ML19262B953
| ML19262B953 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 12/20/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19262B950 | List: |
| References | |
| TASK-15-20, TASK-RR NUDOCS 8001220279 | |
| Download: ML19262B953 (4) | |
Text
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%.a SAFETY EVALUATICN BY THE OFFICE OF NUCLEAR REACTCR RE3ULATION REGARDING THE FUEL HAf4 CLING ACCIDENT INSIDE CONTAINPENT HADDAM NECK NUCLEAR POWER PLANT CONNECTICUT fANKEE AICMIC P0hER CCMPANY OCCKET NO. 50-213 I ntroduction By letter dated January 14, 1977, the staf# requested the Conne::icut Yankee Atcmic 3cwer Cce:any (the licensee) :: evaluate the crevicusly unevaluated :c-tential consecuences of a :cstulated Fuel ".andl'ng i :' den *nside Containment t
(FHAIC) at Maddam Neck. The licensee subnitted the evaluatien of the FHAIC in 1e::ers dated Marcn 21, 1977 and Oc:cber 14, 1977. The 1icensee stated that the
- ctential consecuences of this accicent are 14.55 Ren thyrcid and 0.51 Rem whole bcdy at :ne Exclusion Area Scundary (EAB) and 0.31 Ren thyroid and 0.01 Rem thy-roid at the L:w ?c:ulation Zone (L?!). The licensee ::ncluded that these deses are within the guidelines of 10 CFR Part 100.
- n :ne evaluation, the licensee assumed that after shutdcwn there is a 72-h:ur decay time before fuel handling.
Since this assum: tion is not based en limits in the Ha: dam Neck Technical Soecifi-cations, the staff recuested the licensee, oy letter dated Jar ~ary 3,1979, to con-firm the assume: ion er procose a technical scecification incer; orating this limit.
By le::er datec March 5,1979, the licensee submitted the refueling schedule for
-iaddam Neck wh'ich cu;linec two scenarios. The licensee statec that an :::timistic (cuickened) schedule would allow for 4 days between shutdewn and fuel movement, while a realistic schedule would allcw for 9 to 10 days between shutdcwn and fuel movement.
Evaluation We have completed our review of the licensee's March 21 and October 14, 1977 and Marcn 5,1979 submittals which address the potential consequences Of an accident involving scent fuel handling inside containment. During refueling at Haddam Neck a :ersonnel and ecuipment hatch is maintained cpen.
7he cpen personnel and ecui: ment batch :r:vides an unfiltered :athway to the atmes:here for radicactive ef#luents released fellcwing a ;cstulated FHA!C.
Because of this, the licensee was recuested to assure tha: the :c ential c:nsecu4rces Of this accident are a -
r riately within the guicelines Of 10 CFR Part 100. The licensee stated in -he 3 ::ter la,197' let er that a ter.:crary Occr is 'nstalled wni'e the :ersonnel a :- is ::er and tha, due :: the ::eration of the CO tai-er : urge system, a negative :ressure wcul: be exertec en - e :entainren tuil di g.
T'-is nega-ive
- -essu e wil' end : craw air in :hrecgn -he urge '
ake arc aise s:ce air in r: ugh the :ersonnel hatch (b!ccked :y a tem:crary :::r), and all wculd leave
'ia e #il terec Urge discharge.
.e Mave revieried the Id:ersee's 3c :ber 14, 19'7 ie ter %nich aCdresses this issue, 3nc have c:rClucec tha! All radicaC:ive s
x 2N 800122o
. effluents released follcwing a FHAIC will be filte-M prior :: release to the atmosphere. We have also concluded that the assumption of a 72-hour decay time between shutdown and fuel movement is censervative and that ec tech.ical s:e-cification be required for this limit in the Hadcan Neck Techn':al Specifica-tions.
We have performed an independent analysis of the FFAIC. Our assumptions and the resulting potential consequences at the EAB are given in the attached Table 1.
The difference between tne licensee's and staff's results, are the different X/Q values used in the respective analyses.
The calculated potential consequences of the postulated FHAIC are aopropriately within the guidelines of 10 CFR Part 100 and are, therefore, acceptable. Accropriately within the guidelines of 10 CFR Part ICO has been defined as less than 100 Rem to the thyroid. This is based on the probability of this event relative to other events whicn are evaluated against 10 CFR Part 100 exposure guidelines. Whole bcdy doses were also examined, but they are not controlling due to decay of the short-lived radioisotoces prior to fuel handling. The potential con-sequences of this ostulated accident at the Low Populaticn Zone Scundary are less than those given for the EA3 in Table 1.
1 The results of a recent study / indicate that drocoing a scent fuel assembly into the core during refueling operaticns may potentially cause damage to more fuel pins than has been assumed for evaluating the FHAIC.
The results of this study also indicate that up to all of the fuel pins in two spent fuel assemblies, the one dropped and the one hit, may be damaged because of the embrittlement of fuel cladding material frcm radiation in the core.
'he :rcbability of the costula ed fuel handling at: ice-- i side containment is smal l.
No: Only have there been several huncred ea:::r-years of :lant c: erat-ing ex:erience with only a few accicents inv lving s:ent f.el :eing drop;ed into the core, but none of these accicents has resultec in easurable releases of ac-tivity.
The potential damage to s;ent fuel estimated :y - e study was based on the assumption that a s;ent fuel assembly falls about N feet directly onto one other assembly in the core; an imcact wnich results i the greates energy avail-able for crushing ne fuel cins in both assem: lies.
-i s yce of ircact is un-likely because the falling assembly would be subje: ec to : rag for:es in the water wnien shcula cause..9e asserbly to skew out of a.'erti:a1 'all :ath.
3asec on the above, we have concluded tha: the likel d r:cd f a s:er. fuel assem-
- iy #al'ing in : the : re and damaging a the 'ue' pins in two assamblies is suf-
'iciently s.ali :na: refueling inside contai-~ert is not a safety ::rcarr. which ecui es remedial action.
1/
'. 5 ngn, " uei :ssem:ly 'ancling :::d:er-Analysis," EG&G Idaho Te:hnic31 e:Or: :E 2-227, Oc:::er '973.
1785 324 o
- p a rom n3 e
M J
J1 XlnL
. We have, however, conservatively calculated the potential radiological conse-ouences of a fuel assembly droo onto the reactor core with the rupture of all the fuel pins in two fuel assemblies. We have also assured for this Costulated accident that the source tem for both spent fuel assemblies is consistent with that given in Regulatory Guide 1.25.
This is conservative because (1) these two assemblies should not have the power peaking factor and clad gao activity recommended in Regulatory Guide 1.25 and (2) the pool decontamination factor for inorganic iodine should be greater than that recommended in Regulatory Guide 1.25.
The calculated potential radiological consequences at the exclusion area bcundary for the complete rupture of fuel pins in two assemblies are twice the values given in Table 1.
Because these potential consecuences are aopropriately within the guidelines of 10 CFR Part 100 using the conser-vative assumptions of Regulatory Guide 1.25, we have concluded that the poten-tial consecuences of this costulated accident are acceotable and no additional restrictions on fuel handling coerations and clant ::erating precedures are needed.
Ne also investigated the consecuences of a fuel assembly droo onto fuel stored in the scent fuel pool.
For this, a drop of 2-1/2 feet was costulated ud the analysis was cerformed in the same manner as previously described.
Results indicate trat in tnis scenario, damage to the missile or target is minimal.
.lo fuel cins in ei ner fuel assembly were calculated to be ruotured.
Envirenrental Considerations The envi annental imoacts of an accicent involving the handling Cf scent fuel in-side containrent have been adcressed in Section 7.1 cf ne Final Environmental 5tatement (?ES) datec Cc:ocer 1973, for the coeration of 'addam Neck.
Conclusion The staff has evaluated tne licensee's analysis of the postulated FHAIC.
Af ter perfoming an indeoendent analysis of the radiological consecuences of a FHA!C to any individual located at the nearest exclusion area boundary, the staff concludes tnat the doses for one assembly failure are approoriately within the guideline values of 10 CFR Part 100 and for failure of two assemblies witnin the guideline values of 10 CFR Dart 100 and are, therefore, acceptable.
Attacned: Table 1 Date: December 20, 1979 1785 525
Table 1 ASSUMPTIONS FOR AND POTENTIAL CONSEQUENCES OF THE POSTULATED FUEL MANDL1r4G ACCIDENTS AT inE EXCLUSION AREA : Cut.UARY FOR MADDAM NECK NUCLEAR PCWER PLANT As sumo tions:
Guicance in Regulatory Gui ce 1.25 Power Level 1562 Mwt Fuel Exposure Time 3 years Pcwer Peaking Factor 1.65 Equivalent Numoer of Assem-olies camaged 1
Nuncer of AssemDlies in core 157 Charccal Filter Efficiency Elemental anc Organic 90 per:en:
Decay time oefore moving fuel 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> 0-2 hcurs, X/Q Value, Ex-clusion Area Boundary
-3 3
(ground level release) 1.0 x 10 sec/m
- ses. Re:
Thyr:id ancie 3 coy Exclusicn Area Scunary (EA3)
Ocnsequences frca Accicen s Insice Contair. ment l '.
~.7 e
17815 326
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