ML20205A773
| ML20205A773 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities, 05000000 |
| Issue date: | 03/18/1977 |
| From: | Turbak M COMMONWEALTH EDISON CO. |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20205A758 | List: |
| References | |
| NUDOCS 8810260095 | |
| Download: ML20205A773 (8) | |
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March 18, 1977 l
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Mr. Demte L. "terum. Chief 0,9erating Rosetors - 39anch 2 f
i Dtyteten of C3eratin7 laaeters U.S.1:uelear Ro;mle*eru Cc rsteeton 1
Woohington, D.C.
20'e11 j
Subjoet:
Droeden stetten Unite 1. 3. and R W Cittee station Unita 1 and 3 l
Inquiry Ct<ncerning Eefueling teoid.nt AM3yste NNL N 6 e t ':r. o. 5n-837. till. 3116 and Illj.
References (e):
D. L. rier. ann letter to A. t..
telger Jewd Jvnuany 17. 1977 eeneerntag Despeden Unit 1.
t (b):
D. L. 7.ienenn letter to R. L. telger j
de' red January 17, 1977 concernias Draeden Ustte 2 and 3.
(e):
D. L. Tienienn letter to R. L. Be yer de%d Jenuary 17, 1977 concerning
@pd-Cities Unite 1 and 2.
l Deer Hr. Ziesennt i
References M and (e) stated that your preltninary review of l
a refuelins accident 14 side the rector conteir.ent bailding was een-r l
sidered durint the Itc<pt.r.ing review for Dresden Unite 2, 3 sad @ sed.
Cities Unite 1 and 2.
We eencur that this aestdent has been enelyste i
j and is presented in Seption 146.2.2 of the FSAA fee both stettene.
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Referenee (el requested en evaluetten of the potes(14 een.
i eoquenees of a refuellig seetdent inside the eentalmeent bu14 ding for Dreedon Unit 1.
We ha<re sade en evaluetten of the propeeed seeident and determined that th0 potentist ette bouMary redtatten emposure eue to such en eeeldene wde he relatively leo and well within 10 Cru l
Part 100 p.uteslines eepn assumint ne centstevnent toeletten er efflueet l
2 fiktretten. The ettecited Entleeure 1 provideo the requested enelyste.
I In addition, a brief desertption af fuel neveuent tJring refueling operettene fipr Drreden V11t i us reTuested in sueeelvent rettvers et tone.
Refuel.Ing settvittcn do cut ellcae eere than pne t%el j
acessably ever tr.e core et any tire.
Refer to deettag in Enelesure 2.
The refueling trane (C) to pieced ever tM tore (A). A j
transfer basht te sh'1eee.uently p1v:ce in the North eum (C) by the j
overhead crane (D). W ie basket phyeieelly cannet be reved cret the i
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. March 18, 1977 Mr. Dennis L. 7.iemenn core because of interference with the refueling ersne. M from the core is then inoved, one assernbly et a tir.e. to the transfer basket utilizing the refueling crane. This crane has a talescoping hoist with specisi r,rspple ter use with a fusi ensembly bail. The tronefer baskec has a capacity of sixteen (16) ensemblies and is not phyetestly j
capable of being lifted by the refuel crane.
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with the uverhead crene, the transfer beaket is qved ever (Couth) and down the transfer tube (E), into the fuel basket carrier (r).
The carrier is rolled into the transfer pool (G). i Using the fuel handling crane (H). one fuel assembly at a time is transferred froen the basket to th0 fuel storene pool (!).
Plea 2e addross any additional questions 04 this ahtfor to this a f fle e.
Very truly yours,
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M. 5. Turbek NuoleepLieer.3ingAdsknistrator Boiling Water Reactorp 3
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llNCLOSURE 1.
f DETAILED EVALJATION OF THE POTENTIAL CONSEQUENCkS OF A REFUELING ACCIDENT INSIDE THE DRESDEN NUCLEAR POWER STATION UNIT 1 CONTAINMENT l
I.
Introduction This evaluation lo the response requested by the Nuclear Regulatory Commistion in their letter to the Commonwealth Edison Company daued January 17, 1977 (Reference 1).
II.
Identification of _Causes and Frequency Classif_icatidn_
The fuel handling accident in containment is assumed to occur during refueling resulting, as a consequence of an undefined event, in the dropping of a raised fuel assembly onto the top of the core.
Thi s accident is expected to' occur with the frequency of a li miting f ault.
III.
_ Sequence of_ Events and Systems Operation i
During the refuel ing operation a portable continuou) air monitor is moved to refue ling floor level.
This monitor, upon reaching a high radiation setpoint, produces a local alarm.
A continuous air monitor which takes samples from the containment purge system downstrean of the exhaust f ans, upon reaching a high radiation setpoint, produces an alarm signal in the control room.
In addition, there are several area radiatiQn monitors in containment which produce a local alarm upon redching a high radiation setpoiat.
The radiation moaitors and containment purge systed are envi-ronmentally qual Lfied for operation during the normal station operation and du ring refueling.
The two types of radiation monitors protect against a single failure.
The two isolation valves in the containment purge line supply the necessary redundancy.
The Approximate Elapsed Time heading used in this hootion refers to the timo that airborne activity has been released to the environment.
Tre approximate elapsed time, therefore, remains zero until the a irborne radioactivity in the containment purge system reachos the first isolation valve.
Both the inboard and outboard isolatJ on valve in the containment purge system would i
normally be clooed by station personnel upon the detection of high radiation as discussed below.
The above assumption used to define the approximate elapsed time is conservative because it is assumed that the outboard valve fails open under a single failure.
The analysis of the sequence of events and systemd, operation is l
as follows:
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ApprExicato slapsed Tine Event 0
Fuel assembly is '.>eing handled by refueling equi pment.
The 1.
to the top assembly drops on of the core.
Some of the fuel rods in both the and reactor core dropped assembly lting in the are damaged, resuctive noble gases release of radioate to the reactor and gaseous iodiltion of the gaseous coolant.
A frac radioactivity beccmes airborne in the containment partially mixing with the containment atmosphere.
air enters the The containment intainment purge intake of the ce es the inboard system and reach isolation valve
<1 minube r monitor or one A continuous ai ea radiation monitors 2.
of the' local ar plant personnel.
alarms to alert The conservative engineering activity
<10 ginutes ion is that the plant 34.
rolesse assumpt lly close the contain-personnel manutem isolation valves.
ment purge syst
<30 minutes avative activity 3b.
The ultraconse tion is that the relorse assump never isolated and containment is ne activity in primary all the airbor released to the containment is per Regulatory Guide environment asory Guide 1.25 states 1 25 Regulat,etivity is released that all the ax period.
Additionally, over a two hoto release time of less a conservativos is indiceted in this than 30 minut die release is assumed to analysis and tirely under fumigation take place enthe containment purge rate, conditions,
ef fect on the calculation thus, has no onservative tsdiological of the ultracof this accident.
consequences (
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core and System Perf_ormance A.
Mathematical Medel The analytical methods and associated assumptions used to evaluate the con pequences of this accident are based on the conservative assumptions of Regulatory Guide l'.25 (Reference 2).
B.
Input Parameter 6 an-1 Initial Conditions The input parameter s and initial conditions for this accident are based on the following assumptions.
1.
The radionuclidLe activities at shutdown in the highest rated a ssembly are found by dividing the core inventory by the number of fuel assemblies and multiplying by 1.5.
The multiplicative factor is necessary to correct the activity to the minimum acceptable radial peaking factor of 1.5 as required by Regulatory Guide 1.25.
The core is rated at 700 MW thermal and contains 464
.L.
assemblies.
2.
The containment free volume is 2.873x10' ft.'
3.
The containment purge system is rated at 7200 cia.
4.
There is no charcoal filtration system for radio 4 e
icdine removal within the containment purge system.
5.
The equivalence of twice the gap activity of the highest rated f uel assembly is assumed to be released withir, the reactor vessel water volume upon impact of the dropped fuel assembly with the core.
6.
The accident oteurs 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after plant shutdown.
7.
The EAR is 0.5 miles.
8.
The EAD x/Q is 1 4 x 10"' s/m3 under fumigation conditions at on elevated release of 300 feet (rigure 4 of Rogulatory Guide 1.25).
9.
All the gap acuivity of the damaged rods is released and consists of 10% of the noble gases other than Kr-N5, 30% of the Kr-85 and 10% of the radioactive iodino in the rods at the time of the accident (Reguhatory Guide 1.25).
10.
The noble gas and effective radiciodine reactor vessel water dacontamination factors are 1. and 100, respectiv11y (Regulatory Guide 1.25).
oo,.., oo u.o u..c.,. ~-cm r -
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i rate is 3.47x10~" m'/s (Reguictody J
11.
The breathing Guide 1.25).
4 12.
The airborne activity released into containmen4 by cal accident is.ixed with 10% of the m
the hypothat l containment tree volume before being exhausted by the containm ent purge system.
13.
The adult iotine inhalation thyroid dose conveksion
, factors are from Regulatory Guide 1.25.
14.
The radionuclidic average gamma energies per disin-tegration are from OKNL-5114 (Rafsrance 3).
C.
Re sults_
ionuclidicactivityreleasedtotheenvi-The amount of rad ronment during tr,e 10 minutes (conservative engineering estimate) before the containment purge valves close is calculated to be the following Activity Released to the Environme nt, Ci (Cons _rvative Engineering Estimate) e Radionucl i(g 28.2 1-131 20.3 I-133 4.76 I-135 28.1 Xe-131M Xe-133M 126.
5150.
Xe-133 Xe-135 174.9.67 Kr-85M Kr-85 108.
3.57 Kr-88 dionuclidic activity released to the envi-The anount of ra ronment if the purge valves fail to close (ultracchservative estimate) is calculated to be the followings.
Activity Released to the Tnvironnent, Ci (Ultraconservative _ Estimate) '
Radio nucl_ide 130 I-131 91.8 2-133 21.5 2-135 127.
Xe-131M 569.
Xe-133M 2.32x10'
'Xe-133 786.
Xe-135 43.6 Kr-85M 489.
Kr-85 16.1 Kr-88 I
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Barrier Performancq hi:s acci-
$e barriers is not affected by ttivity is released V.
i The integrity of t dent.
All radioac the containment purge system.
auences Radioloaical Conss (10 minutes release bef ore VI.
The conservative engineeringEAD doses are calculated to be 2.5 1on)
The containment isola 4 and.01 rem to the whole body.d all.acti-rem to the thyroid (no containment isolation and to the environment ultraconservative containment is releaseEA5 doses are calcu vity airborne in ponditions).05 rem to the whole body.
under fumigation d doses at.the EAR thyroid and be 11 rem to the mptions yield calculateCFRICO guidelines of 300 h
thyroid Both sets of assu well below the 1( whole body.
and 25 rem to tho to R. L. Bolger (Cormonwealth VII.
References L tiemann (NRC)Dresden Nuclear Power St.ation Unit 1,
=
1.
Letter, D.
, RE:
Edison Comp any) 0, January 17, 1977.
Docket No.
50-1 (Saf ety Guide 25), " Assumptions Guide 1.25 2.
Regulatory aluating the Potential Radiological Conse-l Handling a Fuel Handling Accident in the Fueracility f i
Used for Ev d Water quences of and Storago Reactors," March 23, 1972.
fpr Selected J., Editor, 'Huolear Decay Data l Labo"dtory, i
fes," ORNL-5114, Oak Ridge Nat ona Martin, H.
3.
Radionucli Tennessee, March 1976.
Oak Ridge, 6
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