ML19289G064

Responds to IE Bulletin 79-06B.Operating Procedures Have Been Reviewed to Provide That Automatic Actions of Engineered Safety Features Will Not Be Overridden

ML19289G064
Person / Time
Site:	Crane
Issue date:	04/20/1979
From:	ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY
To:	NRC COMMISSION (OCM)
References
NUDOCS 7906260041
Download: ML19289G064 (24)

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/ C-2 Power systems Tcl 203/628-1911 70' C' .Comcus: en Evewg inc TEex. 9 3097 w.nuar. cenne::.cm ceces 1CCO ProsyC' Hal RC30 Z3T POWER i hn: SYSTEMS f April 20, 1979 !g' M r / (' [ ' W r l v-1

Subject:

ISE Bulletin 79-CSB Question Response

Reference:

(A) C-E Letter, " dated 4/19/79

Enclosure:

(1) Res; case tc Ouestions 2, 6, and 11 of I&E Bulletin 79-C55, dated April 14, 1979 Dear Enclosure (1) is orovided for your information and use in accordance with the ccrmitrent of Feference (A). This infer acion package is as complete as cessible considering tne limited t1rc available for preparatica cnd may be used by (name of utility) as a basis fer your ".sconse to the NRC questions posed in I&E Bulletin 79-065 relating to the Ril-2 event. Con.bustion Ent;ineering plans to orovide, in the near future, additional informction on *.he referenced questions as.! ell as sete of the other questions presented in this culletin. Furthcr information will be cased on additional clarificaticn and understanding of the circunstances surrounding the ever.ts at T5I-2 and a continued review cf the applicability of the recogni cc arcas of concern to C-E NSSS designs. Ar.y feedback on the content of the enclosure as well as your independent assessment of the situation will assist C-E i.. providing the nost accurate and timely information possible. In addition, continued interfacing between our comanies will allcw C-E to best include ycur interests in cur discussions wiri the.'GC if and when we are called to attend another NRC meeting cn TMI-2 related matters. This information is provided under the tem.s and ccnditions of Contract The precise arrangement associated with the cost sharing and billing ill be the sucject of future correspencence. If you wish to discuss the answers provided as Enciosure (1), please do not hesitate t< contact me as soon as possible. 4g }2) Very truly yours, 7 906 2 60dV/ Q 64 % ?Mr

RESPONSE TO CUESTION d2 Both condensible and non-condensible void generation is possible within the RCS. Condensible or steam voids are produced when the system pressure is reduced to the saturation condition of the core cutlet temperature. This me:hanism has the potential for significant void generation and inhibiting core cooling. There are several scurces for non-condensible vcids. There is an insignificant amount of dissolved gas in the RCS ccolant during normal operation. (30-50cc H2/Kg H20, 400ft3 0 STP) Even witn a significant deoressurization, the cuantity of gas available frc-this source would have a negligible imoact on system natural circulation capability. Foilcwing a LOCA event, there is tne ocssibility of c?r.erating a significant ncn-ccncensible void consisting of nitrogen frc-ne SIS tanks and nycrogen from clad oxidation whicn has th'e cotential to significantly recuce or prevent natural circulation core ccoling. There are several indications cr nethods available to the olant operatcrs to deternine tne ore:ence of veids in tre RCS. A reliable indication of steam voids is a co cariscn of the systen saturation cressure as derived frcn the ccre outlet t n er m re witn the oressurizer pressure witn prc er accour.: fcr reasurerent errcrs and.CP coeraticr.. Indications of voics, both cc-dansi:le anc ncn-ccncensiale, are also obtainable from ficw derived infor stion. Increasing core /T, erratic steam generator d/o, erratic CCP notor current and RCP vi: ration monitoring instrunentation cecvice orcr:t indication of syste voids. With sys tem intagrity kno.,n an: 'Icas to and frcn the syster ?r.can, a measure of void nay De cotaines by cnarg* 2 krewn a. cunt Of ass into the RCS and monitcring the correspcccing cnange in pressurl:er level. To prevent void generation within the RCS, it is of paramount incertance to maintain syste Dressure above the saturation pressure associated with coolant temperatures. To facilitate coerations, the saturation curve should be orcminently displayed in the control roon and consideraticn will be given to providing an on-line nonitoring and alarm of minimun system sub-cooling. Ocerator actions and transients which result in depressurization will be reviewed with the enchasis on understanding resultant consecuences and the necessity for conductinc sucn operations in a controllable nanner. Plant coeraticns to be reviewed include pressurizer soraying, venting and de-c: -ing; overcooling of the RCS by over-feading of the steam generator ith the resultant less of pressurizer pressure and prosurizer.r,mntory control and HPSI pu o cut-off when normal pressurizer pressure control is not available. The presence of voids in the RCS is indicative cf a inss of pressure control and inventory situation. The initial coerator acticns are twofold. The first basic consideration is the capab4'ity to re-establish pressure centrol and increase overall system oressure. This will also tend to collapse stean voids and to linit the amount of non-condensible gases released frcm solution. Operator actions to be taken depend upcn whether or not system integrity can be maintained, b) T ),r, i .m s N M-9

' RESPONSE TO CUESTIC.1 d2 (Cent.) Inherent in the effort to restore pressure control is the check and isolation of paths that could be the cause of loss of primary system inventory. Pressure control is restored by fluid make up by the CVCS and by the pressurizer centrol system, if primary system inventory can be restored. If the pressurizer cannot be restored, pressure control for small break LCCA's is provided by the iiPSI puros while maintaining the forced circulation and heat transfer to the secondary system. Once basic pressure control has been re-establisned and the steam voids condensed, any non-condensible gases can be removed by appropriate venting and degassing procedures. Concurrently, the second basic censideration is directed towards maintaining er re-establisning the secondary heat sink. Central to returring the buik RCS fluid to : sub-cooled ccndition is the ability to maintain or re-establisn RC3 forced circulation and primary-to-secondary heat trans fer. Steam voids swept into and condensed in the steam generators facilitates the stacilization of 1000 concitions. Relative to core decay heat removal, ecuire ents, substantial forced circulation is proviced by the RCP's even ocerating in a cavitating mode. (Item 6.c provides guidelines for continued operation of RCP's). Concurrently, the third basic consideration is that there are multiple parameters available for use in determination of leak locations and the possibility of subsequent isolation. For example, status of the PORV's can be determined from an evaluation of tne following ir iicaticns : - PORV/ Safety Valve Discharge Temcerature - Quench Tank Level - Quench Tank Temperature - Pressurizer Pressure - Pressurizer Level Another example would be the assessment of the chargina/ letdown system through an evaluaticn of the foliowing parameters: - Volume Ccntrol Tank Level - Letdown Valve Position - Letdcwn Line Temperature - Charging Ficw - Charging Pump Instrumentation If the leak path is isolable, pressurizer inventory is restored by the CVCS charging system. Pressurizer heaters are used to restore system pressure and in conjunct in with pressurizer spray used to i control system pressure while isco temperatures are maintained in a subccoled :cncition witn the seccncary plant neat removal systems. If the SIS was activated, the guidance for securing the SIS is found in Question 6. 249 k) . RESPONSE TO OUEST10N 82 (Cont.) If the leak path is not isolable, actuation of the safety injection system (either manually or automatically) will provide additional fluid inventory makeuo and some measure of pressure control. The actual pressure raintained under these conditions will be a function i of SIS flcurate and the size of the break. Forced RCS circulation and heat transfer to the secondary system nust be maintained to reduce RCS tenceratures. Throttid na of the HPSI injection flow rate will decrease system pressure and T.ust be cerforred in an orderly and controlled fashion with corresponding reductions in plant temperatures. Note: Scre of the instru entaticn described in the previcus resocnses may not be qualified nor hase recundancy for these scecific accident carcitions. The oceraticnal cerscnnel will be instructed on the qualification level and on alternate instrumentation for accident conditicns.

4 RESPONSE TO QUESTION 6a: The operating procedures and training instructions have been reviewe ' to provide that auto atic actions of engineered safety features will not be overridden by operator action, unless the continued cperatien will result in unsafe plant conditions or until the plant is in a safe end stable con-dition. In some circumstances continued unattended oceration of engineered safety features may result in undesirable olant conditions. The circumstances which the cceratcr ust be alert to and the brais fcr taking Control in those circumstarces are descriced below. In general, it should be deter-mined by the operator that the function being performed by tne cc ponc..t or system, wnica is to be stopced or controlled bj tne c:.erator, is perfomed by alternate eans prior to taking over automatic actions at engineered safety fcaturer i There are t'.co basic types of engineered safet:. feature actuations; these that initiate active systems desigr.ec to -'it; gate an event and those tnat provice an isolation function and have a ::assive role following tne initial action. The primary active syste s are the safety injection, ccntainment spray and emerrency feec..ater system. The safety infecticr syste can safely remain in oceration for extenced periods t.nen acbated by a lcw cressure condition. however, should it remain in oceration.hile the reactcr coolant system is cooled below 250 0 there is a ;otential for overcressuri 'n tne reactor vessel if RCS rressure is tco high. Cuestion 5 (b) crc. ides infomat:cn cn tne basis for tem;. ating hign pressure safety injecticn flow. The contairnnt scray system actuated cn a high containment cressure signal can operate continuously. Hceever, Me consecuerte o# continued or lengthj operation may jeopardize the operatic, of ecuicrent wnicn would be desire-able if not necessary to minimize the effects of an event. The cnntinuat!" of spray with ooeration of reactor coolant pumos could make the coolant pump motors inocerable. The continued oceraticn of the containment spray system will introduce several hundred tnousand gallons of water into the containment with potential floocing of useful if not necessary equirrent. Early consid-eration should be given to termination of the containment sprays if ccntain-ment pressure has returned to nor al or below. The use and availability of emergency feed. vater is essential for all oper-ational events with the excection of a rajor loss of coolant accident, Feed would nomally be provided to both steam generators. Isolation of a c steam generator may be desireable if high activity is observed in steam releases. If isolation of a stram generator is desireable (e.g. for steam generator tube leak), it is necessary to stop feedwater to the gen-erator to prevent lifting of the safety valves and loss of feed suppiy. In the event of a steam line break the steam cenerators should not be fed until the cooldown transient has been ter-inated and reactor coolant temperature is above OOGcF cn the boron concentration is suf ficient to preclude criticality. d ,4V 32/ 2 I RESPONSE TO QUESTION 6a (cont.) f The principal engineered safety features signals which provide isolation functions are Containment isolation (CIAS) and mainsteam isolation (MSIS). The containment isciation system is discussed in Item 3 of 79-063. The mainsteam isolation signal is actuated by high containment pressure or low steam generator pressure will isolate the main condenser and allow tean venting to the atmosphere via relief valves or duma valves. To mininize radioac;ivity releases, it is desireable to utilize the main condenser through the use of the turbine bypass systen. The decision t7 take this action would be cased on the availability of secondary systems and offsite power. e 1 I {d8 32 6 m-----..-

6-RESPONSE TO CUESTION 6b: Operating procedures and training instructions have been reviewed to ensure that the HPI system, automatically or manually actuated, will remain in operation until the functions it is intended to perform (pressure centrol, core cooling, reactivity control, inventory control) are provided for by other systems. Item 6b of IE Eulletin No. 79-065 provides specific guidance cn the use of the HP! system for inventory and pressure control. We ccncur with tnis guidance anc have expanded it to include the functions of core cooling and reactivity control. Plant operatin: ;rccedu es elated to safeguard syste s are guided by the folicwing :011cy. Te;3rcless of the cause of system actuaticr, the c;crator dces not alter t e sjste ::ereticn ;r.til it is de cnstrated that other syste s and ecui: ent a-e crcvicing w functicrs th n the safeguard syne-4: inte-de to cerfor, Reactor coolant system para ete s must be v.itnin sce:ificnion, anc the creratcr ust dercrstrne contrci of the nsn-aafe;;i-c systems. Sa'e;sard.ystems, when nc longer recuired, are realigned fcr au*.cmated response. Operating ;roce ;res fer "e HPI syne-9 ave been reviewed and revised as necessary to re'le n th. Talic.,ing specifi: ;; cance. Guidance fcr each of the systems ain functions of pressure control, core cooling, reactivity control, and inver.ory control is provided. (pressure control) The FPI syste will re ain in 0:eraticn for 20 minutes and until all RCS hot and cola terperatures are at least 50 cegrees ::elcw tne saturation temperature for the existing RCS pressure. If 50 degrees of subcooling cannot be maintained after HPI cutoff, the HPI shall be reactivated. In providing the above, minimum Pressu e-Tem era ture coera ting res crictions related to RCS integrity take precedence and shall not be violated by HPI systen operation. Figure 1 is provided in the cperating procedures to facilitate the implementation of the above criterion. (core cooling) The HPI system will re ain in operation until the operator demonstrates that core ccoling is provided by the steam generators or the shutdown ccoling system. Forced or natural circulaticn cooling of the core, with the steam generators acting as the heat sink, is demonstrated by having Rt'S and secondary system te ceratures and pressures stable, within specification, functicning and controllaole. Forced circulation ccoling is not considered in effect unless reactor ccolant temceratures are essentially equal, are not fluctuating, and are either decreasing or not changing. Natural circulation cooling is not cons;dered in effect unless T -Tc = ;T is less than SC0F and g 24h 32)

7 RESPONSE TO CUESTION 6b (Cont.) T is stable or decreasing. There must be feed flow to the steam gen-eYators and-feed ficw out of the steam generators. s<,m (reactivity control) The HPI system will re ain in c:eration until the operator de nstrates that reacti/ity centro: is ;roviced by other syste s. Peactivity ccntr:1 is provided by atrer syste s if : Ore power is within s;e:ification and stable, cent-ci rc s 3 e fully inserted or th:..n.to_bt cperable, T.ve is ...=.2 a stable.e-:s,.i tnin s:eca r ica ticr. M~ coolant bcron concentra ticq 'anc ba r a t i o n p a t n. is demonstrated to be operable. finally, it tne n:rm2. v a (inventory control) The HPI syste.. i l l re 3in in eration

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that P.C5 invert: y : -trol is Orc /i:00 by c:'i-sjste 5. Inventcry contr ! is ncrrally assess +: by rea:ir; cressurizer level. To ce onstrate invent:ry control, tre c erat:r will rely en pressurizer level but will c:nfirm tre functioning cf his instrumentation by parferning tre 'cIlcwing cperaticns. a) Initiate chargin: :; : ficw and de :nstrate tr.at tne precsurizer level instr _rentatica resp ncs as expected. (typical) No. of charging purps level change 0 inches /hr. 1 + 21-inches /10 min. 2 + 42-inches /10 min. 3 + 63-inches /10 min. b) Activate pressurizer heaters and demonstrate that the pressurizer pressure and temperature instrumentation respond as expected. (typical) + 15 psi / min. c) Activate pressurizer scray and demonstrate that pressurizer pre;sure instrumentation responds as expected. (typical) - 26 psi / min. c. ~ ~ sL tl 'Z E O 7 -O V E e p Y O .tn O -O Q r. 1 O d ^ o r -R F-J O n 8 W d C:) d = 1 U C

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.g. RESPCNSE TO OUESTICN 6C:. If the possibility of bulk void generation in the RCS exists, then RCPs should be in opera tion to ensure ad_quate system circulation to permit the necessary core nr.at removal by the secondary pl3nt systems. Accordingly the plant operators have been instructed to not trip more than one RCP 0 in each loop if the care outlet coulant temperature is less than 20 F subcooled rec.ardless of tne status of the RCP monitorina. instrumentation. If RCP's are off initially, one RCP in each loop should be started. Some plant emergency procedures, for example, Steam Generator Tube Leak / Rupture, reauire isolat:an of a steam generator and securing forced circulation to the affected stea generator. The essentia! require ent of establisnir; 2: equate subccoling in tne RCS takes prece:ence and is to be confirred prior to carrying out any sucn folic.v-up acticns. C If the core cutle; te cerature is more than EC F subcCol 2d, it is permis:i-ble to trip any or all R:Ts if :ne cnit.. ring ins trurcntaticn and pump operating ;roceca: es ir ::at; m:n action is dcsiracle. H.es s, tne manual tric of all R:Ps is to be conducted in an orderly anrer. Cne RCP may be tricre in eacn loco concurrently. The rt-aining R:P in eacn icop m2y n : be tr::;ec ur.til tne Procedure for Entering t,atural Circulation has been im:icmentec. If all of the RCPs tric automatically, the operators are to take immediate steps to verify :ne exista":e of ade:uate natural circulation. .an indicaticn of tris ccndit;^^ is :ne ability of the core aT to st20ilize within minutes. TAJG sncuid be c:r rcilacie by Teans of tne secondary plant heat sink. Tne ab;iitj cf :ne sjste-to s:Coilize with RCS teT;eratures sub:::le: i

De ciearij ascer:aine: oj closely mcn;;; ring pressuricer ;ressure anc core cutle; tem:eratures.

oncurrently n this evaluation the cause of :ne cutomatic trip should be ceterminec anc :ncrected, if at all possible, to permit restarting one RCP in eacn 1000 regarciuss of the status of ne RC ronitorina instrumentaticn if inadequate natural circulation is indicated.

The remaining RCPs should remain availaole for operation, if needed to provide core cooling. f c. g; o M c i,q e l Y l -{ ') - J '- RESF0:lSE TO n'JESTIO!! 6d: The toilcuing information identifies for the operator the diversity and redundancy of indications available to him as an aid in keeping Reactor Coolant System (RCS) inventory within acceptable limits. During normal operation, the plant control systems are designed to keep plant parameters within narrow operatinn ranges. When these operating ranges are exceeded, the plant safety systens are desianec to automatically keep plant parameters within acceatable linits for a sufficient period to allow for tinely recuired c;erator acticn (e.g., from not less than 10 minutes for initiating auxiliary feed-water, to well over an hour to switch to shutdown ccc ling). These time periods arm adecuate fcr the c;erator 1) to assess the diverse and redundant Jic?'icns described below and 2) to verify tne necessity for operat. action before that action is taken. The purpose of maintaining sufficient RCS inventory is to assure adequate cooling capability for the core and oressure central cf the system. The major factors wnich impact RCS inventory are olant responses unish have the potential for fcraing voids in the ?CS. The response to Cuestion 2 addresses tne diagnosis, crevention, and mitigation of voids in the CCS.

n sum ary, tne primary aut mati:

actions to prevent and mitigate the formation of voids in the RCS are sed upcn redundant pressurizer pressure incication which initiate a., trip and SIAS on respective icw pressurizer pressure setooints. Additional indications to the operator for diagnosing possible void for=ation in the RCS include: 1. Cold leg and hot leg tem eratures near the saturation temperature of the RCS pressure. 2. Changes in reactor coolant pu o temperatures, curre.its or other parameters which indicate punp cavitation. 3. Decreases in indicated steam generator t.p. 4. The absence of or unexplained changes in pressurizer level indication. Additional indications to the operator for diagnosino possible leakage from the RCS which could lead to void formaticn in the RCS include: 1. Increases in containment temperature and pressure. 2. Increase or filling of the containment sump. 3. Increase in indicated steam generator level not due to changes in feedwater or steam flow rates. 4. Increase in the pressure and temperature of the tanks into which the RCS relief valves discharge.

11 RESP 0:iSE TO CUESTIO:1 6d (Cont.) 5. Valve alignnents, pipe flow rates, or pipe temperatures which indicate unintende: RCS fluid flow frca pipes connected to the RCS. If pressurizer level is indicated, it shculd first be used as a diagnostic effort to detemine if programed cha get in pressurizer level and/or pressure show the for ation or absence of void in the rest of the RCS, before it is used as an indication of inventcry control (see section 6b). tihen the operator has diagnosed the potential or actual formation of RCS voids, ne should falica th: eventien or mitigation actions identified in :ne respense to question 2. 249 530

y rn.wywrwayz n.;r= w 'amesnw.pinnemaamvaCmemramWmn'MmeMCNN n 4 1 RESPONSE TO CUESTION vil = d 5 In response to this question, capabilities ara discussed to ai 2 1. Vent accumulated hydrogen and/or other ncn cond2nsible gases frcm the reactor coolant system (RCS) m4 d 2. degassify the reactor coolant i a 3. process the waste gas after removal from the reactor coolant s y Possible additienal ecui: ment it also cresented for consideration il to more ef ficiently vent and process the waste gas. Proter } regard ust be given to the additicnal equiprent for the full consegjences e of inadvertent Operaticn. j A the guidelines are arcvided assuming that all crerations are to be i perforred cutsice tne centainrent. Additional ccerational flexibilit/ j may be a'.ailable in scre situaticns if entry into the cc"tain cnt is i allowed. Sc e transient cr accicent scenarics ay also include the ? presence cf sinnificant cuantities c# racicactive fission cases alcnc 3 withthehydroie,in tre rea tcr ceciant. The cresence cf'the Tissicn I gases could li-it ::ntair en; entry anc, in turn, the rath cs used to y vent and Orccess the hycrcgen gas. o* F I. Existinc Svste s 2 A. Venting the RCS There are several pctential high points within the reactor ccciant systri. nere ncn-concensible gases r.ay accumulata. These incluce tne fcilcwing: J a) Pressurizer a b) Reactor coolant pu o seal cavities t c) Shutdown c:alinc cicing at the reactor coolant system interface. j (applies to Millstcne II and St. Lucie #1 cnly) y d) Reactor vessel head above the hot leg no :les. 4 e) Top of the steam generator U-tubes. J ? In c:. der to remove accumulated gases from various high points, the d folicwing methods are available: 7 k a) The pressurizer steam space may be vented through the primary K_ sample syster steam space sample line. This line penetrates ( the containment, the fluid is cccled, and discnarged to the volume control tank (VCT) and/or other reactor coolant quality waste f tanks su.:n as, the flash tank or equipment drain tank. Each of these tanks vent to the gas waste management system W (G'.?.S) for storage of the gas. t E 2_ b) The reactor ccolant cump seal cavity may be vented through the controlled bleedoff for each reactor coolant pump. This flow is a typically routed to the volume control tank or the reactor drain tank. These tanks can be vented to the GWMS. = A lC /b, J ";} 4 s r

1 RESPONSE TO QUESTI01 dll (cont.)

c) The RCS pressurizer surge line and hot leg sample system es.necticns may be used to partially vent the loops and reactor vessel head. The path for the venting is the same as that described for the pressurizer steam space in (a) above, d) The reactor vessel head may be partially vented throuch tM pressurizer as described in (a) or (c) above if the RCS fluid level perr.its. Ccrolete removal of gas accumulated in the reactor vessel head requires redesolving it in the ccoiant. e) Pressurizer retor cperated relief valves (all clants except Arkensas) can te used to vent gas in the pressurizer (and through the pressuri:er other portions of the RC) to the cuench (reactor drain) tank. Procedures to use these valves cust recognize the following consequences: (1) Operation of cne relief valve will result in an RCS pressure decreas ? on the crder of 900 psi / minute. Caution is this approach is then required since failure to close the valve in a tirely fashicn or failure of the relief valve to close could lead to excessive de;ressu*izaticn and, in turn, to additional gas accurulation. (2) Continued operaticn of these valves cou ' result in exceeding quencn tank capacity causing the rupture disc to burst. RCS fluid t. n has a direct path to the ccntainment. Confirmation and establishment of adequate reactor coolant makeup is required. ) 8. Degassing the PCS - The existing systems tyoically have the following capabilities to cegass dissolve hydrogen and/or non-condensible gases from the reactor coolant: 1. Desessing via the pressurizer: With this method all pressurizer heaters are energized, spray flcw is adjusted to raintain a constant plaat pressure, and the pressurizer is ventea via the existing steam space primary sc 'e connection to the VCT or other locaticn. An example of the t required to degass the coolant is given on Figure I (the ti is dependent on the initial H2 ccncen tra tion ). Table 1 provides examples for specific plant degas half-lifes of the reactor coolant. 2. Degassing the RCS via the CVCS: With this method the reactor coolant passes through the letdown line to the Volume Control Tank (VCT). The VCT is vente.1 directly to the GMS. Figure 2 indicates typical plant capabilith s for various letdcwn rates. Table 2 provides specific plant d tgas half-life of the reactor coolant. 'j f C) h "T t. RESPONSE TO CUESTION ell (cont.) C. Waste cas Processing - The plant gaseous waste management systems and/or hycrogen recombiner may be used to process or store the hydrogen and/or ncn-condensible gases collected from the RCS or containment 1. Gaseous waste management systems The approximate storage capacities of the plant gaseous waste management systems (GS.MS) are shown in Table 3. The capacities of these systems are based upon holding gases from normal sources #cr a pericd of time such as 30, c0, or 90 days, before controlled release to the environment and represent the maximum alle..3 Die volure of the vc :ted and/c, cecassed H7 na could be store: outsice the ccntainrent. The s 5 rage volure may, howevec, be limited by tne technical specifications for tne maxinum curies of radicactive ncble gases. The basis for this technical scecificaticn limit is tyoically one cegassed reactor coolant volume of gas with the source of activity consistent witn 1% failed fuel. 2. Containment Hycrcgen Reccmbiners The hydregt in the cortainrent building ray, for all plants except "aine Yankee and Fort Calhoun, be removed by use of the installed hyde: gen recctbiner. Table a contains saecific informaticn regarding e?ch plant recombiner capabilities. No special shielding..cuid be required for those plants which have recombiners sinca they are located insice containment. The hydrogen removai capability for those plants with reccmbiner can be expressed in a curification as a half-life of apnroximately four (4) cays. Portab'ie recomoiners (external to the containment) may be used on Maine Yankee and Fort Calhoun. II. Consideration of Additional Ecuicment To enhance plant capabili-ty for venting and storing abnormally large quantities of hydrogen and fissior, product gases, the follcwing additional ecuipment should be considered: Proper regard for the consequences of inadvertent operation of any additional equipment should be considered also. A. RCS High Point Ventina 1. Figure 3 shows c possible scheme for venting the reactor vessel head of large quantities of free hydrogen gas. This system provides the capability of venting the head to either the pressurizer or directly to the quench tank. Provisicns are also made to augment the vent rates for the pressuricer steam space s:mpling line and the rcactor drc.in/ quench tank vent to G'n S. Portions of this system would have to be A5"E Code Class I and Seismic Category I. The system must also be designed to minimize interference with the reactor vessel head removal during refueling. ,,/ ~ L'] s: t RESPONSE TO CUESTION ell (cont.) The consequences of inadvertent operation of such a system must be determined. The design must incorporate features which minimize the consequences. 2. Controlled venting of accumulated gases in the pressurizer to the quench tank cculd be facilitated with a vent path from the pressurizer spray line. This will permit Figure 3 illustrates this tethod. This method provides a controlled pathway, which is remotely ocerable, for the collection o pses within containment and also permits a scheduled venting to the GMS, if desirable. 3. The shutdown ccoling syste suction lines for Millstone II and St. Lucie 1 may recuire.igh point vents to precluce gas binding of the decay heat re" oval system since the piping elevaticn is greater than the bc leg elevaticn. ~ is ventir.g could be vented to the pressurizer or tne reactor drain,1uench tan;. A possible method for venting tne piping is shc. n on Figure 4 4. To provide additional storage cacacity for vented and/or degassed H7 and fissicn gases, tne containment i tself is a possible alternative. RCS vents to the contain ent would occur via the quench tank ruotare cisc cnly if tne ru;ture disc is brcken (no additio ni ecui: ent ne_essarv) The VCT can be vented to the containmcnt instead of ne G',a"S by the accition of temporary and/or permanent ::iping as shown in Figure 5. For any venting operation, consiceraticn rust be given to: a) The effects of ra;id depressurization with saturation conditions d the potential generaticn of gas, b) asuring that adequate makeup to the RCS is available to compensate for any tiuid lost during venting. c) for venting of the reactor coolant system or VCT to the containmert, due consideration must be given for methods to adequantely mix the hydrogen gas. Generally, the hydrogen mixing is accomplished by the containment spray system, the containment fan ccolers, and containment air circulatcrs which permit convective mixing and prevents entracment. Each plant must evaluate the discharge pr.:s of vented hydrogen (e.g. rupture disc area of the quencn tanc.) to prevent local concentration of hydrogen. 24h 33b 6 _,. w-- m,. - ,y _-r IN FN- -NM* O I 'O TABLE 1 Pressurizer Degassing Estimated Es tima ted Half Life Half Life Plant N3 e at 2000 PSIA at 1000 PSIA Arkansas (APLL) 8.9 hrs. 8.1 h rs. Baltimore (Calvert Cliffs #152) 10.3 hrs. 9.4 hrs. Florida P&L (St. Lucie =1) 10.3 hrs. 9.4 hrs. (Wss= 50 /hr) Paine Yankee 17.4 hrs. 8.3 hrs. Northeast Utilities ("illstone =2) 10.3 hrs. 9.4 hrs. Omaha (Fort Calhoun) 6.0 hrs. 5.5 hrs. Consumers Pc'.ier (Palisades) 9.0 hrs. 8.2 hrs. TABLE 2 Volume Control Tank Degassing Estimated ~ Plar.t Name Half Life (hours) Letdown Flow 40 GPM 128 GPM Arkansas 25.4 8.9 Cal. Cliffs, St. Lucie, 27.4 8.5 Millstone 23.6 7.4 Palisades 23.9 7.5 Maine Yankee 26.6 8.3 Omaha 16.0 5.0 .T

17-TABLE 3 GWMS Storage Can3bilities Estimated Plant Storage Cacacity Millstone 2 15,100 SCF Maine Yankee ,;00 SCF St. Lucie 1 4,200 SCF Omah3 12,270 SCF Arkansas 22,800 SCF P3lisades 8,775 SCF Calvert Cliffs 1 20,130 SCF Calvert Cliffs E 20,130 SCF (- [ } 's n 'l en_.

TABLE 4 Containment flydregen Recombiners Post LOCA* Containment liydrogen Raraatiou Shielding Post-LOCA 7"tegrated Dose ** Plant Recombiner for Combiner for Equipment Qualification 7 Arkansas 2 Yes fiot cequired 3.3 x 10 rads 0 Calvert Cliffs 1&2 Yes flot required 1 x 10 rads 0 St. Lucie 1 Yes flot required 1 x 10 rads flaine Yankee flone flot Applicable 8 Millstone 2 Yes flot required 1 x 10 rads Omaha flone flot Applicable Palisades fes flot required Not available ? In-Containment Thermal Recombiner 8

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