ML18219E126

Response to Letter of 3/14/1975, Furnishing Information Re Boron Precipitation Following Postulated LOCA & Advising, Investigating Environmental Effects

ML18219E126
Person / Time
Site:	Cook
Issue date:	04/14/1975
From:	Tillinghast J Indiana Michigan Power Co, (Formerly Indiana & Michigan Power Co)
To:	Kniel K Office of Nuclear Reactor Regulation
References
Download: ML18219E126 (33)

Text

'I J IO.'GA'PART 5r}DOC."ET fi,1ATERIAL CONTROL NQ FlLE':ROiyi Indiana&Michigan Pwr c<Dam York, NY~~J Tillin hast DATE'OF DOC 4-1'4-75 DATE REC'D 4-18-75 TM!X APT'QTf<'ER TO:-Mr Kniel CLASS UNC LASS PROP.INFO ORIG one signed.INP.UT CC OTHER NO CYS REC'D ii i'iii'SENT LOCAL PDR DOCKET NO:.DESCR IP flOii!: Ltr re our 3-14-75 ltr':...trans tie'.following:

PLANT NAI<<E cook 1&2 ENCLOSURES:

Responses to Qu'estions.

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INDIANA II MICHIGAN POWER COMPANY P.O.BOX 18 BOWLING GREEN STATION NEW YORK, N.Y.10004 April 14)1975 Docket No.50-315 and 50-316 CPPR No.61, DPR No.58 pock,'g Ep~gcgRC],qgt5 Mr.Karl Kniel, Chief Pressurized Mater Reactors Branch No.2 Directorate of Licensing U.S.Nuclear Regulatory Commissa!5n Nashington, D.C.20555

Dear Mr.Kniel:

4Ip~/Pgg.p In response to your letter dated March 14, 1975, the system capabilities and operating procedures with regard to boron precipitation following a postulated loss-of-coolant accident (LOCA)have been evaluated for the Donald C-Cook Nuclear Plant, Units 1 and 2.The results of this evaluation are discussed below.The operating.procedures for the Donald C.Cook Nuclear Plant require switchover of the emergency core cooling system (ECCS)from Reactor Coolant System cold leg to hot leg injection 21+hours after the accident.This procedure will preclude the possibility of exceeding boron solubility limits as is shown in the attached analysis.This analysis was also transmitted to Mr.T.M.Novak of the NRC staff in a letter from C.L.Caso of the Nestinghouse Electric Corporation designated, in CLC-NS-409 and, dated April 1, 1975.Also enclosed is a copy of the Donald C.Cook Nuclear Plant operating procedure 0HP 4022.008.002 titled"Initiation of ECC Recirculation Phase" which is the operating procedure calling for switchover from cold leg to hot leg injection.

lIItith regard to system capability, redundancy in equipment is provided.in both the high head and low head systems for hot leg recirculation.

Each safety injection pump and low head (RHR)pump share a header which injects into two cold, or two hot legs.The switch-over from cold to hot leg injection is accomplished.

by

~'~~1 Wt a'I 1 e, WI ,.~V~%W I r r~.I~WW~~1~I tW~~~1 1 r w,>>~W~, Ij I~1 Jl w 4 lf'*~A~1 ht~I~'~~1 gtt W'~I'p'ji IW 1~1~1 W'V 1 Mr-Karl Kniel April 14, 1975 closing the cold leg motor operated valve, and opening the hot leg motor operated valve.Thus with the worst single failure at least one high head and one low head pump are available for hot leg recirculation.

This system is described in the Donald, C.Cook Nuclear Plant Final Safety Analysis Report, Section 6 and Appendix I.There is a question on the environmental effects on the motor drives for the valves which are'sed to transfer from cold to hot leg injection which we are in the process of resolving.

We are currently investigating this and will notify the Commission of our findings as soon as our investigation is completed.

Very truly yours, J i ghast Vice President JT:ma cc: Gerald Charnoff, Esq.Richard Walsh, Esq.Robert J.Vollen, Esq.Robert C.Callen, Esq.Peter W.Steketee, Esq.R.S.Hunter R.W.Jurgensen-Bridgman 0'h If~~h~r<'h~c h'Lh'

, ATTACHMENT TO REM-62811!Yethouse El.ctric Corporation Povser Systems P VS Systems ONtstatt Box355 Pittsburt,hPernsyttrerz 15230 April 1, 1975 CLC-NS-309 t Hr.T.H.Novak Chief, Reactor Systems Branch U.S.Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Haryland, 20014,

Dear Hr.'ovak:

As we have discussed, enclosed is a discussion of some phenomena concerning the long tern build up of boric acid in the core region following a postulated LOCA.This discussion is a generic document covering l!estingttouse 2, 3 and 4 loop plants.The discussion re-emphasizes the adequacy of'he current>lestinghouse ECCS desion concept in addressing long term core coolina neer!c.Yery truly yours, C.L.Caso, Hanag r Safeguards Engineering

'LC:jmb Enclosure

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LO;]r, TEP;..CORE COOi I>>C BORG!~CO>>SInLvavInwS It<TRODUCTIGh Immediately after a hypothetical loss of coolant accident, OCA, the safety I injection system is supplied with borated water from the Refueling'l1ater Storage Tank (R!"ST)and delivers to ihe reactor coolant system cold legs.When the low level signal from the RilST occurs, at approximately 20 minutes after the accident, the safety injection system is realigned to draw water from the containment sump.The safety injection system delivers to the cold I legs of the reac or coolant system until 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the acc'.dent.

This is commonly referred to as sump recirculation phase.At 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> the sa et.injection system is realigned to deliver to the RCS hot legs.This is cors-only referred to as the hot-leg recirculation phase.J.COLD LEG BREA~i'Basic'Phenomena Calculations were performed to determine the concentration of boric acid in t.ie core region at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, following a cold leg brea.'.For this analysis, both the core water volume and the water volu:-.e in the upper plenum, but below the lower lip of the hot leg nozzle were consider d.~~Figure 1 presents solubility data for boric acid.Table I summariz s the results for typical 2, 3 and 4 loop plants.The calculations w re r done assuming license core power and AHS finite decay heat.It can b seen that th se conservative calculations are close to'h solubility 1:rats for boric acid of 212'F.S veral approximati"ns in these calculations can be identified.

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~~'A.Basic Phenomena water,.Table I also shows the effect on the-weight percent boric acid at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> assuming that the injected water is subcooled by 80 Bt.u/ibm (H=116 Btu/ibm).As another conservatism, the volatility of boric aci 1 d into steam is ignored.Although the distribution coefficient of boric acid between the vapor and liquid.phases is'small, the integrated effect would be appreciable, due to the large mass of vapor generated.

For example, if it is conservatively assumed that the boric acid concentration is uniform at 10';l of the initial 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and a distribution coefficient, 0, of 0.005 is used, it can be calculated that 1500 lb of boric acid..would be volatilized 1 in the typical 4 loop case.This, in turn,"would lead to!a reduction of the boric acid in.the core from 27;2;l to 25.1ll at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.hore realistic calcu-lations including temperature dep ndent D-values and time history core boric acid concentrations would.be expected to increase this margin.This assumption of not including'he volans~lity, tends to maximize the boric.acid build up rate.Ano her conservatism in these calculations is based on the.specific gravity of bo.ic acid solutions.

As tne concentra'ion of H3803-increases t>>e sp ci i" glavity increases.

Since the solution in the lower plenum is more dilu e than that.in the core,'the heavier core solution would tend to migrate to the lower plenum.This would effectively increase the water volume available for the concentration of H3B03.Table I shows the effect of maximizing-the steam boiloff rate (and consequently the boron build up rate)by assuming that the injected ECC water is at saturation temperature.

This assumption ignores the heat capacity of the subcooled injection A'ore realistic assumption to be considered is to include the effects of voids in the core region.These voids redu'ce the mass of water in the core region, even though the total amount of water above the lower core plate remains essentially the same in such a way that the elevation head in the core region equals the elevation head in the downcomer.

If the mas's in the core only is considered a smaller mass of boric acid would be n cessary to bring this mass o water-to ihe solubility limit.In order to assess som effects of the above considerations, it was decided to perform calculations including the voids in the core and the specific gravity.The results are discussed in the following section.

TABLE I 2 Loop 3 Loop.:.'4 Loop t<SSS Porkier (h".It)l1 1650 2785'425 Total Sump Inventory (ibm)2.5 x 10 6 3.3 x 10 6 31 6x10 6 T.nitial ppm Boron in System 2000 2000 I'2000 I Effective~-Vessel Volume (ft)590 854 1154 Height Percent Boric Acid in~e~';esse: at<>concentrat>on of boron than that sn the core, under isothermal conditions, the fluid in tne core would migrate to the lower plenum.Since the concentration build up tal;es place in the c re, there will be an increase in the density of the solution.Since the water in the lc:rer lenum is t a 1 er However, if it is assumed that the lower plenum is at a lower tempera-I ture than the core, it becomes necessary to establish the point at which I temperature effects on density are balanced by the concentration effects.I For example, if it is assumed that the core is at 212'nd the lo<<!er I plenum is at.130', the difference in specific gravity is 0.9581-0.9860=0.0279.From Figure 2, it can be seen that a difference in concentration of 8.5~~will balance that effect.The boric acid concentration in the'ower plenum is at a'aximum of 1.144'<it/.Boric Acid initially if Boron of 2000 ppm concentration (equal to that used in the RMST)is assumed to exist pt thrp initialization nf the boric arid concentration ralcul a.ion This<<!ould require approximately an upperbound of 9.6 hid~Boric Acid concentration in the core to initiate migration to the lower plenum.In this calculation, the aT was conservatively maximized.

The mixture flowing to the lower plenum>>ill not precipitate boron since concentra-tion g 130 F=11.5/>9.6i..Thus mixing starts before precipitat'ion threshold.

i~Hence, in the worst case, when the concentration in the core exceeds the concentration in the lower plenum by 8.5'.l, down<<!ard migration would b expected.The Davis curves sho<<!that at low pressures the critical l:33 steam velocity for carry-over is about 10 ft/sec.After about 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> the average steam velocities in the core are less than 10 ft/sec and therefore the migration of fluid to the lower plenum is not prevented Furthermore, a continuous supply of water to the core is insured due to.the available driving force of a full downcomer.

One of the effects of this migration<<!ould be to increase the temperature of the lo<<!er

.plenum.A natura')circulation pattern Mould be established vihich will result in subsequent dilution of boric acid in the lower plenum.In sugary, vihen the volume of the lower plenum is included in the inventory available for storage of the concentrated boron solution, th results shoe.n in Table 2 are obtained.These results do not consider boron-volatility vihich viill redistribute boron in all]he water mass above the core thus further reducing t)>e boron concentration.

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"'TABLE 2 p arameters used to Calculate Boric Acid Concentration in Vessel at 24 Hours NSSS Power (tb]t)Total Inventory ln Sump.1650 2.5 x 10 ibm 6 2785 3.3 x 10 ibm 6 3425 3.6 x 10 ibm Initial ppm B in System 2000'000 2000 Effective*

Vessel Volume 819.0 ft 1284.0 ft 1637.7 ft Containment D~craevn (ac 4mb~~e&vl~\$Pv 0<</20.0 20.0 20.0 lft.S Boric Acid.21.7 22.0 20.5-"~Effective Vessel Volume includes lower plenum volume and core volume with a void fraction of 305 in the core.-6 I I~~The above analyses were perform d assuming c=0,3 in the core and mlxlng with the lever plenum volume.'void fraction in the core of 30,'l was used as it corresponds to the void fraction in the core at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.The boric acid concentration in the core at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> depends on the void fraction at that time.Varying the void fraction in the core during the transient has little effect on the calculation of the boric acid concentra-tion at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.The reduction of void fraction in the core caused by a reduction in decay heat results in an increase of water mass in the core.Tflis additional water mass dilutes boron since it is supplied by sump, I downcomer, and lower plenum liquid which has a lower boric acid concentra-tion.Clearly, these results show considerable margin to the solubility limits at 212'F.

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II.HOT LEG BREAK iE.For the large break LOCA in the.RCS hot leg, the safe+y injection flo~delivered to the RCS cold legs during the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> will flow through the cove and spill to the containment sumo via the 1 broken hot leg.This flow will facilitate sub-cooling,'of the core at the time when decay heat energy addition can be matched by th safety injection water.The time at which the core becomes sub-cooled depends on safety injection flow vates, the containment pressure transient, core stored and metal heat energy dissipation, and the decay heat energy.Mter the safety injection system is realigned at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to deliver to the RCS hot legs, the cold safety in'ection flow enters the core and.will absorb decay heat energy.*The safety injection flow rates into the core needed to keep the cove below saturated conditions ave given in Table 3.The;"1 es presented are based on a the)modyncmic eoul-4~Ma'Iu'0 cuscu eat co<~at I's~/sl a anQ an i&ay, neat oxchan" r ouŽ!" temperature of 130 F.The amount of water needed to keep the core belo I saturated conditions depends on the decay h at eneroy addition, containment pressure, and the temperature of the safe.y injection water drawn from the sump and passed through the Residual Heat Removal (RHR)heat exchangers.

• Decay heat energy addition at 24 nours for the 2, 3, and 4 loop plan+s (is given in Table 2.'

For a'hot leg break, there would be no excessive boric acid concentra-tion buildup in the core for the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> due to the direct flow I path going from the cold leg inject on point, directly through the~1 core, and oui the break.After switchover to hot leg recirculation 1 at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, there would be no si'gnificn-t buildup of, boric acid in the core since the hot leg injection will condense or prevent boiloff froii.core.'Jhether boiloff will re-occur 9 24Ihours depends, on the Safety Injection System-flow delivery capability of each specific plant.For a plant d sig>>where the safety injection flow rate at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is not adequate to keep the core below saturated conditions, it is necessary to determine the time at which the decay heat energy addition will decrease to a level that matches safety injection capabHities.

Table 4 gives the decay heat energy addition and safety injection flo::irate neecad to keep the core below satu.ated conditions at various times.Then it is necessary to determine the increase of boric acid coricentration in the core due to decay heat mass boiloff after 2.I ou-.s.However, it should be noted that because of the reduction in Decay heat with time and the absorption of the decay heat by the sensible heat of the injected water negligible or no boil-off will result in this phase.After the switchover to hot leg recirculation, flow patterns are established iri the core, primarily to the density differences between the injected:;ater and the heated water leaving the core.Calculations of these circulation flows in the core are presently underway, arid~will be reported.in th near future.

TABLE 3 2 Loop 3 Loop 4 Loop Core Power (Hilt)1650 2786 3425 Safety Injection Entha3py{Btu/ibm)98 Sensible Heat (hs<-h'.n.)(Btu/lb'>)

82 82 Decay Heat Energy Addition at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (Btu/sec)8600 14520 17850 Safety Injection Cl~e.eve~4~vs~~A~rt~~VI~~V V4~14I 44,Q keep core t>low satu-.ated conditions at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (lbn/sec)106 178 218 10 86400 sec (24 hrs)TABLE 4 10 sec 5 2xl0 sec 5 fi t 4xl0 sec'xl0 sec 5,.5 Decay Heat Energy Addition*(Qtu/sec)17850 17100 13440 10270 8530 l Safety?njection Floe!rate**

needed to I;eep th core bel0Ãsatul ated conditions (lb/sec)218 209 164 125 104>Decay He>t Energy"Addition is based on a 3425 tlllt po<;er.To obtain Decay Heat Energy Addition for another po<!er level divide by 3425 I".lt and multiply by appropriate po;!er level in IPJt.~" SI Flowrate is based on Decay Heat Energy contairr:,'nt pressure and a SI.temperature for difterent conditions d',vide the Decay Addition at 3425 I;"ift, 14.7 psia of 130'F.To obtain SI flo.!rate Heat, Energy Addition by III.SI'tiALL AHD IHTFRiIEDIATE BREAKS s I For small breaks, an analysis similar to that performers for large b reaks was performed to determine the boric acid concentration in the core (0-242."".Thus for a 200 psia case, the marg',n be ween the cal-culated boric acid concentration and the solubility limit has actually increased.

12 For a small'break that completely depr'essurizes by'4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> the'nalysis of boric acid concentration approaches that of t: he large break analysis and the 200 psia case presented earlier is expected to be overly conservative.

Hot Le Recirculation l I I After hot le injection is initiated (9.24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />).a small breal', can offer a benefit:in terms of steam condensation.

For exan',pie, in a 4 loop plant,.at a pressure of 200 psia and a SI water temperature of 130 F only 66 ibm/sec of SI water is needed.to keep the core below I saturated conditions at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> instead of 218 ibm/sec at 14.7 psia.13 1 4 V>X("'S',)i>L'M'M~'~g",,>rgg~"~+,>g/cp q/)pg I l pry od" h'.g l I ,~26V::~iO..

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C...'"-C!2!ES 1.'..his p.ocedu e outlines the steps necessary to ter.in=te ihe':.e t:cn P:.ase'>Safe y Inject on and to.'..:;,;

iate the var ous r:.cdes of=:.';e"Recirculation f'hase" an" the"Res".'dual Spray" opera;:on.2.0 GTSCUSSi0'l 2.'.':he"R'circ~'.ation Pha=.e" is necessary!hen the;;~ater leve!in'.'he R'::ST r=aches the lou level a~arz point, Tpe p)lpp~ce Gf the rec.rcJla-.ion phas"-is to provide sufficie,"".

'.Iate;" to.'ie r-actor vessel to p"e~;ent-ny furi:her core d=vage and tc ri.aintain

-"he core in=-suhcool~d condit.on fcmlo:,.!i" the LCD,~".7er app.Gx'.l..ately 7.;"-nty i oJr (2-.'7 ho.!rs~he i e""."cu.a" on!s"'cned.ro:!i t:.=co l3'i'".""-c".o:i".::o'.e i 0:."" no.cg>necQon 6!o"'" SD a j"UKps s desired"Res;Idual Spray"."..ay b ir it;ated using cne o+'e Br'ui'ios~ltgh hath~I iuto""':.l.l bore~I ," a~ua)4.2.: Cold'n-'ec-'.on Rec.irc lation pe)4.2.1-1 Be..starting.he Cold'eg.'n'=-c'ion, ch>eck th-t the recirculat:on su.";,o level is adecu>;=-io-rovide the rec;:;red YPSH for 4, 2,l the RI R p JEps.{100 in;./e: 'I i:": o.co.:.r".: oan~~'lock the automatic Safe".y~n:e:>on"niti-tion signals at th Con".'rol Board.Ver;y t,".e!i)blocked by the OHo';,'I'.>g ind:cations on>,he Permissiv a.",d'int r;ock Annunciators:

-".2.1-3 a)'ressuriz r S: 8'locked=';.: 0.'I b)S eaaline Lso>ation SL Blocked L'G.'-.'>0:~.c)Pr ssurizer SI P rr>i>ssi~re P-ll moth L:".-:TS GA d J Lo"Lu!avg PerK)ss ive,-2~G~l Clos',"."'-d"'.".R O'J...p ih ischa>-e C"c="-'"or'c""=;ve i.: 3~4"~"-=~-'Sto~'"->"l"'HR Pu)-:o 4.2.1-o C'o<<--'!.-"'>"'-'R P>>>" Suction"~":v-i"3-"'2" 4.2,1-"" 1 7 Stop>..".eont.S p.a,'LZ~jo~=-'-.">>>>P-+=-r-)g o'er:--~-'-r-V~0~M>ls is+.~41 J ww>IV I'/alve>~0-22o, 4.2;Q Clo.th=SI Pump!mini-Flo,.

L'.ne~'solat-:on Valves Il!0-262 c i>'l0-263,~~G,er."r>>Rec',rcula-ing Su!".;p iso'":i"n'lva".~!>-306.

4,2,1" v Start tne'.s1 RHR Pu>.;o.-':.2,1-.1 Ore..: S Pu~p Suction fry"'>'" 8=Val ve'li0-.3."0.

!GCEuURE.GHP 4022.UOU bv'2 GE'3 CF 4 4.2.1-12 4.2.(-13 Sta.~the"il" Containment Spray Pump.C(use the';;o SI Pump Discharge Cross-Connect".alves I!'>0-270 and TttQ-275.4.2.1(-".'~r C!Gse th SI Pumo Suction l'G",l P>'S!Il'(0-26!.4 2,1 15 421(16 Gpe.s S(Pu.;:p Suc"ion Cross-1'ie

'".~charcir>g pu'suc i.i on Ja1 ve It~(0-361 E;Ii(.0-362,!.'hen ti>e R'.;".'o-Lo level alar.: point i (7 4.2.1-1U 211c l cached)stop ii(e'~PIR pulDp Close th,"5" RHR pump=-ction valve'l'0-310.Stop the"E" Ccnta rr..en-.spray:..".p.n"~II (>C!Ose the"!=" Con".ainmert spray p m(p suction va ve'.'.0"215.42,1 20 Gpen"" Rac rcula'"ir.g sue>:p isol=ticr, rn(C nh l Q ((4'4e'>MUD~4.2.1-21 4.2.!-22 crar.rk">wz+p,'nr>ef,.

Sonay<z!o 4 2,1(-23 Gpen (RHR.!"." Charging Pumi S>'c on lG-d 0 Clo=C:;"-I gi.c'a>..o uc'on>t or" 4!'jS!Pal ves.'!:0-910 ar."';."!0-91!, Sw-'t"hing';rc".'.

Colo L-g R'c'.rcul t'.~a to Hot Lcg..O=i-"(-.G..!~o'-.

5,1.1 C!ose the Cola Leg Injection>solation>('0 31 G"en Hot'g>n-'ect':

cr: 'solat on, LGJp (L((&M 3~~, (,3-VeriTy Hot'Ir('ec tiiof.'r>0":.>to Loops 1)-': on ri(vs,cuvvt v.".r-'<vcr, vvo.vu PAGE 4 OF 4 5.1.4, Close the Cole:=g In>ection Isolation ValYe I!6-"326.'.1.5 Open Hot Leg In-'.ection Isolation, Loops 2 8;3, Y"~ve."l".3-32o, 5.],5 s!eri)y Hot Leg'n'ection Flo;Y to Loops 2 5 3 on iFI-320 Fs:;i-32l To cl ic n the"E" RHR PU lp for Pesidual Spray OperatloA, CJIJ I h i I 03't d i r ectly to the core fr or;.the RHR pump 0 Pi.us Le t.'PBinated before lni tiat>rg I sl dual s i"ay.A i lo:.i ng flow i'ro.".)the pLivip c!irectly to the core,.to.he h'.5h head pUBps and to spl ay Bay I'esUl lA a I'UAOUt i io'~,'reater des gn fo".th RHF~.";,p.If on tot Leg Ill-ection,-'soia i0A Yc.lve I.-'.O"3!5.cl ose he..0'" Leg'.iiectl cn oa 2 J.so ic s,ion i'a!Ye..si"~l G.oo2a3 Open"E" RHR Hx to Upper S"~=-y Heaaer Il':"-3-0, Intermediate Break The analysis for intermediate breaks are ex ected to a roach that P PP of the 1arge break analysis but should be bounded by the, large and small break analysis because the-pressure transient is bounded.~8 0 A g 0~" Docket Nos.50-316 American Electric Power Service Corporation ATTN: Hr.John E.Dolan Executive Vice President 2 Broadway New York, New York 10004 Gentlemen:

Thank you for your letter dated January 21, 1975, which forwarded a report pursuant to 10 CFR 50.55(e)describing the safety implications of the welding doficiency that occurred at Donald C.Cook Nuclear Plant~which had been inadvertently omitted from your report dated October 23, 1974.Your report will be reviewed and evaluated.

Should we require additional info~tion concerning this matter, wo will contact ybu.Your cooperation concerning this matter is appreciatod.

Sincerely,-Qaisinrl1 eland hy,$.G.Davis John G.Davis Deputy Director for Field.Operations Office of Inspection and Enforcement t bcc: PDR LPDR NSIC mxaT JG les Region III Central Files odrlcd~FSEB r*0VRHAM0 W R@RRQQAC/,ilh 3/9'//75 C, S B , HD urg/75 DDFO JGDavis/75 Porm AEC-318 (Rev.9.33)hZCM 0240 4 U, 0 44VRRHMRNT PRINTIN4 OPRICRI!074 020 I00

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