ML19289G302
| ML19289G302 | |
| Person / Time | |
|---|---|
| Issue date: | 07/30/1979 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Drey K AFFILIATION NOT ASSIGNED |
| Shared Package | |
| ML19289G303 | List: |
| References | |
| NUDOCS 7908210604 | |
| Download: ML19289G302 (2) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION y
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JUL 3 01979 Ms. Kay Drey 515 West Point Avenue University City, Missouri 63130
Dear Ms. Drey:
Chairman Hendrie has referred your letter of June 21, 1979 to me for reply.
In your letter you have asked questions concerning the Nuclear Regulatory Connission's (NRC) consideration of preparing an Environmental Impact State-ment for allowing an increase in uranium fuel burn-ups (mwd /MTU), including in the statement discussion of fuel integrity with higher burnup and the use of stainless steel fuel cladding as the alternative to Zircaloy.
Your reference to higher uranium "end of life burnups" (E0B) in reactors is directed toward a program between the U. S. Department of Energy (DOE) and the Nuclear Industry considering higher nuclear fuel efficiency by extending the fuel burnups to increase the megawatt days per metric ton of uranium.
In or-der to implement such a program the fuel assesmblies containing the uranium fuel would have to demons: rate sufficient integrity over the extended burnup period. To date, two licensees have requested approval to irradiate a few assemblies (up to 3% of the core) to higher burnups during only one or two fuel cycles. A fuel cycle is the time interval between plant refuelings.
The NRC staff has reviewed these limited experiments relative to the require-ments set forth in 10 CFR Part 51, and the Council of Environmental Quality Guidelines, 40 CFR Part 1500.6. On the basis of these individual assessments, Negative Declarations were issued. Copies of the Environmental Impact Ap-praisals are enclosed for your information.
At present, the industry, primarily through these programs supported by DOE and the Electric Power Research Institute, is developing a data base to demonstrate the integrity of fual rods capable of a higher E0B than the current incustry E0B. These programs are currently at the stage of designing test assemblies and extending the burnup on existing assemblies for specified periods of time as a prudent first step towards the goal of a core relcac with extended burnup fuel.
A core reload of such fuel is still a long time from fruition.
The industry does have limited experience with fuel rods irradiated to high burn-ups. The Shippingport reactor contained four Zircaloy clad UO fuel bundles which were irradiated for 11.2 calendar years with no detrimental effects. Westing-house has experience from the Zorita and Saxton reactors with rods which attained Durnups up to 57,000 Mwd /Mtu. No adverse effects were found upon detailed exami-nation of these fuel rods.
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l Experience such as this gives the NRC staff confidence to allow the lead test i
assambly irradiations to high burnups. These irradiations, coupled with de-tailed pest-irradiation examination, will in turn give the confidence neces-sary to judge their efficiency for core reloads with extended burnup fuel.
Stainless steel is no longer the preferred cladaing material for most light water reactors because it absoros more neutrons than does Zircaloy. Using the thermal macroscopic cross section as an indicator, stainless steel is a factor of 2o more effective at absorbing neutrons than Zircaloy. Therefore, there is a large economic incentive for using Zircaloy cladding because of the lower uranium ore and enrichment requirements due to the better neutron econony with Zircaloy. Stainless steel is, however, used in two U. S. PWRs. The experience with stainless steel has been good in these PWRs.
In boiling water reactors (BWRs), stress corrosion cracking of stain'ess steel during normal operation is an additional incentive to use Zircaloy waich is not susceptible to this problem. Only one BWR in the U. S. uses stainless steal cladding and the cladding integrity history has not conpared f avorably with that in BWRs with fuel clad in Zircaloy.
Zircaloy cladaing has a high resistance to corrosion in both reactor and spent fuel environments under normal conditions. However, under accident conditions there is no advantage to stainless steel over Zircaloy. Above approximately 2200 F, both stainless steel and Zircaloy react with water (steam) to give ort hyarogen. The reaction rate of stainless steal with water (steam) is greater than that of Zircaloy with water (steam).
In addition, both stainless steel and Zircaloy produce the same number of moles of hydrogen per mole of water. Stai n-less steel does have the advantage of a significantly lower heat of reaction.
l Also, stainless steel does not undergo embrittlement with oxygen as does Z1rcaloy.
The melting point of Zircaloy is 3330*F conpared with 2550 F for stainless steel.
For accicent scenerios with some core uncovering similar to that which occurred at Three Mile Island Unit 2, the higher melting point of the cladcing might result in f
less deformation of the fuel pins. Taking all these considerations into accourt, stainless steel does not offer any significant advantage over Zircaloy as a fue' rod cladding but could certainly be used as an alternative core cladding.
Sincerely, Originai S@ed By i
E. G. Ca:e 9
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Harold R. Denton, Director
^0ffice of Nucleer Reactor Regulation
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Enclosures:
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NUCLEAR REGULATORY COMMISSION
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.,, w y ENVIRCNitENTAL IMPACT APPRAISAL BY THE OFFICE OF NUCLEA2 2.EACTC2 REGULATION SUPPORTING AMENDME!!T NO. 44 TO FACILITY OPERATING LICENSE 'Q.
DPR-39 AND AMENDMENT NO. Al TO FACILITY OPERATING LICENSE NO. CPR-48 COHf10NWEALTH EDISCN COMPANY ZION STAT;0N UNITS 1 AND 2 DOCKET NOS. 50-295 AND 50-304 Descriotion of Procosed Action Environmental Imoacts. of Procosed Action A; required.by NEPA and 10 CFR Part 51.7, we have evaluated the potential environmental impacts of the proposed action.
Included in our review has been a consideration of our conclusions in the Final Environmental State-ment (FES) for Zion Station Units 1 and 2 dated December 1972.
The irradiation of the four Zio.11 spent fuel assemblies to extended burnups in Zion 2, up to about 55,000 MWD /T, will increase the amount of long-lived fission products in the core. The only significant long-lived radionuclide with respect to potential consecuences of the postulated cesign basis accidents is the noble gas Krypton 85.
Extending burnups of the core up to about 44,000 tiWD/T will not increase the amodnt of Krypton 85 which was assumed in the fuel at Zion 2 for the postulated design basis accidents. The increase in the amount of Krypton 85 in the four fuel assemblies from 44,000 MWD /T to 55,000 MWD /T is not significant compared to the total amount of fission noble gases in the fuel. Therefore, the environmental impacts of the postulated accidents given in the FES will not significantly change because four fuel assemblies in the core are irradiated to burnups up to 55,000 MWD /T.
As noted in the accompanying Safety Evaluation Report (SER), we expect that operating Zion 2 with additional irradiation of four spent fuel assemblies from Zion 1 could increase the fraction of failed fuel in the core over that previously experienced. This would increase the co'ncentration of activity in the reac*ar coolant (RC) and the amount of activ':y released from the plant as compared to releases during operation of the plant in previous cycles. An increase in the concentration of RC activity would be an indication of fuel failures and an incication.of 1.ater increases in the anount of activity releasec frca the plant.
However,.:s do not ex:i:t tnese increases to :e si;nf #i: ant oe:ause, 'll :C.* fc.
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e in the core (2.1".) will be irradiated to the exten:ed burnups, (2) due to restrictions in the plant Technical Specificati:ns, these four assemblies will be located in the core where the,cperating thermal stresses in the cladding are relatively low and where the tnen al limits for cladding should not be approached, (3) there are no design enanges in these four assemolies from ones previcusly irradiated at Zion 2, and (4) the licensee will examine the four spent fuel assemblies before their insertion in the Zion '2 core for their fourth cycle and will only irradiate them in a fifth cycle after these assemblies have demonstrated satisfactory fuel perfomance in the fourth cycle.
If there is a significant increase in RC activity it will be detected oy monitoring the activity of samples
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of the reactor coolant, the radwaste treatment system and the plant effluents. This is discussed in Section 9.3,11.1.2.2 and 11.1.2.3 of the Zion Station FSAR and required in Table 4.11-1 and Specification
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4.3.5. A of the plant Technical Specifications.
Based on the above, we conclude that the environmental impacts discussed in the FES are still valid for Zion Unit 2 for the proposed extenced burnup program.
The plant contains waste treatment systems designe: to collect and process the gaseous, liquid and solid waste that mignt contain radioactive material.
The waste treatment systems are evaluated in the FES. There will be no-changes in the waste treatment systems described in Section III.D.2 of the FES because' of operation of Zion 2 in the extended burnup program.
We have considered the effect of irradiating four scent fuel assemblies to extended burnups in Zion 2 on the environmental impacts from the uranium fuel cycle and from saipping fuel and waste to and from Zion S tati o n.
Irradiating these four spent fuel assemblies to extended burnups is not expected to change the number of fissions in Zion 2 over the operating lifetime of the plant, therefore, the am:unt of fission products generated by Zion 2 over its operating lifetime would not change due to the proposed program.
The licensee has been adding four low burnup spent fuel assemblies from Zion 2 Cycle 1 and sixty new unfrradiated fuel assemblies to Zion 2 during each annual refueling. The use of low burnup fuel assemblies from Zion 2 Cycle 1 will be postponed for one and possibly two cycles during the extended burnup program to irradiate the four spent fuel assemblies.from Zion 1.
Af ter the extended burnup program is completed, the licensee intends to resume adding four icw burnup spent 'uel assemblies from Zion 2 Cycle 1 curi g Zion 2 refueliags. There# ore.
e 'icensee c0ule use u ::
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fewer ne.. assemolies : vin; the license ::ernig lifetire of j1 a
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. Zion Unit 2.
Eight fuel assemblies are an insignificant fraction (about 0.3%) of all the fuel assemblies that could be expected to be used at Zion Unit 2.
Therefore, on the average, each fuel assembly will have the same magnitude of fission products as if the fcur assemolies were not irradiated to extended burnups. Based on this, we conclude that the proposed extended burnup program will have no significant effect on the environmental impacts associated with the uranium fuel cycle and from shipping fuel and waste to and from Zion Station.
Summa ry On the basis of the above, we conclude that it is ac:eptable from a radiological standpoint to operate Zion 2 with four fuel assemblies previously irradiated for 3 cycles in Zion I without additional restrictions in the Technical Specifications beyond those proposed by the licensee for the four fuel assemblies.
Conclusion and Basis for Necative Declaration On the basis of our evaluation and information supplied by "the licensee it is concluded that the proposed action will have no appreciable impact on the environment due to radiological effluents from the plant and will not affect the cost-benefit balance.
Having reached these conclusions, the Commission has determined that an environmental impact statement need not be prepared for the proposed license amendment and that a Negative Declaration to this effect should be issued.
Date: March 7,1979 208,z 278
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- 5 SAFETY EVALUATION AND ENVIRONMENTAL IMFACT APPRAISAL BY THE OFFICE OF NUCLEAR REACTOR REGULATION 1'
SUPPORTING MENDMENT NO. 65 TO FACILITY OPERATING LICENSE NO. OPR-38 AMENDMENT NO. 65 TO FACILITY OPERATING LICENSE NO. DPR-47 AMENDMENT NO. 62 TO FACILITY OPERATING LICENSE NO. OTR-55 00KE POWER COMPANY OCONEE NUCLEAR STATION, UNITS NOS. 1, 2 AND 3 DOCKETS NOS. 50-269, 50-270 AND 50-2A_7, Introduction 33)and 26,1978(I)
By the applications dated Ag,20,197821,1978j
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August
, August 28, 1978 supplemented April 26, 1978,3)7, 1978
, September 22,1978(4), and September 26, 1978(11),
September Duke Power Company (the licensee) proposed to change the comon Technical Specifications (TS) for the Oconee Nuclear Station, Units Nos.1, 2 and 3 in connection with the refueling of Unit No.1 for Cycle 5 operation.
The refueling consists of the replacement of 61 burned fuel assemblies by 56 fresh assemblies and five previously burned essemblies. The five previously burned assemblies were last irradiated in Cycle 4 of Oconee Unit No. 1.
These assemblies will be irradiated for a fourth cycle as part of a joint Duke Power / Babcock & Wilcox (B&W)/ Department of Energy program to demonstrate reliable fuel perfomance at extended, burnups and to obtain post-irradiation data.
Because of performance anomalies observed at other 8&W plants, orifice rod assemblies will not be used in Cycle ~5.
Cycle 5 will nominally extend for one year. The design cycle lengt is 320 effective full pc*er days (EFPD). The mode of operation will be.
feed-and-bl eed. Operation of the reactor was conver.ted from the rod!d mode to feed-and-bleed to increase operating margin because of a quadrant -
tilt problem in Cycle 4.
The Cycle 5 fuel shuffle pattern was designed
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4 to minimize the effects of any po DUPLICATE DOCUMENT 2 0 8 22 7 9 Entire document previously entered into system under:
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