ML20127H231
| ML20127H231 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 07/15/1975 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20127H228 | List: |
| References | |
| NUDOCS 9211180449 | |
| Download: ML20127H231 (4) | |
Text
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< SAFr*1Y EVALUATIor. LY TPE 0FFICE OF t.UCLt.AE REACTOR kEGULATION ;
Sl&PCPTI'G AFENDMENT TO LICENSE NO. CPR-22
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. C"TICTLLO "JCI.T 'Jt CCPFRATir'G PL ANT wuL1 i D. '.n-M 3 L[
INTR 00l'CT10N ty letter datea rtarch 24. 1975. :.orttorn i,tates Fower Company (oLTC) '
,! recuested a chance in the Tecnnical Specifications appended to racility Operat ine 1.icense l'o, LPP-22 for the l'ont icello buclear Cenerat ine- +
Plant located in Wright County, hinnesota. The proposed enaneo in Technien1 Specitications $4as subitted in remporse to our rer1uest to the licensee dated Fectuary 14 1975, and is rosnonsive to the =
cuiuelinov set !a rt 't in eur . let tar. tie havo made additional modili-cations to inese proposea Tecnulcal $ pacific.at ions to iraprove the clarity and intent of the specitication and it s basis.- 1hese aocitionct
- chanc,es woro discussed with and aproed to by the GSFC statt :centiers.
The croposad chance in rechnical Speca ticat ions detinea new temcereture l ic.it s for t he rurtression rool t ater to provide addit ional assurante
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et ~ air.tsinine tri.ary containment function and intecrity in the . event et extended re i let "' . :t .
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The : ont icella plant . is a i:o t litm cat e r reac t or ( .M) Uticn is hcuseu in- art ! :ri arv cant n in-i'nt . ' r.e Ort "ric tr'
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pressura surnression type'ot erinary contsinment that const81s et ti '
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tiertression cheber (also referred to as~ t he L orus ) . he ,
supptc5Hien cnacoer, or torus, centrien . mol at tat er ar d it .?vs t am to supprers_. t be P res sure 'tur ti 1. postuleteo loss-ot-coolant ccctcent (if,.,CA) by copaensine thd Fle 2 .reldaSed t rora thd ' re8Cl or primary Syst e'r.
% ract dr s"a t en ,ner-" ralen d ~ rallet u lve ever .t i tn d ur in --
arerat ine t rarsient s also is. released into the coo l . ot ua t o r tu toe torus.
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TT u. s. GOVERNGIENT PR$NTING OFFICES 1974 936196 ~. g
---. Fons ABC.518 (Rev 9-53) ASCM 0240
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shown that demane to the torus st ruct ure can occur trom two phenomena associated with relief valve operations. La.:: age can result from the forces evert ed en the st ructure when. On first openine tha relict valves, steam and the air within the vent are discaaruod into t ile
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torus unter. ';his phenomeuon is roterred to as steam vent clearing. .
The second sourco of potential structural damage 'ste:as trom Lno
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vibrations which accompany extended roliot valve discharee into i t he torus water if the pool water le at elovated temperatures.
. hic etteet is inown as tne st em au. men in : vier..t a en poenomenon.
1 't er teur clearine Fhenomenon it h renard to the s t e a n v.> n t clearint r o etiono n on . 'o tre activuly reviewine this r.eneric proolem an; in uur letter cateu rebruary 14 1975 we also requested eacn applicable licensee to .
crevide intornat ion to neronstrate that the t orus structure will maintain it s intecrity throuenout the anticipolco lite of the
!:cilit". -ecause et vinrent 9109 -rooresaien el t re mat erial tSt iPue 8sSociateo wit h t ree Eleum Vent Clocrtur p e ropenu n . ;e
' O ve Concluded that (Dere iF not i. ned i a t e 'at ent i >l 7PZd rd resultine tro. this type or ptienotunon ; never t heleus , su rve i l l once and review action on Lhic ratter ly the nC ai nf f till cont inue durine this "ver.
. Leer C uenchin s Li'rnt ion . beno:wnon
.av st ear quenchla? v i b r a l i st. phenomenon ecmce a tene rr .a result of occurrences at two T.uropean reactors. With Lotua pout s.aler t empe raturec inc re aced in excess of 17? e due to prolonged steam cuenching from relief valve operation hydro- s avectic fluid vibret ions occurren with subsecuent -ooerate to bich reliet valve ila retes. These tinid viorations proauced larte dynanic loads in the torus at ructure ace extensive caeacu to torns in t ernal (t ri e t "res. !! '111 o ;a m te ..mtir.oe, tne
'm a ~ i c lenti s coul< ve re sul t ec in yt ructural danape to tne t orus itsell cue to "aterial 'altrue. !hus, te repert, crorr.$rces v( t: e cte:+ "e e n e u i n e- O rnt i au rneremenor mt tne two Luropean reac t o rs inticate tant actuut or i n c i t. t e nt ratlure et the t o rtis can occur tren such an evout . "uen tailure vould
- a expectoc to trvolve e r::ce.ir t .:e t oru; all no 1 ss at !
l containment in t ecr i t' areover, at a W... m e u r r. .t.;<uuai with or atter such 3n event . tae concecuences couli . ::c e s s ive ]
rodiolocieel doses te the roolic, ome s
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f Forna AEC 318 (Rev. 9 53) ALCM 0240 W u. s. oovsmMMENT PRINTING oPFlCE41974 524-9 88
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in crata ri r o6 vi t h t he tit eam vent clearing pnenomenon, tne potent ial risk casociated with the steam uuenchiny vibration phenomenon (1) raflects the tact that a <'enerally smaller safety narrinl/ exist s between the present license reauirement s on suppression pool temperature limits and tha point at snien marece cau e erin an. is) ,; ole . e i .a c .
"!J 1.liATION W existiny Tochtiical Specificaltons for the t!onticello ritet l i.- i t the torus t ool tecipe ra t ure t o 90* l . This t em pe ra t u re lic1L
- n9eures that t!e ecol sater has tre capability t o re r t orn as .c const ant ly ava t lable heat-nink with et reasonable operatine tempere-ture it at can to nair.tained by use o1 nuet er.cranvers -hose seconaary coolinc wat er ( t he service cooline wator) is expecteo to remain uell below '>0*F. While this 90'f limit provides normal operatine i tiexibil it y, sho rt -t erm t e-- s r o c ures . e r- i t t ed "v eperat ir ,
procedures exceed i t'e no rma l reve r ope r r t t e r te ,rerature linit .
- Lut acce moaates tne neat release resulta.w :ro, nnor.a1 operativo.
such as relio t' valve mal f unct ion , wnile st ill maintainine the recuired neat-aiink (absorption) capccity of t he pool bater needixi lor tne postulated 1.CCA concil i018. tosever, in v i e w o t' the Ni ent ia l rish associated with t he st eam auencnine vibration ohenoc.enon, it is recessary to rocify tre terperature lintt s to the schnicci _poc111-cations.
This action Lt.s. onnnna 1 ) oo +a c'rlier r. iter e us of tue st eam ouenching vibration occurrences at a meeting on Eovember 1, l ') 7 !. , r. nd provtded relatec infor~ation ry let t ern la as dated hovember 7. ano pecember ?O, 19 7!. . h letter ot recenber 20. 1974 statea taat 6 e aa intoreen all ot it s custoeers witn eparat ine MF (vcili t les nna . ark I containeents of the rhecomenon ono in c l udeil in t home communicet ions GE's recomc' enc ed interim operatint temperat t re l i r i t :. nd prorosed operatinc procedures to -:inimize the p rar,at t i t t ,
ot encounterine the damacine recine of the steam auenchine vibration
" coo e::an .
r ur implerent st ton or t ne fr recom enceu crececured nac temperature linits via enances in tne lecr. vical ;nectiicnttann a re vs i 2 t . i- -
e t e l l o i. i v ' mrecr m s:
1/ *ae uttterence, in rool : st e r t e- rera t ure , netween the license 1[ Sit I.) ~ r '. . 1:e t r ir e ra ll, re 'l
'ich s t ruc t ural Lara 'e .L '.t al occur is tue sutetu ,or in tvailr le ta relect stainst the ettects et the (denenen00 e i bc uS Si'd .
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D ATs > . . . . . . ~~~ aaa Form AEC 31s (Rev. 9 53) AFCM 0240 W u. s. oovsanusar rnintino orrics: to74.sas-toe
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The new short-term temperature limit applicable to all reactor
- a. l operating conditions requires that the reactorThis'new be scrammed if the temperature torus pool water temperature exceeds 110* F. l limit and associated requirement to scram the reactor provides ,
an additional safety margin below the 170*F temperatures related '
to potential damage to the torus.
~ b. For specific requirements associated with surveillance testing, i.e. , testing of relief valves , HPCI and RCIC, the water temperature shall not exceed 100*F, i.e., 10*F above the normal
- power operation limit. This new limit applicable to surveillance testing provides additional operating flexibility while still maintaining a maximum heat-sink capacity. The current limits in the Technical Specifications made a provision for these require-ments but were less restrictive on the maximum water temperature, ~
i.e., current limit is 130*F. The time allowed for return to normal operating temperature is unchanged. .
For reactor isolation conditions, the now temperature limit is 120*F, above which temperature the reactor vessel is to be depresstirized. this rew limit of 120*F assures pool capacity for absorption oL heat released to the torus while avoiding Upon reaching undesirable reactor vessel cooldown transients.
120'F, the reactor is placed in the cold, shutdown condition #
at the fastest rate consistent with the Technical Specifications on reactor pressure vessel cooldown rates. ,
- d. In addition to the new limits on temperature of the torus pool water, discussion in the Basis includes a summary of operator actions to be taken in the event of a relief valve malfunction These operator actions are taken to avoid the development of
- temperatures approaching the 170*F threshold for potential ,
damage by the steam quenching phenomenon.
CONCLUSION ,
We have concluded, based on the considerations discussed above, th at :
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Date: JUL 15 275
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