ML17194B320
| ML17194B320 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 09/24/1982 |
| From: | Oconnor P Office of Nuclear Reactor Regulation |
| To: | Delgeorge L COMMONWEALTH EDISON CO. |
| References | |
| TASK-06-10.B, TASK-6-10.B, TASK-RR LSO5-82-09-077, LSO5-82-9-77, NUDOCS 8209300214 | |
| Download: ML17194B320 (8) | |
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- jJ September 24, 1982 Docket No. 50-237 LS05 09-077
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Mr.*E. DelGeorge Di*rector of Nuclear L icensirig Cormnonwealth Edison Company Post Office Box 767 C~tcago,/Illinois 60690
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Dear Mr.-DelGeorge:
SUBJEdT:
SEP TOPIC VI-10.8, ELECTRICAL, INSTRUMENTATION AND CONTROL PORTIONS OF SHARED SYSTEMS - SAFETY EVALUATION REPORT FOR DRESDEN NUCLEAR POWER STATION, UNIT.2 The enclosed staff safety evaluation is a revision of a report forwarded by D. M. Crutchfield's letter of April 22, 1982.
The report has been revised to reflect a_dditfonal infonnation developed during our.review and the additional infonnation contained in a letter from Thomas J. Rausch to Paul 0'.Connor dated August 30, 1982.
We continue to recorrunend modifications to the Technical Specifications to
- prevent parallel ling, the 125V de systems during reactor operation. The need to actually im~lement these changes will be detennined during the Integrated Safety Assessment.
This safety evaluation may be revised in the future if your facility design is, q~anged or if NRC criteria relating to this topic are modified before the Integrated Assessment is completed.
Sincerely, Origixml signe*d bY.~
l)Su 1.tt> t ( Uo)
Paul O'Connor, Project Manager
Enclosure:
As stated Operating Reactors Branch No. 5 Division of Licensing Anv:
~. sJo.le1 cc ~~enclosure:
See next.page 8209300214 820924 PDR ADOCK 05000237
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NR9FORM31B(10-BO)NRCM0240 OFFICIAL RECORD COPY USGP0:1981-335-960
Mr. L. DelGeorge cc Robert G. Fitzgibbons Jr.
Isham, Lincoln & Be~le Counselors at Law Three First National Plaza Suite 5200 Chicago, Illinois 60602
. Mr. Doug Scott Plant Superintendent e*
Dresden Nuclear Power Station Rural Route #1 Merri~. Illinois 60450
- The Honorable Tom Corcoran United States House of Representat1v.es
- Washington, D. c. 20515
- U ** S. Nuclear Regulatory Commission Resident Inspectors Office Dresden Station RR 11 Morris,. Illinois 60450*
Mary Jo Murray Assistant Attorney General Environmental Control Di~ision 188 W. Randolph Street Suite 2315
- Chicago, Illinois 60601 Chainnan Board of Supervisors of cGrundy County Gruncf.Y*tounty Courthouse Morris, Illinois 60450 John F. Wolf, Esquire 3409 Shepherd Street Chevy Chase, Maryland 20015 Dr. Linda W. Little 500 Hennitage Drive Raleigh, North Carol Lia 27612 Judge.Forrest J. Remick
.The Carriage House - Apartment 205 2201 L Street, N. w.
Washington, D. c.
20037 Dresden 2 Docket No. 50-237 e*.
Revised 5/19/82 I111noi s* Department of Nuclear Safety 1035 Outer Park Drive, 5th Floor Springfield, Illinois 62704 U. S. Environmental Protection Agency Federal Activities Branch.
Region V Office
- ATTN:
Regional Radiation Representative 230 South Dearborn Street Chicago, Illinois 60604 James G. Keppler, Regional Administrator Nuclear Regulatory Commission, Region III 799 Roosevelt Street Glen Ellyn, Illinois 60137
I.
INTRODUCTION SYSTEMATIC EVALUATION PROGRAM TOPlC VI-10.B DRESDEN NUCLEAR POWER STATlON, UNIT 2 The sharing of engineered safety features (ESF}. systems, including on-site emergency power systems, and service systems for a multiple unit facility can result tn a reduction of the number and of the capacity of on-site systems to below that which nonllally is provided for the same n~mber of units located at separate sites.
II.
REVIEW CRITERIA The review criteria are presented in Section 2 bf EG&G Report 0117J, "Electrical Instrumentation and Control Portions of Shared Systems."
III.
RELATED SAFETY TOPICS AND INTERFACES The scope of review for this topic was limited *to avoid duplication of effort since some *aspects of review were performed under related topics.
Related topics and the subject matter are identified below; Each of the related topic reports contatn the acceptance criteria.and review guidance for its subject matter.
VI-7.A.3 Vl-7.C.l VI-7.C.2 VI I-2 VI I-3 VIII-2 ECCS Actuati'On Independence of OnsitelPower Single Failures Isolation of ECCS arid Control Systems Safe Shutdown Diesel Generat6r~
Topi cs VI-7. C. 1, VI-7. C. 2 and VII-3 are dependent in the pres*ent topic infonllation for their completion.
IV.
REVIEW GUIDELINES
- v.
The.review guidelines are presented in Section 2 of Report 0117J.
EVALUATION As noted in EG&G Report 0117J, the Dresden Nuclear Power Station, Unit 2 is not in compliance with current licensing requirements with regard to some of the EI&C features of shared systems.
They include:
- l. Single failure that, because of the way loads are assigned to electrical supplies and because of the way that electrical supplies are shared between Dresden Untt 2 and 3, could result tn the.
inabil Hy to provh1e poweY. to the requi'red safe shutdown loads in one unit upon a less of t!>ffs.i'te power cotnc1'dent w*i'tlt an acci-dent in the other unH.
Specific examples are given i'n the EG&G report.
Evaluations of these examples are pres~nted in the following pa~agraphs~
A.. Theie are no physical or electrical interlocks or LCO preventing parallel operation of the shared 125V and 250V de battery systems.
Such operation~ combined with a single failure, would result in a loss of capability to supply accident or safe shutdown loads fol-*
lowing a loss of offsite power.
The staff's audit of operating procedures (e.g., DOP 6900-4) indi-cates that there are no procedures requiring paralleHng of the 250V de systems duri'ng reactor operati'on..
However, DOP 6900- 6 requ ir'es that the l 25V b.a tteri-es be para 1 led as a part.of the ground detecti'on procedures.
Purthennore, there are no requirements to prevent the paralleli-ng of the 250V battertes.
NUREG-0666 and Regulatory Guide 1.81 establ i'sh the basis for the staff's position that de systems in multi-unit nuclear power plants should not be. shared.
ln* the case of parallel operati'on, a si*ngle failure could result in a 1 oss of engineered safety, features tn b~th plants. and, simultaneously, inttiate plant trans*tents.
Given that a ground fault extsts, the wisdom of paralleling a second battery (and doubling.the avai'lable fault currentl ts questfona!:>le.
The added possibility of a major upset occul"fog simultaneously ts
. neither acceptable nor necessary given the availabi'li'ty* of other ground fault detection systems using di-fferent techni-ques.
B.
There* are no LCO requirements or interlocks preventing th.e nonnal/
bypass switches for the DG2/3 from being in "bypass during operatton of either unit.
Such operati'on, combined wi'th a single fatlure could render the required accident and safe shutdown loads tnoperable following a loss of offsite power.
In a 1 etter from J. Rausch to P. o.* Connor dated August 30, 1982, *the licensee stated that the operating procedures had been changed to require a "normal-normal" alignment of these*swttches.
9' C.
Complete information of the status of the shared de batteries, chargers and buses is not avatlable to operators of each unit.
Battery status indtcatton will oe addressed under SEP Topic VIII-3.B.
O.
The 125V and 250V de systems are shared, which is not in compliance with current licensing requirements.
However, the staff's review of the present de designs shows that they satisfy the single failure criterion (when they are not parallelled) if credit can be g~ven to the electrical circuit protection devices. These devices are to be re-evaluated as a part of the resolution of Topic VI-7.C.l.
E. *stoied energy for DG operation does not meet the.seven day minimum or time to replenish, whichever is longer: required by current licensing criteria. However, suffici~nt oil is available on site to operate one diesel generator for seven days.
Only one *diesel is required for the shutdown cooling of a unit and the post~accident*
cooling of a second unit.. The licensee has stated that administra-tive controls require the monitoring of the* fuel star.age tank levels on each shift and specify a minimum operating level corres-*
- ponding to approximately a three.and one-half day supply per diesel.
Additionally, the tanks are equipped with a low-level alarm which will annunciate at a level corresponding to approximately a two day supply for each diesel.
An oil refinery is located within about one-half hour of the plant ~nd the metropolitan Chicago area is only about one hour away.
F.
The 250V de battery chargers are not capable of restoring the battery to its fully-charged*condition from ~tntmum charge condition~ during normal and.post-accident steady state loads.
The 250V de.battery chargers have been replaced by units* of suffi*ct-er:it
- capacity.
The plant modification i"s Ml2-2-78-16, G.
The loss of Diesel Generator 2 or a loss of the Unit 2 125V de Reserve Bus (which supplies the Division II Control power} and a loss.of 6ffsite power with an accid~nt in Unit 3 re~ults tn a lo~s of ac for Unit 2.
Under these conditions, according to the licensee's August 30, 1982 letter, the Unit 2 shutdown will convnence with the isolatton condenser and HPCI System.
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The swing d*iesel generator is required by Unit 3 only until the core has been reflooded.
At that point, only one LPCI pump is required to maintain level, and two contaiment cooling servi'ce
. water pumps wi 11 remove the heat from the contafoment (see FSAR Section 6.2.4). This combfoatton of pumps ts wittiin the rating of a single diesel generator.
Once reflood has occurred in Unit 3, the operator can manually swirig Diesel Generator 2/3 to Unit 2 to support long-tenn cooling.
This scenario is covered by Procedure DGA 12, "Partial or Complete Loss of AC Power, 11 which instructs the operator upon loss of ac to cool down using the isolation condenser and/or HPCl, and also to restore power via Diesel Generator 2/3 using the nonnal bypass switches under emergency conditions.
The staff's audit of the cit~d procedure and drawings.12E-2328 and 12E-2346 supports this statement.
H.
The Isolatidn Condenser System (lCS) is susceptable to stngle EI&C failures which would render the system inoperable.
Pai lure of*
250V de Reactor Bus power or failure of the motor operator for valve 2~1301-3 results in inabi'lity of the system to automatfcally initiate.
This valve can be operated manually.
Time is available to operate it, and it is located outside of containment.
- 2.
In addition to the work done by EG&G, a second contr-actor (franklin Research Center) has informed us that at least one shared engi'neered safety.feature (ESF) is powered from diesel generator 2/3..
- From Franklin's review *of' the ventilation systems (SEP Topic l'X-51, it was detennined that part of one Standby Gas Treatment System tSBGTS) is powered from Bus 28-2 (Unit 2) and diesel 2/3.
Th.e other SBGTS ts powered from diesel 3 in Unit 3. ff there is a LOCA in Untt 3 and
- offsite power is Jost and diesel generator 3 fails, bot~ SBGTS will fail (because diesel 2/3 will swin[ to Unit 3).
The staff was concerned that similar problems may exist wi"th the s*hared cooling systems.
The staff did not have sufficient, current drawi"ngs
- of Unit 2 and 3 shared systems to resolve this concern.
ln addition, Franklin identified the battery room venti'lati'On systenras not being powered from an onsite source.
The staff i's concerned because a recharge from the diesel generator is the time* of htghest hydrogen concentration.
The licensee's response was that manual methods could be used to load the vent fan onto diesel generator 2.
A review of procedure DGA-12 does not include loading of any fans, although Bus 27 is re-energized.
Further telephone discussions, a site visit, additional drawtngs, and a letter from J. Rausch to P. O'Connor dated August 30, 1982, have served to resolve some of these concerns, as follows:
A.
Alternate power sources via manual transfers can be made available to assure that suffi*cient engineered safety features* such. as the SBGTS are avai-lable i"n a suffi-ctent period af ttnie..
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B.
The l i-cens*ee wi'l l attempt to demonstrate that battery* ventila.tton i*s not required.
C.
In the event of :the LOCA i"n Unit 3, loss of offstte power, and failure of DG3, the operator can manually restore power to the SBGTS by use of the bus tie between 480V Bus* 28 and 29.
Such a transfer will have mfoima 1 effect on Dt*es-el t'ienerator 2, because many loads are shed from Bus 28 on undervoltage and safe shutdown loads for Unit 2 total only 1340 KW (see FSAR Table 8.2~3:2} far below the diesel output capacity.
Use of the bus tte breakers is governed by procedure DOP 6700-2.
A review of loads fed by DG 2/3 indicates that other shared ESf Systems powered by this diesel are the diesel auxili-aries (cooling
. water pump, fuel transfer pump, room vent fanL
- 250V de battery charger 2/3.
The diesel auxiliaries all have redundant power feeds from Unit 3. which automatically close in upon 1 ass of the Uni't 2 ---
feeds.. Backup 250V de batter charger 2/3 can be manually connected to the Unit 2 battery upon loss of charger 2.
The 125V de battery
- charger 2/3 is normally not connected to either battery; however, this charger has an alternate feed from Unit 3.
Use of the battery chargers is discussed in procedures DOP 6900-1 and -2.
The staff's audit of the procedures and drawings referenced by the licensee supports this analysis.
VI.
CONCLUSIONS Although the present leveJ of sharing of 125V and 250V de systems is not tn.
agreement with current criteria (and is prohibited by the recommendati~ns of NUREG-0666), *the staff has determined that the design satisfies* the single failure criterion and is, therefore, acceptable provi~ed that the Dresden 2 l 25V de systems are modified to prevent para 11 el operati'on *of de sources during r~actor operation and SEP Topic VI-7.C.l ts resolved in a manner.
acceptable to the staff.
The procedures for positioning the diesel generator bypass switches are a*cceptab 1 e.
The battery status indication should be modHied as outli'ned i'n SEP VIIl-3.B.
The existing fuel oil storage capacity, combined with the close proximity of replenishment sources, is sufficient, therefore, acceptable.
- Sufficient 250V battery charging capacity is available.
The loss of power to valve 2-1303-3 is not a safety problem for safe shutdown because it can be operated manually.