ML19256E899
| ML19256E899 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 09/10/1976 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19256E896 | List: |
| References | |
| REF-GTECI-A-36, REF-GTECI-SF, TASK-A-36, TASK-OR NUDOCS 7911150517 | |
| Download: ML19256E899 (7) | |
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UNITED STATES y '.
NUCLaAR REGULATORY COh* MsslON JW j
WASHINGTON,.D. C. 20555 N.-J }
SAFETY EVALUATION AND ENVIRONMENTAL IMPACT APPRAISAL SY THE OFFICE OF NUCLEAR REACTOR REGul.AT:0N SUPPORTING AMENDMENT NO. 32 TO FACILITY LICENSE NO. DPR-38 AMENDMENT NO.32 TO FACILITY LICENSE NO. DPR-47 AMENDMENT NO.29 TO FACILITY LICENSE NO. DPR-55 DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNITS NOS. 1, 2 AND 3 DOCKETS NOS. 50-269, 50-270 AND 50-287 Introduction By letter dated August 10, 1976, Duke Pcwer Company (the licensee) requested a change to the Technicai Specifications appended to Licenses Nos. DPR-38, CPR-47 and CPR-55 for the Oconee Nuclear Station Units Nos.1, 2 and 3.
The amendments would require that spent fuel assemlies stored in designated areas of the two Oconee spent fuel pools be decayed a minimum of 43 days prior to spent fuel cask movement.
Discussion By letter dated July 22, 1974, we requested that the licensee furnish, as an amndment to 'the Oconee FS AR, additional infomation on the Oconee facility design and operating procedures related to spent fuel handling that demonstrates that the objective of Section 50.34(b)(4) of 10 CFR 50 is met, or will be met by appropriate plant modifications. Section 50.34 (b)(4) requires that analysis and evaluation of the design and perfomance of structures, systems and components of the facility with the objecti';e of assessing the risk to public health and safety, in partictilar, including determination of the adecuacy of structures, systams and components provided for the prevention of accidents and mitigation of the consequences of accidents, be included in the FSAR.
Revision 36 to the Oconee FSAR, issued by the licensee on Septenter 23, 1974, included a description of the equipment used to handle spent fuel casks at the Oconee Nuclear Station. By letter dated August 29, 1975, we advised the licensee that revision 35 did not contain sufficient analysis to support its conclusions on spent fuel cask handling system accept-bility.
We therefore requested that tne licensee provide additional information.
By letterc dated November 3,1975, March 19,1976 and July 26,1976, the licensee provided the additional information we requested.
33b Ol 7 911 no 5jq
. The licensee was requested to specifically address the possibility of a spent fuel cask dropping onto spent fuel stored in the pool and the resultant radiological censequences.
In addition, the licensee's submittal was to include the effects on the spent fuel pool liner should the spent fuel cask strike it during the postuiated accident.
The licensee has
.nservatively estimated that up to 76 fuel asseslies could be damaged should a failure of the spent fuel cask handling crane or other cask handling equipment occur.
In order to maintain the resultant whole body and thyroid doses well within the exposure guidelines of 10 CFR Part 100 it was determined that all fuel asseelies in the spent fuci pool areas which would be vulnerable to impact from a postulated.
spent fuel handling cask accident should have previously been decayed for a minimum of 43 days. The licensee has therefore proposed that, prior to spent fuel cask movement, spent fuel stored in the first 13 rows of the Unit Nos. I and 2 connon spent fuel pool and in the first 20 rows of the Unit No. 3 spent fuel pool :losest to the spent fuel cask handling area in each pool, shall be decayed a minimum of 43 days following its last activation in the reactor from which it was removed.
Evaluation _
Our review of the Oconee spent fuel handling system involved an evaluation of the consequences of a spent fuel cask tipping and falling onto spent fuel asseelies in the spent fuel pool. The review included consideration of both the safety and environmental aspects of such a postulated accident.
Safety Considerations As indicated by the licensee, the path of travel of the spent fuel cask handling crane does not allow the spent fuel :ask to pass over stored fuel in either the pool common to Units Nos.1 and 2 or in the Unit No. 3 pool.
However, assuming a fdlure of the crane or handling equipment, and that the falling cask strikes the rim of the spent fuel pool or cask pie. form in the pool, it can be postulated that the cask would be deflected onto the stcred fuel closest to the cask handling area. The licensee has mmidered the worst situation to be a hoist cable failure when the cask is positioned over the fuel pool wall with a resultant eccentric drop of ths cask onto the wall. In such a case, the cask, as well as the yoke and load black of the cask handling system could be deflected onto spent fuel. The licensee provided an analysis of the failure postulated above to determine the nuntar of fuel asse211es which could be contacted. The Oconee Urit No. 3 spent fuel pool was selected for the analysis since it will have a higher fuel storage density as a result of the license amendment issued by us on Deceder 22, 1975, which authorized an increase in the fuel asse21y storage caoacity from 216 to 474 asse211es. The licensee described the assumptions employed and censervatisms considered be affected in the postulated accident.in its analysis and concluded that a maximu J
. Regarding the assumptions used by the licensee to detemine the resultant radiation exposure doses from the postulated accident, we indicated to the licensee that a fuel radial peaking factor of 1.65 and a X/Q, value of 2.2X10-4 sec/m3 (5% meterology at 1609 meters) would provide more con-servative estimates.
Using these values, exposure doses of less than 1 Rem Woole Body and 150 Rem Thyroid would be predicted if the 76 fuel asseslies assumed to ba damaged have first been allcwed to decay a min' mum of 43 days following reactor shutdcwn. These conservative assumotions and others we empicfed in our independent analysis of the spent fuel cask tip accident and the resultant estimated doses are summarized in Table 1.
In view of the above, the if censee has agreed to place technical specificatien restrictions on the storage of fuel asse211es in both Ocenee spent fuel pools to assure that spent fuel which might be certacted in a postulated dropped f.e1 cask accident has decayed for at least 43. days follcwing its last activation in the reactor from which it was removed.
The licensee also provided an analysis of the effects en the spent fuel pool liner should the cask strike it during this postulated accident.
I*. was indicated that the spent fuel pool concrete was originally designed for the cask drop accident. Should the t ! k. strike the bettem liner plate
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on the edge, hcwever, locali:ed concrete crushing of the fill concrete would occur and the liner plate would be ruptured in the area of imoact.
The licensee therefore analyzed this possibility to determine the rate that pool water would escape. The results of this analysis shcw that the calculated leakage would be 21.3 gallons per day and would be well within the capacity of the pool water makeup systems. We have neviewed the licensees analysis and have concluded that the conditions assumed were appropriately conservative and agree that more than adequate makeuo water would be available should damage to the spent fuel pool liner cccur.
In sumary, it is considered that the postulated dropoed fuel cask accident evaluated herein ~ excremely remote. Given a dreoced fuel cask, it is highly unlikely.
. damace woulo occur to a significant number of stored spent fuel assenuhes in either of the two Ocenee spent fuel pools due to the fact that the crane travel dces not pass over stored fuel assemolies.
Nevertheless, we have detemined that the analysis of the postulated dropped fuel cask accident submitted by the licensee uses conservative assunptions to obtain the maximum number of fuel assemblies affected. We have concluded that the assunctions and analytical techniques utilized are acceptable and that the licensee has adequately predicted the maximum number of fuel assentlies affacted.
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_4 Conclusion We have concluded, based on the considerations discussed above, that: (1) because the amendments do not involve a significant increase in the probability oc consequences of accidents previously considered and do not involve a significant decrease in a safety margin, the amendments do not fr6volve a significant hazards consideration, (2) there is reas;nable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in ccmpliance with the.Comission's regulations and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.
Environmental Imoact Acoraisal If, in a postulated fuel cask accident, the cask and associated handling device are assumed to tip and fall into the spent fuel pool and camage 76 fue? assemblies, the resulting thyroid and whole body doses would be well within the exacsure guidelines of 10 CFR Part 100 for 5 per cent meteorology as discussed above, and would be <1 Rem to the thyroid for 50 per cent meteorology. This is not significantly greater than the excected consequences of other accidents previously evaluated in the Oconee Fi.nal Envirenmental Statement (FES). Radioactive effluent releases frem postulated fuel handling accidents remain unchanged frem those presented in the FES of March 1972. The realistic assumptions and estimated consequences for the spent fuel cask tip are sumarized in Table 2.
In our Safety Evaluation supporting the license amendment issued on Cecenter 22, 1975, we indicated that the transfer of spent fuel from the Units Nos.1 and 2 spent fuel pool to the Unit No. 3 spent fuel pool would possibly start in about 4 years. The licensee has indicated to u:. that such transfers my actually commence in September 1976 following completien of the design modifications to the Unit No. 3 pool. As concluded in our Environmental Imoact Aopraisal supporting the December 22, 1975 license amencment, a maximun of about 150 spent fuel assemblies are expected to be transferred from the Units Nos. I and 2 pool to the Unit No. 3 pool over the life of the plant. The dose rate for the transfer of 150 assent 11es was calculated to be approximately 150 man-rem.
This was considered not to involve a significant increase in the expected occupational exposures as previously reviewed. We therefore conclude that the transfer of spent fuel assembifes between the.wo scent fuel pools earlier than previously expected is acceptable and should be allowed to proceed as is now planned.
- 7. regard to possible contamination due to the maximum expected spent fuel pool leakage of 21.3 gallens per day der to a ruptured liner plate, the licensee provided information indicatin-eut the nearest water source used by the public that would become contaminated is Lake Hartwell (Keowee River). Based on penneability tests conducted at the Oconee facility, it would take a minimum of four years for any leakage to reach the oil collection pond which is ultimately discharged to Lake Hartwell.
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5-This route is the most limiting of those examined. We agree with the licensee that four years would provide more than sufficient time to correct any damage to a spent fuel pool liner plate or to take att.tr measures '. ) prevent contamination of the Lake Hartwell Water source Conclusion and Basis for Necative Declaration On the basis of the foregoing analysis, it is concluded that thera will be no significant environmental impact attributable to the proposed action.
Having made this conclusion, the Commission has further concluded that no environmental impact statement for the proposed action need be prepared and that a negative d 2claration to this effect is appropriate.
Dat3: September 10, '976 1336 015
TAM.? 1 CONSERVATI7Z ASSUMPTIONS AND ESTIMATED CONSEQUINCIS FOR SPENT FUEC CASI TIP AT OCONEE 3 Power level 2928 Mwt Operating time 3 years Power peaking factor 1.65 Decay times 43 days
' Fraction in gaps:
Kr-85 30%
All other noble gases 10%
Iodine 10%
Number of assemblies damaged 76 Number of assemblies in core 177 Iodine Decontamination Factor in pool watar 100 Inicial inventories at time of shutdown:
I-131 25,080 ci/Mwt Ze-131m 259.5 ci/Mvt Ie-133 56,220 ci/Mvt T.r-85 410.2 ci/nvt 3reathing Race 3.47 x 10" =3/sec Dose, rem (43 davs) 3 5: I/0, sec/-1_
Thvroid
'a'nole Body 4
EAB C609 m) 2.2 x 10 150
<1 LPZ Boundary (9656 m) 4.0 x 10-5 27
<1 1336 016
TABLE 2 REALISTIC ASSUMPTIONS AND ESTIMATED CONSEQUENCES FOR SPENT FUEL CASI TIP AT OCONEE 3 Power level 2928 Mut Operating time 3 years Power peaking factor 1.0 Decay times 43 days Fraction in gaps:
Kr-85 20%
All other noble gases 2*
Iodine 27 Number of assemblies damaged 76 Number of assemblies in core 177 Iodine Decontamination Factor in pool water 500 Initial inventories at time of shutdown:
I-131 25,080 ci/Mwe Ie-131m 259.5 ci/Mwe Ie-133 56,220 ci/Mvt Kr-85 410.2 ci/Mwe 3
Breathing Rate 3.47 x 10-4 m /see Dose, rem (43 days) 50: I/0, sec/m3 Thyroid Wole Body EAB (1690 m) 4.7 x 10-5
<1
<t LPZ Boundary (9656 m) 2.5 x 10-0
<1
<1 1336 017