this detes= taction involves the increases in the severity of the consosteences of a postulated feeduster line break and steamline breek.
As presently conceptually designed, a tup-out-of-four low stoma nonerator levet signal in either steers generator would start both motor-driven AFW pumpa and.
place the turbine driven pump at the miot== governor speed at Millotone Unit I
Wo. 2.
Flow control valves would be preset to result in delivery of approx tnately l
300 syn to each eteen generator at the no lood steam Renerator preneure, approxi-mately 900 pois, as==ing an intact secondary system and all three AFW pumps operattag.
The operator would thee be eutpected to adjust flow me necessary to maintain level to the proper reage. At the Haddam Neck Plant, the conceptumi design calle for a low steen generator level in any of the four steam generatore to ctart both steem driven AFW pumpe and fully open all four bypass flow contrni valves, delivering water to all four loops through a common header.
The operator would them he espected to throttle the velves as necessary to maintain level in the proper range.
If o feeduster line rupture were to occur, the auxiliary feedwater. once auto-
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matiselly initiated, would preferentially flow to the break loestion rather than to the intact Isop(e). Ustas the comoervative ameumption that all AFW flow f e delivered to the break, only the unter inventory remaining in the intact steam generator (s) is available to remove decay best.
In the abeence of operater action, time to da, 2st would be 75% of that for four intact loops at Maddam Neck, and 50% of that for two intact loops at Millstone Unit No. 2.
Thus, the operator unet recognize that egen though AFU has been initiated. none of the water sa providing a host stak for the BCS.
Manus 1 isolation is. therefore, 1
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regoired for each a beesk, despite entomatic initiation. With the presently 1
installed AFU configurettee, the operator immet recognize the cause of the accident, initiate AFW, and direct flow to the ietact loop (e).
The corresponding acenar to for the pumpeeed automatie echase le that AFW would not he provided to an totace loop f
wentil the operator correctly diagessed the effects of the feedveter line braak as perterbed by the effects of Arv system initiation, and isolated the effected loop.
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The astere of the perturbation le a function of the break stae.snd location.
The
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time eve 11ehle for operator action is comparable for both cases.
j la the case of a eteenline break, asetating a lose of normel power, the proposad AFV eFotos would be amtematically initiated when the effected sense generator eenchem c leer level setpotat.
Since the intact steen generator remains at a higher pressure them the generator with the break, the majority of the AFW flow will be to the depressurized generator, thereby feeding the break and escessively cooling down
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the ES.
Vtyr the Beddam Week Flast, decketed steamline break analyses dowcribed
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in Eeforesces (16) and (17) and approved in Refereoce (18) assumed that for the limities case, the main feedwater system perforised properly and ther auxiitary t!
feedenter flow use sat initiated duries the accident. A preliminary inweariaation
$f of the fzow chareet.wi.tice of the test.11ed Arv syst.c indtcete. ch.c ir hoen av ei pummye are in operatima, the flow into a broken stem generator would be substantial.
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For R111 stone Unit Be. 2, steam 11ee break enalysee documented in Reference (19) k and approved im Reference (20), aseanned that five percent of full esta feedwater famw wee maintained threeghout the incident. Any fluid injected by the AFV systone
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deries the tecident escoede that assumed in the current analysis.
For both plante, t:
this ph======aa resulte sa e positive reactivity insertion in escoes of that tj j!
decamented in current safety emelysee potentially reeutting in a return to criticality. Amether adverse effect of this phenomemon is the steam produced s
from the muniliary feedwater inntenses the ases and energy relsened to the
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contatsmaat.
Currently, the IACA is the governing incident with respect to
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mass and emergy releases in contaissent.
In the obsenes of quantification of i,
the effects to the contrary, the potential existe for the above scenario to i,
be more severe, considering both costatement integrity and the environmental
{j gaelfficatism teaue, than corrently approved analysee.
It le noted that such 3
quantification would not change CTAFCO's and WhT40's determination with respect j
to the unreviewed safety question issue, but rather affect only the magnitude l
ef the samlyrieel and poselbly procedural end hardware efforts associated with 1
resolving these esfety geestions.
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Aweg that asteentic initiation le mandated, recognisia6 that CTAPCO and 80tTIO have esecluded that anneh is not the case to ensure safe plant operation, scne foss of antamatic isolatise or flow restricting orifice, plates are judged to j
he sa integral and necespery festore of the deelsn. An additional concern with the esacept onder discussies is that it is not autossatic in the context
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esses 117 essestated with estematic protective functines, is that oosse forse of agerator intervention is required to control flow even under eco-eccident i
a== N ea==.
'therefore, it alters the operator functice free one in which the f
T operator semesimuely plans med insplemente AFW delivery to one in which he has serely a corrective role.
It can be argued that during postulated feedline i
breaks or steenline breake, seeeenery operator actione may be delayed since
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the operator would tend to concentrate on required manual actions first atxi he passive with respect to the "enteestic" systame.
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The shortcomings forusing the bases for the unreviewed safetfquestion determina-tion de mot esist with a==rmaally initiated eyetam. because of the gequence of cperator actions as prescribed by current operatint procedures. CTApCO and WCCO have determined that an accurate and timely diagnosis of the accident by the operatore can be accomplished with a manual eyeten.
At thf e point, it is ennentini to recogatae the casuneet ande on Fase 2 of this lettar regarding accident d iagnost ica ;
during a steamline or feedline break, an autoestic system initiates a detrimental procese servtag to complicate the diagnostic evolution. With a manual system. the cperator would be cognizant of relevant plant parameters prior to initiacion and just as importantly, be cognisant of the effects of his actions, whether banet te at cr detrimental.
This point le east relevant considering the substantial amount of time available before steen generator dry-out.
It is further acknowledged that the above points only identify the existenc= of unreviewed safety questions, and does not quantify their significance.
It is again noted that quantification would not alter the determination made pursuant to 10CFR30.59, beoed upon our interpretation of the intent of the requirement e and praemda=ea established from evaluations of related issues.
Forwerding thia determination to the lac Staff is one of the principle purposes of this suheitttal.
l Quantificaties would be difficult to perform at this time, due la part to the l
choence of a crucial criterion from the Staff, asseiy a specified tiano delay from the start of a steamline or fa+111ae cupture before operator action to l
Samlate the broken loop. Regarding this question, a staff response of any time duration less than the stess senerator dry-out time would be viewed me the ultimate paredes, wherein credit could be takse for the more complex diagnoatic avaluation tavolving automatic initiation, yet could not be takers to justify the adequacy of the less comples oraluation tavolvios neoual initiation.
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Other points previously identified to the Staff remain supportive of CYAPCO'e and MElO's position.
In the case of N111 stone Unit No. 2, the license condition restricting the flow of feedester under certain conditions due to water hammer concerns remains in effect.
In Reference (21), NNECO justified and proposed deletion of this condities, but it has yet to be dispositioned by the Staff.
In the case of the Haddam Neck Plant, topic wealuations mesociated with the SEP heee the poteattel to engaificantly impact the ultimate conflauration of the AFW oystem. These conceras were articulated in Reference (3).
The infosmetion presented above is also responsive to the Staff requeste domented la recommesadations GS-8 ami GL-5 of Reference (13), and recommendations CS-8 and CEr-1 of Reference (14).
He trust you find the above taformation adequate to coeprehenf the hente for CTANCO's and MIECO's positions, determinations, and evaluations.
We Icok forverd to a detailed Staff reply to the above-noted concerne.
Very truly yours, COMMECTICUT YANKEE A10MIC POWER COMPANY NORTHEAST NUCLEAR ENERpT Cot @ ANT l
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M6 a
ti. G. couns11 Vice President Attachment
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