ML19224A757

Discusses NRC Procedures for Decision to Recommend Evacuation

ML19224A757
Person / Time
Site:	Crane
Issue date:	04/01/1979
From:	NRC COMMISSION (OCM)
To:	NRC COMMISSION (OCM)
References
NUDOCS 7905300211
Download: ML19224A757 (7)

Text

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[f!hbh[1bbb b h. i. h i i i l' I 1 !.. ) Unplanned Events l. EXPECTED PLAllT AEEASE UAidituG EVACUATION EVEliT , RESP 0t!SE ARID TIME TIMF. SCErlARIO

1. Loss of vital Restore function withir flo significant Possible pre-function or un-1 hour change cautionary planned leaks.

evac 2 mt; sta) ~ inside 5 mi Switch to Alternate Small leak less possible pre-Examples Function involving than 1 gal / hour cauticna ry 4 Primary Coolant in evac 2 mit Reactor Coolant Auxiliary But1 ding stay inside Pump Trip; 5 mi Loss of offsite Large leak 2 hour Evac 2 miles power; 50 gal / min Stay Inside S miles Loss of feed-water; Serious possibility of failure to restore a Depressuriza tion vital function to go oa RHR; Leak in Auxi-liary Building mNu-{ ~ co s. u These tables incl >de a number of ass imptions about activity and weather, chosen calistically4 In in actual release, the release rate and weather should be evaluated as they are at the time, and N the decision base 1 on those values.

~ E.XPECTED PLAtiT RELEASE. ImElllG EVACUATI0ri EVEllT RESP'IISE AtID T IME T_13. SCFl{AftIO

2. Sequence lead-liaintain Containment Design Contain-4 hour Precautionary, ing to Core Integrity (likely) with ment Leak Rate Mel t Containment Cooling Evac 2 mi all i

around and 5 mi, 90' sector stay inside 10 mi 3i l; Containment expected to Significant 24 hour Evac 5 mi all Breach release of core (time for con-around and 10 fission products tainmen,t failure) mile, 90" sector, stay inside 15 mi l

3. Ilydrogen flame Hixture in flammable Precautionary 9o*

or explosion range 2 mi (?) f 6 -N bf, l possible inside 1 j reactor vessel Explosion; major j 7q. damage Core Mel t See 2

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4. Evacuate or Lose Loss of Control Treat Evac 5 mi all Control Room like major release around and 10 l

. as mi 90* sector, N stay inside 15 miles t.n m g .. +. l ' - l.~ ~; y,'f i l F' ) A 9 5

i EXPECTED PLAllT IILMi\\SE IlARillflG EVACUATI0tl EVEtiT RESP 0tlSE Arid TIME TillE JCFNARIO Planned Probability of losing Timing of maneuver Precautionary !!anuever vital function can be set.to evacuation 2 l provide as much iniles, stay time as necessary inside 5 miles PLUS 1 See releases under See outcomes loss of vital under loss of function vital function. e M bw 1 6s

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Action Guidelines LM; 'nd R=?s Notify evacuation authorities two hours in advance (if possible) a. r.,s-h1 I;$) to standby for a possible eYecuation. i5 7:it FJJ b. Projected doses of I rea whole body or 5 rems thyroid. stay Sw SS inside. yA !3 '@T5:!M+% Projected doses of 5 rems whole body or 25 rems thyroid mandatory c. h [ evacuation of all persons. t,z:w i=g U m<f D353 ?> Assumes general warning already that some form of evacuation may >s w% L lM become necessary. m.W, $m F%9

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mb m SM E. ~ 4.1 Mr W, M_ @hl @Ni 167 154 5??$ g; A$g$ tr ~ m%i wa

gw 222 55i Mi gg Veather -53 70 The table is based on a realistic prediction of the weather for the next c?i

e gjj few days, based on the April 1 forecast which would result in high doses m$

S at a given distance. At the approach to decision time for evacuation, the EF appropriate meterological condition will be factored inte the dose estimates 8 k,. ta determine the evacuation time, sectors, and distances for the evacuation. $3 NRC is predicting the dispersion characteristics of the region for the 6 k{q currently measured meteorology as the incident progresses. Rain could lead g$5i to higher local radioactivity levels. N 911 : if Heat Generation 9 13 h The reactor core is now quite cool compared to the conventional design-b?; G9 basis calculations. N 1. The reactor is new, so no fuel has more than 3 months equivalent h,, operation, compared to 1-2 years average for other plants, e a

• i0 2.

The neutron chain reaction has been shut down for over 4 days, .mQ {h, It should also be noted that the concrete basemat of this plant is m m unusually thick.

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As a result of the above differences, calculations for this piant at this time predict that the core will not melt its way through the containment. a e n R 167 155

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ig) 5L15 2 5 o / C o e-e. 7n1e.t-I-pouas) '~ e-r ~ Evsa y / Spesej s f c.colen o}mhos y,cn Ec3 ff=4 $m ave b C [g$ p g o SIOV) A 8.o w E u>dd*GL 'SW 05Abu.l> g .x san; starr sv ,.1 2 d l1re=100' min Cor'e starts to - .s u n co v s /R. ....;g/. Eg

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$3 7 Time 150 min. Core begins to n%1t a s/f. e g Q." r :' q . 3-Tir,e=200 ain Molten core is in lower hean of reactor vessel, pressure M- ,,g:.wi. - is 2500 psia ~~ a ik .. Tine =210 min Reactor vessel fails, containment pressure goes to 25 psia e. Q #. q:.. k > Steam explosion possibility;.- c:inor consequence ~)Tice=216 min Hydrogen burns, co'ntainment; pressure goes to 67 psia ms y ara..x ,,8

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?p-l COHTAINMENT SURVIVES (Failure assumad 130 psia) an ,. 7,.., : { Tjr.a=10 hours P.olten core'has celted about 1 r.eter into bassmat 3 h4 (( ice days-P.ajor problem - handle hydro' gen, oxygen - r.aintain contain-a y r.ent integrity wt .? M - Keep sprays. running CAUTION: Mh - Keep water many feet over rolten debris -( - UITHOUT RECO BILLERS Hydrogen continues to' build up d, ?? BASEPAT SURVIVES Y3 fEven't 1

Conclusion:

This event should not produce major releases g 9 w g ~ - Sprays'and Coolers Failed Before Flow Stops Event 2 Time =0 to Times 210 min'. Same as Event 'l - containment pressure is 25 psia 18 g m Time =810 min Contairment pressure is 70 psia %? }$ Ti=e=1 day '. Containment fails due to steam (mostly) overpressure - S about 135 psia ' 1:. ~ ]p . C0!!TAltifENT FAILS r g [i Event 2

Conclusion:

This event leads to major releases. s g R:.L 167 156 O. . u' t Q ~~ ^ s a .}}