ML17193B281
| ML17193B281 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 03/26/1981 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Abel J COMMONWEALTH EDISON CO. |
| References | |
| TASK-08-04, TASK-8-4, TASK-RR LSO5-81-03-070, LSO5-81-3-70, NUDOCS 8104070090 | |
| Download: ML17193B281 (7) | |
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- Docke~ No. *50-237 LS05-:~l-d3-d70 '
. MAR. 2 6 1981 D s.. ~f-Rtt~JN NR L PDR SEP reading DCrutchfield RScholl RHermann WRussel l P0 1Connor Glainas TNovak RTedesco NSIC TERA ACRS(l6)
Draft... l:echnieal Evaluation Reports (TER) on Topic VIII-4 have been prepared and fon1arded -to a 11 SEP L1 censees for comment.
Comments from some licensees (e.g., Northeast Utilities letters dated August 29, 1980 and January 29, 1981) lndicated concern-with the model used and. assumptions made 1n the,initial conditions an~ material properties. Unfortunately, most respon~4nts have. not proviCleq.:isufficient technical information nor detailed schem~tics to support their comments.
Our audit calculations failed to esta~lish that the fault current protec-
_tion for *containment electrical pe.netrations in SEP fac11 ities =is generally "adequate..This de>~s not necessar1Jy mean* that the.-protection is iriadequ~te.
Our calculations were simplified and conservative so that there is.room* to impro.ve the result by usin,g_ more' realistic models.
In addition, licensee
-.-comments- -have indicat~c! thal:..there *may--be-s*ome**-errors tn**our-*ca*lculatfo*ns-:---
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- I your facility in acc9rdance with th'g enclosed position *
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Generally; where,'needed:*:our postti9n.calls for more realistic calculations.
than were used in *our audit.
In rel~tion-to current licensing criteria, it pro vi des re 1 i ef from the need for red1.mdant circuit protective devices in *
- .,.certain instances and_ specifically provides for using fuses as an alterna-tive to**cir.cuit*breakers. Other straight~;~orward alternative such as de;-ElQ.e!!J'f'zing.ci"rc~its are also *provided for.
If ariy *tnstan*ces ~rise where you-r calculations cannot demonstrate circuit protec:t1on in accord(lrice with our. position, you are requested to inform us of your intended corrective act-iQ,ris.
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-'In order to complete our review of Topic VIII-4, please provide a report describing th~ penetrations for the specific circuits identified in the staff's previ.~us report within 90 days of receipt of.this letter.
Th~ rep0rt as ~ minimum should address the following items:
- 1. Protection'for penetrations like X205E (both nonnal and backup protection).
- 2. Circuit design a*nd theory of operation for differential current protection of pump motor circuits for (a) Motor Faults (b) Condootor Faults at the penetration (single phase and bolted faults).
- 3.
An analysis of how the desfgn of the line relay and differential protection satisfies the single failure criterion for all faults.
The requested infonnat1on will be used to revise our topic Safet.Y Evaluation Report.and will be used in the preparation of the integrated assessment for your plant.
Enclosure:
As stated cc w/enclosure:
See next page Sincerely, Original Signed by Dennis M. Crutchfield, Chief Operating React<>rs Branch No. 5 Division of Licensing
~ee previous yellow for additional concurrences.
OFFICE. SEPB: DL SEPB; D.L SEPB; DL; c.
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"!\\I RC.FORM 318.110180> NRCM*0240 OFFICIAL RECORD COPY
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- A report, *-de*scrit>in:g* the calculatfons perfonned and criteria used.for evaluating the penetrations identified* in the staff's previous report should be submitted with>'n 30 days of receipt of this letter.
The report as a minimum should address the following items:
- 1. Protection for p§netrations like X205E (both normal and backup protection).
- 2. Circuit.*design and theory of operation for differential current protection of pump motor circuits for (a) Motor Faults (b) Conductor Faults at the penetration (single phase and bolted faults).
- 3.
An analysis of how the design of the line relay and differential protection satisfies the single failure criterion for; all faults.
The requested infonnation will.be used to revise our topic Safety Evaluation Report and will be used in the preparation of the integrated assessment for your plant.
Enclosure:
As stated cc w/enclosure:
See next page Sincerely, Dennis M. Crutchfield:, Chief Operating Reactors Branch #5 Division of Licensing
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NRC FORM 31.8 110/80) NRCM 02"40
- ..,, USGP0:.1980-329*824:
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Mr. J. S. Abel cc Isham, Lincoln & Beale Counselors at Law One* Ftrst National Plaza, 42nd Floor Chicago,. Illinois 60603
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Mr.
B~ B.
Ste~henson Pl ant Superi n't 1endent Dresden Nuclear Power Station Rural Route #1 Morris, Illinois 60450 Natural Resources Defense Council 917 15th Street, N. W.
Washington, D. c; 20005 U. S. Nuclear Regulatory Com:nission Resident Inspectors Office Dresden Station RR.#1 Morris, Illinots 60450 Susan N. Sekuler Assistant Attorney General Environmental Control Division 188 w. Randolph Street Suite 2315 Chicago, Illinois 60601 Morr i s P u b 1 i c L i bra ry 604 Liberty Street Morris, Illinois 60451 Chairman Board of Supervisors of Grundy County Grundy County Courthouse Morris, Illinois 60450 John F. Wolfe, Esquire 3409 Shepherd Street Chevy Chase, Maryl and 20015 Dr. Linda W. Little 500 Hermitage Drive Raleigh, North Carolina 27612
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MAR* 2 6 1981 Illinois Department of* Nuclear Safety 1035 Outer Park Drive, 5th Floor Springfield, Illinois 62704 Director, Standards and Criteria Division Office of Radiation Programs (ANR-460}.
- u. S. Environmental Protection Agency Washington, D. C.
20460
- u. S. Environmental Protection Agency Federal Activities Branch Region V Office ATTN:
EIS COORDINATOR 230 South Dearborn Street Chicago, Illinois 60604 Dr. Forrest J. Remick 305 East Hamilton Avenue State College, Pennsylvania 16801
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.e Et.ICLOSURE. '
POSlTlO~ O~ PR01£CTl0t; OF CONTAlh""i~t.11 £L£C1RlC"L 'PEl-iE1Rl-1lO~S AGA1~~1 FAILURES Cl-USED BY FAULT A~~ OV[RLO~D tURRE~lS
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1r.trodu:tion* 1*
/...s pert of the Syster..:tic [\\*c.luctior, Program (SEP) the HRC staff performed in
~uC:it, co~aring sar.iple cont.ainrr.ent electricel penetrations in SEP facilities
~ith current licensing criterit for protection ~gainst f~u1t and overlo~d currents fo11o..*ins ! postuhted HCide-nt.
The s'irn;:>hfied ~nd conserv~tive r:.ocel used did not sho..* that the SEP hci1ities P?et current licensing criteria nor did it sho.< the ex.isting circuit protection to be eclequ~te.
.l.ccordingly, the SEP licenHes ere requested.to c12m:instnte, usins n:ire rec1ist'\\c c~lcula tions ~here necess~ry. t.hct the circuit prottction is ~clequ~te in iccor~nce td th the position 0-escri bed be 1 oi.*.
ln 11cer..sing ne"' ph.nts, the stdf rec::u~res cor.:;*litnce.,;th the recor.r.rendctions of Reg-uhtory Guice 1.63 or ir, tccep~ble t1t.trnttive rethod.
Fer e~ch contc.in~ent ele:tricc.l pe~etrcticn, :~e ~;cte:tive syste~s provioe pri~~rj and b2cku~ circuit protection devices to prevent 2 single failure in con-jur.ction ~;ith a circi;it overload fror.. impairin~* containment integrity.
The prir..cry and backu;:J protection devices hc.ve trip time vs. current response charc.c-teristics 1'.'hich assure protection* 29ainst penetrction faiiure.
The protection de-.*ices are periocically tested to verify tri~* st:tpoints and adequacy of resp:Jnse.
No single failure allows excessive currents in the penetrc.tion conductors which
~ill degrade the pe~e:rc.tion seals.
Where external control power is use~ for actuating the protection systems the po-...*er for primary and bc.ckup breakers are derived from separate sources.
Ove:current si~*~cis for tripping prim::ry c.nd backup systerr: devices c.re e1ectricc:i1y indepe:nder.t and physically sepc.rcted.
Staff Audit The safety objective of SEP Topic \\'lll-4, Electrical Penetrations of Reactor Containment," is to c.ssure thc.t ell electrical prnetrc.tions in the containmE!Tlt structure are desicned not to fail from electrical faults durino a high energy line break (LOCA or secondary syste~ line bre!k).
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~. l We have perfonred preliminary eva1uat1ons. on a conservative basis*, ~f ihc fnult current pro~ection for three sar.p1e containrrcnt electrical penetratfQn$.for
. each of the e*ieven SEP plants. The.entire penetration was assumed to b~ iniUa11y at the peak calculated LOU te~erature. Then, for a given f au1t current. the time to heat the wire to the limiting material terr?erature (usually the m:lti.ng*
point of the seal *mat.erial) was calculated.
This tim= "as corrpared to the"tine for the.prote,ctive device(s) to interrupt the fault current.
On this basi~
1
- ~* seve*ral penetrations exceed lfmiting te~eratures 1f the pri~ry protection. device fails.
Others do so without postulating primary device failure.,
Two of the sa~le penetrations even have m:lting terrperatures less than the pea.k.
LOU te~erature and thus exceed the limits of this rrode1 even if there is no fault current.
(References l through 11)
This does not necessarily mean that the penetrations would actually fail.
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The analysis was conservctive, part'icuhrly in assuming that the penetration tt~s initi~lly at the p~l c.tlcuhted cont~innent ten{>erature.
Ttie penetrations
\\liould not reach such *a te!T\\)erature follo*,dng an accident.
ln addition, licensee co~nts have indic2ted tha~ there ~y be so::-e errors in the calculations.
(For exa~le, Northeast Utilities le~ter dc~ed August 29, 1980. Docket No. 50-245, providing corrments on the staff calculations for fl'\\illstof\\.f. Unit l). J\\evertheless, this ~udit clearly did not put the ~tter to rest.
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Position Each SIP licensee is requested to evaluate the adequacy of the existing fault current protection for containr.ent electrical penetrations in accordance "'ith the position discussed in rrore detail bel~ ~nd to propose rerredies where neede~
- n order to rreet the position.
- l. *The basic requirement of Regulatory Guide 1.63 that all penetration circuits, Class IE or non-Class IE, be provided with overcurrent protection in confonrance with the redundancy and 'testability requirements of *I EH Std 279-1971 should be met;
- 2.
A Single ctrcuit breaker to protect a penetration serving a Clas~ IE circuit or a non*.:safety ci'rcuit contah.ing only components that are qualified to Class IE requtre~ents ts ~cceptable provtded that each con~onent of such circuit is qu~l ifi'~d to the acctdent environment;
- 3.
A circuit whose loads inside contatnment are not required to mitigate the consequences of accidents may be automatically disconnected from its power source on recetpt of an accident.signal or it may be maintained deenergized by positiv~ means such as those outliend in Branch Technical rosition ICSB 18 (PSB) of Appendix BA to the Standard Review Plan whenever ~untainment integrity is required.
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- Notes for the purpose of eva1uating the i!dequl!cy of protection for contiinr.ent protection, faults.should be postul~ted up to a bolted c~ble fault inside contain~nt at the* penetration (a bolted thre-e phase fault for three phase circuits)~. The prirr.cry protection device should have a trip tine vs. current response chcfracteristic t.hat assures ~gainst penetration failure under all
.fault conditions.
Circuit b,reale~ should be tested periodically_ to verify their trip !.etting va 1ue and response t im:.
Brealers should be designed to interrupt the sre.xiJ11.Jm possible fault current for the circuit or bactup protection fast response current limiting fuses should be provided.
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In addition. fuses irie.y be used in lieu of circuit brealers as protective de\\*ices *.
'-'here fuses are used, documentati.on oftheir response characteristics derived f.ror.. production.testing should be a\\*ai_!~!?..l~ __ for audit.
It is acceptable to \\:Se less *conHniative rodels than "'ere used in our pnlir..inary evalua~ions provided that they address fault currents ~p ~?
b-o1tec fa:;lts ~nd still pro~*idt rt-esonabl ~ss~r~n~e thet the.pene:..rchlOn
".-ill not fail.
For exa~1e, ~ m:ire rea1ist1C rn,t,a1 te~era~ure of the n* pene'.. r"'~ion could be determined rath.er. than assur..rng the co~... n~..
t h
t pene'"..rat; on has reached the peak calculated con... a rnm:nt a rrosp ere e~-
e rature.
Circuits may values by the transformers, be modified to reduce the short circuit curre~t to ac7epta*b~e use of current limiting devices (such as resistors, ~solat1on and chanoino transformer taps) external to the containment.
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