ML19269C783
| ML19269C783 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 02/05/1979 |
| From: | Moody D YANKEE ATOMIC ELECTRIC CO. |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| WYR-79-9, NUDOCS 7902120194 | |
| Download: ML19269C783 (9) | |
Text
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Telephone 617 366-9011 TwX 7to - 3 9 0-o 73 9 YANKEE ATOMIC ELECTRIC COMPANY B3 1
Y.h 20 Turnpuke Road Westborough, Massochusetts 01581 9'auxes WYR 79-9 February 5, 1979 United States Nuclear Regulatory Commission Washington, D. C.
20555 Attention: Office of Nuclear Reactor Regulation Dennis L. Ziemann, Chief Operating Reactors Branch #2 Division of Operating Reactors
References:
(a) License No. DPR-3 (Docket No. 50-29)
(b) YAEC letter (WYR 78-89) dated October 16, 1978, from D. F. Moody to D. L. Ziemann,
Subject:
Fire Protection Evaluation Safe Shutdown Methods (c) USNRC letter dated November 1, 1978, from D. L.
Ziemann, to R. H. Groce,
Subject:
Staff Positions on Outstanding Fire Protection Issues (d) USNRC letter dated December 20, 1978, from D. L.
Ziemann, to R. H. Groce,
Subject:
Request for Additional Information on Safe Shutdown Capability T.ar Sir:
Subject:
Additional Information on Shutdown Capability Enclosed is the Yankee Rowe Fire Hazards Analysis which discusses safe plant shutdown and cooldown capability in the event of a fire.
This information is provided in response to your letter, Reference (d).
We trust that this additional descriptive material adequately responds to your c.ancerns. Should you have any further question, please feel free to contact us.
Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY D. E. Moo y Manager of Operations 0
DEM/cm 9
\\
79 0a! A 0 /W
ENCI')SUilE 1 Y/E EE R:.is FIRE HAZARD /SALYSIS Re:uest for Additional Inf or a tion DISCUSSION:
Yankee Atonic Electric Coupany conducted a Fire Ehzard Analysis (FHA) cf the Rowe plant in response to a gt.neric 57.C letter on fire protection. This response was submitted on January 1, 1977.
Later, an 14RC incpection tcan visitcc the site in Septe:Ser 1973 and subsequently provided a list of Staff Positions on varicus tatters relating to fire protection. The Staff Position of interest in tl.is response was:
O.
Ehutdown Considera_tices l.
An alternate shutdown tethod should be provided which is independent of the turbine building, switchgear room, control roca, canhole #3 and single cable run in PA3 for charging and shutdown puars.
YAEC letter of Cctober 16, 1978 responded with a description of the existing systen equipment and procedures to shut down the plant under all the condi tions described above. YAEC's grectest concern cas the complete loss of the entire turbine building; however, operatienal cethods and casucity precedures were described which would provide maans of shutting doun t.he plant in this event.
Additional canpower, in excess of the normal chift complement, would be receired to provide instruccntation and casualty connections, but these would be available in the time befort the building van lost.
In addition to this, two nodifications were described which would improve the redundancy of equipment available for plcnt shutdown in the event of a loss of the turbine building.
A sab.;equent riceting at Eethesda in Novenber revealed no unsatisfied sconditions concerning equip:ent or procedures for safe shutdown under any of the postulated conditions.
However, the NRC cxpressed conceras regarding available instrumentation in the event of fires in the areas stated in that Staff Position.
Specifically, would the innediate failure of any instrumentation require assistance frem the nanpower concitted to the fire fighting tea 2 to either regain the instrumentation or shut down the plant without it?
YAEC responded by Telex on November 27 stating that:
1.
The cciplete loss of the turbine building would not be preceded by an it.aed i a t e loss of inr trunentat ion.
2.
The routing of the instrezentation required avoin d all the listed I
fire areas except the m itchgear roon and t.he control roen.
l a forcation was 0
3.
Once the plant was coole-to 300 F all necce available in the pri r) auxiliary building (lu",), or could be obt aine-i 1
by c: uc.Ity procedure: outside of the ctated fire area.
A lat er telecon uith thr MC revealed that this inf orr'ation was not sufilciently detailed to provide assurance that he nanpower assip,ned to the fire brigade could not be unurped by the opt atJonal needs of a saic chutdown, especially in the event of an instrument failure.
To clearly define the inforuation witich would provide ansurance that cafe shutdowa could be accomplished without af f ecting the fire bri:;cde, the NRC on December 20, 1978 r.chaitted four questionn.
The questions and the YllC responnes are provided beleu.
The responses are nomewhat detailed in order to casure adequate inforcation.
QUESTION 1 Provide a listing <.. the infotration required by the operators to perforn a safe chutdown and cooldown 01 the Yankee-Rowe Plant.
RESPONSC The Fire Ec. ards A. lysis (F2A} lists the following actiona required to safely shut do.:n the plant:
1.
Incert negative reactivity into the reactor 2.
Remove decay heat and control cooldown 3.
Maintain nain coolant inventory and uteu:a generator inventory 4.
Control primary plant overprensure The actual steps involved in a safe shutdown are:
1.
Control rod incertion by scramming the reactor 2.
Decay heat renoval and cooldown via the stean generator
'3.
Initiation of shutdovri cooling at approxicately 300 F and cecuring the st.eam generators The parameters which require monitoring during the shutdown and cooldown are:
1.
Main coolant te=perature 2.
Pressurizer level 3.
Main coolant prensure 4.
Steam generator level s
Negative reactivity is prov' led by incerting control rods into the reactor.
The reactor ser.nr. Is a f ail-r :f e procer which occurs when the control red holding, coils are de-energind and the red
- all into the core.
Sutficier.t negative reactivit) is available in the cont rol tods to keep the reactor 2
shutdowa at anbient tc2perature.
The presence of xenon insures cuberiticality for approxinately 20 heues.
QUESTION 2, Identify the instimentation channels that will provide thic inforration.
RESPONSE
Table 1 provides a listing of the priunry and backup instrument channels which would be avallnle to provide the information necessary to complete
- a. cafe chutdown. A survey has been conducted to investi;; ate the rou t in:;
of each instrv=ent channel and its vulnerability to fire d nage. The results of that curvey follo" here and in the responnes to the following questions.
To aid in understanding the narrative, refer to drawings FM-1B and C providea with the Fire liarard Survey. Of particular laportante in the cylindrical biological shield, the divinien walls between the inner conpartnents and the walkway around the outside of the biological shield known as " Broadway".
The containment penetrations ate not chown on these drawings but are located on the " called north" side of the contairmnL adjacent to the control building at apprcxicately e] cvation 1090',
lhin Coolnnt Terrerature reter in the Main coolant temperature is normally obtained from a T3yg73qe uain control roca.
The T signal is obtained by relecting the highest ave ra c,e of four available hot leg tcuperatures and the highest of four available cold Icg temperatures and avercging these two signalc.
All of thece signals are indicat.ed in the rain control roca.
During shutdown corditions, the hot leg and cold leg temperaturcs are nearly the came value so there are essentially twelve temperature channels available, two narrow range and one wide range detector fron cach loop. Any one of the twelve will provide the required Information.
The temperature detectors in the hot leg and cold leg of a given reactor coolant loop are located in the co partrent assigned to that loop.
L' iring frca these detectors is routed radially cutward through the biological shield to a terminal box on Broadway. The wiring in a nineral insulated (MI) cable which doen not pass through any other compartment. MI cable consists of a conductor surrounded by a mineral insulation contained within a copper cheath.
Fron the cetal terninal box, both hot and cold leg tenperature channels in a conduit to one of the vapor container for one loop consist of cableu run penetration boxes.
The conduit is routed at an elevation just beneath Broadway. There is no platforn beneath the conduit and no area where conbuntible naterial nay accumulate.
The conduit follows the shortest route to the penetration.
Loops 1 and 2 run clockwise and Loops 3 and 4 counterclockwise around shield wall to the penetration.
This inrures that Leopa 1 ' :d 2 channels follow a di: f orent route than the c h a.. '!:
frc~ Loops 3.and 4, necting only at the penetration.
The penetration in enclosed in a steel box structure on the innide of the contaircut.
Tho reuperature cham els are not in conJuit inside the u t. c e l 3
So specific atra pt has been cade to separate the channels in structure.
the penetration enclosure but by chance different channels are located in different parts of the panetration. The penetration enclosure is appronitately 6 feet square and two feet deep and contains no ccabustibles other than the cable insulation itself.
The channels penetrate the v211 of the containment in a nenber of cartridges and the external penetration bon is similar to the one on the inside.
.21 loop temperature channelc are present in one penetration box.
From the cuter panetration box, the cables are op,ein run in conduit through the cable tray house, the control buildig roof nnd luto the control rce:
where they 3enve the conduit as they enter the nain control board.
All temperature channels are located in clcse proxicity in the reactor operating sectJon of the cain control board.
Power for these temperature channels i; supplied by the vital bus inverter located in the switchgent roon directly below the nain control board and the power cables are run by the shortest and nost direct route.
Alternatives are available.
An additional cold leg detector in Loop 3 follows essentially the saae route as the other Loop 3 channels to the control toca.
In additien, several thertocouples installed in the reactor Cables vconcl at the core outlet provide additional temperature chanacls.
from these theraoccuples exit the vessel through the rer.ctor acad, run radially to and through the biological shield near Loop 3 to the scre The Loop pruetration and then follow the sanc route to the control room. Transformer 3 detcetor is powered by Tcansformer A in the switchgear roo=.
4 is located approximately 16 feet froa the vital bus panel. These charnoccuples are run into the control roca no.d ray be read uithout the use of a power supply.
l
!!ain Coolant Pressure Pressure in the reactor coolant system is obtained from a pressure detector From the detector, the signal is
. located in the pressurizer conpartrent.
routed in !!I cable through the biological shield to a terninal box on
' Broadway. The circutt is continued by cable in conduit routed under Eroadway clockwise around to the inside of a penetration. This is not the same is penetration used for the temperature channels described above but constructed essentially the same and is located thirty fect away.
Frca the outside of the containment, again in conduit, the cable is routed through the roof of the control building to the main control the cable tray house, roca and to the reactor control section of the nain control board.
Power is supplied from the vital bus inverter and follows essentially the saae route as the temperature channels to the control board.
An alternate is available.
A detector located la the Loop 1 compartnent conducted directly outward throegh the biological provides a signal which is h !"!d wall in '!I cabl e to a terninal box outside of Loop 1 shich also Froa the terminal box to the
( mtains the Loop 1 tenparature channels.
i pene t ra t io n bo.~., the cable runs in conduit above B ro adwa y.
This is tne The contains the pressuriner pressure cableu.
penetration box that te sinila r cartrice and is &s
- innal trancita the cout.aintent u ll in a rooted via cable in conduit to the cain control board.
ruwer is u; died 4
by Tranciormer A and follec, the ca~.c route as the other instrument chanaels powered f rom this transf oruer.
Prersnrizer Level Pressurizer level in obtained from a narrow range and a wide range detcetor both located in the precsuricer compartnent.
Both cignnis are brought out thror;h the shield 'all to the pressurizer terminal box with M1 cable.
From the terminal bo:c, both signals run in the same conduit under arcadway clockwise around to the penetration bav. containing the preccure signals.
1;oth signals transit the containrent wall in a simila cartridge and agcin routed incide the name conduit to the main control board.
Powcr to both chanacls is supplied by the vital bus inverter with the direct routing deceri'2d above.
Stena Canarator Level Stenn generator level information is provided by two detectors on each generator, one wide and one narrcw rani;e, located in the compartcent assigned to that loop.
Frou cach detector, the signals are brougl't directly out through the chield 'eall to the terminal box for that loop.
As with all the previous chacnola, MI cable is used.
Frca each loop terminal box, cables run in conduit under Broedway to the containment penetration box, the saae one used for prersure and Icvel channels. Loops 1, 2 and 3 level signals run clochwise to the penetratir n, while Loop 4 runs countercicekwise.
Fron the outside of the penetration box, the cable again runs in conduit through the roof of the control building through the nain ccatrol race to a rack in the went end of the switchgear room wher the signal is converted Another branch to pneuaatic and then routed to the aain control board.
of the pneuratic signal is alco routed to the feedwater control statica near the feedwater control valves.
Level indication is provided in three areas, at the rack, in the control room, or at the feedwater station.
Power for both wide and narrow range channels is supplied by Trancforcer B in the cuitchgear room to the inctrunent rack in the switchc, car roca.
'Another alternate is available.
Ecch steam generator has another level signal run in conduit above Broaduay thich goes directly to the control roca and is not converted to a pneu=atic signal. Power for these is supplied frea Transformer A in the cwitchgear room.
I j
QUESTION 3 Describe how this information will be obtained, includinp, time and ~anpover required, if a fire in any location of the plant disibles instrument channal; and 3'{STION 4 Identity which channele cculd be disabled by a fire in any one location unattected.
and on what 1,m is the other channels are assumed to be S
__"SPO';M r
In c previcus sub Lttal, a description of the shutdown rethods to be used in the ev at of a catastro%1c loss of the turbita building., switchcar roca and/or control rm - Sve been providtd.
- .sentially t hin connisted of filling cll stena,:cuerators with V:tter.
The coolir' capability stortd in the nten: L;enerators u sufficient to rt cve decay heat and to cool dcun the ructor coclant -yctcn by stcening to a teaperature and preasure where shutde n cooling would be catablished.
Any instru.cntation netda would be obtained at t.he vapor container panttration uith power supplied by the crernency diesel,<neratot.
Table i lista the c cethods in the last coluun in e r casualty resV.,ase.
The survey has been entet.ded to cddress instre cat d na:.;c from fi.res of a lencer ca",nitude and to include the possibility cf drm ge inside the containnant.
Several aaditional ce= rents are in order at this point.
1.
All cabin for the licted instruments is run in conduit except insidc the r.ain montrol board and the penetration box and is unenposed to outside danage.
2.
The ccabustiole locding in the suitchcear rova, control roca, contaitr:en; penetration bon, and in the containcent ic low and ccasists rencrally only of cable insulation. Transient conbustibics and ignition sources are strictly controlled by administrative procedures.
3.
Continuous nannirg cf the control roon encores early detection of overheating and petuits prompt corrective action to limit damage.
4.
The alternate channels are not specificclly ceparated by fire barriers and in some locations; (the main control board) are deliberately brcught to a"ce=uon location for operational convenience.
Interaction in these l
areas cannot be pocitively ruled out acd, in this instance, the ccsualty in the control procedures, which are completely divorced frca equipment l
switchgear room, and turbine building will be invoked.
- roca, S.
The casualty responses listed in Table 1 provide cecus of acquiring the needed infornation in the event of any fire damage anywhere in the control roca, switchgear room, or turbine roca.
Fire in the i
penetration is difficult to conceive since the conbustible material is li11ted to insulation and the low voltage instrument circuits are unlikely courcen of ignition.
Should this damage occur, the casualty procedure listed in the fourth colunn of Table 1 would simply be trnunferred luto the contain.ent and the information obtained on the inside of the panctration box.
Tire and nanpower requirecents recain the, wuc e.
In ti e n l ike l', evcat of this area being ccapletely danaged despite tP ' lack of co: austibles and sources of ignitien, the casualty precciurcs would be transferred to the teruinal box cutstce et cue z.u t dd wc.ll or t the dettetor.
Wit.h one exception, all the information required it available frca widely separatad arcas.
d th presuu.:er level ninnals are brou :t cut to the sne terainal b m.
However, during f ull powe r ope ra t a '
6
the radiation level in the pressurizer cespartment is low enough co that entry is possible and the signal can be obtained at the detector itself.
67 ~Many of the casualty procedures have been executed and the time allotted for action found to be conservative. It should be made clear that the time quoted is for restoring tne first paraneter only, since the technician and equipment will already be available and subsequent parameters will be restored in less than 10 additional minutes.
7.
While it is desirous to provide level indication froa all four steen generators and all efforts will bn directed to thic end, it is possible to cafely chutdown and cooldown the plant using only one steam generator
,for heat removal.
Our revicu of the instrument requirenents and operational tethods available to the operators also investigated if the tice required to restore the instrunent channel by casualty procedure was commensurate with the time available considering safe plant operation.
It was deterained that so long as a constant cain coolant temperature was caintained and if bleed flow was secured, the plant could be held in a safe condition untfl the casualty p:cccdure restorcd the fire damaged instrementation.
Previous analysic has shown that sufficient cooling is available in the steam generators to renove decay heat for 1.5 hourc with no makeup.
In the event of a loss of all steam generator level indication, feed would be initiatad at a low flow on a rotating basis to each steam generator.
Main coolant tenperature will be kept constant to prevent nain coolant shrinkage and loss of heated water in the pressurizer.
In the event that main coolant te=perature indication is unavailable, feedwater will be added to the stean generators to caintain steca pressure just below the safety valve set pressure, thus caintaining a constant main coolant temperature.
Operation in this condition is possible for sufficient time until the casualty procedures restore the damaged instrunent after which cooldown can proceed.
W 4
- ~emg=
I 7
TABLE 1 I
s.
Parameter Primary Channel Alternate Channel Casualty Response from loop 3,or In-core thermocouples at T
- hin Coolant Temperature T
- Resultant of any Ibold-CORE thermocouple vapor container penetration.
1 oh ~4 T and any 1 of 4 3y hot Tcold. (Power from Vital recorder.
(Power 1 man - 40 minutes (Note 1)
Bus)
Supply-Transformer A)
(No power required)
!!ain Coolant Pressure PRESSURIZER PRESSURE MAIN COOLANT PRESSURE lleise gage in PAB always (Vital Bus) provided for low temp.
available.
overpressurization (No Power Required) protection (Transformer A)
Pressurizer Level NARROW RANGE LEVEL WIDE RANGE LEVEL Both available at vapor
~~
(Vital Bus)
(Vital Bus) container penetration.
1 man - 40 minutes.
(Note 1) (Emergcacy Diesel) i Steam Cencrator Level NARROW RANGE AND WIDE ELECTRONIC Available at vapar RANGE (Transformer B)
NARROW RANGE container penetration.
(Transformer A) 1 man - 40 minutes.
(Note 1) (Emergency Diccel)
Note 1: Time specified is for restoration of first channel.
Subsequent channels can be restored in less than 10 minutes additional.
On back shifts or off days, add 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> for call in.
now
.m,