ML17320B063

Forwards Responses to Questions Raised by Anl at 840329 Meeting in Support of Cycle 5 Reload Application

ML17320B063
Person / Time
Site:	Cook
Issue date:	05/17/1984
From:	Alexich M INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML17320B064	List: ML17320B063 ML17320B065
References
AEP:NRC:0860I, AEP:NRC:860I, NUDOCS 8405220199
Download: ML17320B063 (17)

Text

REGULATOR'l '4FORHATION DISTRIBUTION S,EM (BIDS)

ACCESSION NBR: 8<i 05220199 DOC. DATF: 84/05/17 NOTARI'C'ED; NO DOCKET ¹ FACIL:50-316 Donald BYNAME C ~ Cook Nuclear Power Planti Unit 2i Indiana 8 05000316 AUTH AUTHOR AFFILIATION ALEXICH<M.P. Indiana L Michigan Electric Co.

RECIP ~ NAME RECIPIENT AFFILIATION DENTONgH.Ro Office of Nuclear Reactor R'egulation~ Director

SUBJECT:

Forwards responses to questions raised by ANL at 840329 DISTRI.BUTION CODE+ A001S TITLE: OR COPIES RECK'IVEDeLTR Submittal: General Distribution

(,',~~+

meeting in support of Cycle 5 reload application.

KNCL l SIZEed K NOTES RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL NRR ORB1 BC 01 7 7 INTERNAL; ELD/HDS3 1 0 NRR/DE/MTEO NRR/DL DIR 1 1 NRR/DL/DRAB

~ I B 1 1 NRR/DSI/RA'B 04 1 1 RGN3 EXTERNAL: ACRS 09 6 6 LPDR 03 NRC PDR 02 1 NSIC 05 NTIS 1 1 L

TOTAL NUMBER OF COPIES REQUIRED: LTTR 25 ENCL 23

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INDIANA 8 MICHIGAN ELECTRIC COlttIPANY P.O. BOX 16631 COLUMBUS, OHIO 43216 May 17, 1984 AEP:NRC:0860I Donald C. Cook Nuclear Plant Unit No. 2 Docket No. 50-316 License No. DPR-74 Cycle 5 Reload Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555

Dear Mr. Denton:

We are t;ransmitting Attachments 1, 2, 3, 4 and 5 in response to a verbal question raised by your consultant, Argonne National Laborat;ory, during a meeting among the NRC st;aff, Argonne National Laboratory, Exxon Nuclear Company, and American Electric Power Service Corporation. The meeting was held on March 29, 1984 at your facility. This response is submitted in support of the Donald C. Cook Unit II Cycle 5 reload application.

This document has been prepared following corpor ate prooedures which incorporate a reasonable set of controls to ensure its accuracy and completeness prior to signature by the undersigned.

Very truly yours, ls4 M.P. Alexkah Ill I Vice President bus cc: John E. Dolan W.G. Smith, Jr. Bridgman R.C. Callen G. Charnoff E.R. Swanson, NRC Resident Inspector - Bridgman 8405220i99 840517 PDR ADOCK 050003th P . . . PDR

L I

Attachment 1 Question: How is the inadvertent boron dilution at shutdown while on RHR transient treated, and why is enough time to anticipate the consequences available2 Response: On July 14, 1980 a letter from F. Noon of the Westinghouse Electric Corporation to the Donald C. Cook Nuclear Plant, Plant Manager was received. The identifier for this letter is AEP-80-71. Zt is identical in content to Attachment 1 of the July 8, 1980 letter from T.M. Anderson of the Westinghouse Electric Corporation to Victor Stello of the NRC. The identifier of Mr. Anderson's letter is NS-TMA-2273. AEP-80-71 is included as Attachment 2.

The Donald C. Cook Nuclear Plant's response to the inadvertent boron dilution at shutdown while on RHR transient is based on AEP-80-71. When one of the Donald C. Cook units is in modes 4, 5 or 6 on RHR, the boron concentration is maintained so that the plant is in the region of "acceptable operation without bank withdrawal" of Figure A-1 of Appendix A to AEP-80-71. This is accomplished by increasing the required boron concentration required by the shutdown margin calculation near the beginning of cycle. The boron concentration required for N-1 rods, no xenon, Unit 2, Cycle 5 is displayed in Attachment 3. Zt is figure 4.5 of D C Coop ~U~t P ggt~Te ~gg~~t~Bggk. At boron concentr ations higher than 640 ppm, the boron concentration required for shutdown is increased above that required for Keff = 0.984. The 68 0 F curve, which is developed for use below 350 F, is calculated by the method described in Attachment 4.

The dilution rate is assumed to be 225 gpm, the value used for the Unit 1 dilution during refueling transient. See Section 14.1.5 of the FSAR. The calculation is done in a conservative manner so as to maximize the boron concentration and hence the time required to dilute to critical. lt is also conservative in that typically all rods are inserted in modes 4, 5 or 6 where as the Keff in Attachment 3 is calculated on the assumption that the most reactive rod is sticking out. This results in approximately 1$ of additional reactivity to dilute out prior to criticality which is not included in the calculation. Furthermore, the calculation is conservative in that a 100 ppm allowance is added to the shutdown margin curve. This 100 ppm must also be diluted prior to achieving critical.'t BOL (C approximately 1600 ppm) CZP, half loop when the plant is most vulnerable, 100 ppm amounts to approximately 1.2$ of additional reactivity.

A'ttachment 1 0 Page two The operator has the information available which was assumed in AEP-80-71. These are:

1. Source Range Neutron Flux with,

a. High Flux at Shutdown Alarm set at half a decade above background.

b. Use of the audible count rate indication to distinguish significant changes in flux, i..e., a doubling of the count rate.

c. Periodic, i.e., frequent surveillance of the Source Range meters performed by the operator.

2. Status indication of the Chemical and Volume Control System and Reactor Makeup Water System with,

a. Indication of boric acid and clean makeup flow rate,

b. CVCS valve position status lights, and

c. Reactor Makeup Water Pump "running" status light.

Procedural guidance for respond1ng to an inadvertent boron dilution incident is contained in the annunciator response for Source Range H1gh Flux at Shutdown and Emergency Boration procedures. These procedures deviate from the recommended Westinghouse response in that our preferred action for a reactivity increase is emergency boration. Use of the "refueling water sequence" is an alternate response. We believe this .is appropriate for several reasons:

1. 75 gpm of concentrated boric ac1d when mixed with 225 gpm of water has a boric acid concentrat1on greater than 2000 ppm.

2. In modes 5 and 6 the "refueling water sequence" may not be available as a boration path.

3. Our operators have repetitively and traditionally been tra1ned to emergency borate for any unexplained or uncontrolled reactivity increase.

To reduce the probability of this transient occurring, certain plant makeup water (PMW) valves are tagged shut prior to dra1ning the primary system to half loop. The valves 1n question supply the boric acid blender, 2-PW-263, the chemical mixing tank, 2-PW-256, and the PMW flush to the emergency boration line, 2-PW-265. These tags are lifted as part of the valve lineup for fill1ng and vent1ng the primary system. Attachment 5 1s a copy of 2-OHP 4021.002.005, "Draining the Reactor Coolant System".

Page three AEP-80<<71 indicates that operating the plant in the region of "acceptable operation without bank withdrawal" on Figure A-1 ensures that "the plant operator has fifteen minutes from the initiation of the dilution event to terminate the event before a return to critical occurs". As indicated above, we, have applied

'Figure A-1 with significant conservatism. Therefore, the transient will require 15 minutes or longer to reach criticality in the absence of operator intervention.

ATTACHMENT 2

'"DIDYM' '!I gag';(

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Westinghouse Water Reactor 00HAID t'- coop Electric Corporation Oivisions p;g;tt NsS- QI (c

~'(rs" re a~zrs... ywzma!5225 I r.

/~6 JU1y 9, 1980 AEP m<I Mr. 0. V. Shaller, Plant Manager O. C. Cook Nuclear Plan-Indiana and Michigan Power Company

"~CEtVZO P. O. 8ox 458 JULI 8 tgso Bridgman, Michigan 49106 Techrricat pept Oear Mr. Shal 1 er:

American E1ectric Power System

0. C. Cook Units 1 and 2 TNAOVERTENT 8GRGN OILUTION AT SHUTOOWN WHILE CN RHR On June 27, 1980, you were notified of cer.ain Westinghouse concerns and recommended ac:ions regarding the potential for an inadvertent boron diluticn event at cold or hot shutdown conditions while on the Residual Heat Removal System. This notificaticn was in accord with Westinghouse determination that these concerns constitr;te an Un-reviewed Safety question under 10CFR Part 50.59. The NRC Office of Inspection and Enforcement was also notified on June 27, 1980 that these concerns have generic applicability to Westinghouse-supplied nuclear power plants. Further clarification was made to the NRC Office of Inspection and Enforcement on June 30, 1980 that Westinghouse concerns are not applicable while the plant is greater han 5~ shutdown.

This letter is intended to formally document these concerns and to prov:de addi t onal relevant information. This letter also modifies the earlier recommended ac- ons oy a more detailed specification of applicaole plant operating conditions.

Inadver.ent boron dilution at shutdown has been generally regarded as an event which can be identified and terminated "y operator acticn.

prior to a return to cri.ical. Autcmatic protection has not been a standard feature for Westinghouse plants. Westinghouse has recently been conducting a general investigation of this potential event relat',ve to the licensin'g requirements imposed cn newe. plants not yet in operation. Tnis investigation is nct yet complete. However, it has been determined that under certain shutdown conditions and with certain ass"med dilut on rates, adequate ".'me for coeratcr action to prevent a return to critical may not be available.

~ ~

July 9, 1980 Page 2 The current westinghouse evaluations are based on plant conditions as noted below:

1. The Reac-or Coolant Svstam effec=ive volume is limi o he vessel and the active acrticns or the hot and cold leos <<hen on i.a. stem+ enera ar v ~

m 1 ~

Z. The plant is boratad o a shutdown margin gr a er than or equal ta I ak/k.

3. Uniform mixing o clean and baratad RCS water is not assumed, i.e., mixing cf:,".e clean, injec ed water and the arfacted loca is assumed but instantaneous, uni orm mixing wi h the vessel, hot legs, and cold leg volumes u"stream of the charging lines is not assumed. Tnus a "dilution front" moves hrough the cold legs, downc"mer, and lower plenum to he core volume as a single volume front. This results in subsequent decreases in shutdown margin due to dilution fronts moving thraugh the active care region with a, time constant equal ta the loop transit time <<hen an RMR (five to seven minutes).

If a return to cri ical occurs as a result of an inadvertent dilution, the following potential concerns have be n identiried:

1. A rapid, uncontrolled power excursion into the low and intermediate power ranges occurs, resulting in a power/flow mismatch due a the low flow (approximately 1 - 2 of nominal) provided by the RHR clumps.

z. The'potential exists ror significant system averpressurizatian.

Pressure increases above the RHR cut of, head (approximately 500 psig) further accentuate the ef,ec:s of a power/flow mi'smatch when all RCS (RMR) flow is lost. An investigation of the adequacy of existing cold ever"ressuri at cn protec 'on systems is necessary in order ta assess the full impact oi this potential orablem.

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3. The 'catential exists for limited f el damage. Tnis is not c r r ently a significant concern.  ? rel iminary evai uati on 'indicates hat the potential or exceecing OHB limi>>s is law due ta the cold initial ooera.ing conditions. iurther investigation of this "raolem is uncerway.

The recamme..ced ;ntar.'m ac=.'ors :" "."event ar mitcata an inadver ant "aran d t':cn at shu-"cwn c nc';:i-ns =-",e detailed in Acpencix A.

nc =cc'<ed c"ntral raas are r equi rec, as spec ried in ; .'c re A-l, ne

July 9, 1980 Page. 3 plant operator has fif een minutes from the intiation of dilution event it to terminate the event oefore a return to critical oc"urs. is 'he Westinghouse cosition that a iftaen minute time interval from the initiation of the diRution to the time shutdown margin is lost is suf-ficient time for operator ac.ion..'f cocked control rods are reouired, the source ran e reac:"r tria QroviCes "osltsve 1nascat-on';or >mmeolata operator act;on to terminate ai utlon.

t is expected that the operator has available the following information for determination that a dilution event, is in progress'.

Source Range Neutron Flux with,

a. High Flux. at Shutdown Alarm set, at half a dec de above background.

b. Use of the audible count rata indication to distinguish significant changes in flux i.a., a doubling of the count rate.

c. Periodic, i. e., freouent surveillance of the Source Range meters performed by .he operator.

2. Status indication of the Chemical and Volume Can rol System and Reactor Makeup Mater System ~ith,

a. indication of boric acid and blenced (total) flow ra a, or

b. indication of boric acid and clean makeup flow rate,

c. CVCS valve position status lights, and

d. Reactor i4iakeup Mater P mo "". unning" status light.

The operator action necessary upon determinat'on that a dilution e'ient .

is in progress (by High Flux at Shutdown Alarm, Source Range Reac or Trip, "P-6 Avai lanle'naicztion, high indica:ad or audible count rates, or make uo flow deviation alarms) is:

l. ammed-'ately "cen:"e c.".argirg/Si pump sue= on valves from the RMS7 (that open on receipt "I an "5" s;,"ra i ). (For 312 pl ants t"esa -"~ IrV-'=-~ 0 =or 412 piarts these are LCV-112-9, =.)

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eg ~ g July 9, 1980 Page 4

2. Immediately clo e the charging/SI pump suction valves from the VCT (that close on receipt of'n'S" signal). (For 312 plants these are LCV-11S-C, E. For 412 plants these are LCV-112-8, C.)

3. For two-loop plants, immediately open the charging suction valves from the RWST. (For 212 plants these are LCV-113-8 and LCV-112"C.)

Also immediately close the charging suc-ion valves rom the VCT.

(For 212 plants these are LCV-113-A and LCV-112-B.)

Through the use of Appendix A ana the above noted operator action requirements, Westinghouse is at.empting to minimize the operational burden placed on the plant to prevent or mitigate an inadvertent dilu-tion event while mqintaining adequate safety margin. Our investigation of this event is continuing. A detailed analytical model of the system response o a dilution event at shutdown conditions is being developed and the potential for sys em overpressurization and fuel failure will subsequently be assessed, The Westinghouse investigation is expected to be completed by September 15, 1980. We will keep you informed as to the results of our efforts.

Very truly yours, Eastern Region WNI Support

'I SR4/B819/20 cc: R. W. Jurgensen J. E. Owyer W.

APP~HOIX A Figuro A-l, attached, provides -.he shut"cwn margin r quirem nw s a =unc:ion of Qeactor C"olant System boron c"ncentrat;cn ard maximum possible dilution flow rate. Prior to use o= this inure e Giant mus: determine .he maximum dilut Gn rlow rat4 of all charging pumps not rencaroa inooerable onc '.he :lant is placed on ~uq. 7o cover all modes, it should

'ssum d that the flew r'te is based on

" ng de'Ilcas n "'le system,'ol l cas, pump runout unless there are f'.cw I 1 p p-ing resistances, e c.).,lne Reactor Nakeup 'Qatar pump capacity may be limi ing in the determination of the maximum poss ibie dilution f',cw ra=a.

Flgur A-1 notes ar4as or accept4ble operation of thro e dif-,ar4nt -ilution rlcw rates as a function of RCS boron cconcactration and boratad shut"own mar,in (< --).

For a given dilution flow rate, i-'he RCS boron conc ntration and shutdown margin result in a point plac& to:he lert of the rlcw rate line, no contml rod bank wi".hdrawal is neca4ssarI. !f the r4sults place:he plant to the right the line, then either the snut"cwn margin must be incr4aSad such that the plant is moded to ".he a. ea 3 ac 49 4bie pera ion, Gt I, "k/k in control r ods withdrawn to crovide adcitionai shutdown mar".in. The =ripoing cr withdrawn rocs provides posit ve ope. a:-r lnolcatlon that a dilution event is;n progress and additional time =or operator ". rminat cn o= the event. In all cases, a shut"own margin of 5">> ak/k (< - ) < pig5) is considero> su-.=icient for contin-ued operation wf hout a requireAient =o-contrql rod bank withdr wal.

Figuro A-1 is based on bes- stimat calculations -or the "all rcds in" configu-ration. It is reccamended t",.at the 'Pest-ingnouse Nuclear pesign Repol ol Jour plant be used as a rererence in determining .he RCS borcn conc ntr tion wl tn le appropriat censer Iatism to e used in -he;igur4. ~.".e '<<estingnousa '(ucl ear Fuel pivision is available to provide ssis=nc in .;.e ti;.g -.e c"rstr in:s imcosad ."y the Figure A-1 requirements.

Ose of Figure A-1 fs applicable any "i-e tnere .'s beret on/dilution pability

r -~e normal boric acid'blending sys=~i. Tne abo'Ia procedure

'= mboration and/or mak4up during cold =nd hct shu="'c<<n is per-,c...,ed ut.l i-ing is not r4qurr4d wa 4r fry the 3 AS7. i ni s r4qui r es =.".at =.'"e norma 1 "" 1 uti on/ c ration .:ath i s Sclatad from .he Chargina'pa:h. Twc meanS Or 1OCk"ut tc iSOla a the C:la ging path are available:

L."ck out Reac:or .'<akeup via ar '"ciy 7115 is ac PiQl l shed y 'Ia ve A ~

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Lan&, nd va.ve =-'==;;l. -1 c,'.

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l.ocz out valves ".e-~e n ".".e d'or'c acid blencer nd -4e VC7.

7hese are;C'!-III3, C'I-IIQB, "339, 33="", and 8361 ".or 212 pIano;,=C'I-II4A, FC(-II".g, gage, 0<'I, and 8~3o;or 312 Planets; FC'l-IIIB,;C'/-IICB, 3'53, 8441, 8439 =or "12 plan~.

j 'q is reconmenda 7, i on pr c udes t e oc "r ence 0 i an inadver ~en ~ di I union ~ni e L

borax ng or ask-'ng up ~at r =rom i".e i'AST under -.geese conditions.

llW l(~E lu x lu lO Is INCII I x lo IIICIILu 46 1320 IILIIIFA.4 L3>LII cls ssaoauluia ~

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2 FIGURE 4.5 D. C. Cook Unit 2 Cycle 5 Boron Concentration for N-1 Rods Inserted No Xenon Keff = 0.984 PREPARED BY ISSUE DATE~~ >~><

1600 b EXPIRATION DATE ~4 APPROVED APPROVEO FOR USE IN ~'~

DEPT. 5Y 1400 1200 8

C4 C4 o 1000 800 0

O o 600 68 F (CZP) 350 F 400 450 F

• NOTE: Includes 100 ppm allowance for 5470F (HZP) 200 conservatism 1 EFPH = 1.797 x 10 GWD/MT 6 8 10 12 16 17.9 Cycle Exposure (GWD/MT)

Attachment 4

~hdmm~~3m>~Mmo Since the boron concentration required to maintain a shutdown margin of 1600 pcm varies with core lifetime, the fuel vendor supplies curves of required boron as a function of core life and moderator temperature. The assumption is made that the most reactive rod is stuck out of the core. Also, 100 ppm in boron concentration is added for conservatism.

The curves supplied by the fuel vendor do not take into account the boron dilution accident. Therefore, the curves are modified as specified in AEP-80-71, Attachment 2, before incorporating the curve in the Plant Technical Data Book. Figure A-1 in AEP-80-71 gives the required Keff, hence the shutdown margin for a given boron concentration. The following procedure is used to recalculate the required shutdown boron.

Step 1- Interpolate Figure A-1 in Attachment 2 for dilution flow r ate of 225 GPM for "all banks in" case.

Note: maximum dilution rate possible is 225 GPM.

Step 2- Obtain boron concentration SB1 from the interpolated line (Step 1) for a Keff of 0.984.

Note: Keff of 0.984 corresponds to a shutdown margin of 1600 pcm.

Step 3- From the vendor supplied shutdown boron curve for moderator temp of 68 F find the burnup (B1MWD/T) corresponding to S 1.

Correction to the shutdown boron concentration is nolf necessary for concentrations less than SB1.

Step 4- Obtain the shutdown boron SB2 / for 0 MWD/T from the vendor supplied, curve for moderator temperature of 68 0 F.

Step 5- If SB2> /

SB1'hen SB2/ needs correction.

Step 6- Obtain Keff2 corresponding to a boron concentration / from, SB2 Figure A-1 and calculate dp'ef4 - 0'f8't Kefh.

/

Step 7- Increase dP by an arbitrary factor of 1.4 Ap = s9 xdp Note: A factor of 1.4 is conservative for the iterative solution required.

Page two Step 8 - Obtain the required shutdown boron concentration where 88/SC is the boron worth. To conservatively calculate SB>, the boron worth is chosen to be lowest value in the boron concentration and temperature range for which SB> is being calculated.

Step 9 - Draw a straight line between point (SB , 0 MWD/T) and point (SB1, B1 MWD/T). For burnups higher tkan B1 MWD/T, the line specified in the vendor supplied shutdown boron curve is applicable.

5'8a Sea S8L M%ID/7 B1 Step 10 Verify that the straight line approximation is conservative.