ML20085D009
| ML20085D009 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 11/16/1971 |
| From: | Haueter R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20085C988 | List: |
| References | |
| NUDOCS 8307180048 | |
| Download: ML20085D009 (15) | |
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JACKSON MICHI GAN
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DR PETER A MORRIS g,
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l DOCKET-50-255 D
LICENSE DPR-20 i
THIS TWX IS TO APPRISE YOU OF A RECENT DIFFICULTY WITH SEVDtAk 0F THE CONTROL ROD DRIVE MECHANISMS AT THE PALISADES PLANT. AT THE i
TIME THE INITI AL PROBLEM WAS DETECTED, THE PLANT WAS IN A SOLD l
SHUTDOWN CONDITION WITH THE PRIMARY COOLANT SYSTEM AT 200 PSIG AND DROP TESTING 0F THE CONTROL RODS IN PROGRESS.
AS CONTROL ROD NUMBER 27 WAS BEING DROP TESTED FROM 66 INCHES BY MEANS OF THE TEST PANEL SWITCH ON NOVEMBER S,1971, IT *APPARENTLY" FAILED TO DROP ACCORb!NG TO THE PRIMARY ROD POSITION READOUTS.
f SUBSEWUENT CHECKING ON THE SECONDARY ROD POSITION INDICATION SYSTEM DISCLO::iED THE ROD WAS STILL AT ZEHO OR FULLY INSERTED POSITION.
g THE MOTOR-CLUTCH ASSEMBLY WAS REMOVED AND FOUND TO HAVE A BROKEN CLUTCd ADAPTER SHAFT.
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A SPARE UNIT WAS INSIALLED AND CONTROL ROD NUMBER 27 SUCCESSFULLY j(_g ///
DROP TESTED AND MOTOR Tch;UE MEASUREMENTS OBTAINED WITH NORMAL RE-
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G30718004g 711110 Fi ll\\; ' j~, Gq hDRADOCK 05000255 5
PDR SUBSEEUENT INVES TIGATIOh INDICATED INE PRO 3 LEI HAD ACTUALLY OCCURRED I
l y1Y AT 0517 ON NOVEMtsEh I, 1371,1 SHEN InE CONTROL ROD HAD 3Et.N TEST DROPPED WI TH AIMCF :ir'IC PH ESSURE ON !HE SYSTE. JUSS Gu Ni I '. -
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- VES TIGA TI Oh DISCLOSED IHAT DAMAGr. alas SUSTAINED IN FIVE ADDITICNAL 5016
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ALL DAMACED SHAFTS
~I REPLACED W'1TH NEW PARTS AND THQ1TS RE-
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SteUENCE OF EVENTS
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FILLINC 0F THE PRIMARY COOLANT SYSTEM TO NORMAL OPERATING LEVEL IN b.
THE PRESSURIZER WAS INITI ATED ON OCTOBER 29, 1971, FOLLOWING AN i
O(TENDED OUTAGE FOR M001FICAII0hs To THE SECONDARY PLANT.
f PRIMARY COOLANT SYSTEM FILLING OPERATION REACHED THE LEVEL OF THE CONTHOL ROD DrtIVE MECHANISM AUTOCLAVE NUT /84 PERCENT IN PRESSURIZER /
i AT 0400 Oh OC TOBER 31, 1976.
CONTROL RCD NUMBER I WAS TEST DROPPED FROM 66 INCHES AT 05S5 AND 0603, H OWEV ER, FURTHER DROP TESTING WAS DELAYED DUE TO INABILITY OF THE COM-PUTER DROP TIME PROGRAM TO FUNCTION AND A GEAR PR08LEM IN THE MOTOR i
PACKAGE OF NUMBER 1 CONTROL ROD DRIVE. THE MOTOR PACKAGE WAS REPLACED.
AT 1119 ON OCTOBER 31, 1971, NUMBER 2 CONTROL RCD WAS SUCCESSFULLY DROP TESTED AND THE TESTING OF OTHER CONTROL RODS CONTINUED.
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THE CONTROL ROD NUMBER 27 WAS TEST DROPPED NOVEMBER t,1971, AT 0314 FROM 66 INCHES AND REPEATED AT 0317. THE DROP TIME WAS NORMAL, HOWEVER.
IN die SAME MINUTE AS THE SECOND DROP THE COMPUTER PRINTOUT / PRIMARY /
f INDICATED ROD 27 AT 166.5 /POSSIdLE INDICATION OF SHAFT FAILURE /.
j INITI AL COLD DROP TESTING OF ALL DRIVES FROM 66 INCHES WAS COMPLETED PRIOR TO 0800 NOVEMBER 1, 1971. PRIMARY SYSTEM / PRESSURIZER / WATER i
LEVEL WAS MAINTAINED BETWEEN 92-99 PERCENT DURING DROP TESTING 0F THE CONTROL RODS.
1 ON h0VEMBER 3, 1971, CONTROL RCD DRIVE MECHANISM NUMBER 22 WAS INSPECTED I
TO DETERMINE THE CAUSE OF A SUSPECTED SHIFT OF THE ENERGY ABSORBER /HARD S TOP /.
AIR PRES $URE WAS h0Ir.D IN THE DRIVE HOUSING VHEN THE AUTOCLAVE NUT WAS REMOVED, IWDICATING THAT PROPER VENTING WAS NOT ACCOMPLISHED DURING THE PREVIOUS FILL OPERATION. AT IHIS TIME, THE TESTI:)3 PROCEOURE WAS CHANGED To I NS UR E Pa 0P t.d n. I; hG /etLFint.NCE Tit t C GAR EJ u n ac t ie Sc:T!1. UF 5016 ppqp y h'
L, THIS K EPOR T/.
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THE MOTOR PACKAGE ON CONTROL ROD DRIVE MECHANISM NUMBER 2 WAS CHANGED
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05 NOVEMBER 3,1971 BECAUSE OF GEAR NOISE.
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ON NOVEMBER 4, 1971, THE PISION GUIDE TUBE WAS REPLACED IN MECHANISM i
NUIElER 22 AS THE ENERGY ABSORBER WAS FOUND TO HAVE MOVED APPROXIMATELY t
j 1.9 INCH ES.
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Olt NOVEMBER 5, 1971, THE PRIMARY SYSTEM PRESSURE WAS BROUGHT To i
200 PSIG AND DROP IIME TESTING AND TORQUE MEASUREMENTS OF CONTROL R0D k
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DRIVES STARTED. AT 2150 THE CLUTCH OUTPUT SHAl-I 0F CONTROL ROD DRIVE MECHANISM NUMBER 27 WAS DETERMINED TO BE BROKEN AS THE UNIT FAILES TO RESPOND TO TEST SIGNALS.
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A SPARE MOTOR CLUTCH UNIT WAS INSTALLED ON CONTROL RCD DRIVE NUMBER 27 BY 0200 NOVEMdER 6, 1971, AND ROD DRIVE TESTING RESUMED. THE DROP TIMES AND TORQUE READINGS WERE NORMAL ON ALL CONTROL ROD DRIVE UNITS.
FURTHER INSPECTIONS AND REPAIRS ARE BEING MADE AND ARE COVERED IN OTHER t
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PORTIONS OF THIS TWX.
CAUSE OF INCIDENT l
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THE INVESTIGATION TO DATE INDICATES THAT AIR IN THE CONTROL ROD DRIVE I
MECH A NI SM, DUE TO INCOMPLETE VENTING, ALLOWED DRY TRIPS TO TAKE PLACE DURING THE DROP TIME TESTING OF THE CONTROL RODS ON OCTOBER 51 AND NOVEMB ER 1, 1971.
h ALTn 00Gn Inc. PRESSua1LER WATER LEVEL WAS 4LW4YS AB0VE THE AUTOCLAVE NUT OF THE MECHANISM, THE AVAILABLE HEAD WAS INSUFFICIENT TO DRIVE THE AIR 5016 THR OUGd Tdd PR ESS UR E SdAL.
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.THE CONTROL ROD DRIVES ARE DE31GNED TO OPERATE t:
,I ITH TH BUFFER ZONE
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..n,.\\ l AMD ENERGY ABSORBERUEA3 FILLED,VITH WATER SO THAT W A DRIVE IS pp q3, SCRA'MMED II COMES 10 REST GENTLY ON THE HARD STOP AT THE BOTTOM 0F 7,
ITS TRAVEL. THESE DRIVES ARE ALSO DESIGNED TO WITHSTAND AN ACCIDENTAL lf IRI? WITH A DRY CONDITION Ih THE BUFFER ZONE ENERGY ABSORBER AREA.
THIS IS To PROTECT THE DRIVE FROM EQUIPMENT DAMAGE IF, DURING INITI AL t
r1 INSTALLATION OR A REFUELING OUTAGE, THE DRIVE WERE TO BE TRIPPED IN A DRY CONDITION AND IS ACCOMPLISHED BY A PRESSED FIT BETWEEN TWO CON-CENTRIC CYLINDERS. IF A DRIVE IS TRIPPED FROM A DRY CONDITION IT IM-l PACTS THE HARD STOP WITH SUFFICIENT ENERGY TO CAUSE MOVEMENT OF THE INN ER CYLINDER.
THE FRICTION FORCE DECELERATES THE ROD OVER SEVERAL j-INCHES OF TR AVEL.
A THE DRIVE CONDITIONS EXPERIENCED DURING ThE SCRAM TESTING ON OCTOBER 5 f
AND NOVENER 1 WERE SUCH THAT THE BUFFEH ZONES RANGED BETWEEN THOSE VENTED EN0 UGH TO PROVIDE THE ADEQUATE WATER TO DECELERATE THE ROD NORMALLY TO THOSE POORLY VENTED SUCH THAT THE' BUFFER ZONE AREA WAS DRY OR VERY NEARLY DRY. THE CONTROL ROD DRIVES VENT CCNTINUOUSLY THR OUGH THE SEAL FACES OF THE PRESSURE SEAL. DURING THIS CONTROL ROS DRIVE TESTING THERE WERE ONLY SEVERAL FEET OF WATER PRESSURE AT THE CONTROL ROD DRIVE SEALS AND THE TESTING OCCURRED ' SHORTLY AFTER FILLING THE SYSTEM. THE DIFFERENCES IN AMOUNTS OF WATER AND AIR IN THE CONTROL ROD DRIVES /UNDER THESE PRESSURE CONDITIONS / ARE RELATED TO TME IN-DIVIDUAL SEAL LEAKAGES. THIS INADEQUATE VENTING ALLOWED SOME DRIVES t
I TO IMPACT THE ENERGY ABSORBER /HARD STOP/ WITH SUFFICIENT ENERGY.TO CAUSE DAMAGE TO SOME PARIS OF THE MECHANISM. THIS INSTANTANEOUS DE-f CELERATION CAUSED TORSIONAL DAMAGE TO SOME CLUTCH ADAPTER SHAFTS AND DAMAGE TO SOME OF THE COUPLERS. ELEVEN OF THE FORTY-ONE CONTROL ROD DRIVES FELL INTO THIS CATEGORY. WITH THE EXCEPTION CF THE CONTROL RCD DR I VES NUMB ERS 1, 2 AND 27. THE DRIVES ALL TESTED NORMALLY WITH N0 g
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MAINTENANCE ATTENTION. n0 WEVER, ALL ELEVEN BLADES REMAINED COUPLED TO l
THE CONTROL ROD DRIVE ASSEMBLIES AND EXHIBITED NORMAL COUPLING AND UN-t COUPLING CHARACTERISTICS.
i SEVERAL COUPLERS THAT REQUIRED REPLACEMENT WERE DEFORMED / EXPANDED IN THE COUPLE AREA / SUCH THAT THEY INTERFERED WITH THE CONTRCL RCD DRIVE I
MERMAL SLEtVE UPoh REMOVAL OF THE CONTROL ROC ; RIVE A3SEMBLY PACKAGE.
I PRIOR TO EXERTING SUFFICIENT F0hCE TO RENOVE THESE PACKAGES. COMBUS-TION ENGINEERlhG J. ulATh Ini REMOVAL FCRCE in s 00ULO M ar-LIED WITHOUT CAUSING LAMAGE TO PLANT EQUIPMENT. In ES E FORC - S ' 'ER E.wN I -
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ALL PREVIOUS CONTRO OD DRIVE TESTING.HAD BEEN PERFOR WITH THE TOOL FLANGE REMOVED OH
. SYS TE.M PRESSURIZ ED, BOTH OF WHICH PROVIDE GREATER
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VENTING EFFICIENCY. IHE INADEQUATE VENTING WAS DISCOVERED ON NOVEMBER 5, 1971 WHEN AIR PRESSURE WAS RELEASED UPON REMOVAL OF A CONTROL ROD DRIVE ll
/NO 22/ AUTOCLAVE NUT WHILE INVESTIGATING AN UNEXPLAIN,ED SHIFT IN LOCA-l TION OF THE ENERGY A6SORBER UNIT OF !.9 INCHES ON THAT CONTROL ROD DRIVE IEN ENERGY ABSORBER U11TS WERE DISPLACED, A TOTAL OF 0.5 INCHES OR i
GR EA T ER. THESE DISPLACEMENT MEASUREMENTS WERE MADE USING THE PRIMARY ROD POSITION I N DI CA TI ON.
THE CLUTCH ADAP TER SHAFTS ARE S AE 4140 MATERI AL HEAT TREATED TO ACHIEVE A RCC A DELL "C" 33 HARDNESS. THE SHAFT DI AMETER IS 0.560 INCHES WITH TWO 0.188 INCH WIDE BY U.110 INCH DEEP KEYWAYS.
S UMMA RY OF INSPECTIONS AND REPAIRS A.
SINCE IHIS INCIDENT OCCURRED, ALL CONTROL ROD DRIVES HAVE BEEN TESTED FOR MOTCR RUNNING CURRENTS AND SCR AM TIMES. THE RESULTS OF THIS TESTING WERE NORMAL.
B.
ALL MOTOR DRIVE PACKAGES MAVE BEEN INSPECTED, INCLUDING THE FOUR PAR T LENGTH RODS. THESE INSPECIIONS RiVEALED NO DAMAGE TO THE FOUR PARI LENGTH RODS, ONE CLUTCH ADAPTER SHAFT BROXEN / NUMBER 27/, FIVE CLUTCH ADAPTER SHAFIS w!TH VARYING AMOUNTS OF TWIST AND FIVE CLUTCH A DAP T Eh SHAFTS WITH bAR ELY PERCEPIIBLE UPSETTING OF THE CLUTCH ADAPTER SHAFT XEY AYS. THE REMAININC 29 MOTOR DRIVE PACK AGES SHOWED NO SIGNS i
0F DAMAGE. THE ONE BROKEN AND FIVE IWISTED CLUTCH ADAPTER SHAFTS HAVE BEEN REPLACED.
C.
THE PRIMARY ROD POSITION INDIC ATION REVEALED THAT THE ENERGY ABSOR-DER UhlI3 UN SlX DHIVLb nAO a6EN DISPLACED. THE EN ER GY ABS CRBER WI TH THE MAXIMUM DISPLACEMENT sAS REPLACED.
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THE COMPLETE C0hin 0L ROJ DaiLE P40% AGES LISTED IN THE FOLLOWING IABLE HAVE BEih A Ln EA DY 08 e1LL BE nE.90Vt3 Fod I N S P EC TI ch. InIS TABLE 8
LISTS TH E DAMA Gt:... c.; c. T-
~ et CPcCTIChJ e-4' a: 06 g Ol6 NOV EM3 ER IS. 197!.
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ENER GY REMOVED IR/
ABSORB ER NUMBER OF I
CR DM OR NOT COUPLER SHAFT DISPLAC EMEN T ',
TRIPS ON NO REMOVED /N/ CON DI TI ON CONDITION
/ INCH ES /
10/31 AND 11/1 I
R DEFORMED TWISTED 0.8 2
2 51 DEFORMED TWISTED OK 1
f 4
R OK OK OK 2
8 N
OK 0.5 1
j 14 N
OK 0.7 2
15 N
OK OK 2
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18 N
On 1.2 1
19 N
OK OK 1
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22 R
OK OK 1.9 2
25 R
DEFORMED TWISTED OK l
24 R
DEFORMED TWISTED OK 2
27 R
DEFORMED BROKEN 0.5 2
29 N
OK 0.9 1
30 R
DEFORMED TWISTED OK I
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32 N
UPSET OK 1
33 R
i 36 R
37 R
DEFORMED UPSET OK 1
39 R
DEFOR MED OK 1.5 3
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40 N
OK 0.5 2
l 41 R
DEFORMED UPSET OK 1
i E.
ALL CONTROL ROD DRIVES WILL BE TESTED IN ACCORDANCE WITH THE TECH-NICAL SPECIFICATIONS AND AS SUMMARIZED IN THE CONCLUSIONS SECTION OF THS s'
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LETTER AFTER THEY HAVE BEEN REASSEMBLED AND PRIOR TO ANY REACTOR CRITIC &
OPDIATION. CRITICAL OPERATION WILL NOT BE PERFORMED UNTIL THE RES' L*S U
i CF THE AFOR EMEN TICNED TESTING IS NCHMAL.
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- SAFETY ANALYSIS
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n THE REVISION OF PLANT PROCEDURES PROVIDES ADEQUATE VENTING TO INSURE f
THAT CONTROL R0D DRIVES WILL NOT BE TESTED OR OPERATED UNDER CONDITIONS f
SI MI LAR TO THOSE DISCUSSED ABOVE. THIS WILL PRECLUDE FURTHER FAILURES OF THE NATURE PREVIOUSLY DISCUSSED. HOWEVER, THIS SAFETY ANALYSIS ASSUMES FURTHER FAILURES OF NATURE DESCRIBED ABOVE COULD OCCUR. A DE-l' TAILED FOLLOW-UP REFORT IS CdRRENTLY BEING PREPARED AND WILL BE SUB-i MITTED BY DECEMBER 5, 1971.
I f
ASSUMING IHAT A CLUTCH ADAPTER SHAFT ON A CONTROL R0D DRIVE WERE TO BR EAK WI TH TH E R EAC TOR CRI TIC AL-4 A.
IF A CONTROL ROD WAS IN A GROUP ThAT IS EITHER FULLY OR PARTIALLY WI Th DR A WN, IT WOULD DROP IN TO ITS FULLY INSERTED POSITION /THIS FAILURE ALWAYS CAUSES THE DRIVE TO DROP RATHER THAN IMPEDING IT FROM DROPPING /
AS ON A TRIP WI TH THE EXCEPTION THAT THE PRIMARY POSITION INDICATION WOULD BE MEANINGLESS. THIS OCCURRENCE WOULD BE EVIDENT ON BOTH NUCLEAR INSTRUMENTATION AND SECONDARY ROD POSITION INDICATION. IN THE EVENT OF
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A DROPPED CONTROL ROD, IT WILL BE IMMEDI ATELY DETERMINED WHETHER THE DROP IS DUE TO A CLUTCH SEPARATION AS IN A TRIP OR SOME OTHER CAUSE SUCH AS FAILURE OF THE CLUTCH OUTPUT SHAFT. IF THE DROPPED ROD IS DUE TO A MECHANISM OTHER THAN A CLUTCH SEPARATION THE REACTOR WILL BE SHUT DOWN IMMEDI ATELY TO MAKE APPROPRI ATE REPAIRS. UNTIL THE REACTOR IS SHUT DOWN, II WILL BE OPERATED IN ACCORDANCE WITH THE TECHNICAL SPECI-FICATION LIMI TS CONCERNING OPERATION WI TH A DROPPED ROD.
l B.
IF THE AFFECTED CON TROL RCD WAS IN A GROUP THAT WAS IN THE INSERTES POSITION DURI NG R EACIOR OPERA TION, II WOULD BE DETECTABLE BY A COM-I PARIS 0N OF PRIMARY AND SEC0hDARY ROD POSIIl0N INDICATION. THE POSI-1*
T10h INDICATION CF CONTROL RODS IN THIS CONFIGURATION WILL BE CHECEED EVERY Sh1FT FOR CONFIRMATION THAT THE CON TROL ROD DRIVE ASSEMBLY IS FUNCTIONING PR OPERLY. IF IT IS DETERMINED THAT A CONTROL ROD DRIVE r
MECHANISM IS NOT FUNCTIONING PROPEHLY DUE TO A MALFUNCTION OTHER THAN A CLUICH SEPARATION, THE REACTOR WILL BE Shut DOWN AS LE3CHIBED IN 1 <h b
'A' ABOVE.
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C.
FROM *B' IT IS CONCLUDED THAT IF A *FAILt2E WERE TO OCCUR IT l}
s -j ",l COULD REMAIN UNDETECTED FOR UP TO 8 HOURS. A FAILURE OF THIS NATURE i
SIPARATES THE CONTROL ROD DRIVE FROM THE ANTIREVERSE CLUTCH. IN TME r
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.UNLIXELY EVENT OF A SEVERE FAILINtE OCCURRING IN THE REACTOR PRESSINE
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SOUNDARY AB0VE THE CONTROL 200 BLADE AT THE SAME TIME A FAILURE IN A
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CONTROL ROD DRIVE ASSEMBLY EXISTS, IT IS CONCE!VABLE THAT A CONTROL BLADE COULD BE EJECTED FROM THE CORE.
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I ANALYSES OF CONTROL ROD EJECTION INCIDENTS HAVE BEEN PERFORMED AND
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i PRESENTED IN SECTION 14.16 0F THE PALISADES FINAL SAFETY ANALYSIS RE-PORT.
A SUMMANY OF THE RESULTS OF THESE ANALYSES ARE PRESENTED BELOW.
j TABLE I
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ZERO POWER ROD EJECTION INCIDENT VARI AB LES BEGINNING OF CYCLE END OF CYCLE
<1 DELAYED NEUTRON FR ACTION 0.0060 0.0052
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MODERA TOR TEMPERATURE COEFFI-CIENT OF REACTIVITY / DELTA I
RH0/ DEGREE F/
0.0 2.0XIO TO THE MINUS4 I
EJECTED ROD WORTH PDICENT 0.963 1.17 I
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MAXIMUM PEAK-TO-AVER AGE PWR 9.07 11.7 f-,
R ES ULTS AVERAGE ENTHALPY OF HOTIEST 176.2 267.5 5 o16 PELLET /MO HEAI TRANSFEa AS-(:
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SUMED/ CAL /GM
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i AGO AVER AGE EK THALPY OF HOITEST s I.
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PELLET /WITH HEAT TRANSFER /
CAL /GM 146.0 237.1
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FRACTION OF RODS THAT SUFFER CLADDING DAMAGE /ENTHALPY 0.0 0.001 I
GR EA TER TH AN OR EQUAL TO 200 i
CAL /GM/
FR AC II ON OF FUEL HAVING AT 3
LEAST INCIPIENT CENTER LINE 0.0 0.0 t
MELTING / CENTER LINE ENTHALPY GR EA T ER TH A N OR EQ UAL TO 250 CAL /GM/
FRACTION OF FUEL HAVING A FULLY MOLTEN CENTER LI NE CON-DITION / CENTER LINE ENTHALPY GREA TER THAN OR EQUAL TO 310 CAL /GM/
0.0 0.0 TABLE 2 FULL POWER /2200 MWI/ ROD EJECTION INCIDENT VARI ABLES BEGINNING OF CYCLE END OF CYCLE DELAY ED NEUIRON FR AC TI ON 0.0060 0.0052 MODEh ATort TEMPERAIURE C0iFFI-CIEbT OF REACTIVIlY / DELTA PLJS 0.5X10 TO THE -1.5X10 TO THE MINUS4 RH0/DEGNEL F/
MINUS 4 EJ EC T ED R 03 = 0R Tn F cn c EN I 0.45 0.54 1s016 I
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I AVERAGE ENTHALPY OF HOTTEST I
PELLET /NO HEAT TRANSFER AS-227.2 2 73.9 SUMED/ CAL /GM i
I AVERAGE ENTHALPY OF HOITEST PELLET VITH HEAT TRANSFER /
197.0 2 43.7 CAL /GM t
FRACTION OF RODS THAT SUFFER CLADDING DAMAGE /ENTHALPY 0.0 0.003 GR EA T ER THAN OR EQ UAL TO 200 CAL /GM/
I FRACTION OF FUEL HAVING AT LEAST INCIPIENT CENTER LINE 0.0 0.001 6
MELTING / CENTER LINE EN-ThALPY GREATER THAN OR EQUAL i
TO 250 CAL /GM/
FRACTION OF FUEL HAVING A FULLY MOLTEN CENTER LINE CON-0.0 0.0 t
k DITION /C EN TER LI N E ENTHA LPY t
GREATER THAN OR EQUAL TO 310 CAL /GM/
THIS INVESTIGATION OF BOTH THE ZERG-POWER AND FULL-POWER ROD EJECTION
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INCIDENTS IhDICATES THAT ThERE IS NO GROSS CENTER LINE MELTING OF THE FUEL FOLLOWlhG A R0D EJECTION AT ANY TIME OF CYCLE LIFE AND THAT THE 5016 HESULTANT FUEL CLAD 0iMG DAMGE IS MINIMAL.
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FOUR OF THE FORTY-FIVE CONTROL R0D DRI'/E ASSEMBLIES ARE TERMED y ;.. (
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- PART LENGTH RODS.* THESE FOUR ASSEMBLIES ARE ESSENTI ALLY IDENTICAL IN T '4 l
2 1 CONSTRUCTION TO THE OTHER FORTY-ONE ASSEMBLIES EXCEPT THAT THEY DO NOTp ;';
HAVE A CLUTCH ASSElGLY AS THEY HAVE NO TRIP FUNCTION. ASSUMING THEY M.'
.e ARE SUSCEPTIBLE TO FAILURES OF THE CONTROL ROD DRIVE MECHANISM, A o
FAILURE SIMILAR TO THE FAILURE OF CONTROL ROD DRIVE NUMBER 27 WOULD ALLS u
THE INSER TION OF A PART LENGTH ROD. IN THE EVENT THAT A CONTROL ROS DRIVE MECHANISM FAILURE CAUSED A PART LENGTH CONTROL R0D TO DROP INTO I
v THE CORE, IT IS POSSIBLE THAT REACTIVITY WOULD BE INSERTED. REACTIVITY
{
IS AVAILASLE BECAUSE THE THIRTY-ONE IhCH ACTIVE LENGTH OF THE CONTROL ROD HAS A HIGHER WORTH WHEN PLACED NEAR THE AXI AL MID-PLANE OF THE CORE a
THAN WHEN PLACED IN THE LOWER FLUX REGION AT THE BOTTOM OF THE CORE.
I IO EVALUATE THE CONSEQUENCES OF A PART LENGTH, ROD DROP, USE WAS MADE OF THE RESULTS OF THE PALISADES ZERO POWER PHYSICS TEST. WITH ALL OTHER t
2005 WI THDR A WN, THE FOUR PART LENGTH RODS HAVE A MAXIMUM WORTH AT So INCHE.C. THE INSERTION OF THE FOUR RODS TO ZERO INCHES /ALL IN/ ADDS 0.144 PERCENT IN REACTIVITY. ANOTHER TEST, MADE WITH THE int 00PS 3 AND 4 i.
i REGULATING RODS INSERTED, YIELDS AN INSERTION OF 0.155 PERCENT IN j
REACTIVITY BETWEEN 46 INCHES WITHDRAWN AND FULL INSERTION. USING THIS t'
LATTER VALUE, EACH PART LENGTH ROD HAS THE P(TIENTI AL FOR INSERTING APPR0xlMATELY 0.039 PERCENT IN THE EVENT IT DROPS.
l' i
REACTIVITY INSERTIONS OF THIS ORDER ARE GUITE ROUTINE IN REACTOR MA-I N EUVER I N G.
THE RESULTANT PERIOD, APPROXIMATELY 180 SECONDS, IS EASILY CONTROLLABLE BY ROUTINE OPERATOR ACTION. II MAY BE COGCLUDED, TH ER EFOR E, I
i THAT THE DROP OF A PART LENGTH CONTROL ROD FROM ANY POSITION IN THE CORE I
HAS NO NEGA TIVE SAFETY IMPLICA II ONS.
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AS THE WORTH OF A PART LENGTH ROD IS LESS THAN InAT OF A FULL LENGTH ROD, A ROD EJECTION ACCIDENT WOULD BE LESS SEVERE THAN THAT ANALYZED f
IN "C' ABOVE. HOWEVER, AS A POTENTI AL FOR A ROD EJECTION ACCIDENT DOES D(IST IF A FAILURE OF THE DRIVE SHAFT WERE TO OCCUR, THE SAME TESTING A h D OP ER A I! ohs C ' I e.d I A WILL Si APPLIED TJ THESE F00:1 RODS AS And gg
~"AND'C' ASOVE.
DISCUSSED AhD COM.".ITIED TO IN A
pAGE II 1
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IT IS NOT CONSI ED CREDIBLE TO HAVE TWO OR MORE TROL ROD DRIVE ASSEMBLIES FAIL AT ThE SAME TIME, IN A MANNER SUCH THAT THE ANTIREVERSE 6
CLUTCH IS DISABLED.
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THE TECHNICAL SPECIFICATIONS REQUIRE REACTOR SHUTDOWN IN THE EVENT OF
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MORE THAN ONE CONTROL ROD DRIVE MALFUNCTIONING. AS THE DAMAGE TO THE
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CONTROL ROD DRIVES OCCURRED DURING TRIP TESTING, FURTHER DATA WILL BE y
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l OBTAINED DURING TRIP TESTING TO INSURE THE ROD INSERTIONS ARE NORMAL.
THIS DATA WILL BE OBTAINED BY RECORDING ROD POSITION VERSUS TIME DURING i
ROD TRAVEL WHEN IT IS TRIP TIME TESTED. A NORMAL TRIP /THE BUFFER ZONE AND ENERGY ABS 03BER FILLED WITH WATER / HAS A " CHARACTERISTIC TAIL" WHEN THE DRIVE DECELERATES IN THE BUFFER ZONE AREA. IF THE DRIVE WERE TO AGAIN BE TRIPPED WITHOUT PROPER VENTING OF THE BUFFER ZONE AND ENER GY ABSORB ER AR EA, THE " CHARACTERISTIC TAIL' WOULD BE MISSING.
}
THIS ADDED SURVEILLANCE WILL ELIMINATE ANY POSSIBILITY OF UNDETECTED DRY TRIPS DURING TESIING.
i THE ENERGY ABSORBER UNITS ARE DESIGNED TO HAVE 5 INCHES OF TR AVEL.
TEST STAND MEASUREMENTS YIELD AN AVERAGE DISPLACEMENT OF THE ENERGY ABSORBER OF 2.7 INCHES ON A COMPLETELY DRY TRIP.
l THE MINIMUM AVAILABLE REMAINING TR AVEL OF THE ENERGY ABSORBER UNITS DISPLACED IS 1.7 INCHES. THIS IS SUFFICIENT TO SLOW A DRIVE ON A DRY f
TRIP SUCH THAT IT IS HIELY IMPROBABLE THAT THE DRIVE WOULD SUFFER f
l ANY DAMAGE.
i A TEST ASSEMBLY HAS BEEN TESTED BY COMBUSTION ENGINEERING. THE t
DEFOH MA TION OF THE COUPLER ON THIS TEST ASSEMBLY WAS GREATER THAN i
THAT ESERVED IN THE COUPLERS THAT HAVE BEEN I NS PEC TED.
THE COU-i t
PLING AND UNCOUPLING ABILITY OF THE TEST ASSEMBLY WAS NOT DE-8 l
STROYED. THERE WAS NO APPARENT DAMAGE To ThE STRUCTUR AL INTEGRITY k
0F IHE TEST ASSEMdLY BLADr. DUE 10 THIS TESTING. A SLIGif UPSETTING b
0F THE BLADE LOAD tsEARING SURFACES WAS 06 SERVED. AS TH E WORS T C AS ES OF COUPLER DAMAGE DURING THE CONTROL RCD TESTING PERFORMED ON OCfodER 51 AND NOVEM5Ei ! '4ERE LESS SEVERE !HAN THE TEST ASSiASLY COUPLER DAMAGE, IT IS CO.NCLUDED ThAT ho DAMAGi TO IHE BLADES EXISIS.
THE BLA DES WILL 32. J.2 EC TO FOR EV10tEi C F '#
^ TING DF TMe LOAJ 5 01(o BEARING SudFACES THE NEAT TIME THE REACION Ve.SS tL dt.AJ IS H ei10ViJ. Qg
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.IN In c. U% L I K ELY EVEm/ IH A T A DR Y TRIP VAS A0AIN 10 OCL/ AN D TH E EN ER GY
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ABSORBER UNIT HAD BEEN PREVIOUSLY DISPLACED ITS FULL THREE I4CHES OF y
o TRAVEL AND NOT RESIGRED TO NORMAL, IT IS POSSIBLE THE CONTROL ROD BLADE f*j,:
1 MIGHI BE DETACHED FROM THE COUPLER. THE MECHANIS1 IS THAT AS THE SLADE
/g i REACHES ITS FULLY INSERTED POSITICN AND IMPACTS THE HARD STOP II IS h
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DECELERATED INSTANTANEOUSLY AS THE ENERGY ABSORSER URkT HAS NO FREEDOM TO TRAVEL. THE FORCE APPLIED BY InE CONTROL ROD BLADE TO THE COUPLER MAY BE SWFFICIENT TO CAUSE Tite COUPLER TO RELEASE THE BLADE. IF THIS WERE 10 LCCUR, THE dLADE WOULD CONTINUE TO TR AVEL DOWNWARD UNTIL IT IMPINGED UP 0h IHE COR E SbrPORI PLA TE.
THEhE WOULD BE NO DAMAGE TO THE FUEL AS THE CONIROL ROD BLADE IS NOI RELEASED FROM THE COUPLER UNTIL IT R EACH ES THE FULLY INSERTED POSITION AND IT IS TR AVELING STR AIGHT DOWN WnEN IT IS RELEASED, ANY DAMAGE THAT OCCURS WILL BE LIMITED TO THE IIP OF THE BLACE IISELF.
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THIS SITUATION WILL NOT OCCUR BECAUSE AT LEAST 1.7 INCHES OF TRAVEL RE-MAIN 04 ALL ENERGY ABSORBER UNITS. HOWEVER, ENER'3Y ABSORBER UNITS WILL BE MONITORED FOLLOWING ALL SCRAMS AND CCNTROL RCD DRIVE TESTING TO INSUE THAT THEY HAVE NOT BEEN DISPLACED. THIS MONITORING WILL BE ACCOMPLISHE9 SY READING THE PRIMARY ROD POSITION INDICATION WHEN THE RODS ARE FULLY INSERTED AND COMPARING THE READINGS OBTAINED TO PREVIOUS KNOWN VALUES.
THE ENERGY ADSORSER UNITS THAT ARE DISPLACED GREATER THAN 0.5 INCHES WILL BE RIPLACED BY THE COMPLETION OF THE FIRST REFUELING OUTAGE.
CONCLUSIONS FRon THE FOREGOING DESCRIPTION AND ANALYSIS OF THIS IhCIDENT AND DISCUS-SIONS WITH AND TESTING PERFORMED BY COMBUSIION EN GI N EER I N G, IT IS CON-CLUDED THA T IHE CA dSE OF THE INCIDENT HAS BEEN CORRECTED. THE DAMAGE TO THE CONih0L ROD DNIVE MECHANISMS WILL BE REPAIRED AS DISCUSSED ABOVE PRIOR TO REACIOR CRITICAL OPERATIONS.
I e
THE RESULiS OBTAINED DURING THE TESTING OF THE CONTROL ROD DRIVES ON I
NOVEMBER S AND 6 DEMONSTRATE IHE RELI AdILITY OF THE CONTROL ROD DRIVE SYSTEM. TH ES E R ESUL TS wire NOR.uL 'alIn CNE EXCEP TION / NUMBER C7/
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WI I'H OU T P ER FOR '4! h G MY MI:,Ii:ANCE ON THE CONTROL ROD 3 RIVE NEChA-EN NISM3 PAGE 13 I-
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..d5 p6e D1E SAFETY ANALYSIS ASSUM4S THAT FURTHER FAILURES COULD OCCUR. BASED l
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ON THIS SAFETY ANALYSIS, IT IS CONCLUDED Thti TME FAILURE OF THE l
t CLUTCH OUTPUT SHAFT ON CONTROL ROD DRIVE NUP.3ER 27 OR FUTURE SIRILAR I
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FAILURES OF A CONTROL ROD DRIVE MECHANISM DO NOT INVOLVE AN UNREVIEWEB 6
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SAFETY ITEM. THIS SAFETY ANALYSIS TOOK CREDIT FOR INCREASED SURVEIL-f g
LANCE AND OPERATING LIMITATIONS IN CERTAIN AREAS, NAMELY.
i t
A.
IF A CONTF CL ROD IS DROPPED AND THE CAUSE OF THE ROD DROPPING IS OTHER THAN A CLUTCH SEPARATION, THE REACTOR WILL BE SHUT DOWN IMMEDI A TELY /SAFET) ANALYSIS, PARAGR APHS A, 8, AND D/.
B.
ADDED ROD POSITION INDICATION COMPARISONS 'AND VERIFICATION
/SAFErr ANALYSIS, PARAGRAPHS B AND D/.
l l
C.
ADDED SURVEILLANCE WEN TESTING COETROL.20D DRIVES / SAFETY ANALYSIS, PARA GRAPH E/.
D.
ADDED SURVEILLANCE OF HARD STOP LOCATIoss / SAFETY ANALYSIS /.
THESE ADDED SURVEILLANCE COMMITMENTS AND OPERATIONAL LIMITATIONS WILL REMAIN IN EFFECT UNTIL A DETAILED REPORT OF THIS IDCIDENT IS SUBMITTED p
i TO THE DIVISION OF REACTOR LICENSING. IT WILL BE SUBMITTED BY DECEMBER j 1971.
i YOURS VERY TRULY ROBERT L HAUETER ELECTRIC PHODUCTION SUPERINTENDENT - NUCLEAR
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i IF AhY QUESTIONS OR GARBLING PLS CALL 517-788-1989 1X IOMNG so's tu Pg 15
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