Page 1
V-J
UNITED STATESNUCLEAR REGULATORY COMMISSION
WASHINGTON, D. C. 20555
MAY 5 1981
L LICENSEES-OF OPERATING PLANTS AND HOLDERS OF CONSTRUCTION PERMITS
;lemen:
: ENGINEERING EVALUATION OF THE H.SYSTEM LEAK ON JANUARY 29, 1981
B. ROBINSON REACTOR COOLANTGENERIC LETTER NO. 81-22)
Enclosed is our Engineering Evaluation Report for the Robinson Event. The
primary reason for our evaluation.was the loss of approximately 6,000
gallons of reactor coolant water from two separate leaks in the letdown
train of the Chemical and Volume Control Letdown System (CVCS).
The evaluation is being forwarded for your information and.training purposes.
The evaluation of the event did not identify any safety concerns or any
required immediate actions. There are four areas, however, which are under
consideration for further action:
1. Whether a requirement should be placed upon.operating plants toestablish a procedure for identification and recovery from a
spurious safety injection actuation (if such a procedure is not
already in place).
2. Whether criteria for terminating SI should include provisions for
isolating charging since charging flow could be considered high
pressure safety injection for very small breaks.
3. Whether there is a need for a direct reactor trip on a safety
injection actuation at other Westinghouse plants which do nothave a direct trip.
4. Whether operation of the isolation valves in theis causing the system to be 'operated in a mannerto its design bases.
If you have any questions regarding this evaluation,Project Manager.
CVCS at Robinson,which is contrary
please contact your
Enclosure:
ccw/encl: Service List
2/O6 ) 3 o 3 %t(.
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�6'4 ." , 1.V� I - CeA44. FajesALL POWER REACTOR LICENSEES
Docket No. 50-348Farley Unit 1
Docket No. 50-313Arkansas Unit 1
Docket No. 50-368Arkansas Unit 2
Docket No. 50-317Calvert Cliffs Unit 1
Docket No. 50-318Calvert Cliffs Unit 2
Docket No. 50-293Pilgrim Unit 1
Docket No. 50-325Brunswick Unit 1
Docket No. 50-324Brunswick Unit 2
Docket No. 50-261H. B. Robinson Unit 2
Docket No. 50-10Dresden Unit 1
Docket No. 50-237Dresden Unit 2
Docket No. 50-249Dresden Unit 3
Docket No. 50-254Quad-Cities Unit 1
Docket No. 50-265Quad-Cities Unit 2
Docket No. 50-295Zion Unit 1
Docket No. 50-304Zion Unit 2
Docket No. 50-3Indian Point Unit 1
Docket No. 50-247Indian Point Unit 2
Docket 50-286Indian Point Unit 3
Docket No. 50-155Big Rock Point
Docket No. 50-255Palisades
Docket No. 50-409Lacrosse
Docket No. 50-269Oconee Unit 1
Docket No. 50-270Oconee Unit 2
Docket No. 50-287Oconee Unit 3
Docket No. 50-334Beaver Valley Unit 1
Docket No. 50-302Crystal River 3
Docket No. 50-335St. Lucie Unit 1
Docket No. 50-250Turkey Point Unit 3
DocketTurkey
No. 50-251Point Unit 4
Docket No. 50-321Edwin I. Hatch Unit 1
Docket No. 50-366Edwin I. Hatch Unit 2
Docket No. 50-315D. C. Cook Unit 1
6Docket No. 50-213Connecticut Yankee (Haddam Neck)
*2068 X& zS-,*-1 -_ k 1.,
. . .. . .5 . %. I I t U
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DISTRIBUliON OF GENERIC LETTER 81-22, DTi, .,'5/81
BraidwoodBeaver Valley 2BaillyBellefontcByron
CallawayCnmanche PeakCherokeeCatawbaClinton ;Diablo CanyonFarley 2Fermi 2
Grand GulfHartsvilleHope CreekHarrisIaSallelimerickMarble HillsMillstone 3McnuireMidland
50-416/41750-518/519/520/52150-354/35550-400/401/402/40350-373/37450-352/35350-546/54750-42350-369/37050-329/330
Nine Mile Pdht 2Phipps BendPalo VerdePerryRiver Bend
50-41050-553',55450-528/529/53050-440/44150-458/459
SummerSusquehannaShorehamSan Qnofre 2/3Salem 2St. Iucie 2SeabrookSouth TexasSequoyah
VogUeWolf CreekWaterfordWNP-2WNP 3&5Watts BarWNP 1& 4
50-39550-387/38850-32250-361/36250-31150-389 ,50-443/44450-498/49950-327/328
50-424/42550-48250-38250-39750-508/50950-390/39150-460/513
Yellow CreekZimmer
50-566/56750-358
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ENGIItEERING EVALWUTN OF THE H. 9. ROBINSON
REACTOR COL T SYSTDI LEAK ON JAIUARY 29, l9Rl
by the
Office for AMlySis and Evaluationof Operat1onal Data
march 23, 19R1
M
Prepared by: Wayne D. LanningLead Reactor Syste
Engi neer
NOTE: Tis rort documets results of studies completed to
ate by the Office for Analysis and Evaluation of
Operatiobal Data with regard to a particular operating
event. The findinlQ and recoendat10ofs contained in
this report are provided In support of other onoo1na UC
activities concerniQ this event. Since the studieS are
ongoing, the report is not necessarily final, and th
f~inings and recomendations do not represent the
position or requirents of the responsible promra office
of the Nuclear Requtatoty ColSSion.
I
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TABL OF CONTENTS
page
11. EVENT DESMUPTIOli . .. .. .. .. .. .. .. .. .. .. .
2. EVALUATI OF THE EVENT .T.......... 3.. . * * * S
2.12.22.32.42.52.62.72.82.9
Operaor Actions .............Charwtng Flow Terminatlon. . . . . . . .SafeV Injection Actuation .......
Pressurizer Spray. . .... .. . . ..Relief Valve Bellow Fa1iluW. . . . ..
LetUi Isolation Valves ... ....
LedLage Inside Contalimeft . . . . .
Drain Valve and Pipe Cap . . . . . .
Failure of Fire Protectio Isolation Valve
* 0 � 0 5 � S
0 0 * � S � 0
* S * 0 5 5 *
. S 0 6 � 0 �
S *�. * * 0 5
* . . . S * S
* 0 S * S 5 6
* 0 � * S * �
* . . S � 0 0
* . . . - S S
34S77
101011
3. CONCLUSIOS .S. .... .... 0 . .. .0 S * S 0 .
134. REFERM. .. ... . ... . . . . . . . . . . . .
Table
Number
1 Sequere of Events . . . . . . . . . . . . . . . . . . . . 14
APPENDIX A - Iformation Provided by Licensee at Meetinq onFebruary 20, 9Rgl
1.Z.3.4.
5.6.
Draft Plant Operatina Experience ReportOperator's LogShift Foreman LogStrip ChartsFigure 1 - CVCS Diearam (excerpt)Figure 2 - Contaiuent SOW Volume
) I
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1. EVENT DESCRIPTION
A sequence of events is contained in Table l. problems with both oil PUMPS
in the turbine etectro-hydraulic (E-H) system forced the plant to initiate
a plant shwtdown. During the promess a safety injection signal was gererated
by a high steam flow coincident with low MCS average t~erature. The nigh
steam flow signal was generated by the governor valves spiking open, believed
to be caused by the erratic operation of the turbine E£H system. The low
average tperature was the result of overcooling the RCS by excessive injection
of boric acid solution. The safety injection (Sl) signal tripped the reactor.
'he reactor power had been reduced from lOOt to approximately 6% at the time
of trip. The duration of the high steam flowflow average temperature signal
v's apparently not of sufficient duration to latch the 0^" train nor close
the main steam line isolation valves. Both were manually actuated. A containnm
fire alarm was received shortly after the St.
After having determined that a spurious SI had occurred, the operators initiated
actions (e.g.. reset SI, feedwater isolation, restore letdown) to :ontinue
to hot standby condition. During the automatic isolation of the CYCS letdown
line due to the spurious SI, it Is believed that the outermost isolation
valves (see Figure 1. valves 20UMB) closed faster than the two open orifice
isolation valves (CYC-200B and C), or that leakage past the orifice Isolation
valves resulted In the opening of the relief valve and the rupturing of the
bellows on the relief valve (CYC-RY-203). In addition, a pressure surge
due to the isolation valves closing caused a drain cap to be blown off.
Unaware of these two failures, letdown now was reestabllshed. Subsequently.
containment pressure and dew point increased. The coatafinent pressure
and humidity increases attached additional significance to the already decreasi
I
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RCS pressure. Letdown was secrad (valves closw and sequeftC W*nOl) about
15 minutes after letdown was reestablished. A contaInlflt tJ was mad.
A le* was identified in the letdown system wea but no fire isted. The
heat sensitive fire alarm detected the steam from the leak in tie let
syst, which implies that this leak occurred In the CYCS durio the first
SI. Approximately 3,0oo qallons was estfmated to be In the com i St sUP
based on level indication in the control row.
After the letdown was thought ti be Isolated, the pressurizer pressure cont11med
to decrease and the level to increaSe. A seond safety injection occurred
on low pressurizer pressure. Both trains of safeguards equipfnt actuated.
The level Increase was the result of continued charging flow aid heatup of
the primary system (the 14SIYs Wad been closed to recover aver" teprttre
earlier). The cause for the deressurizatiOm could not be identified positiWely.
Four hours after the first en, a second containment entry was made aad
the leak was identified to be from a drain line which was still leaki*g.
The drain line Is located uastream of the orifice isolation valves (see
Figre 1. The cap on the *ratn pipe was missin' and valve (CVC-?OO) was
manully closed. water in the contaimnent sup had now Incresed to
avoroxziatelr 4,500-6,nnn qallans. Evidently, the two level control valves
(CV-4LCV-46OA&B) were leakinq at five to se gallons per inimte becen
053 and 1120. After the AraiR valve was closed durisng the second cantairmeat
ewrty, the qCS Pressure conutimsed to decrease.
*Wry steps were taken to 4eternine the cause of the aecreasinc RCS pressure
after letdown had been isolate; e.Q.. isotatinQ charging line auxiltawy
spray, checkina pressurizer relief and safety valve leakaqe. and increasina
pressurizer heater output. Te cause was identified when the operators
IM �831� 11 I I I 11111 I � : 11 I ; 1: 11111 I Hill 11111111 11.4. I MI MINE q I Hills I - 11,11
Page 8
stopped tw of the thre reactor coolant p05" in *e loeps with th pressurfuw
spray scoops and the pressume bqan to Increos. Omt of the two pressurizer
spray valves was not fully closd. Positive 01Mtlicat" of swu valve
RC-455B as te leking valve was made later. The s"y valve position is
Indicated by demand, not stem position. whiic delayed Adentificatiof of the
cause for depressurization-
During this event. steam qenerator samples tilcatat a pr y-tosecodry
leak of apprvxiiately n.5 gpo based on activity of TO aCll. Stem
generator *I' was isolated on t1e secondary side. Subsequent samles
indicated decreasing activity ad no leak. The licsee has concluded
that the Increased activity was the result of cvw beWoo agiUted during
isolation of the steam generators during the evest-
Repairs were made to the spray valve and the relief valve bellows. The cap
was replaced an the drain line and all draiN valwes were verified closed.
The unit ws back online on Febrary 1, 1981.
2. EVALUATION OF THE EVENfT
2.1 Operator Actions
Operators responded to the evects In a systemtic wrf timly fashion. Data
entered In1 the logs were detriled and accurate. Afte- the plant was stahilized,
the I iceuse contacted Westinghouse to ensure that their diaonoses were correct
avd no other unforeseen problems existed.
One shortcmIng Identified was the lack of a procedure for recovery froa a
spurious safety injection actuation. Guidelines Vw1ld be available to the
operators to differentiate betbeen a real amd s~uotzzs St actuation. The
licensee Indicated that a procedure will be writtei for recovery from a spurious
SI (identification criteria not included). For tts event, resettinq the SI
I =21 I I I I . t 11 W, 11, I . 0 0 I MCMIM11
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. 4.
-%- oiaeover, prtssurizer preussar. " .- .O A4w ue erttu re
*Is '! %* tc:resslf Clor to the SI ard had Starl'!eA'14 tr *nly efout
t d r.st~e :,reow-e reset-.inq SI. In etrospect t, ce -41 sil; a S -
I C4.ta *. ol4rft teak nd the spray valve was Ooen, nowever, S: mad neetf
1.-rldc-CJ ^.jfn 3wou"Is Inttcative of a steam line b"ea a.1 sisce secondary
systo condi tiors wre stable and the govnor valve posi tion recorder indicated
spuitows valve IWeq. the operators correctly diagnosed the St slwll as
sfu-!s for tWS event.
M J 9-es f i-Orovemert ul'i have been to test the safety injection actuation
I -. , eam!4u'' tsolat'on slqnals since one tain of SI failed to latct
Vt Vow -tiIs faled. to close. Both were manually actuated. Althou0" both
il Cra'.s actuatec on tte second safety injectior signal, this was not adequate
.titi~tn of omerabi'ity on high steam fiaowl¢. averaae tafperature actuation
t'cfire returnine *a power. These tests could have heloed substantiatte that
. soaw'at was Pm of saf'lcient Duration to latC~h the SI relay antl close
Z !>arging Flew Tewuutiofon
a; -.osrn S' actwuai1 occurred twice, no boric ac4d was Injected into the
'a- tSiej on sWvpes of the boric acid injectlon tUnlc. This war because
t:nc ;CS s;Stem presssur exceeded the shutoff head SCl,50 psig) of the SI
s: Icre cte of actuation. Hence, the cria1to snms aere xakvino uo
, - .-'-. *rJfsaG the event.
_. - U.c AEt"teS to identify the Cause for toe .jepressurizitiof and recoanizinqf
- -eiia--lzef oray coull cause the dePressurIzation, the cnaraivc flow
* iJ! tet1 il:seA vilve CYC-1CV-1211 to terminate a possible leak fro
:-. ig.1lrary sorsy vave (Ficure 1). This operator action did not 'terminate
Page 10
all makeup flow to the RCS. The flow path was maimutned to the RCP seals
which would provide makeu flow (appwiOnaltelY 60 Mm. RCS corndIzns
(approximately) at this time were: Pressurt a 16i1 psiq; Tavq * 5cWFa
pressurizer level a 56 and iumcreasing; normal steam geerator leve' for
the condition; and margin to saturation was approximately sn ss'.
The charqing line was isolated from 0126 to sometime after 1932 (shift foreman's
log). No consequences resulted from isolating the notsal charging now for
this event althouqh SI now was not available due to the pump head limits.
However, it is suggested that URR *etermine whether isolating the c9-arginq
flow is advisable for small loss-of-coolant accidents or when the system
pressure is above the shutoff head cyf the SI pumps. Westinghouse has Indicated
that no credit was taken for charqimg flew for the ECCS analyses. The emerqency
procedure for depressurization (El-11 does not include criteria for terminating
charging flow. The charging pumps are a part of the CVCS and not considered
a part of the safety injection syste at Robinson. However, the clarqIng
pumps provide high pressure makeup flow %Aen the RtS pressure exceeds the
shutoff head of the SI pumps. Enswrina that charging flow is not interrupted
for the systems employinq low/iediwum heat SI pumps may be desirable to enhance
safety.
2.3 Safety Injection Actuation
The first safety injection actuation occurred on a "high steam line flow/low
Tavg' sigral. 'he licensee's review of the event indicated that the momentary
spike-opening of the turbine Qovermor valves caused the steam flow, in at
least two steam lines, to exceed tke steam flow set point for a period of
about 25 -sec. The combination of high steam flow in 2/3 steam lines and
the existing low average temperature of the reactor coolant generated a main
steam isolation valve ORSIV) closure sional and a SI actuation siqnal.
Page 11
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onwevet. only train a of safeguards Mdi i"moir. r*espo0 ed - tne other
train *-, ;sfeouards eqipCent and 11 tne "VS did not actuate. Licensee's
CnServations are that the MSIVs require 4 sICn1 duration of one Weeond
to close an that the SI actuation relays. Including SI logic train latching
relay, require a siGM1 duration greater than 25 usec to actuate. Since
the SI sinal was of less than 25 sac duration, only the train B latChinq
relay actuated. Rextor trip, inrgency diesel start, feedwater isolation
and other safequards equipment actuations for train B occurred as a consequeace
of SI train B actuation.
Reviewino the logic diagram of Robinson's Safequard Actuation Signals (3q
CP 300-5379-2759 sb A* rev 5) It is seen that the reactor trip siq.al is
initiated on SI actmation along with emerqercy diesel start, feedwater isolation
and safequards sequece actuation. A review of a later Westinghouse locic
diagram (typicalI s1ows that the reactor trip signal is derived separat ly
fron the SI actuation signal; i.e., the reactor trip signal Is taken of
supstream" of the St actuation signal, similar to the MSIV closure s1iqal
on Robinson. This could mean that on certain spurious SI actuation events
of short slal duration, SI, feedwater isolation and auxiliary feedwater
system actuations wy occur with no simultaneous reactor trip occurring.
The comparison of logic diagrams also shows that the P-4 interlock (reactor
'rip breaker position) in the the Reset/Block feature of SI logic of later
desitino"use units is not provided in the Rotinson design. Add1itlondl mie
woul4 he needed to ascertain the significance of different reactor triz 1--
for Aestinghouse pt ants. The nW to provide a direct reactor tr4o on spu -
safety injection actuation Is referred to ORR for review.
) 1
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2.4 pressurizer Spray
The Ope spray valve could not be identified due to lack of spray flow indicati"n
or atual spray valve position. The failure of the valve to close evidently
did omt affect the capability of the valve to open as evidened by subsequent
testing. The Licensee is evaluatinq the possibility of relocating and replacing
the spray valves during the next refueling outage. Previous problems have
been exaerienced with the spray valves and their location im contain ent
reduces their accessibility for maintenance.
2.S Relief Valve Bellows Failure
The licensee has experienced previous failures of this Crosby rel
4ef valve
(number JB-36, Type B. shop drawing number H51380). Basic imfornation about
the valve and the discharge piping configuration were obtained from CP&L
and Crosby Valve Company and are as follows:
Relief Valve
- 2- diameter inlet, 3- diameter outlet
- Set pressure. I00 psig
- System pressure, 300 psiq (approximate)
- Dynamic backpressure, 25 psig (specified)
- Bellows tested to lSfl psig
Piping
- A horizontal run exits from the relief valve before turning
vertically up for at least 12 feet to the pressurizer relief tank.
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. R
CV. %nGicateo that the bellows falls every time the relief valve lifts.
St'ce tie bellows has been tet*te to 150 psi,. It woul4 apper that the %yitem
-: m..4*Iwi differently from the anticipated mode. Me 4ynaaic
-*ssssrt probably eiceeds 15n psig (isx times the spect led 2S ps';I.
I *e-C'.s t fsa that could cause the high pressure might be stalate water from
v-!o steW Condensation or valve leakagt fit the line from tft relief valve
U --e preswrizer relief tank. Boric acid crystal formations na also be
* a5sbtl1ti. when the valve opens, water or other debris in this I In
zcia U restrict steam flow and csuse a h1qh ytnamic backpressure until the
1,.c is cleared. Also. if Ute line is filled with staq'nat borvid water.
te ze'lows say be susceptible to corrosion attack, but coarson has not
beawr. 11eft1fe1d from previous failures and relacements. Frw in operational
vIwIDint, the failure mode for the bellows should be identliied and changes
Nessary U prevent ad1'tioeal failures should be imolemefud. The operation
' -e CitS Isolation valves may be a major contributor to tne bellows failures
mll is dIsussed in Sectijn 2.6.
2?S Let " Isolation Valves
Te 4solation valves played a dominant role in the :quence of events at
X=ci'son. The failure of tP* bellows on the relief valve *as attributed
- 'te clostiq of the out board valves KCVC-204A&B) before "c Clos4ng of
vw orifice isolation valves fCYC 200BU) upstream of the relief valve.
,2sewue'tly. the set point '600 psig) of the relief talve was reached since
s ar. if the CvCS was pressurized by the reactor coolant system
T-:' .as tt aporoximatelj I.AOO psi. 'he Cesign pressure downstream of
-r eS' IEC-20O ser1es: ts T00 pSTq. The sequential =e'ation of the
-sxa'ton *alves is evidently causing this part of the C'ICS to be pressurized
c a: least tte setonint of the relief valve. as evtdenced ty the ovening
r ve rel'ef salve whenever the CVCS is isolated.
Page 14
U 9 -
In addition to the Isolation valueS. wal"v tCW A and R (FigWre 11 were
closed In an attept to isolate ti le ig b*', valvefpipe. Both of these
valves leaked %ich pefritted a" aMItina' 3LOW gallons (approulately)
to leak Into the containment after tV letft-0 yst was thougt to be Isolated.
The licensee did not perform any saiiia on thse valves to ensure their
operation before returning to ptr Once thls we not contaii't isolatin
valves. These valves are part of the reactor oomlant pressure boundary and
are designed to close on low ,resste' level to conserve RCS inventory.
The design and operation of this part of te CWCS raises two concerns:
first, the potential for overpressurltzina the system to 2,?2n ps1la assu"Il
the dowmstre' Isolation valves MCCIA) we closed; and secondly. the
capability to Isolate a potential br*A ibtrew of valves LCV-46nA&S.
The licensee has indicated that the relief valve is designed to vrevent
overpressurization of the CYCS. The failvre af the bellows does not apoear
to affect the pressure relievisg furnrtiO of tVe relief valve. In addition,
the flow control valves (CVC-LCV-460&9) have been designed to isolate a
break downstream of these valves for re mwiimw sire break and ACS conditions.
The functional and testing reqrvllts For tv flow control valives are
not clear. These valves should be A99 Class 1 since there are no valves
upstrem and the valves downstream are classified as ASME Class 2. However,
these flow control valves are mot iodteifed In the Robinson Inservice
Inspection and Testing Program (Reference 4). Since these valves are on the
RCS pressure boundary and are desigmet tc Isolate the RCS on low pressurizer
level. It Is not clear why .aimtenance om the valves was not required after
they were known to lea and bore rewrmifg to power.
Page 15
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goth of these concerns could lead to a s11al loss..f.coolant *"v"t Iside
containment. This postul ' event ill wthin the scoop of an SIR .n11S small
break loss-0f.Conlant acci~ent and mit a row safety conce". 'IO"vt'. wfrom
an operational consiieIt1i". o0 oW'esWsu551UiZ the CMC could he 9Tpolvotoo,
provided the orifice Isolation valv" were close before tVe outbcaM f solation
valves. Correctlnf the valve closiw sequence for Isolation woult also reduce
the challenoe to the relief valve.
2.7 Leakage Inside Containment
The licensee has acknowle4"e that the quantity of water that lelef fato
containment can only hp aproxivutef. The estimatoda 6.nn0 qallnIs 1coerospondino
to 4pPrnfin^ately 1; In the sump) ts a sMll fraction nf the raw f IndicatiOn
in a 65,000-gallon capacit sup tSee FViure 2). A mass balance was zt
possible since neither charaing fln nor volume coetrol tank level are recorded.
The major leak was after letdown flc had been restablished bee 635
and O050. This could account for m¢poximately one half of the 3.rrf uallons
indicated at MP5n. The 4-ain valve Could have also been letkikn at wr unknown
reduced rate from the init4al S'- umt1l letdown was restored (&oppotRately
ten minutes). The ruptured bellows on the relief valve also conT ut el
so'e amour' to the inventmry I1n the Sump. These sources in cOWiftaition with
tne inaccuracy of the su'o iearsuwents can lead to the concluston that all
the leak sources had heen 14ent@flfel.
.al nlrin Volvo and Dir'p' Sp
'he leakitnn valve was Cwf-?nOEF :.ee clqurp 1) not CIC-7ndC as rrvrfoo' 4 hy
IF (Reforence 1). This helps to jxWl¶taod the leak r4tes an ontoV if
water reported in the _E° 'Referece t2) and the tE evaluation.
The licensee's explanation for the .tssinQ cap on the pipe was ta She
Page 16
- II
tte Drfice Isolation valves clos. a pressure pulse Was applied to the
valve an cap. Since tte valve ws partially oe and ti cap not tiqhtly
sacugrd, the cap was blown off. The lice*g" believed that vibration in
the CCS (induced by the charging pumps) caused movent of the valve and
cap. Th valve positioi was last verified on October 11, 1180 during a refueling
outage. Since the drain pipe is located close to the pressure reducina orifices.
the now Instabilities at these orifices could also Induce vibration in the
CMCS.
All drain pipes with valves have been verified closed. Most valves have
been chained and locked.
2.9 Failure of Fire Protection Isolation Valve
When a Phase A isolation signal was generated by the safety Injection actuation,
one (FP-248) of the four containment isolation valves failed to close due
to a tripped breaker. Since the other isolation valve in the line closed,
containment Isolation was achieved. This failure had no bearing on the leak
and was a separate reportable event.
3. CONCLUSIONS
The event at H. B. Robinson involved four separate, somewhat unrelated failures:
(1) pump failures in the turbine E(C system; (2) two separate leaks in the
CYCS (related failures); (3) an undetected open pressurizer spray valve;
and (4) leaking valves in the CYCS. The event did not appear to Include
any safety concerns.
The following areas of review concering this event are referred to NRR for
consideration:
Page 17
* It a
S. ethr a requireent should be placed VpoW _fttfg4 Pnfts to Ostblish
* procedur* for Identificatilon Gnd recovery frw a sw" 1 W afety
injection actuation (if 5ilh a procedure Is "alrAe, is prlae).
b. Mether criteria for teinitlfig St should IRleft ~ Sion fCW
Isolating charging since charging flow Coult a coomiti 1hicht oressure
safety Injection for very s&ll Iress.
C. Uhether there is a ne for a direct e*act trip o a Sda'oMs safety
Injection actuation at other uestlnghouse IPuT& Wch lt NC* t NM*ea
direct trip.
d. whether operation of the isolation valvet in VW tS at RMI"tOf
Is Causing the system to be operated In A wMne Whitt I S CO"XFrY
to Its design bases. The closing sequence f thV IS61@iI0 vlves
appears to cause part of the CVCS to be pressiwrize ta e SetVoCnt
of the relief valve and may be contributifn = thW fatllwt of the
relief valve bellows wh"never the system Is tsolateC.
AEO0 did not find any basis for a need to study tts, evemt ftrtel'. A foral
respone from NPR Is not requested.
Th1s event and the operator' s response provide a 7=d txale Can oaPerating
oxoet"mence which should be disseminated to other Ttoees favr tInoation and
ttra1 frf puposes.
!
Page 18
_ 13 -
4. REFERCES
(1) tMorandum, H. Woods to F. Jordan. Svbjct: H.S. Robinson Event on
January 29, 1081. dated Fehbruey 12, l9"l.
(2) Licensee Event Report 81-nffS. 91.8. Robhwson Steam Electric Plant, Unit
2, Docket 5f26l1, dated Febhwry' 12. 16R1.
(31 "eetinq with Carolina Power wd Ligt CMpany In RethelA on
Fthruary 2n. lORi.
14) Letter, E. E. 'Itley. CP&L to S. VWMga. Subject: H. R. Rohinson Steam
Electric Plant Unit No. 2, Inservice tmspectlon and Testing Program, dated
-arch 10, 19A1.
Page 19
. 14 a
Table IvrniirMcU os rvEwTs
jaflUay 701. Lq~ )MPlant at 100'Orloary to secoMary 1.k of Irn^1ItE'l I,. .
500 O A ENC oil pump seal leak. OF ENC wump alrealy out of service dut to vtibrtioA.
0s41 Started lead reucto10n.
0S42 *ided boric acid to RCS.
0543 Started *C chaNrtng puop. "3d charninc pump runninq, OA charging pup
Inoperable.Opened CVC-2'1O0 oriflce isolation valve. CVC-Ve0C already open.
"49-130n Continued to add boric Acid.
'WI1 ftn1p#A '0' ..dwftitr W.IMp And Cn"AeQ'tAtP pUmp 00 tgI OratIc FWP ht-havifr.
MMn Tavq reached low 'avn setpoint (K4AVFV alarm.
WI62 Generator Output hreakr opened.Turbine governor valves Spike open.St siqnal and 4S!V c'osure signal on high steam flow/low Tavo.
St train '8 automatically started.Phase A isolation; safequard B emergency equipment started.
Reactor trio nn S' slqnal.Tavq a 53?"F.Pzr pressure * 721- psln.Pzr leve' * 1r-.
0625 Fire alarm in contaisoent.Pressurizer relief tank level alarm due to noemina of CTCAV-203 relief valve.
Bellows ornhahly ruptured and drain cap was blown off.
MS Ys clospo lanually.
Sl train 'A" starteA manually. Started "A4 tI, AFWP, RH. manually.
Letdown valves CCV-AFAA&B manually ClOSed (should have automatically closed
on PZR level of 11.).
067 Reset St and feodwater Isolation.
nA34 Atte-oteW to restore letdown flnw %ut CYC.?nnA would not oaen (instrument
a'r tysrsm lolwte4 on Phase A Isolation).RestoreA let4wftn flow after resetting Isolation sionals.
Pve55urlie- or*ssur& started iecrlas'inq sharoly (-2000 9sig).
Containment new point and pressur0 started lncreasina.
0637 Received condensate :ollection alarm from the coolers.
01esel aenerators A ant B stooped manually.
Page 20
a 6
- 15 .
064O Isolated letd flow. (Isolation valves closed from control room.)
Contalmnt d" point and pressure decreased.Pressurizer pressure still decreasir'o ( i;n psi').Tavg [email protected] pressure increaslnc.Notified NRC by ENS.
0650 Containmmnt sun level ind1cated approximately 3000 aillons.
0700 First contauinmt entry to check for leak and fire.
O070 Second SI actuation on low pressurizer pressure.Both trains rW all equipment started.Pressurizer pressure a 17I5 psiq.Pressurizer level * r01.
0705-0727 Operators attept1na to dtermine cause of depressurization.
0722 Steam dumps opened manually to control pressurizer level.
0727 Reactor coolant pumps B amd C stopped and charqinc lineIsolated to eliminate possibility of leaklnq auxiliary spray valves.
Increased pressaiizer beater output to maximum.Pressurizer pressure started 1 icreasinq.
0729 Continued cooldwn uslna steam dwups.
0735 Pressurizer pressure increasing (1 172n).Tavq cofstant a S40.Pressurizer level * SoM.
073R Stopped diesel aenerators A&B.
0741 Stopped 80 lWI pup.
0744 Opened breakprs on containment sump punos.
OR25 Secured St pivs.
1000 Continued plant cooldovn.Sample on 'R steam aenerator indicated O.; ape primary to secordary
leak. Isolated B steam aenerator.Second sawle showed decreased leakage 0n.25 gpm).
1120 Second containmelt entry. Found ClC-200E open and cap m1ss1na.
Found bellows on relief valve CYC-213 ruptured.
Contacted Westinqhouse.
Page 21
- 1.0 .
IFIm &ock.4 10f 9?sWsr St.
1230 Clow M00.solte0" letdo by closing CVC-3090.
CoKOMt sup level was #,SOO4.0 tallons.
1"S Ol 0e9lg VW out of ServiCe du to leaking relief va1lv
lA3M AlIqgd A' charginm p for operatlO! after COMlet1ift surveillance tists.
(latentry) TaitSd prtssurizer spray valves.
1013 Started .'S RCP.
IQt% Start" "CO RCP.
(Latr) #l*M c' OP0164n1 lite &nd CTCS leton i servict. fttFv excelS
lIt lipe from survice.
2315 Spray valve RCS-49% Identifies as leaking spray valveSo aditit1on 1 primary to secondary leak Identified.
Jaawyr 30. 191 at IMO plant on-line
Page 22
WPONh A
twomIgtroN PA* oEt Iv LICOM . AMWt ON FEBRtUARY to, IMi
Contents:
1. Draft Plant Operatim EaPIMl bPOrt
2. Operators Lop
3. Shift Forema Loq _
4. Strip Charts
q. fire I - CCS Da (sexcerpt)
6. fle 2 - Contal Sa Volga
I
Page 23
?1AWr W2tA11 1o vMMI 12CV 1w0nuT
R. k0t I1t
Janary 29, 1981
2. Identification of Occulrncl
A) JA spuriousaiety Injection signal initiated by & -High Ste ine
now/Low Tsv" signal.
5) Reactor Coolant Systm 1ek through letdown line draln valve CC-200E.
C) Primary plant depressurilation leading to a second *safet injection
signal initiates by a -Low Pressurizer Pressure' signal-
3. Conditioms Prior to Occurrence
A plant shutdown to hot standby vas in progress to repair a secondary
plant problem. The unit had been operating at 100: reactor power (72! We)
with normal Reactor Coclant System pressure and temperature.
4. Description of OccurreacC (All Times Are Approxil~te)
A) At 062L hours on January 29. 1981, a safety inject1on signal Lnitiated
"r train of safeguards. 'A" train equipment was manually started at
0625 hours.
h) At 0635 hours on January 29. 1951, the che ical and volume control
letdow systm was restored and system pressure bega= decreasing vith
an increasing containment pressure and dew point. Letdown was secured
at 065S hours.
C) At 0705 hours on January 29. 1981. a safety injection signal initiated
both trains of safeguards.
-DRAFT-
1
Page 24
5. hjiE tiOS of Aisereft Cause of occurrence
#A appz1*Itelt 0400 hours, "A" M DOS electro hy4dulic (1-H) oil Pump
developed a sea look. "fr &- ouS Pp md ben t l out of serwice
earUer due to hih vibrations. Az 0541 Murs, the decision was md to
sbut doWn to hot standby before receivin a trip signal due to the 10
of t-l oil. Attacbent to. 1 contains .dditional Infouatice on tbS
failure of the 4 Oil Systm.
AJ 062 hours. towdiately follovimg opening the generator output br"kersa.
the reactor tripped and a safety Zzjectiot was ix:tiated b! * "ig4t Stem.
Line flov/Lw/v T "uignal. Only 'r tr:aIn of the safeguards was activate.
"A" trait equipmet was manually started at 0625 hours. t: was Deterulned
that the erratic operation of the E1- Oil System and :he fact that the
operators re switching from "A" EAI oil pump to "8" -B OL pm 4a d
the governor valves to spike open. The resul:ant steat lo'w s:ie was
hIgh enough to cause a "igh Stem .ine Tlowlow T. " sign. bu t: t wits
insufficient duration to fully Latc' the "C safeguards train seal-Irt
relay. The seal-in relays in the saf eguad trains are latching -e avs
that requirs a finite period of ti5 In the energized mode co mechanica.1.'
latch them into the losed positin. Attactent o. ' contains additinual
information on the partial safety injectio.
The stem line isolation signal th wa generated frc the Higth Steami tg
flow/LAW T " signal was of infficielnt duration to allow the _ain st
isolation walves co go shut. The orven @f 412 was reinstatC so quICkly
-DAFr-
- 2
Page 25
-DLAT-
S. D"imton of Arcent Cause of Occur cce (coalnued)
after the IsolAtion signal that the valves were unble to t3MVel far enoush
to Isolate the *tem f lw. The Maiu steam isolatin Valves Were slanually
abut to rduce the secondary stam dmaad follwin the reactor trip, thereby
pioting the return of Ton to the no load s.tpoint.
At 0627 bours it vws determined that safety Injection cwditons did not
exist and that the initiation was spurious. The safety injection and
feedvtcr isolation signals were reset. The checal vlum control
letdown Systt was restored at 0635 hours. The Reactor Coclszt Syst
pressure had been slowly decreasing, but whan letdown was returned to
service, the containment pressure and dew point began Sincrsinig. Another
indication of abnormal containment conditions was a fire &Zarn from the
area of the contaimrent operating deck which was received at approximarely
0624. Letdown was secured at 0650 hours with leator Coolant Systez
pressure at 1850 psg. The initial containment entry rade at 0700 hours
to Investigate the abnormal conditions confirmed that te RCS leakage wa
fro the letdown line and that no fire existed. A subsequet containment
entry at 1120 hours further identified the source of the l2Ak as valve
CVC-200E, a drain valve on the letdown llie. which was found open and the
pipe cap missing. The leak that resulted from the opes drain valve was
approximately S to 7 gtp with the letdown air operated valves closed a-.d
approximately 100 gpm with letdown flow established Tbe leak was coe-
pletely stopped by shutting valve CVC-200E. The ltdow= flow was not
restored until after the condition was fo-jnd ad repaired- Additional
information resarding the RCS leak and contalit fire alarm can be found
in Attachmnt No. 3.
Page 26
*pgurr- -
S. DsUnstin of Auotwrlt Cause of Occurract (CotiouU)
owever, evn with the Letdom contro: vS1Wv clo*0d, the pr.ssurizSr
pressure continued to dweres, l U g to the secod safety injection
1nit atloI at 07S hours from a Lw Pressurizer Pre"aue . Both trais
of the satesuards equipuw't functioned as 4asfgne. At 0727 hours.
charging was isolated (except reactor O4OInt pump sel injection) to
SllinatO auxilary spray and "'" and C' reactor coolant pups were
secured to prevant the pressuriZer spray valves from circulSting cooler
vater from the Reactor Coolant Syste lnte the 7ressuriser through the
spray valves, dtcresing the pressure. It was subsequently discovered
that the pressurlztr spray valve from reactor coolant loop had prob-
ably opened and not fully ressated. The ;resurx15r pressure imedistcely
started co increase. Tc h reactor coolant gyStCi mas stabillred at
approxiately '205C psig and 5350T vwth 7ressura coctrolled by the pras-
suriter heaters and teaperature concrol:-ed by te secondary sctam dump.
Attachcent Se. ; contains addition&. infornitiot cc the reactor coolant
systcs pressure transient caused by the s;ray valv malfunction.
Coincidental with the decreasing pressurizer pressure. pressurizter level
was increasing. This was caused by to fa-ctors. 1) The charging flow
from two charging pups was .aintainxi g ar Increasisg the systen vcluse,
including the sst*2 losss through CC-Z0. Te slightly open
pressurizSe spray valve was causing the pressure to decrease. 2) The
density changes in the reaccor coolant c" to rb. s*ovly increasing RCS
tmperatures and thC heat wp of the ralattvolr cold watsr added Sv the
charging Syste :aused the systm to enpend. '.ase factors combined to
cause an Increasing pressurizer level. The arrin to subcooling remained
t- _ _
Page 27
*. DsuIton of Apiet CauS of 9CCurrenCe (Continued)
greeter than S$Or throuShout the antire trrasien The iniaum subcooline
Mrgin occurred at 0120 hours, vith reactor coolant system pressure at
1620 psig and tmperature at S510.
The relief valve on the letdown line, CVC-tV-203, lifted following the
tist safety injection initiatiOU. This was apparently due to the sols-
tion valves, CVC-204A and CVC-2041. closing slightly faster than the
orifice isolations, CVC-200A. CVC-2001 and CVC-200C. or leakage past one
or mort of the orifIce isolation valves. This caused the pressure between
the valves to increase above the set pressure for CVC-lV-203 (600 pelg).
The valve rcset after the letdovn isolations closed, but the belloas had
ruptured. Attachent No. 3 also contains additional information regardiqg
valve CVC-RV-203.
6. Analysis of Occurrence
Beveral problems with the turbine E-H Oil System had occurred within approxi-
Mately one week preceedilng the reactor trlp and safety injectlio on
January 29. 1981 which could have contributed to the Initiation of the
ev t. These problems are *simrised as follows:
1) The X-R oil had become contaminated with water due to a ruptured £E-
oil cooler approiimately one week prior to this vent. However, the
"- oil had been purified (replaced) end restored to spe%.'ficaticn
prior to this vent. It is not felt that this contributed to the
following problems.
1) On January 28, 1981 "S" E-H pump unloader developed a fatigue crack
In its discharge nipple. While replacing this nipple, air was
introduced into the "3" E-9 oil pump portion of the systsm. When
-DIkFT-C
Page 28
0. "Anlzelf Of zourfrenc (CMUntl"
"a" g24 oal pwwp wes retearted. it caused esxe@S1vs vibTraitU5
th Mhout the L-aM Oil Syst§0- -Al £4 ai. tPU was Mctrted and
05" T-14 oil pUM was secuzd after a brief perisd of OPeration.
3) The seal leak which developed on "A!$ E-I oi- V oI Januar 29
1951 which necessitated t turbine shutcdOn is felt Co hzve been
caused by either age or CMe Secessivi-SySC vibiratiocn
4) As the sel leak on 'A E- ell puap becae laqrer during the re-
asining samnts of the tcttze shutdown, 0he operators decided :o
run "B" £-H oi. pump des;::- the vibration prcb; * in order to
allow the leak to be iso:Ated so a nomrl %urblze shutdown could be
completed. Ccinc;-eta.'-" -2" E-H *LI pumo vas started as tbe
generator output breakers were opened. 'ten -ba generator output
breakers are opened the zts±ne witches froa Load control to smeed
control.
One, or some conbination. of the above probab!7 caused the srbine governor
valves to spike opez. 7e exac: cause cannot be tccrmiLeCd. Ths caused
the first safety injection in.tted on a low rse~tc coclant sys:en
average teperature coincident vr :h high stean line flow. The high s:eam
flow was of a very short duratiac. thus only "**5" safeguarts train was
activated and the main steas sz:Ation valves rcma. td open.
Letdown lnc drain va-ve CVC-2WCE had vibrated open since it had las: been
verified shut os October U, :.SC It is postalatec chat the pressure
transient caused by cne .ecdowu :.zne Isolation caused %he ;ipe -ap to blow
off. 7hus, * Reac:or Coolant S-stsm leak existed.
) )
Page 29
6. AlSIS of Oc ccu @ (Cotuitifkud)
The contimld decrease in pressurizer PresSure was caused by :re failure
of the pressuritar spray valve from "C" reacter coolant srste! .oc'p
(RCS-4553) to fully shut after opening during thc transient. The event
identification was complicated by the letdwfn relief line lifting to the
pressurizer relief tank- vhich indicated that there were two separate leaks.
The Usactor Coolant Syste_ pressure decrose was stopped when "B" and "C"
reactor coolant pumps were secured and the charging line was isolated to
elniziate auxiliary spray. With the pressure decrease stopped, operator
control of the Reactor Coolant Systm was re-established and normal hot
shutdown conditions were established.
TollowinS the first safety injection at 062' bours, the trc vrotcctilon
contairelmt Isolation valve FP-248 did not shu: autoaticaC.1 and had to
be manually closed. Attachment 'o. 5 contains additional inlorrazion on
the performance of the fire protection contaiment iscla:icn valve.
A s*uary of the PZSO computer output for this event is prc:,ded as
Attachbent No. 6.
7. Corrective Action
A) The £-H oil was completely replaced with now oil.
B) "A" E-H oil pump and unloader were replaced.
C) he unloader and discharge nipple on "B" E-H ol: pt.p were replaced.
D) The valve stes on RCS-455B was lubricat"e, stroked and vaive p0s1-
tioner was adjusted to ensure the valve will fully close. RCS-455A
was also checked for proper operatios.
-DLAFT-
Page 30
-PAfrr-
7 .eeStvL ACUM (COetimUid)
Z) CVC-200t vs lockd closed Md CM pi"e CAP Was rlAced. SIMIar
valve La the letdown ad cbsrg le & Were also locked close
or otbrvi verified to be serd.
7) The breakr o current trip saints an tbs four tire Protectios
fttsi costarmt isolation ualves 'm be adjusted and checked
to Lasure proper valvc performwc*.
C) The eent was fully analyzed bw the plant staff and Vestizghousa,
and the results discussed vith the IaC, esion Sl. to ensure that
all safety concerns wure idencif ed ad rewolvod prior to retcrnuhr
the ut to operation.
.mg _
UaitZ Operating s0iFTJv'r
II
_ / a-a / naT34 I 4A el ltvdl
. ., / /
. -2 ."I-
Crexa Hanager
-DRAFT-
Page 31
r-DSAIT
SIQUMNCE OF EVENTS
0S41 Unit *hutdown vas initistod due to E-H SYstem trouble.
0620 Tavg reached the low Tavg setpoiat (5430F) during
plant shutdomm.
062; Generator output breaker is opened removing unit from system.
Load on unit is Ah.
Turbine governor valve(s) spike open (see Attachment No. 1)-
High Steam Flow/Low Tavg signal generated.
4SIVts closure signal (see Attacnment No. 2).
SI signal, train B" actuates (see Attachnent No. ).
C' isolation valve FP-248 fails to close (see Attachment No. 5).
Minimun Tavg n S32°F (based on incore thermocouple).
PZR pressure * 2100 psig.
ZR level a M.
0625 Fire alarm at Ct' operating deck (see Attachment No. 3).
Pressurizer relief tank level alarms from C'VC-203 discharge
(see Attachment No. 3).
Page 32
0625 (Concd.) Prtmary pre*surr bales to decre"e (#" A ttCesC No. 4).
"SVs mayay closed.
SI trfl "Ar equipamt m1maly started.
Lerdown yalves LA & 5 sMAfly shut.-
0627 Manuafy reset SI.
C635 Restnred letdown.
Cont:ignmnt -low pc.rnt and 9ressure begin to Lucrease.
Isolated letdown (suspected leak in letdown system).0650
'56 .avg reaches maxim= vat ae of 55:TF and olds steadY .
P R pressure I' . nC Psia.
PZR level a 50.
Cantaimeflt entry to check for leak anc !ire (see t&:C:ent tNCo 3).070C
0705 Second Si signal due to ow PZR pressure. 1715 psV.G.
Both "A" and e.tavns atvse.
o7c5-;:'72 Operators attempt to deter2Ln* ;ause of depressurzzstC0n. The
foilowing equipWe.t vas cmecked:
Page 33
-ISA?-
O7CS-0f27(CorAtd.)
a)
b)
C)
d)
f)
PZ safety Valves flow 1Infcitors.
PZt P0V discharge line tG.rstur8.
PZR block valve positioc.
P2B relief tank level.
PZR relief tank pressure.
PZR spray valve poItLo (the valves indicated closed
but since this 1udic*tiCU La dea indicDtioU the
valve controllers were again Ma ly closed).
072' The RCS temperature wa lovered slightly using the secondary
stean dumps to help control the increasing pressurizer level.
Tavg - 5490F.
PZR pressure a 1620 psig.
PZR level a 62.
0727
0'35
Thc charging line was isolated to el-imnate tke possibility
of auxiliary spray causing the depreenurtZAti~n. RCP "B"
and "C" wera stopped to eliminate the pissibaLIty of main
spray flow causing the depressurization.
Pressurizer pressure begins to rise.
Tavg a 543PT.
PZR pressure * 1715 psig.
P7i: WVvuI - '0L~..
Page 34
)SIO pZR presmawe stabilize.
RUvs * 535OF.
PZR prossurO a 2050 SOpl.
PZR level * 452.
Made toad cgcntim5t entry -a isolated CVC-ZOOE at 1230 bour.1120
1o c0 '-'9-81)
to San ;:-L8. Review atnd analynLx of tranaient wLth 4istinglhOUsR. OUicuaiLOU
ut trannfisn't Wit! !RC ello&C It.
231! t;.-29-81) aCS-653 Positively identlfiLd " 1"lem2 sPray valve.
.7, C i:-I-B1) Plan: on-L.ne.
-DlAF:-
I
Page 35
CDM=r go. I
SYS si TAILWX
Thn - System bad wM rzecwe sq*ralr probLems prizr ta the trlanSt c
1-29-81. During the prewicrl week the E-v nad W becese coote5luld with
vater. (This contasinstcc ws restored to within spe ficati) On Wseds-
day mnoring. 1-2-81U, a smain: steel nIpVl on Efe 1£4 9;Sven UnIO&Ver on
"B" pump cracked. This caused a loss of approxiwtall- X eaocws of £49 flvid.
The fluild and nipple were rep:aeed and "I" pup restartec. gcwever. the pump
was imediately stopped fte tc scise and vibcatio- Svera. atecPCS were made
to troubleshoot the prob:= hot so def nite canse sas fo*co. :Ee system vas
lef: cperating satisfact'r'-y with one pUC; . C: A= -9-n1 the
second E-H pump, "A". deweioped a sea leak which caamef £-E ':aid leak owt
of the system. ^t 0541 =be operators begaz to t~aU che c= off ir to reto tar
tt.e E- Systet. At 062-_ wti* the unl: was being ea.-a:ec frw tani Vrste0,
the E-U System generated a pressure surge cc the weamnc es vho--' resulted
in the valves mozentaril- ape-ing. Three factors r-L.d %-v rantri'rt:ed cc thf
pressure surge. The turftie conro: was switchizg :- speec :o . he cre-
tors wre trying to star$ '5 E1- oil pump cz sup;;.w T- 5 ;: ting z.lw final.
soments of the turbine s;dcn. The E-9 Srstem t beec :cc iza-d by water
during the previous weeLk- TIs caused a -- n;ary g sreas !loi- t- be sensed
on at least 2 steam lines. T%. spike shows up oc s. tbrei sate f charts.
The effect of this flow ipska Is described in Atta It % :-
The failure of "A" pump *seal on tVc E-11 Syscem was .u to ag e *d t-areferre
vibration from "see pump. -is equent to these pui fe.±xres. :he uc:oader c'
pump Op" has been replaced ad pump "A" was replarad 5n iCs entiretr. .The
copl-tce system was resczred to service mnd is opcr=eimg awc:sf actor' 7.
1
I Ism o -I 11 1 1 INICOM I 1311011 'I 51111P E I I ; 0505010"NOWMW in 1XIMM 3 I
Page 36
?tim-, St A? 0624 NMMS
on Jwouay 2g. 198: at 054- a vuit absatdwn was 0o~esmcod to do repair work
on the tuzbl.m 14 S~atm. At ",proimzate 1 7 0620 hours Tavg dropped below the
low TOV .etpotint of 5401r Cut to at Snadverunft overshoot duzring plant sbutdwnf.
At 06..*t v~ct the vaic Fe4 pwer the generster output breakers were opemed
discomc:WC the acit fr= th m~tam. At this tiae the turtbLoc E-F control
Sstem switched te "ef onT a Idut cc gme55ure instabLttlItte is the E-Hr
conr-: osyte tz txti-iCw Sovernar ?ralves .;citd t'i"n. A revicu ofb cte' event
lndlz.es that thc sz,..;e ca*J'Cd o? tzdlcatet etex !,ow ini at least two ate&'
lines to exceed Chu~ *tozz set:cimt for a time* 7erted ees ~than 2s vze
7his d~icated t4gh sitom .. w to '3 eteag inee continedd vW tm he low Tavg
setle'M0- .arl'ler ;~efo:tat a ea=L stoam Iscaticf vavG-. closu~re sp.jA. at.. a
St st4!a.. The 4ira.?aLt ce! :woes~avad1 te tte same as tV.e Ste~az fecw
opike- It &as bees abserro! duriz( "redi~c t1s05 tI tht the NSO.s requ,-.te a
signm,. Suraizo-, of sr .~y sec. to ct-use a-W. so none of the ?S~
Closed, or the mczeg*T fL'low low lava *Itnal. ('.be KS'Vs Were Menus ::
closed £indiately by tte 0erator in order. to steb~ltZC US temperaturt.)
The S7 sips 1 is givldeC altz : trains 'A' and 'I'. Eoch of these traits cpe
tAILS &seseral telavs Inc-wI~d3 a "Czr.tanica: :atcming cola? tWee inthosse -C
WA6) uhic1h is used uo lock ft the 5S train unri manually reset. A s£gr1.8
dura10o greater. tb=1 ! mee. is reguired to Lnsure that al relays tdose '6nd
the archimg relays loce is. Usne* the ST Signal was 'Iess thr 25 *sc o:
the :Atch~flI rel~ay for tCm=i got fia:y engaged. "A op~erators waied:Ate~y
rsotized that trai0 ~A" o WCt engaged and so they. -Paniaay started the :Vain
'A' equipment. CauessmaL t ssolation Phase A was LnI1tL~td by trsaln "P*." 6
St woer was a je-med late theosyste since RCS pressure was ftzlO0 -PSIC and the
CM1
I I== EJ Mm sit I . , .I I - --- - ---- -- - --- - -
Page 37
EU.?-
smm off bead ofthe 5!POM* URO 61' 1 e glva u&aly rmetOat06
*Loce the SI £uin±LuLL gm WSSdUb5led Qpurtbul.
Ounc train "Ar was smagaa Li1±um the tl 5iqtm perfacrvid as expected, vIth
the uceptLon of CV IsdIstZ= w,'.N FL-1&S (O05 Attacbmftt SO. 5). The actI3-
tiara of the SI Syatm 4d4 t efl the cphysical course of evets durtq the
trausleft. boveve? it 4LU mbcure :e cauS. of the KMS depresaurtzatLon (stuck
pressuaazer spray valve). St rep.?s to the St logic or componerats are
comSidete aecassury.
ta
U- � - -
Page 38
mDRAFr-
ATLUtME ND. 3
LzW LUE XU
At 0624 an St signal latched in the "B" train relaey vutcl gestrated a Phase A
containment isolation. As part of the Phase A _ontzint iSolatioC five letdwn
valves closed (CVC-200A, B, C and CVC-204A. 5). Drir this time the relief
valve on the letdown line, CVC-RV-203; lifted. This us apparently ide to
the Isolation valves, CVC-204A and CVC-2045. closinl s&LLbtly fa"ter than the
orifice isolations, CVC-200A, CVC-200B and CrC-200C. c 2eakMe past one or
more of the orifice isolatior. valves. This then case he rressurier relLef
tank level to increase from approximately '0: (noraL: level) to ,5.= full.
The pressure transient while causing relief r&:: -- 2' to lift also
caused the relief valve bellows tc rupture. A :his sae tinie, whet the
CVC-200A, a & C valves closed, a pressure su.rge was a:-::ed to C'C-200E. This
valve is normally closed but had apparentl- r' te ;atay' y cen dzrfle
plant operations. The valve position was las: ver-'1 on cm Sl8. One
possible cause for the vibratior at CVC-ZE-_s ..s he ;ttve dispa:tnt
charging p=ps. These pumps have a histor of vibraLtc: in'tuced protem5 f'or
which solutions are currently under develcren;t. CT-=DOE is also caped bu:
the cap apparently was cot tightly securee as eviden by the stripped threads
on the end of the pipe. When the pressure s&ge ws *rlied to the CLC-200E
cap the cap was blown off, causing a primary le"a estimated at aproxintely
100 1pm. This estimate was based on the pipe dl.im.en amd qwntlty of water
discharged to the C: sup. This leak was qui_ . e tc 5- M wher.
valves 460A * B were shut by the operators. Appirez:T some leakage occurred
past these air operated control valves. The ;00 = leak ws restarted when
letdown was re-established at 0635 causing consitae de poin: and pressure
to rise (.2.5 psi). At 0650 letdown was isolated azd the leak rate again dropped
to 5-7 pm. lased on the sup level indication cess tan 6000 galloas of primary
coolant was discharged into the contaiment sz::. Ve the lOC pr leak occurred
Page 39
MUMM M. 3 (Contim")
at 0(?4 it apparently coneed hat #4AIdIY LTG detector Ca tof LX
contaimmt. the detector was locaed abmov te draft "LTe tM oN " atC4
deck. Since the opezators had indicatLOn of IS lInkae end * tIt" In ts
countijnt* &a Individa using espiratory protection _a _nt Into the
coottaimt to LavostLsate. This Udivldual nftmed the Loags and
Lsnat£ed the ource as the bstdown Lin but Was 1able CO UIntIft the exct
Leak point because bLs air supply wed low. DurLM cbs Laspet@U s evldemce
of fire vwa found.
To prevent future occurrencs the CYC-2O0E pipe thrds vore dresed and a
nev ed zap installed. CVC-200 ard several other valvelpLp cap errangeents
which could be eooed to the sam condition were inspecced and physically
locked or verified secured in the closed position.
CaZ
Page 40
mActM"W U. 4
a TS I) MUSMUATION
The "ain concern dWring the transient of 1-124L wr an uAMxpllifd decr"se
in E pressure. The pressure dropped ften 2O0 psi& to 1620 psug ID Wtopo-
Ustely mae hour. VA" steps were takes diauri the first bour of the transient
to determine wbet v causig the deprseasqaatif. The ToeesuiZer (tsr)
safety valve were chocked by lookiag at the accOustic flow indicators dwn-
stres of the vlves. No flow was indcated. The par rcVs were checked by
looking at the pipe cmperature downstre55 of the valves. Again. oo flow was
Indicated. The tsr block valves vere checked to verify that they were shut.
The Prr relief tank level and pressure were als checked to verify thac they
were not increasing. The main tsr spray valves we then switched to manual
control and Closed by the eperator. The indication on the RTCS shoved the
valve to be cloesed. bevee. mince this Iicatin ie oway of demand position,
the operator tried to insure that the valves had closed by manua-ly cloeing
them. The charging line was then Isolated to ass If the auxiliary spray valve,
CVC-31l. was leaking. Additionally. RO "" and "VC were stopped so that flow
through the main wry valves ASIA & * was not possible. Par pressure began
ncrasiUg. Later that night (231S bous) epray valve 4553 was positively
Uentlfled as the leaking valve.
An inspection of the valve showd that the atm vs binding on the valve park-
L34. One reason the binding problem was not identified earlier is that the
spray valves do not move such during pover operation. RZ pressure control is
accomplished by varying the ?sr heaters with the spray valve partially opered.
The valve was repaired by ubricatlng the stm. The valve was then tested
four times to inswe proper operation. In addition, the electro-echanliCal
poltoner garv setpoLit ma discoverad to be *l htly off and therefore was
reset. -DtroT-
ta 1
Page 41
ATuACHNl W. S
cou- umr - I3OLUATIOIE YALY IFAIK Mi- 248)
At 0624 on 1-2981 a SI digal generated a Ph^a A contAiL.Ut LBolntLO . .ss
pert of this Lsolatlon the nSwly imtallh firx protection containt .; 'ation
valve F?-2469 Fl-2'9. 77-256, 7-25 vere sigled to shut. Vi-248 did not
sbut. The valve Wu then Manually sut. The cause of failure Was a tripped
breaker hich Wul, not &llow power to the motor operator. Subsequent reviw
i6dcated that the trip point on the magnetic overload breaker was not set igh.
enouh to Insure proper operation.
The breakers had been tested successfully upon I a lastion, however, the currect
demd of the valve motors can chane wvith tum and so if the trip point is tot
Oet with enough magin the breaker cAn pass A test and yet fail at a later tica.
The setpoints on all four va1ves hve been r"edjusted to ccmpeusate for the
above problm aad tested. This should correct ay future problem vith these
r1 1
Page 42
£?Aft~ww No. G
S A W 0? I5O CoIvtru WTMt
0620 Alarm- Low Tavg Iezulasive Set
0620 Alarm - Lov Tavg 541.2 (setpotat La 543.0)
0623 OU - Control 1.4 UA C Usertod (reactor trtp)
0634 Alan - 1.0 ?a 'I' W (Oc0e4 (St esLPa)
0624 Ala - Lov Tavs 532.7 (alanas Tavg)
0625 t= - 1.1 F1 DAltaf TaSk 75.2! (Valve CVC-203 lifts)
0627 UTRX - K hop "3" BXI open (St reset)
0705 I gm -rZ Low I L St (SicW s: I l)
WITS AJ -_* R ?,MP "I" 31KI MOWs
0705 _ . - "A" R. cowd
0 26 Alarm - RCL8 L rlow (4CP 'I" stopped)
C^27 Alarm - =CLC 1 Flow CRC? "C" stopped)
-DRA"-
1
Page 43
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Page 47
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