ML19249D805

Safety Evaluation Supporting Amend 14 to License NPF-4

ML19249D805
Person / Time
Site:	North Anna
Issue date:	01/29/1979
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML19249D803	List: ML19249D801 ML19249D805 ML19249D806 ML19249D807
References
NUDOCS 7909250423
Download: ML19249D805 (10)

Text

"an.n. 20, ;: c SAFETY EvalgAT;0N SY THE OFFICE OF

'4UCLEAR GEACTCR GEGULATION RELAT!NG TO NDIFICATION OF THE SPENT FUEL $70' ;GE 1ACKS FACILITY OPERATING L CENSE NO. NPr t VIRGINI A ELEC*1IC A 7 00WER :Ot'PANY NORTH ANNA DOWER STAT';N, UNITS 1 AND 2 DOCKET NOS. 50-32 AND 50-329 iD@

7 900250 4 Z 3 1026

.J5

!AFE*Y EVALUAT!CN SY TwE CF: ICE OF NUCLEAR REACTOR REGULAT!ON RELAT!Y. T3 90 F! CATION OF 'FE SPENT FUEL STORAGE RACKS FAC:L:TY CPERAT!NG LICENSE NO. NPF-4

/!RGlNIA ELECTR*C AND 20'aER C09ANY NORTH ANNA #0ER STATION, UNITS 1 AND 2 JCCKET NOS. 50-328 AND 50-329 P(M# RER 1.3 lNTRCOUCT!CN n a letter datec May 1, fr78, the Virginia Electric and Power Company recuestec an amencment to Facility Ocerating License No. NPC-4 to increase

he s;ent fuel storage capacity of the fuel pool for the North Anna ?ower Staticn, unt:s 1 ana 2, frem the present capacity of 400 fuel assemolies (appecximately 2-1/2 cores) to 366 fuel assemolias (approximately 5 cores).

'he expandea storage cacacity would allow the storage of all spent fuel to ce generatec Dy the aceration of North Anna Power Station, Units 1 ana 2, frem the present until about 1987 ana s:til provide storage scace for the discharge Of a full care loading.

2. 0 EVALUAT!ON 2.1 Criticality

'he cresent scent fuel storage racks, which utilize a center-to-center spacing cf 21 inches, would be removed and replaced with new stainless steel racks uttitz?ng a center-to-center spacing of 14 incnes ce: ween individual storage cans (cells). The licensee has provided a criticality analysis utt1tring these revised scent fuel storage rack dimensicns for normal, acncrmal, ano accident conditions. A fresn fuel enrichment of 2.5 weignt percent uranium 235 was assumea ana the water in the :cci was assumed to Oe at 68 degrees Fahrennett and *o be free of soluole boren.

Creatt was taken for *he neutrcn poisoning effect of the stainless steel cans, cut for no other cotsons in the racks. *he fuct rack array..s assumea to :e infinite in all three simensions.

~he if censee performed calculations asing the NUS Cor:oratten eersion of the LECPARD Coce, wnich has been serified my : mcartson with critical experiments. Further verification was done by c:xroarison of selected cases with results of KENO calculattens. From these c0ccartsons, a calculational uncertatnty was cetatrec. Sensitivity studies were :er-fer ec which investigatec the effect of lattice ptten uncertatnties, uncer*ainttes in thtexness and c:mcosition of the stainless steel cans, variations in :oci temcerature, ana ancertaintfes in the fuel enrichment.

~he Leccarc Coce anc (ENO Code are 'ncustry standarcs anicn have :een veriff ed ay exper' ment and, theref:re, we fine these calculational methces to :e ac:e::acle.

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qg 3 b'l u

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The calculations resulted in a nominal effective multiplica:1en facter B effective)* cf 0.283 for the racxs and a value of 0.924 wnen all

.ncertairties were al;eoraically :ccoine:. This value is more c:nservative than cur acce::ance criterion of 0.95, as scecified in Section 9.1.2 of the Stancard teview Plan, ano 15, therefore, acce: table Accitionally, there is an existing technical s:ecifica:icn +n the North Anna ccerating Itcense.nicn limits k effective in the s;ent fuel ; col to 0.95.

• he limiting accident condition is that in whicn an assemoly (without stainless steel can) is placed next to the storage rack array at the closest point (5 inen watar gac) permitted by a mechanical restriction en the rack. Thit resulted in an increase of the effective multiplication

< actor (t effective) af less than 0.1 ;ercent fto 0.325) which meets cur acce:tance criterton of 3.95 ano ts, therefore, acce:tante.

2. 0 Desten The scent fuel pool ts a reinforced concrete seismic Category I structure with a 1/4 inen thick stainless steel liner. 3e scent 'uel : col is located in the fuel builcing wnten is suppcrted by a reinforcec concrete mat on bedrock.

• he modifiec storage rack design will preclude storage of fuel assemblies in other than their :rescribec iccations as did the racks being reclacec.

The new storage racks are classiffec as seismic Category I and *he design is in accorcance with the appitcable portjens of Sections 2.7 and 2.3 Of the Standara Review Plan considering loads, Icad c:moinations and structural acce:tance criteria. The crocosed storage rack cesign *s also in accord with the reccmendations of Regulatory 'luide 1.29, " eismic Cesign ::assificatten*. Cesign codes are based on Part 1 of the 4erican

nstitute of Steel Construction "Scecification for the Cesign, Fabrication and Erection of Strue: ural Steel for Buildings," dated Fecruary 12, 1969 anc its Supolements 1, 2 and 3 for their elastic cesign methocole.gy and alicwaole s:ress criteria. Yield strengths we c actatned from acarceriate Merican Society of wechanical Engineers Soiler and ?ressure 7essel Cece, Section ::: tables fer stainless steel structures and :ne Mertcan Institute of Steel Ocnstruction

• Manual af Steel Construction

• was 2 sed for guicance to detemine the alicwable design stresses. We

'inc the ceces and standarcs usec in the esign af the mw storage racks to se in como11ance with the Stancar: Review Plan. and, therefore, ac:e::acle.

~he acceling and analytical metheas 'er seismic analysis af the s:en: 'uel stcrage racxs are in : moliance alth the rec:mencatiens of Sections 2.7 anc 3.3 :f he Stancard Review ?lan. Racks are acceJec in ce:ai! 2stng :eam and

% enec:tve s ne aatic of 9eutrens ' rem f'ssicns in eacn geaeration tc

• ONe ::tal vcer Icst by soscret*cn anc Ieatage in *se :receecing ;enerat ens.

c acnteve crt *cality in 'inite sys:em,k effective ust ecual i.0.

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late finite elements with consiceration,f ;a

s between assemolies and su:rergence in licuid. A ressense 5:ectrum tocal tynamic analysis is em:loyed

1. Cr seismic design and :ne resCCnse s;ectra ssed for the 0;erating basis earthcuake and safe shutcown earthcuase are the same as those Jsed in other %r*.A Anna Power Station, Unt:s 1 anc 2. seismic Category

• structures.

The 'uel racks cculd slide uncer seismic concitions, but will be designed against tipping and overturning. The prcposed modification does not change the physical cenfiguration of the s:ent fuel pool, uowever, two additieral ficor pads to accommodate seismic loads from the proposec fuel storage racks are presently installed in the fuel acol. 31s installation was performed before the issuance of the operating license for Unit 1.

The additional enoec.m.ents :r sacs, wnich are anchorec to the :encrete <1a use of rock ancnor bolts, nave been seismically cesigned and analyzec, and would not imcair the structural integrity of the ;ool structure nor cause any leakage

r olem.

We have ceterminec that, although the load in the fuel ;ool will be more than twice the original load, no significant set:1ement cf the fuel building is ex;ected :ecause the fuel building is supported by a reinforced concrete mat en bedr0ck as stated above.

ne concluce nat the precosed spent fuel storage racks do not involve any significant change in design methods anc criteria of structures, nor cause any :otential arcolem in structural integrity and are, therefore, acce table.

2. 3 v terials a

Tne materials to be used for const ucticn of the scent fuel storage racks have :een identified by scecification and found to be in conferr:ance with the recuireme.ts of Secticn III of the American Society of 'dechanical Engineers MSN) Boiler and Pressure vessel Ccce. The rechanical ;recerties f the selectec matertal satisfy Accenoix ! of Section III of the American

• ety of Mecnanical Engineers Boiler and Pressure 7essel Code anc Parts

, 3 and C of Section II of the Coce.

The revised spent fuel stcrage rack material is Ty;e 204 austenttic stainless steel as was the :revious material. Ty,;e 204 is comcatible with the excected environnent, as graven by testing anc satisfactory :ast service :er'crnance.

• herefore, general cerrosion of the ta:erial mill be negligible. Salvanic corroston is avoiced since statnless steel Ty;e 204 materda! !s also used

+n the C:nstruction of the base structure angle :Tates, eccecment 214:es anc the s:ent ; col liner.

• he controls t: se imposec 2:en the fabrica icn of the sustenttic stai ess steel aterial.sec in the cens:-;cti:n of tre scen: 'uel s:Orage acxs satisfy the recutrements af Regulatory Ltce !.21, "Cantroi :f Fereite

cntent af 5:stnless Steel We!a v tal" arc ter?can ?:attonal Stancard e

Ins:.te iANSIl ::ancarc W..1, " Cleaning Of M uic Iystems anc Associated 1026

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Cceconents ;uring the Constructt:n Shase of Nuclear Dower Plants." 3e welding procecures and the welders are qualtffed in accordance with the requirements of Section :X of the American Soctety of vechanical Engineers Botler and Dressure vessel Ccce.

Since materials selectf on, faerication ;ractices and cleaning :receaures will te perfor ed in accordance with the reouf rements of the ASME Ccce, the ANSI standard and the regulatory guide referenced above, we conclude that there is reasonaale assurance that the scent fuel storage racks will cerform sat 1sfdCtorily in service.

2. 4 Safety Analvsts In Section 7.1.. :f the North Anna Power station, Units 1 and 2 Safety 9/aluation RerCrt, we cCncluded that the %el nandling system and facili-ties sesign sas not in conformance with paragraph C.5 of Rsgulatory Guide 1.13. " Fuel Storage Facility Cesign Basis", regarcing prevention of coving cranes car ytng heavy loads into the vicinity of the ;ool and was not acceptable. Sucsecuent to the issuance of the Safety Evaluatien Report,

he licensee modified *he design of the s;ent fuel pool to provice a wall between the spent fuel storage area and the fuel cask loading mit to preclude damage to stored fuel in the event of a cask deco. Our evaluatien of this modiff cation is contained in Section 9.0 of Succlement 3 to the Safety Evaluation Re: ort, dated Cecemoer 1977.

W'e determined that the ifcensee's cdtffcation to ;revent the ;ctential damage frcm a cask drop was acceptable.

The proposed increased spent fuel storage rack design will not affect this conclusion since there will be no structural modiffcations 1 tace to the scent fuel pool or the separating wall.

We 9 ave underway a generte revf ew cf Icad 'tandling ocerations in the vietntty of scent fuel acols to determine the line11 hood of a heavy load imoacting

+

fuel in the pool and, if necessary, the radf ological consecuences of sucn a event. Howver to mtntmtre :he creccing of heavy loads on the s;ent 'uel

ocl, Section 3.9.7 of :Pe Techn*.;al !cectf tcattons for the North anna ?cwer Station Unit I coerating Itcense Ifmits ! cads ever the irractated assemolfes in the cool to 3250 pounds. ~his is the accro.stmate wetgnt of a single assembly wntch was used in the cesign basts 'uel element drco analysts

iscussed teicw. Therefore, we conclude that the Itkelihood of a heavy 1 cad 54001199 acetcent is sufficie9tIy small so

• hat the acceDtaD111ty of the creocsec todification is net affected, and that no accitional restrict *ons an Icad *tancllig cDerations in the vicintty 3f the scent 'uel ;ool are necessary wntle Our gef'eric mytew 15 uncerway.

'4 1026 109

n Sectien 15.4 :f the Safety Evaluation Re:crt fcr the North Anna Nwer Station, Lntts I anc 2, cated June 4, 1975, we evaluatea the radiological c:nsetuences tf a ;ostulated fuel handling accicent (cesign oasis event) in the s; tnt fuel storage area, ano determined that the resultant offsite cases are = ell witnin the guicelines af 10 CFR Part 100. ine analysis for this evaluation conservatively assumed that an element that had ocerated in the maximun ;cwer region of the core and had decayed for a minimum cooling time, is dre;;ed the full hetgnt to the bottom of the s;ent fuel pool and all of the cladding is damaged. The consecuences of an element drcpped onto the stcrage racks would be less severe since the f f rst Pack suc; orts extend above the stored fuel asserblies themselves ano the drop height woulc te significant!y less.

'he ;recosed dcuoling of tne stcrage capacity of the spent fuel ;ool will not change the results of the above evaluation since the same ancerlying assanctions are still valid. Therefore, me conclude that the orcocsed modificatiens will not increase the radiclogical consecuences of the costulated design basis fuel hanaling accicent.

'he flood design criteria for the North Anna Power Station, " nits I and 2, was evaluated in Section 3.4 of the Safety Evaluation Report, and found accectacle to preserve the structural integrity of seismic Category :

structures anc seismic Category systems and comoonents within these structures. The 3esign criterion 'or the *crnado missile pr0tection 'cr the facility was such that tor 9 ado-generated missfies would not cause damage to more than one spent fuel assembly within the s;ent 'uel ; col.

This matter was evaluated in Sections 3.5 and 9.1.2 of the Safety Evaluat'en Re; ort and Jur basis for accepting the design of the fuel building and

. V 3:ent 'uel pool, with regarc to missile ;rctection, was that there is a Icw prcoacility that a tornaco-generated missile would damage sufficie9:

'uel assemclies to cause offsite deses in excess of 10 CFR Part TCO.

• he cesign :rovisions for protection from ficed and tornaco missiles are y

anaffected by the ;roposed modification and are, therefore, acceptacle.

2n the tasts of the above, we c:ncluce that the increase in the nuncer of assecolies in the fuel storage pool of the North Anna Power Station, Units 1 and 2, will not increase the offsite raciological consecuences oeyond the design basis fuel 'iandling accicent.

0.5 hereal analvsts

.e,aa previously 'auna the cesign 'or the s;ent fuel ;oo! 00oling anc curt cation system to De accectacle, as discussed in Section 3.1.2 af the Safety Evaluation Ae:crt.

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• he Itcensee has ;erformed a design neat load calculation for the existing scent fuel pool cooling system asstatng 966 s;ent fuel assemolies in the

col and that the plant had operated at a power stre

ch rating of 2990 megawatts thmal. We have ;erformed an incependent evaluation of the capaci11ty of the scent fuel pool cociing and purification system to handle the increased cooling requirements resulting from the accitional s;ent fuel storage withou liodification to the system. For this evaluation, we conservatively assumed that the decay *ieat load 'or the cool based on back to back annt.31 refuelings of each unit would include the heat 1 cad frem a third of a core from one unit at toutlibrium condittons wnicn is placed in the pool 150 nours after reactor shutdowi plus the heat load

' rem a thted of a core from the other unit placed in the pool 150 nours after reactor snutdown, 45 days creviously and 16 previous one-third core annual cyclic refueling disenarges.

Each scent fuel ;ooling cooling system is designed for a heat removal capability of 56.3 million British themal units (Bi!J) per hour. Our evaluation vertfies that the revised normal spent fuel heat load will ce 19.4 million 3rttish thermal units per nour anich is an incremental increase of 5.6 million Brttish thermal units per hour (40 percent increase) attributaole to the ;rcoosed modifications. The present system is adequate fer removing this incremental increase in heat load, and it results in an increase in the heat load to the service water system of approximately 'ive

ercent.

'ur evaluation of :ne s;ent fuel ;ool cooling system for the original I storage configuration, as presented in Section 9.1.3 o# the Safety uation Report, disclosed that the scent fuel ; col cooling system will maintain the pool water temperature below 140 cegrees Fahrennett asstzning s

(

a total scent fuel inventory of one third of a core and below 170 cegrees Fanrenheit for emergency conditions where total scent fuel inventory of one plus one third core at equilibrNn conditions is stored. Cur evaluation of the crocosed scent 'uel ocal modification has eerified that the existing 4

scent fuel ;ool cooling system can also maintain these s:ecified *emceratures for the oreposed mocification. Therefore, we 'ind that the existing scent fuel ;ool cooling system is acceptable for the ;rocosed modifications.

• he maximum load on the 'uel pool :urification ::ortion of the system occurs

uring refueling c:erations nhen fuel is :eing moved or wnen larger than nomal amounts of efective 'uel are stored in the aacks.

~he purificatd en

crtion of

ne system has the sesign ca:ao111ty of accorroaating any antici:ated increase in the amcunt of stored :efective 'uel resulting 'r":m

ne increase in the s:crage ca:acity.

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On :ne Oasis of cur review, we Conclude tha: One ; resent cooling anc

urification cacac'ty of the s;ent fue! ;, col will be suf'ictent te nancie the incremental neat 1cac and ;otential water Quality cegradation in the ; col that culd oe added by the ccification and

nat the 5;ent fuel ;ool ecoling anc :urification system ts accectacle for tne ;roceseo 9actfication.

2.6 arciatten 2retec:1cn

• he licensee plans to :er*orm the codification to the s:ent fuel 2001 storage capactty prior to any contact with radioactivly contaminated scent fuel ;ool storage coolant ano shielding water. If this takes place, there will te no :easonnel raciation excesure associated with :he mocification. In the event that the mocificat en taxes place after s:ent fuel is storea in

~

the s:ent fuel storage ;ool, den there will be some ractation exposure to the plant personnel who replace the racks Mat nave been exposed to radioactively centaminated c:olant. Based en infomation that we have en excesures to ;ersonnel from pressuri:ed nater reacters which alreacy have mocifica their s:ent fuel storage cools, we would expec: the ex:osure at the Mrth Anna Nwer Station, Units 1 anc 2, to be less than 20 man-rea.

• his installation is ex:ected to be ;erformed only once during the lifetime of the station and, therefore, any resultant excosure would recresent only a small fraction of the total 9an-rem burcen from expectea occucational excosure. This small increase in radiation exposure will 90t affect the licensee's act11ty to maintain incividual eccupational cases as low as is reasonaoly achievaale anc within the limits of 10 CFR 20.

We have evaluated the radiation protection design 'eatures to assure that y%.

cccucational raatation excesures to plant :ersonnel cue to the orecosed modification will not significantly increase.

• lthougn it is ex:ectec that the accitional s;ent 'uel in :ne cool 4f11 increase the amount of corrosion and 'ission ;rocucts intreauced into the cooling water to scre extent, as noted above in Section 2.5, the existing urtfication system will ;rovice acequate *emoval of those nuclices ::

assure that the radiation fielcs will not exceec 1.5 to 3.0 mt11 treat per hour at naist level at the ecge of the : col. We censicer these radiatten

'*el:s and resultant ex:csures curing fuel nanaling c:erations to :e acce:tacle. Acattionally, ne licensee :rovicea actual radiation " eld ata arc acta: ten ex:csure data from :setr Surry hwer Statten, Units i and 2

(;ccxet Ncs. 50-280 anc 50-231) wnten nas a scen: "uel storage :acact:y anc

estgn statiar to inat preccsec ':r the North Anna 0wer Station, Unt:s !

anc :. Tne rac14tten sateic water in the stcnge : col 4111 :rovice acecuate snt elcing 'ar the accitt enal 'uel elements. Based an 0:erating ex:erience a: the Suray :cwer Statten, Units 1 and 2, tne ex:0sure of ;erscnnel :o strecere racicac:1vt:y will :e atthin the 11mits of 10 ;FR ?ar: 20.

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Ac roingly, we concluce that storing additional fuel in the scen: 'uel col will not result in any signif' cant increase in deses received by ac:spational workers ar c tnat the radiation protection design is accectacle without enange for the procesed octficatien.

2. 7

ncustrfai Security ae nave reviewc the prooosea modification with respect to incustrial sabotage. We consider the 'uel array comcaction in the spent fuel pool to have no effect or relevance to the security plan for the trth Anna 3ower Staticn, Units 1 and 2.

Our conclusion is cased on the 'act that

he s:ent fuel pool is designated as a sital area. As a sital area,1:

's afferced the protection recuf red my 10 CP Iection 72.55 to crevice nigh assurance against su:cessful industrial sacotage by both of the following:

(1) A cetermined violent external assault, attack by stealth, or ceceptive actions, of seversi persons with the 'ollowing attributes, assistance and ecuipment: (1) well-trained (including ::lilitary training and skills) and cedicated individuals, (ii) insice assistance which may include a knowledgeable individual wno attempts to :articteate in both a ;assive role (e.g., provide infor-ation) ano an active role (e.g., facilitate entrance and exit, disaole alarms and comunications, participate in violent attack), (ti t)

A suitaste weapons, up to and inclucing hand-held automatic wea;:ans, O

ecutpped with silencers and having effective long range =-

ty,

h

'1v) hand-carried equi;rient, inclacing incapact:ating age and ex:losives for use as tools of entry or otherwise destroyir. the reactor integrity, and (2 ) An intental threat of an insicer, inclucing an e',cloyee (in a.iy position).

1 fignt :f the aoove, comcaction of the fuel array :n the 5:en: 'uel storage pool does not cnange the recaired level of ;rotec:fon nor :he structural cesign of the exter9a1 :arriers of the : col against :ne

nreat of incustrial sacotage.

2.0

$U WAR' Our avaluation succor s *Ne c nc!usi:n -a* tse :rocosec moci'fcat:On 50 t.'e 5:ent 'uel 3 col 'Or the North An9a 2 wer Stat'an, Units 1 anc 0

's acce::a:1e ecause:

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(1) The anysical cesign of the new storage racks will preclude criticality for any mcderating concition with the fimits imposed.

(2 ) The spent fuel pool cooling system has adecuate cooling capacity.

(3) The increase in occupational radiatten exposure to irdividuals cue to the storage of acattional fuel in the spent fuel pool would be negligible.

(4 ) The installation and use of the new fuel racks can be accomplished safely.

(5) The likelihood of an accident involving heavy 1caos in the vicinity of the spent fuel cool is not affected by the precosed modification

'(

and ts sufficiently small that no accitional restrictions on lead

. v handling operations in the vicinity of the spent fuel pool are necessary whfie our generic review is underway.

(6 ) The structural cesign anc the materials of construction are acecuate and meet the applicable design riteria.

4.0 CONCLUSION

3ased on the considerations discussed above we conclude that: (1) there is reascnacle assurance that the health and afety of the puolic will not be endangerec by coeration in the preco ed manner, and (2) such activitias will :e conductea in comoliance alth the Cr itsston's regulations and the issuance of this amendment will not be inimical to the comon defense and security cr the health and safety'Of the ;ublic.

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