ML17199R321

Safety Evaluation Supporting Items III.G.3 & Iii.L of App R to 10CFR50 Concerning Proposed Rev to Alternate Shutdown Capability

ML17199R321
Person / Time
Site:	Dresden
Issue date:	07/17/1987
From:	Office of Nuclear Reactor Regulation
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ML17199R320	List: ML17199R319 ML17199R321
References
NUDOCS 8708140248
Download: ML17199R321 (32)

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{{#Wiki_filter:UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO APPENDIX R TO 10 CFR PART 50, ITEMS III.G.3 AND III.L DRESDEN STATION, UNITS 2 AND 3 COfttONWEALTH EDISON CO. DOCKET NOS. 50-237/249

1.0 INTRODUCTION

By letter dated January 19, 1983, a safety evaluation was 1ssufd regarding Appendix R to 10 CFR Part SO, Items III.6.3 and III.L (alternate and/or dedicated shutdown capability following a fire event in the plant) for Dresden Units 2 and 3. Subsequent to the issuance of the safety evaluation, C011110nwe1lth Edison Company (the licensee) and its contractors discussed issues relating to their Appendix R cmip11ance in a 111eeting with the NRC staff on June 14, 1984. In that meeting, the licensee stated that, based on their review of NRC's Generic Letter 83-33 dated October 19, 1983, it was found necessary to CQllPlete a reverification effort relating to their CQllPliance with Appendix R require-ments at Dresden. The licensee presented its reverification findings, which included revised alternate shutdown paths based on its zonal interaction analysis, which it cmmitted to, as well as newly proposed non-outage and outage-related modifications, interim CQllPeftsatory.. asures (ICMs) as required, and associated circuits analysis. On request from the staff, the licensee provided follow-up subll1ttals dated August 10, 1984, and March 1, 1985, wherein they identified all the hot shutdown paths, the newly proposed llDdification with the schedules for their CQlllPletion, the previously comftted modifications with their current status, Ind the ICMs. Additionally, in the August 10, 1984 submittal, the licensee requested both scheduler (for CCllPletion of the pre-viously c0111itted swing dtesel generator modtftcattons 1s.. 11 as newly proposed modifications) exemptions and non-schedul1r ex111Ptions fl"Gll the requirements of IIl.G.l, 111.6.2 and 111.6.3 1s applicable and provided just1ficatton for the su. based on their f1re hazards analysts. Based on the staff's revtew of the above subll1ttals, and cl1rtftc1t1on*provided by the ltcens* tn 1 telephone conversation wtth the staff on May 28, 1985, the staff, by letter dated July 1, 1985, requested 1dd1t1ona1 tnfor81tton 1n the area of assoc11ted c1rcufts concerns (such 1s electrical tsolat1on deficiency, fire-induced spurious operations, and htgh impedance faults wh1ch can i11p1tr safe shutdown capabfl tty). By letters dated August 9, 1985, January 9, 1986 and May 30, 1986, the ltcensee provided the requested fnforNtton., Also, by letter dited September 18, 1985, the 11censee subllftted Revision 1 to thetr August 10, 1984 sublltttal. By letter dated October 16, 1985, the licensee provided their cold shutdown analysts and requested 1dd1t1onal ex111Pt1ons pertaining to alternate hot and cold shutdown caP1bfltt1es at Dresden wfth Justification for the requested exemptions based on thef r fire hazards analysis. In these submittals, the licensee provided a safe shutdown analysts based on

2 their ~ire hazards analysis, including possible zona1 interactions, to demonstrate that adequate safe shutdown systems exist and/or alternate shutdown capability is available at Dresden Units 2 and 3. Additionally, 1n these submittals, the licensee proposed repairs,*i.e., pulling out fuses or replacing blown fuses, for achieving and maintaining hot shutdown of the plant following certain fire scenarios. Also 1n the above submittals the licensee requested exemptions from III.G.l requirement, i.e., one train ~f systems needed for hot shutdown be free of fire damage, insofar as the require-ment 1s interpreted as disallowing repairs for achieving and maintaining hot shutdown. This safety evaluation (SE) addresses the deviations from the earlier safety evaluation (ESE) dated January 19, 1983. Exemptions from the requirements of III.G.2 and from the_ requ1rements perta1n1ng to alternate hot and cold shutdown capabi11t1es for Drefden Units 2 and 3 are provided separately. 2.0 POST FIRE SAFE SHUTDOWN CAPABILITY 2.1 Systems Required for Safe Shutdown In add1tion to the systems and components 1dentified for achieving safe shutdown in the ESE, for a fire in certain fire areas or their equivalent fire areas (see Section 2.2 of this SE for a definition of equivalent fire areas), the licensee identified the utilization of the High Pressure Coolant Injection/low. Pressure Coolant Injection (HPCI/LPCI) Systems. This approach would achieve hot shutdown in lieu of the isolation condenser (IC) shutdown method identified in the ESE. Additionally, for a fire in certain plant areas/Zones (RB2-I: Zone 1.3.2, RB2-II: Zone 1.1.2.3, RB3-II: Zones 1.3.1 and 1.1.1.3 - see Section 2.2 of th1s SE for 1 fire area description), the licensee identified the utilization of the LPCI/containment cooling service water (CCSW) system for decay heat removal to achieve and maintain cold shutdown in lieu of the nol"llll shutdown cooling system and its associated supporting systellS identified in the ESE. The safe shutdown systellS identified above are expected to be used during a severe fire event when other means of shutdown identified in the plant pro-cedures are determined to be unavailable. 2.2 Areas Where Alternate Safe Shutdown Is Required As part of their reverification effort, the licensee ex111ined the need for providing alternate safe shutdown capability for Units 2 and 3 for a fire in any fire area or its equtv1lent fire area. The licensee defined an equivalent fire area as one or *re ftre zones which border other fire areas, and. 1s either separated by a 3-hour rated fire barrier or by equtvalent fire protection.....,.. a 3-lmr barrier~-.. °"'"~~ ttf0¥fd9d i11e--~1i*c1*11,i*' 0:,....1ed an ***ti*.f,. app1tcable*App111dfJfl-*ncrut,iiiuitif Further, in their reverification analysis, the licensee considered the zonal interaction; i.e., fire spreading from zone to zone (the licensee's earlier subllittals assumd that f1res would not spread from zone to zone). When the analysts indicated that the requirements of Appendix R were not explicitly *t, tlMt *11cen\\ee verified that the s111e alternate hot shutdown path and the s1111 cold shutdown path (i.e., the nonaal shutdown cooling system path) was available for all the zones within a ftre area or 1ts equivalent with a few exceptions. The cold shutdown exceptions are for fire zones 1.3.2, 1.1.2.3, 1.1.1.3 and 1.3.l as

3

• P discussed 1n S~1on 2.1 above.

The hot shutdown exceptions are for fire zones 1.1.1.S.~, 1.1.1.6, 1.1.2.SQ and 1.1.2.6 as discussed below. L, iJ The licensee also proposed modifications to provide either a 3-hour rated fire barrier, or equivalent fire protection feature(s), for the affected zone(s) to ensure safe shutdown capability. Based on their zonal interaction analysis, the licensee concluded that alternate shutdown capability was required for 10 areas (total 13 areas) as the requirements of Section 111.G.2 were not met for these areas. These are:

1.

RB2-I Unit 2 Reactor Building Equivalent Fire Area I This area contains Unit 2 IC and its pipe chase zones. Elevations 589 1-0*, 570'-0N _and 545 1-6* (zones 1.1.2.5.A, 1.1.2.5.B and 1.1.2.5.C)

2.

RB2-I Unit 2 Reactor Building Equivalent Fire Area I This area contains Unit 2 shutdown cooling pump roo11. Elevation 517 1-6* (zone 1.3.2)

3.

RB2-II Unit 2 Reactor Building Eguivalent Fire Area II This area contains Unit 2 HPCI and LPCI valves, LPCI pumps, 480-V Motor Control Center (MCCs), local reactor level and pressure instrumentation, 4 kv switchgears (SWGRs), 125-V de reactor building distribution panel, 250-V de MCCs, 480-V SWGRs and the Unit 2 part of the connon refueling floor for both the units. Elevation 476 1-6* (zones 1.1.2.1, 11.2.1 and 11.2.2), elevations 517 1-&*, 545 1-6*, 570 1-0*, 589 1-0* and 613 1-0* (zones 1.1.2.2, 1.1.2.3, 1.1.2.4, 1.1.2.5.D and 1.1.2.6)

4.. RBJ-I Unit 3 Reactor Building Equivalent Fire Area I This area contains Unit 3 IC and its pipe chase zones. Elevations 589'-0", 570'-0N and 545 1-6* (zones 1.1.1.5.A, 1.1.1.5.B and 1.1.1.5.C)

5.

RBJ-I Unit 3 Reactor Building Equivalent Fire Area I This area contains the traversing incore probe (TIP) roo11. Elevation 517 1-6* (zone 1.4.1)

6.

RB3-II Unit 3 Reactor Building Eguivalent Fire Area II This area contains Unit 3 HPCI and LPCI valves, LPCI puq>s, 480-V MCCs, local reactor level and pressure instrumentation, shutdown cooling PUllP. 4 kv SWGRs, 125-V de reactor building distribution panel, 250-V de MCCs, 480-V SW&Rs and the Unit 3 portion of the cOllllOn refueling floor for both the units. Elevation 476 1-&* (zones 1.1.1.1, 11.1.1, 11.1.2), elevation 517'-6. (zones 1.1.1.2, 1.3.1), elevations 545 1-6*, 570 1-0*, 589 1-0*, and 613 1-0* (zones 1.1.1.3, 1.1.1.4, 1.1.1.5.D and 1.1.1.6)

4

7.

TB-I Turbine Building Eastern Zone Group Fire Area This area contains essentially the Unit 2 cabling and equ;pment. Elevations 469 1-6", 495'-0" (zones 8.2.1.A, 8.2.2.A), elevation 517'~6" (zones 8.2.5.A, 8.2.5.B, Unit 2 diesel generator (DG) room 9.0.A, dirty oil tank room8.l), elevat;ons 534'-0", 538 1 -0 11 (zones8.2.6.B, 8.2.6.A), elevation 549 1 -0 11 (zones 8.2. 71 station battery rooms 7.O.A)

8.

TB-II Turbine Build;ng Central Zone Group Fire Area This area is comnon for both the units and contains the mechanical control rod drive (CRD) cross-tie valve and a 480-V MCC. Elevations 517'-6n and 534 1-0* (zones 8.2.5.C and 8.2.6.C)

9.

TB-III Turbine Building Western Zone Group Fire Area This area contains Unit 3 cabling and equipment. Elevations 469 1-6*, 495 1-0* (zones 8.2.1.B, 8.2.2.B), elevation 502 1-6* (Unit 3 cable tunnel zone 8.2.4), elevation 517 1-6* (8.2.5.0, 8.2.5.E, Unit 3 06 roo11 9.0.B), elevation 534 1-0* (zone 8.2.6.0), elevation 538 1-0* (zones 8.2.6.E, DC TIJ- /panel roOlll {6.1)), elevation 551 1 -0* (station batterx room 7.0.B) \\. ~ fr~'~aL ~o~"{(t-E£/? hre /frt:x

10. i11Sfreaiita1ns Units and 3 ~ntrol room and auxiliary electric

\\ ()..)~~ equipment room. Elevations 534 1-0* and 502 1-6* (zones 2.0 and 6.2) \\\\.Cc,;;.~ The licensee has provided alternate hot shutdown capability for a fire in any specific area 1 isted above. tndepenfiut-of=ttle=-r_eqyl_1H--hot-1hutdown--equipment ~.. --aftd -cabling for the specific area as required by-Appendix-ft, Section III.6.3. ' Additionally, the licensee has identified the fire zones listed above which lack fire detection and/or fixed fire suppression system as required by III.G.3. The licensee has requested ex111Pttons fra11 the III.6.3 requt~ts for the above zones and has provided Justtfic1tfon t>.sed on thefr ff re.,.zards aulysfs. _ten In its submittal s, the licensee ltsted (if{/;1 ternate hot shutdown paths, (four utilize the respective unit IC and two utilize the respective unft HPCI/LPCI system) for achieving and 111intaining hot shutdown of ef ther Unit 2 or Unit 3, or both, depending upon where a fire.. Y occur. Two of the IC alternate hot shutdown paths (Bl for Unit 2 shutdown for a f1re fn TB-1 area or R82-II area, except for zones 1.1.2.6 and 1.1.2.5.D; Al for Unit 3 shutdown for a f1re in TB-III area or R83-II area, except for zones 1.1.1.6 and 1.1.5.D) utilize the unit IC, the Unfts 2/3 swing dfesel generator (06 2/3), the other unit' power train, and local 111nual operat1on of the IC valves. The re111fning two IC alternate hot shutdown paths (both A2 and 82 for shutdown of both Unfts 2 and 3, respectively. for a ffre either in TB-II or TB-V area} utflfze the swing 06 2/3, the respective unit IC and power tratn, and local 111nual operation of the IC valves. The HPCI/LPCI alternate hot shutdown paths (C for Unft 2 shutdown for a ff re in RB2-I area; O for Unft 3 shutdown for a ffre fn R83~I area) use the respective unit HPCI/LPCI system, power trafn and 06. For a ff re in the Unit 2/3 reactor building COlmOn refueling floor (R82-II-Zone 1.1.2.6/RBJ-II-Zone 1.1.l~* or TB-IV (turbine building operating floor and vent floors), the two f~ hot shutdown paths A and B are genera 1 ly used for Units 2 and 3 shutdown, respectively, since the refueling floor and TB-IV area do not contain any safe shutdown equipment or cables. These ~ hot ( (fl .___.-'1 (.~ r',-,,. {-- - C/ -f_~ 0 1 o v-

5 shutdown paths utilize the swing OG 2/3 and the respective unit IC and power ;J train and do not require any manual operation of the IC valves. These ~nfii'l'J paths are also to be used for a fire in either zone 1.1.2. 5.O ( RB2-II) or -- 1.1.1.5.D (RS3-II) for the same reason mentioned above, provided the fire does not spread into another zone. In such a case, the alternate hot shutdown path Bl or Al described above is to be used. JL .Ln ,,.. t:e r II IJ..Y'- VI For a fire in one of the two remaining fire areas (i.e., the RB-2/3 area which contains the Unit 2 HPCI romn (zone 11.2.3 Unit 3 HPCI room (zone 11.1.3), and the swing DG 2/3 room (zone 9.0.C)}, onna *hot shutdown paths E and F (which involve the respective unit IC, power train and DG and not requiring manual operation of the IC valves) are to be used for Units 2 and 3 shutdown, respectively (zone 11.2.3 - path E* zone 11.1.3 - path F; zone 9.0.C - paths E and F}. The required equipment and cabling for these paths are independent of the fire area RB-2/3~ Also, the zones in this area are provided with fire detection and suppression features. The re1111fning fire area (i.e., the crib house - zone 11.3) is discussed in Section 2.3 of this SE. The staff has reviewed the above mentioned alternate hot shutdown paths for Dresden Units 2 and 3, and finds the11 acceptable. 2.3 Section III.6.2 of ApP!ndix R The licensee indicated that the crib house (i.e., zone 11.3) which contains the service water and diesel generator cooling water PUllPS CQllP11es wtth the requirements of III.6.2 with a few exceptions dealing with barrier destgn and cable separation for whtch the licensee has requested exemptions. The licensee provided Justification based_pn thetr fire hazards analysts. For a fire tn the above area, either nor111lV~hhot shutdown paths A and B or E and F described above *Y be used for Units 2 and 3, depending upon where the ffre occurs.

• ci fi,'.' r r1.d:1* i1-c The licensee also indicated that for SOlll of the fire zones in AB2-II and RB3-II areas listed tn Section 2.2 of thts SE, SOlll of the safe shutdown functions will be protected tn accordance with the requirements of III.6.2, with a few exceptions. The licensee has requested ex1111>tions for these exceptions, which have been evaluated separately.

2.4 Alternate Safe Shutdown Sxst.. Besides the modifications identified in the earlier SE for achieving safe shutdown utiltzing Hfe shutdown paths, the ltcensee has identified t~ following new llOd1f1cations in their recent subllitt&ls:

1.

Relocation of the local control station for MCC 38-1 *1n feed which powers the swing 06 2/3 auxiliaries from its present location in the turbine butlding mezzanine floor (zone 8.2.6.C) to the D6 2/3 room in the RB-2/3 area. This ensures the availability of one of the a-o redundant sources of power to the 06 2/3 auxiliaries outside the turbine building (the control station for the other redundant source of MCC 28-1 Min feed to the 06 2/3 auxiliaries is located in the turbine building ground floor (zone 8.2.5.C)).

4----:<-¥4*,-~!i~~- ~"\\. dt&v.~/~~/- z_

2.

Pro on for alternate feeds to reactor pr~ssu"r9--an*d--l-evel- -tr_______ .\\ This i ion to the rerouting of the pressure evel1nstrumenta-tion cables in the --Z~nd 3 reactor b mezzanine floors. This\\ ensures availability of the-*reac~ sure and level fnd1cat1on fn the \\. contro 1 room for a fire b e react ding mezzanine floors. In 1 0\\-' \\ the fnterim (i.e.* the alternate feeds are ted during the fa11J1,* i 1986 and outages for Units 2 and 3, respectively), jnstrumenta- ! t ich is available either at the mezzanine floor or the gnfund-fJ-0..or I _<-,. ~- \\.of the reactor buildings wi 11 be used as appropriate. ~ In addition to the above modifications the licensee has CClllllitted to provide a number of other fire protection features. The adequacy of these modifications with regard to ensuring separation of alternate shutdown paths has been considered in the evaluation of the exemption requests. The staff has reviewed the interim.compensatory measures (ICM) for applicable modifications referred to above and/or existing features that wf 11 ensure the alternate safe shutdown capability in the interim period and finds th111 acceptable. 3.0 EVALUATION The safe shutdown systems identified in the above Sections 2.2 and 2.4 are expected to be used during a severe fire event when other.. ans of shutdown identified in the plant p~cedures are determined to be unavailable. The following Sections (3.1. l. through 3.5) identify how the perforMnce goals outlined in Section III.L of Appendix R to 10 CFR 50 are.. t ""8n alternate shutdown paths described in Sections 2.2 and 2.4 of this SE are utilized: 3.1.1 Reactivity Control Reactivity control ts achieved by following the procedures 11 stated tn the ESE. 3.1.2 Reactor Coolant Inventorx Reactor coolant inventory ts proposed to be controlled by following the procedures as stated fn the ESE except for the following:

z.

~---~-------------'*--*-----------*-*-----*--~-- -~-. ~--*-* Excessive loss of reactor coolant inventory fra11 the reactor vessel via the main steam lfnes during a fire event ts prevented by clostng the MSIYs frma the aatn control panel. For a fire fn TB-Y area this procedure ts folla.ed prior to evacuatton of the control roo11 and, addf ttonally, the atr supply to the outboard MSIVs ts cut off utt~tzing the air valves located in the turbine buildtng after evacuating the control rooa to prevent possible ftre-f nduced spurtous opening of these valves. The above procedures will be followed rattler than securtng the MS I Vs closure by deenergtzing the P<*!r to the MSIYs at the appl tcable breakers as stated tn the ESE. -F~r-a-ft-~ tn -;it...r RB2-I or RB3-I area, the HPCI/LPCI shutdown path ts uti lfzed to achieve hot shutdown. The operator frcm the control room places the HPCI into operation to matntltn proper reactor water level. The reactor coolant inventory control ts 1ccG11Pltshed by.. nually operating the flow-controller to regulate water supply to the reactor vessel by the HPCI pump which takes fts suctton from either the \\

l . Ml 7 ,/...,, ~ n J.,. b J J I <...-~ Ct/' T)ti CCS'J ~- " Yu..'/ /1 1 1 t' v'f ( I~ y . L ~e"'~ Y 1_. (condensate storage tank (*m), o~ the torus afte etion of ttieci:sr~- ,\\, ~- .f;... _;:y I~ During th1s '!'Ode of operati4n, ~he aper. tor will place the HPCI

• .::crt'~. ~

~~~~~~oler in operat1on, supplying 1t wlth cool1ng water from the serv1ce water system or the DG cooling water pump. 3.1.3 Reactor Coolant Pressure Control ~eelant pressure corrtrol 1s established 1A1t1ally by ut111z1ng the.:- c;:;;J

• elee!f"Glllat1c relief valves. Should**t-hese be affected._by--..1__fi re., --the Yr~r:~;~

Rock valve (mechanical mode) and the mechanical safety valves on tht steam lines will be utilized for reactor coolant pressure control. 3.1.4 Reactor Decay Heat Removal For a fire in any plant area other than RB2-I or RBJ-1, decay heat removal during hot shutdown 1s acc011p11shed through the use of the isolation condenser (IC), associated supporting equipment and procedures as described in the ESE. For a fire 1n RB2-I or RB~-[A~a using the HPCl/LPCI hot shutdown path, -~

• \\ the opera tor wi 11 place the ~

syHem in the torus coo 11 ng imde to acc~..11..Jb __ '-"'. I LfL..1.-* '.;,;.decay h'a~.~YaL.dur.1ng-.bot shutdown. In this mode of ~erat1on, the . * 'c..r ~ ope_r.a.tor_wi 11 start~'two ~pumps (01v1sion II) and open valves in either the ~rus test return nne, or' the torus spray 1 ine, to return water to the torus /oi\\ ~f.t~r_ i_~ i~. cooled by the containment coo11ng heat exchanger. The operator C?o will also staroKtwo containment cooling service water (CCSW) pumps (Division

• \\-"v-l'.-'

II) to provide cooling water flow to the tube side of the heat exchanger and, ~* additionally, open the discharge valve for the cooling water discharge header.

• The operator w111 throt~le flow as appropriate to obtain the desired cooling and verify that the-ftttttVLa~~~~W room coolers are in service.

For a fire in any plant area/zone other than RB2-I/l.3.2, R82-11/l.l.2.3, RBJ-II/1.3.1 and 1.1.1.3, decay heat removal during cold shutdown is acc0D1plished by using the normal shutdown cooling system, reactor building closed cooling water (RBCCW) system, the service water system, and the procedures outlined in the ESE. For a fire in the zones identified above, the LPCI/CCSW (Division II) method will be utilized to acc011p11sh decay heat removal during cold shutdown. In this inethod, the vessel is filled using LPCI, with hotwater overflowing to the torus through the relief valves. This method yields ~--. continuous cycle of water though the core, through the relief valves to the ~

~)torus and back again after cooling via the containment cooling heat exchanger *

. f<- Y,~_.Water... to_.tbe MRfroom cooler 1s provided using the unit D6's cooling water ~,, /. pumps or service water pumps. Water to the CCSW room cooler is provided from the CCSW pump discharge and routed through the cooler to the pump suction. 3.1.5 Process Monitoring Direct indication of.process variables (such as reactor vessel water level, reactor coolant system pressure and condensate storage tank water level) are ~~!~d~:ri>::= ~~c~!!1;rufd:!ft~i::e:'nf::=s~~::* ~~i:~!~ l::e~c,:~t~~e., HPCl/LPCI hot shutdown paths, are available -be-th locally, ~~f-at*:-Uli..... ~ rcumt'~-Supp~ssion pool teq>erature indication for the HPC shutdown path is providedJia&h1 cantrof l'OOlf;

• Diagnostic mnitoring includes local aftd.,:

~l-r-ootn-indications for service water system pressure and condensate ~\\\\~~')transfer pump discharge pressure for. the IC path and HPCI and RHlf(pumps \\ti{.,. ~/ Lt::. c '.I. -~...:: ____. -

8 discharge pressure for the HPCI/LPCI shutdown path. Diagnostic monitoring available for cold shutdown systems include 1nd1cat1ons of system pressures for the-RBEW!, nonnal shutdown cooling system and the eewg-. R~ (cw '11. (-c S'v./ 3.1.6 Support Functions .. y, ~r~ In addition to the systems needed to support the IC hot shutdown paths and the -~hutdown cooling system cold shutdown path identified 1n the ESE, the

• HPCI, tU:t8 and CCSW room coolers are also available to provide necessary support for the alternate shutdown systems.

The control and monitoring capability for these systems are provided loca lly.,...attd at the control roe.. ~--- 3.2 72-Hour Requirement The licensee has reaffinned that Dresden Units 2 and 3 have the capability to achieve cold shutdown within 72 hours after a fire event in any plant area, even assuming a loss of offsite power. 3.3 Repairs ~

• Besides the~-lngle-eold-shutdown-npa-tr----nfeltt1fied in the -ESE', khe licensee has ident~fied -edd1-t-4ana-l*~npa. 1rs _in their recent submittals. These are discussed below.

L h,Jt Sh.i:.d~c::*.,JY\\

1.

IC hot shutdown paths A2 and 82 which are utilized for achieving hot shutdown of Units 2 and 3 for a fire in TB-II area or TB-Y area requires two condensate transfer pumps for the untts (located in TB-1/8.2.5.A and TB-III/8.2.5.E) to be placed under local control. Th1s in turn, requires electrical isolation of these pumps. The licensee proposes to achieve isolation by pulling out one fuse per pump at the applicable MCC on the floor above the pumps. The licensee further states that the pumps are not needed to provide makeup water to the ICs unttl at least 20 minutes after the UPI* =alRf* initiation Of the lCS, and that this provides ample t1me to remove the fuses. The staff concludes that the licensee's exemption request fro11 the 111.6.1 requirement for the above hot shutdown repairs is acceptable since it involves only pulling out two fuses and there is reasonable assurance that this can be done in a tt111ly manner. / 2. Until alternate power feeds to the nor1111ly open Units 2 and 3 IC inboard--. ( valves are in place (previously COlllTlitted to be completed by Fall 1985 ""\\ and 1986 Untts 3 and 2 outages), possible spurious closures of these \\ valves result1n9 fro11 a fire tn etther zone 1.1.2.2 (R82-II) or zone 1.1.1.2 (R83-II) will be mitigated by reopening these valves by ltfttng the leads and installing a jumper for each applicable valve. The staff \\"'--- concludes that thts hot shutdown repair, whtch is an tntert* compensatory ~ 7 ~ - ---measure, ts acceptable.

• \\

3.

The licensee has identified the need for possible repatrs 1n seven \\ circuits for achieving hot shutdown, as a result of electrical 1solati/n deficiency in these c1rcu1ts. The staff has evaluated these repatrs in Subsection 3.4.4 of this SE. 1

• 1 1*

j 5 fTif</ I fl ,.!. i..f.;.; />".f-fr.* (~ '7..,,, i l'.f.. I '- +:: ft;; ~ ~- /1 d f.. I / f'Y'l,; /t;ffr: Co /J S~ hlltl1..F') (Pf~'r.s 'N,-i/ fir:. fer-}oo,,.,,J. . //

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9 3.4 Associated (ircuits and Isolation As part of their reverification effort, the licensee has also examined the associated circuits concerns, such as corrmon power source including the elimination of high impedance faults, conmon enclosure, fire-induced spurious operations fncludfng possible high/low pressure interfaces, and electrical* isolation deficiency. The licensee has addressed all these concerns in their recent submfttals as discussed below. j 3.4.1 Conman Power Source µL- ~t/L/"'1. Z /

• ---*---*~*----

./--Instrumentation -and power_c_i.rcuits sharing a conman power source are protected / with coordinated fault protection for safe shutdown equipment by breakers, / fuses, or other isolation devices with special fusing ar.rangements (for further discussion of isolatiqn devices, see Section 3.4.4 below). The licensee has also considered fire-induced high impedance fault(s) (i.e., faults in circuit(s) supplying power to non-safe shutdown loads from a cOlllllOn power source) which may cQ11promise the power supply to safe shutdown loads fro11 the same power source. Regarding the above, the licensee states that the safe shutdown procedures require the operator to manually trip all the non-safe shutdown loads supplied by a coamon bus. Additionally, for a fire in one of two specific plant areas, these procedures require the manual action of pulling the 125-V de control power fuses. The above action will, however, be required only for electrically operated breakers associated with non-safe shutdown* loads supplied by the essential 480-V or 4kv switchgear COllllOn buses. The licensee further states that the needed equipment will be easily identifiable, readily accessible, and under pertodtc survetllanc1. Based on the above, the staff concludes that contingent upon verification by the NRC inspection te111 the licensee's ability to COllplete the needed manual operations in a tt*ly manner, the procedures for handling fire-induced high illpedance faults are acceptable. The staff further concludes that the licensee's request for exemption from III.G.l requirements, which will be needed for performing the

• -,above mentioned hot shutdown repair, be granted *

--*------**~------*-------*~. ----------**---- --*.. *--*--*-... 3.4.Z Connon Enclosure J I / ~ding cOftlftOn enclosures, the licensee states that Drei sden usefs alte;.,,ate* -.) shutdown paths ;ndependent of the fire area of concern nstead o redundant I shutdown paths within a fire area. Additionally, assoctated ctrcutts that i I \\ ~~~re a c0111110n enclosure wtth those required for safe shutdown are provided ~ tsolatton dlvtces. Thi staff finds the above acceptable. 3.4~3 Spurious Ope;~;;*~~~----**----**---**----*---*----.. **-*-*---**-*-------------*\\.J<-c (t!t;(,/_,,-1J-.1-2 Fire in some areas can i11p1tr safe shutdown due to ftre-fnduc~_SP,U,.fous operations of safe shutdown -tpnent. "'-nf...e~".Jal*~~J:..,f !:t~:' s:O~'~:..~ *a~d W'f;~~;~,'f£!.,Z:*~r s:1VY : 213 provided in the near te,... Loss of reactor coolant (RC) inventory resulting frm fire induced spurious opening of the motor operated HPCI stum supply valves (when the HPCI is not supplying reactor vessel 111keup), and the spurious operation of the RWCU valves, ts prevented by trtpptng the applicable breakers (for the RWCU, the associated breaker for 1 nol"llllly open motor operated upstream RWCU valve) at the 250 VDC MCC iA 11 -:located at Unit 2 or

A ffcn!:- ~ ' l ve f, -r~.'I 1'fj ~ / /)"9 j4 10 l/rl rAfi~

• j1>t.J I

10 -(jit_.../~/,/( /.)*.. : 1 -~ - '*' /0 s_.r 11J ! **- 3 reactor buildings (El. 570'-0"), or by tripping the feed to the MCC at the 250 VDC MCC in the turbine build1n

• The above procedure w111 close the HPCI steam supply valve and isolate th RWCU system.

n he "Target Rock* valves, or electromatic relief valves, and the MSIYs can " spuriously operate only due to a fire in the TB-Y area. These valves are 1 1 closed from the main control panel within a minute after initiation of a ~<J' manual scram for a fire in any plant area. The "Target Rock" or electromatic 1 \\ 1 relief valves, in particular, are closed from the main control panel by -.~' ' turning the newly installed "inhibit" switch to the "inhibit* position (in \\ this position, the inh1b1t switch disables the "low reactor water level" and the "high drywel l pressure* inputs to auto blowdown) and the \\ previously-existing key-operated *Manual-off-Auto* switch to "OFF" position. ~ For a fire in TB-Y *rea, the operators will additionally cut off the air ~~ supply to the outboar'd MS I Vs uti 11zing air valves located in the turbine -~~ J , building and remove the 125 YDC power from the *Target Rock" or electro111tic relief valves at the turbine buildin9 MCCs after evacuating the control room. 1 Removing power frm the *Target Rock valve will not disable its mechanical ~ operation mode, which is required for reactor coolant pressure control in the event the electromatic relief valves are disabled by a fire. The -~.' above-described procedure will prevent loss of RC inventory via MSIYs in steam lines and venting to the suppression pool via automatic operation of the.

• Target Rock" or electro111tic relief valves, and also prevent spurious
• --uerat1on of the valves.

Spurious opening of the solenoid operated reactor head vent valves resulting in RC inventory loss will be prevented by a pre-fire action; i.e ** ensuring closures by raoving powr frcm these valves. Steu venting of the *in steu lines v1a spurious operation of the air operated IC valves is prevented by manually closing the applicable upstre.. valve. To prevent fire-induced spurious closure of the 1110tor operated IC valves.that are required to be open during IC operation. potMr to these valves is..,... rellDVed by tripping the applicable breakers located at the 250 voe MCC 2A or 28, or by tripping the feed to the applicable MCC at the 250 YOC MCC in the turbine building. These valves 1111y be subsequently opened *nually. The spurious closure of the control rod drive (CRD) valves in the cooling water line w111 not disrupt the supply of makeup water to the reactor vessel during IC operation. This is because flow will be available through the charging water lfne and the scr111 injection valves. and also b,y ensurfng that the sen. 1tgaal ts. 1t9t*reset. Regarding hfgh/low pressure interfaces, the licensee stated that their reverification analyses did not indicate existence of any such interface utiltzing only 110tor operated valves for isolation. Further, as discussed 1n the ESE, the staff has concluded that the shutdown cooling system does not contain a high/low pressure interface with the reactor coolant system. The staff has reviewd the above inentioned procedures for handling fire-induced spurious operations and concludes that tlley are acceptable. ~~~ ' kl 1-<* :: J

~ ~¥ \\ :~:~f~ ~:~:~~;o: ~:i~j:f::::::ncy (

1.e., a fau It Ofl ~-~te circuit blowing a fuse needed for local control prior to isolation. and consequently i impatring the capability for local control of the needed safe shutdown equipment), the licensee identified a~**tl-1 of,1' safe shutdown circutts,,..as r~.---* t--* \\ \\ I

1 l1 I

. \\/r_* --- ___ -l-l- -- "">.\\£"' fs;ngly fused. Tbe licensee stated that ~of thes~-.to' kv sw1tchgears \\}J ( wh 1 ch a-f!e equ 1pped-wi-t-h---loc-a-1----mechan1-<:a-l--µ--t-ri p!!---afld~-Gff"--bvttons that a re ( / geed for affe close and e~--5en..~,,ttaou-t--t-he*--&enef1t-of*-eil!*ctr1-ca1 .JY i control. Add1t1onally,NV 7 -V sw1tchgears which can be jacked \\ ':

. closed following a f1re event.

The rema1ning five circuits involve local 1.. - , f'* ~I controls for the in-board IC valves (4 of them) and engine starting controls 1 at the 2/3 DG (1 of them). They may need fuse replacement due to a fire . event. However, a maxi!lllm of four cfrcuits may need fuse replacement due to a single ff re. A concern was a fire fn the DG 2/3 room may affect the local controls for IC valves located in that room. For a fire 1n the DG 2/3 room, the licensee proposes to replace a fuse at each of the isolation switches in the Unit 2 shutdown cooling pump room (zone 1.3.2) and the Unit 3 TIP roo11 (zone 1.4.1). The licensee has COlllllitted to ma1nta1n the -replacemen~ fuses and the fuse pullers under surveillance in the proximity of t~e zones 1.3.2 \\ and 1.4.1 and DG 2/3 $tarting controls to facilitate fuse replacement(s) in a i \\ timely manner. The licensee further states that all these areas where the / -, replacement fuses will be stored will be readily accessible and that / '~icient time w111 be available for replacing these fuses. The staff concludes that the above procedures are acceptable contingent upon verification by the NRC inspection tea* that access to the needed areas are not compromised by the fire event and that the licensee has the ability to complete these repairs wit~in the time periods tdentifted for th111. The staff further concludes that the.licensee's request for exe11ptton from III.6.1, whtch will be needed for perfonntng the hot shutdown repair, be granted. 3.5 Safe Shutdown Procedures and Manpower In recent submittals, the licensee states that safe shutdown procedures have been developed to incorporate the above-described alternate shutdown paths, including procedures for handling possible fire-induced spurious operation of equipment needed for accQ111plish1ng safe shutdown. The licensee further states that these procedures w111 provide reasonable assurance that the necessary shutdown functions can be performed at all times by available.. npower. Since ut11izatton of alternate shutdown capabt11ty.. Y require a nUllber of m1nual actions in some cases, ftnal approval ts contin~ent upon veriftcatton by an NRC inspection te111 walkthrough of the required procedures and vertftcation that the necessary actions can be completed within the specified t1111s for assuring safe shutdown.

4.0 CONCLUSION

The safe shutdown system 1dentifted tn Sections 2.2 and 2.4 of thts SE are expected to be available durtng a severe ftre event when other means of shutdown tdent1fted tn the plant procedures are determined to be unavailable. The staff has reviewed the ltcensee's currently proposed rev1s1on to thetr originally submitted and approved alternate shutdown caP1b11tty for Dresden Untts 2 and 3 in accordance with Appendix R cr1terta. As stated 1n Section 1.0, thts revision has been necessftated due to the lfcense*s rever1ftcation of their fire protection program'at Dresden Untts 2 and 3. Thts included

1) consideration of zonal interaction, high impedance faults and electrical isolation deficiency; 2) proposed new modtficattons and hot shutdown repairs to ensure alternate shutdown capability; and 3) proposed tnteri* CQllPensatory

12 measu~~s for applicable mod1f1cations and/or discussion of existing design features that w111 ensure alternate shutdown capability in the interim period. The staff concludes that the perfonnance goals for accomplishing safe shutdown in the event of a fire { 1.e., react1vHy control, inventory control, decay heat removal, pressure control, process mon1tor1ng, support functions and handling associated circuit concerns) are met by the proposed alternate. shutdown methods. As noted above, evaluation of licensee's request for exemptions from app Jicab Je I I I.G.2 and II I.G.3 requirements is provided separately. Based on the above, the staff concludes that the licensee's currently proposed revision to the alternate shutdown capability at Dresden Unih 2 and 3 satisfies the requirements of Appendix R, Section III.6.3 and III.L, contignent upon verification by the NRC inspection team of the licensee's capability to complete needed manual operations and hot shutdown repairs in a timely manner (3.4.1, 3.4.4 and 3.SJ. Pr1ncfpa1 Contributor: T. Chandra Dated: July 17, 1987

i** 3549K ATTACHMENT 2 "INFORMATION IN THE ALTERNATE SAFE SHUTDOWN SAFETY EVALUATION REGARDING CLARIFICATION",

ATTACHMENT 2 Information in the SER Requiring Clarification

1.

Section 2.2 (page 2) In this section the following statement is made: "As part of their reverification effort, the licensee examined the need for providing alternate safe shutdown capability for Units 2 and 3 for a fire in any fire area or its equivalent fire area. The licensee defined an equivalent fire area as one or more fire zones which border other fire areas, and is either separated by a 3-hour rated fire barrier or by equivalent fire protection. Where a 3-hour barrier was not provided, the licensee requested an exemption from applicable Appendix R requirements. 11 Originally, CECo interpreted 10 CFR Appendix R Section III.G.3 requirement for independence of alternate safe shutdown systems to mean that these systems and their associated components are required to be separated by 3-hour rated fire barriers. Where barriers between alternate safe shutdown systems could not be upgraded to 3-hour barriers, an exemption request from the requirements of Sections III.G.3 and III.L of Appendix R were submitted and justified. On April 8, 1986, CECo personnel participated in a meeting with the NRC staff. NRR reviewer John Stang stated NRR 1s interpretation of Section III.G of Appendix R. According to this interpretation: A. The separation criteria of Section III.G.2 does not apply to alternative safe shutdown systems,

~ATTACHMENT 2 Page 2 B~ If the alternative safe shutdown capability option is employed in the Appendix R compliance analysis, then exemption requests are only necessary from the III.G.3 requirements for fixed fire suppression and detection in the area, room, or zone under consideration, and C. The independence requirement of III.G.3 is demonstrated by the presence of fire protection measures or combina-tion of measures (e.g., substantial barriers, spatial separation, automatic detection, automatic suppression) which assure that the alternative safe shutdown systems will be free of fire damage for fi~es in the area, room, or zones for which the alternative capability is provided. Thus exemptions from the requirements of III.G.3 for lack of fire barriers between alternative shutdown components are not necessary and will not be granted: Based on this NRR interpretation of Appendix R Section III.G.3, CECo withdrew several exemption requests [See Refe~ence (l)]. Thus, the statement in the SER is not completely accurate.

2.

Section 2.2 (page 4) The SER states on page 4, The licensee has provided alternative hot shutdown capability for a fire in any specific fire area listed above independent of the required hot shutdown equipment and cabling for the specific area as

required by Appendix R, Section III.G.3." Dresden station has alternate hot shutdown capability that is independent of the affected fire area~ In order to establish independence, local isolation and control switches have been installed; It should be noted that the independence of this equipment is established when local control is taken.

3.

Section 2. 4 The second modification described in this section has been cancelled. The NRC was informed of this change in Reference (2). The NRC was given a list of all Appendix R modifications in the schedular exemption request.

4.

Section 3. 1. 2 In paragraph 2 it should state that the HPCI pump takes "suction from either the contaminated condensate storage tank (CCST), or the torus after torus high level or depletion of the CCST, whichever comes first." In the event torus high water level is reached, HPCI pump suction will be switched over to the torus even if the CCST has not been depleted.

5.

Section 3. 1. 3 The electromatic relief valves are not used to control reactor coolant pressure. Instead, the "Target Rock" valve in its mechanical mode and the mechanical safety valves are used for pressure control.

6.

Sections 3.1.6 and 3.1.7 No credit is taken for the availability of control room instrumentation.

7.

Section 3. 3 ~ACHMENT 2 ~ge 4 Since cold shutdown repairs are allowed by Appendix R, reference to these repairs should be deleted. This section should only discuss hot shutdown repairs. A listing of the cold shutdown repairs is provided below for your information. A. Shutdown Cooling Pumps and RBCCW

1.

If a fire takes out the main feed cables to reactor building Buses 23-1 and 24-1, or 33-1 and 34-1, attempt to establish the crosstie between 24-1 and 34-1 and/or to simultaneously feed 23-1 and 33-1 from the 2/3 diesel generator. If these actions are not possible, connect temporary cables from the required motors to spare breakers at the opposite unit.

2.

If only the motor feeds are damaged, remove the damaged cable section and splice a section of new cable in its place.

3.

In either case, jumper the breaker controls (or use local control) to force closure. Verify proper direction of rotation. B. LPCI Pumps and Auxiliaries

1.

If Bus 24-1 or 34-1 is disabled, attempt to establ~sh the crosstie between these two buses. If this cannot be done,

!.~ A *. ~ CHMENT 2 p 5 connect temporary cables from the required motors and 480-V switchgear to breakers at the opposite unit.

2.

If the 4-kV buses are still energized but the feeds to LPCI loads are damaged, remove the damaged cable section and splice a section of new cable in its place. In any case, jumper the breaker controls (or use local control) to force closure. Verify proper direction of motor rotation at both the 4-kV and 480-V levels. C. CCSW Pumps If Bus 24-1 or 34-1 is disabled, attempt to establish the crosstie between the two buses. If this cannot be done, connect temporary cables from the required motors to breakers in the opposite unit SWGR 23-1 and 24-1 or 33-1 and 34-1. D. Relief Valves

1.

If any one valve is still operational, disconnect cables from the penetrations for the disabled valves and jumper these pene-trations to the energized 125-Vdc penetration.

2.

If all five valves are disabled, remove all relief valve cables from their penetrations, jumper the penetrations together, and connect a temporary cable from them to the 125-Vdc source at

ACHMENT 2 e 6 th~ nearest switchgear that has control power available. Use the opposite unit, if necessary. Verify energization. (NOTE: The cable used for this purpose must first be used for repositioning the recirculation loop valves, if necessary.) E. LPCI Emergency Air Coolers/CCSW Emergency Air Cooler Connect temporary cables to a spare breaker or starter at the nearest energized MCC (probably in the opposite unit). Close the breaker, or jumper the starter controls to force start. Open normally closed valve to provide cooling water from the 2/3 diesel generator cooling water pump to the LPCI emergency air coolers. F. Recirculation Loop Valves and Shutdown Cooling Valves (Inside Drywell) Connect temporary cables from the drywell penetration to a spare breaker or starter at the nearest energized MCC. It is not necessary to use a reversing starter. Determine first whether the "open" con-tactor of the original starter is the one with straight-through or with phase-reversed connections. If phase-reversed, interchange two of the leads at the temporary source. Close the breaker or jumper the starter controls, while monitoring the current in one phase with a clamp-type ammeter. When the current sud lenly increases,

3549K ATTACHMENT 3 "LIST OF SEPTEMBER 1, 1987 CONFERENCE CALL ATTENDEES" ~--C --

3532K NAME B. Barth I. Johnson J. Kelly

w. Pierce F. Fischer J. Silady

c. Launi C. 'Ruth CONFERENCE CALL w/NRR Re:

DRESDEN APPENDIX R SAFE-SHUTDOWN SAFETY EVALUATION REPORT September 1, 1987 10:30 a.m. (CST) ORG Sargent & Lundy CECo - Nuclear Licensing Sargent & Lundy CECo - Engineering Sargent & Lundy CECo - Nuclear Licensing Sargent & Lundy Sargent & Lundy M. Grotenhuis NRR - BD III-2

DRESDEN 2&3 REVISION 3 SEPTEMBER 1987 7.0 APPENDIX R EXEMPTION REQUEST FOR HOT SHUTDOWN REPAIRS Per the prov~sion of 10 CFR 50.12, Commonwealth Edison Company (CECo) requests exemption from the requirement of. Section III.G.l of Appendix R that one train of systems needed for hot shutdown be free of fire damage, in so far as this is interpreted as disallowing the use of repairs to implement hot shutdown (SECY-83-269, Section 1.2.1). CECo specifically requests that an exemption be granted.

1)

To allow the pulling of fuses in order to place the condensate transfer pumps into local control.

2)

3)

4)

To allow the pulling of*clostng fuses to defeat high impedance faults. To allow the pulling and replacement of fuses on selected control circuits in lieu of redundant fusing as suggested by IElN 85-09. To allow the pulling of fuses to preclude spurious operation of the reactor relief valves. Section 7.1 7.2 7.3 7.4 Justification For Hot Shutdown Repair Removal of Control Power To Defeat High Impedance Faults Pulling and Replacement of Fuses in Lieu of Redundant Fusing Fuse Pulling to Preclude Spurious Operation of Reactor Relief Valves Justification for this exemption request is provided in the following sections. 7.0-1

• ~

.. ~ __ J

• • 1

°.l ~ DRESDEN 2&3 7.1 JUSTIFICATION FOR HOT SHUTDOWN REPAIR REVISION 2 SEPTEMBER 1987 Condensate transfer pumps 2A and 3A are located on the ground floor elevation of the Dresden 2&3 turbine building in Fire Zones 8.2.5.A and 8.2.5.E, respectively. Isolation condenser alternate shutdown path A2 utilizes condensate transfer pump 2A under local control. Isolation condenser alternate shutdown path B2 utilizes condensate transfer pump 3A under local control. The condensate transfer pumps are used to provide makeup water to the isolation condensers (see Section 2.2.1.2 of this enclosure). The service water pumps and fire pump are also available to provide makeup water to the isolation condenser. To locally control the condensate transfer pumps, it is necessary to electrically isolate the pumps. This isolation is accomplished by pulling one fuse per pump located on the floor above the pumps at MCC 28-2 for pump 2A and MCC 38-2 for pump 3A. The condensate transfer pumps are not required for makeup water until at least 20 minutes after-~he initiation of the isolation condenser following a fire. This provides ample time to remove the required fuses and place the pumps into local control. Pulling of fuses is an accepted practice at Dresden and in the industry as a whole. However, because the pulling of fuses is considered a repair for the purpose of Appendix R, an exemption to Appendix R is necessary for the use of this procedure to achieve and maintain hot shutdown

• 7.1.1

-= ... --.":!'*~-"-

DRESDEN 2&3 APRIL 1986 7.2 JUSTIFICATION FOR REMOVAL OF CONTROL POWER TO DEFEAT HIGH IMPEDANCE FAULTS 7.2.1 Discussion Common power source concerns were addressed in the safe shutdown analysis. All of the safe shutdown loads on a given bus are known to be free of fire-induced faults whenever that bus is cal led upon to power safe shutdown loads. The non-safe shutdown loads that are also connected to the essential buses were not analyzed to determine if a high impedance fault could cause a tripping of the feed breakers. The safe shutdown procedures address high impedance faults on non-safe shutdown loads by instructing the operator to trip all such loads *... After.tripping these loads an additional manual action of pulling the control power fuses is specified as a precaution against spurious closure of electrically-operated breakers. When a breaker at a motor control center (MCC) is tripped, no further action 9*-, is needed to.prevent spurious closure. The same is true for manually-operated ~~) breakers at the 480V switchgear buses (28, 29, 38 and 39). When an T.1:~;~/ electrically-operated breaker at 4kV or 480V switchgear bus is tripped,

• spurious closure remains possible until 125V de control circuit fuses are pulled.

These fuses are rated 15 amperes or less, and the actual load .currents are.considerably less therefore no personal safety equipment is needed. In each of the 480V switchgear buses, the control circuit fuses for all breakers on the bus are housed in a single fuse compartment. Each breaker's fuses are mounted in a plug-in fuse block that is equipped with a handle for fast, safe removal. The control circuit fuses for each 4kV breaker are mounted in similar plug-in blocks, and are located in the relay compartment directly above the affected 7.2-1

--~ 'i.:...:J DRESDEN 2&3

• APRIL 1986 breaker.

Separate fuses are used for the closing _circuit and the tripping circuit; only the closing circuit fuse block needs to be removed. The operators routinely rack out 480V and 4kV buses prior to working on the equipment. The first step in racking out a breakers is the removal of the closing fuse. Removal of the fuses precludes spurious closure and makes it unnecessary to rack out the breakers. The time necessary for removal of these fuses is being considered in the manpower requirements for the safe shutdown procedures. The tripping of unwanted 480V loads needs to be performed only for shutdown paths that use the affected unit 1 s own power train. Two of the hot shutdown paths that wil~ be used for fires in most fire areas, use equipment and cables in the unaffected unit, where the potential for fire-induced faults does not exist. Only two of the identified fire areas have the potential for fire induced faults which may affect 480V and 4kV non-safe shutdown loads.* The addition of an isolation switch on the non-safety shutdown loads would not increase the operator safety or decrease the time necessary to perform this operation. Some safety related equipment will be disabled by the removal of these fuses, however this operation as it is incorporated in the safe shutdown procedures follows the requirements set forth in 10 CFR 50.54{X). The pulling of fuses is considered a repair for the purpose of Appendix R therefore an exemption to Appendix R is necessary for the use of this procedure to achieve and maintain hot shutdown. 7.2.2 Conclusion Based on this analysis, the intent of Appendix R requirements are met also, the pulling of the closing fuses would not affect safe shutdown of the plant. The justification for removal of these fuse is summarized as follows: 7.2-2

• r.

~ DRESDEN 2&3 ' e APRIL 1986

1)

The operation needs only to be done for electrically operated breakers at the 4kV and 480V essential switchgears.

2)

This procedure will only be used to guard against possible high impedance faults for a fire involving two plant areas.

3)

The fuses are easily identified and removed.

4)

The operation is familiar to the operators.

5)

All equipment necessary for these operations is in the proximity of the equipment of intended use and is kept under periodic surveillance. 7.2-3 _* )'.-~: :

• • .\\~{fi

- l *:T.1:i . ~* f

j DRESDEN 2&3 REVISION 1 SEPTEMBER 1987 l ( 7.3 JUSTIFICATION FOR PULLING AND REPLACEMENT OF FUSES IN LIEU OF REDUNDANT FUSING

7. 3.1 Discussion Each safe shutdown equipment item for which local control is utilized was checked to determine whether a fault on the remote circuit (prior to isolation) can blow a fuse needed for local control.

Several items were found to be deficient in this regard (Table 1). Dresden Station does not use a remote shutdown panel in performing safe shutdown procedures. The shutdown procedures have identified manual operation of switchgear -and l-0cal control of equipment. A majority of the required safe shutdown circuits protected by a single fuse, are 4-kV circuit breakers. These 4-kV breakers are equipped with local mechanical "TRIP" AND "CLOSE" buttons that are good for one close and one trip without the benefit of control power. This stored energy within the switchgear is equivalent to redundant fusing since both require a manual action. Some of the remaining identified circuits are 480-V breakers on buses 28 and

38.

These circuits feed the condensate transfer pumps 2A and 3A. These pumps are needed to provide shell side makeup to both isolation condenser. If the control circuit is found to be inoperable, then isolation condenser may be jacked close. These pumps are not needed until at least 20 minutes after isolation condenser initiation (Table 1). The remaining circuits are associated with the inboard isolation condenser valves and the engine starting controls for the 2/3 diesel generator. For a fire in the reactor bui I dings where shutdown paths Al and Bl are used, fuses (2) for the opposite unit's inboard isolation condenser valve isolation switches in the Unit 2 shutdown cooling pump room on the Unit 3 TIP room may need to be replaced. For a fi~e in the 2/3 diesel generator room where safe shutdown paths E and F are used, fuses (4) for both units' inboard isolation condenser valve isolation switches may have to be replaced. Procedures will require operators to be sent to these rooms to operate the isolation switches and replace fuses as necessary. Replacement fuses and fuse pullers will be 7.3-1

e DRESDEN 2&3 REVIS ION 1 St::PTEMBER 1987 ma~ntained under surveillance in the proximity of these rooms and will be readily accessible if fuse replacement is necessary. The remaining circuit for which fuse replacement (actually four fuses are replaced) will be the only available solution is the engine starting controls at the 2/3 diesel generator. The possibility of fuse replacement arises for a fire in the reactor buildings where safe shutdown paths Al and Bl are used. Again, replacement fuses and fuse pullers will be maintained under surveillance in the proximity of these controls. An operator will be in the 2/3 diesel generator room to locally control the diesel generator and inboard isolation condenser valves for all paths which use tne 2/3 diesel generator. Because of the minimal number of possible fuse replacements (at most six for a fire in the reactor building), sufficient time is available to replace these fuses. The pulling and replacement of fuses is being considered in the manpower requirements for the safe shutdown procedures. All of the proposed fuse replacements are in low-voltage circuits (120 V ac or 125-Vdc). The fuses are of t he c a rt r i d g e type and can be removed or inserted under 1 oad by means of a standard fuse puller. All are in control circuits (not power circuits) and are rated 15 amperes or less. Actual load currents are considerably less, therefore no personal safety equipment is needed. The operators have been'trained at pulli~g and replacing similar fuses for routine testing and maintenance operations. The fuses are presently connected at the point where control power enters the equipment, prior to any connections to switches, relays, lights, etc. The presence of a redundant fuse would leave certain terminals of the LOCAL-REMOTE selector switch hot if only the original fuse is pulled; in LOCA position the entire circuit could be hot. We maintain that the small quantity of required fuse replacements, combined with the small likelihood of a serious fire, does not warrant this personnel hazard. Fuse pulling and replacement is considered a repair for the purpose of Appendix R; therefore, an exemption to Appendix R is necessary for the use of this operation in lieu of providing redundant fusing. 7.3-2

=--: 7

• 3. 2 Conclus~on DRESDEN 2&3 REVISION 1 StPTEMBER 1987 Following is a summary of the justification for pulling and replaciny fuses in safe shutdown control circuits.

1)

Pulling and replacement of fuses is routine practice at Dresden Station and the station operators are familiar with this operation.

2)

Replacement fuses and fuse pullers wil I be maintained in the proximity of the fuse replacement locations and kept under periodic surveillance.

3)

The circuits that are involved in this procedure are low-voltage control circuits. The fuses are rated at 15 amperes or less, and are actually carrying currents that are considerably less.

4)

The fuses in the equipment of concern can be easily located and replaced. 7.3-3

I. I I. DRESDEN 2&3 TABLE 7.3-1 REVlSlON 1 SEPTEMBER 1987 LIST OF CIRCUITS PER IEIN 85-09 CONCERNS WHlCH MAY REQUIRE MANUAL ACTION FOLLOWING A FIRE 480 V BREAKERS A. Bus 28 Main Feed B. Bus 38 Main Feed OTHER A. 2/3 Diesel Generator Local Contra ls (Engine Starting) B. Isolation Condenser Valve M02-1301-l Isolation Switch

c.

Isolation Condenser Valve M02-1301-4 I sol at ion Switch

o.

Isolation Condenser Valve M03-1301-4 I sol at ion Switch E. Isolation Condenser Valve M03-1301-4 I sol at ion Switch 7.3-4 Time of Use (Minutes After Isolation Condenser Initiation) 20 20 Time of Use (Minutes After Scram) 10 30 30 30 30

7

• 4 7
• 4. l DRESDEN 2&3 JUSTIFICATION FOR FUSE PULLING TO PRECLUDE SPURIOUS OPERATION OF REACTOR RELIEF VALVES o;scuss;on For fires occurring in Fire Areas RB2-I, RB2-II, RB3-I, RB3-II, TB-I, TB-III or TB-V, it is possible that damage to electrical circuits could occur, e.g.,

shorts in power or control cables, which would result in spurious operation of a Unit 2 and/or Unit 3 reactor relief valve (203-3A, 203-3B, 203-3C, 203-3D, or 203-3E). To ensure against s~ch spurious operation, it will be necessary in some cases to manually disable the relief valve circuitry. Generally, this involves removing power to the valves and is commonly accomplished by opening breakers at electrical distribution panels. However, for a fire in Fire Area TB-I or TB-III, it will be necessary to remove control power fuses to deener9ize the valve circuits. The removal of fuses to achieve or maintain hot shutdown is considered a repair for the purposes of Appendix R, and thus is not permissible without specific exemption. There are 20 fuses per unit which will need to be removed in order to deenergize the circuits to each unit's five relief valves. The Unit 2 fuses are located in electrical panel 902-32 in Fire Zone 6.2 (Auxiliary Electric Equipment Room) in Fire Area TB-V. The Unit 3 fuses are located in electrical panel 2203-32 in Fire Zone 1.1.1.3 (Unit 3 Reactor Building Mezzanine Floor Level) in Fire Area RB3-II. For a fire in Fire Area TB-I (Turbine Building Eastern Zone Group), only the Unit 2 fuses, located in Fire Area TB-V, will need to be removed, since such a fire will not affect the Unit 3 relief valve circuitry. A fire in Fire Area TB-I will not affect Fire Area TB-V, but access to Fire Zone 6.2, where the panel containing the fuses is located, must be gained through Fire Area TB-I. Access to Fire Zone 6.2 is available through either of two 3-hour fire rated doors which separate the zone from Fire Area TB-I. The two doors are separated by approximately 100 feet. Automatic suppression systems partially protect the area between these two doors. It is not credible to postulate that a fire in Fire Area TB-I would result in both such widely separated entrances being inaccessible. Emergency lighting is provided in the vicinity of each of the doors, facilitating operator access. 7.4-1 ~ -- - ~*.::.._- _. -.~ :

y DRESDEN 2&3

• I For a fire in Fire Area T~-111 (Turbine Building Western Zone GroJp), only the I

Unit 3 fuses, located in Fire Area RB3-ll, will need to be removed, since such a fire will not affect the.Unit 2 relief valve circuitry. A fire in Fire Area rn-111 will not affect Fire Area RB3-ll and the panel containin9 the fuses will be readily accessible. The 40 fuses (20 per unit) under consideration are cartridge-type fuses and are rated at 20 amperes. No personal safety equipment is needed for their removal and the station operators are trained and experienced in removing such fuses for routine testing and maintenance. 7.4.2 Conclusion As~demonstrated in the preceding discussion, the removal of fuses to prevent spurious operation of the reactor relief valves would not interfere with timely performance of safe shutdown operations. Justification for the acceptability of removing the fuses as part of postfire hot shutdown operation is summarized as follows:

1.

The number of fuses under consideration is limited to 20 for each unit. All the fuses for a given unit are located on a single panel and fuse pullers are located in the vicinity of the panel.

2.

Removal of the fuses will be incorporated into the plant Appendix R Safe Shutdown Procedures.

3.

The fuses are located at panels in fire areas different from those fire areas in which the postulated fire occurs that requires removal of the fuses.

4.

The fuses under consideration* are easily identifiable, low amperage fuses, which are easily removed without threat to operator safety. 7.4-2}}