ML20040F973
| ML20040F973 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 01/29/1982 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20040F971 | List: |
| References | |
| NUDOCS 8202110014 | |
| Download: ML20040F973 (9) | |
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JAN 2 91982 SAFETY EVALUATION REPORT BY THE OFFICE OF NUCLEAR REACTOR. REGULATION RELATt.D TO AMENDMENT N05. 3 TO CONSTRUCTION PERMITS CPPR-108 AND CPPR-109 Introduction On May 1,1981, Georgia Power Company, acting on its own behalf and as agent for Oglethorpe Electric Membership Corporation, Municipal Electric Authority of Georgia, and the City of Dalton, requested an amendment to the Construction Pemits CPPR-108 and CPPR-109, for the Alvin W. Vogtle Nuclear Plant, Units 1 and 2 (Vogtle), to reflect a modification in plant design. The modification would substitute a single-point, submerged plant discharge stri iture for the original multiport, submerged discharge structure des,jn.
Modification of the plant discharge structure had been prompted by the U. S.
Corps of Engineers (COE) review of the original Vogtle nultiport discharge structure design. To install the Vogtle discharge structure in the Savannah River, a pemit was required from the COE. An application was submitted for this permit by Georgia Power Company on August 15, 1980. By letter dated November 14, 1980, the COE infomed Georgia Power Company that the discharge structure as designed could not be pemitted under the navigation and maintenance operations criteria of COE.
Georgia Power Company has proposed a modification to the original discharge structure design that would (a) neet COE criteria: (b) represent environmental inprovenent over the original design in that it reduces the potential of naintenance and operational problems due to biofouling by Asiatic Clans which are present in the Savannah River; and (c) most importantly, result in a plant discharge having a smaller predicted chemical and themal plume than predicted for the original design and assessed in the construction permit stage Final Environmental Statenent (FES).
In support of the reduced environmental effect, Georoia Power Company has submitted themal and chenical dispersion studies with the request-for-anendment letter dated May 1, 1981.
In conjunction with the request for approval of the design change, Georgia Power Company also requests amendment of Construction Pemit CPPR-108 and CPPRm109 to delete related conditions 3.E.(5)(a), (b) and (d) which concern plant chlorine discharges. Conditions 3.E.(5)(b) and (d) assume four unit operation and as written are inappropriate for the present two-unit plant.
These same two conditions are based on the use of a multiport diffuser discharge structure and are inapplicable for the redesign. Georgia Power Company states that, in any event, all three conditions en chlorine releases and related nonitoring should be deleted as a matter of law, as they are properly subject to National Pollutant Discharge Elimination Systen (NPDES) linitations. Georgia Power Company has discussed this request with the State of Georgia which has NPDES pemitting authority granted to it by the Environmental l.........
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JAN 2 91982 Protection Agency (EPA) and has learned that effluent limits and monitoring requirements on chlorine will be considered by the State in issuance of the Vogtle NPDES pemit.
Based on the infomation submitted in the Preliminary Safety Analysis Report (PSAR) and the request-for-amendment letter dated May 1,1981, the NRC staff has completed its review of all safety-and environmental-related matters pertinent to the issuance of the Construction Pemit amendment as requested in the May 1,1981 application. This Safety Evaluation is issued in support of Anendment Nos. 3 to Construction Pemits CPPR-108 and CPPR-109, allowing the design change of the discharge structure and the deletion of three related construction pemit conditions for plant chlorine discharges.
The construction pemit conditions, which Georgia Power Company requests to be deleted, address chlorine discharges and the themal mixing zone. Conditions 3.E(5)(b) and 3.E.(5)(d) are no longer appropriate because they relate to the original four-unit plant with the nultiport diffuser; the Vogtle plant is now proposed for two units, only. Also, conditions 3.E(5)(a), (b) and (d) address effluent limitations and nonitoring requirements which are now under the jurisdiction of the State of Georgia's HPDES pemitting system pursuant to the Clean Water Act. For these reasons we agree with Georgia Power Company that the three conditions should be deleted from the Vogtle construction pemits.
Deletion of water quality related requirements are done as a matter of law and is a ministerial action for which no prior Environmental Impact Appraisal need be prepared. Therefore, the irpact of the deletions of the water quality requirements from the Vogtle construction pemit are not addressed in the following review.
Furthemore, the staff finds that the design change fron a multiport to a single-point diffuser does not impact the functional perfomance of the discharge structure. The requested amendment has no effect on the staff's prior safety review of the discharge structure as the design change does not involve a significant increase in the probability or consequences of accidents previously considered nor a significant decrease in safety margins. Therefore, safety inpacts are not discussed in the following review.
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JAN 2 91982 The purpose of this Safety Evaluation is to exanine the impact of the proposed nodifications to the discharge structure for Vogtle 1&2.
Specifically, the Safety Evaluation addresses environment-related items with regard to hydrologic and biologic considerations.
Evaluation We have reviewed this application for amendment, submitted May 1,1981.
Our review of environment-related matters and our conclusions concerning each iten are described in the following subsections of this evaluation report.
Hydrology Georgia power Company has submitted a design change for the Alvin W. Vogtle Nuclear Plant, Unit Hos.1 & 2, which replaces the submerged nultiport diffuser with a single-port, horizontal jet, submerged diffuer located on the shoreline (Ref.1). The new diffuser consists of a 24-inch diameter pipe angled 70 degrees from the downstream shoreline and pointing 5 degrees downward from the horizontal. Heated effruent.from the closed-cycle condenser cooling systen will be discharged at a rate of 5,500 to 55,000 gallons per minute.
The high-velocity jet will disperse in the Savannah River and be carried downstrean. Flow in the river is regulated by upstream dams. Flow at the site is maintained at or above a ainimum of 5800 cubic feet per second (cfs),
primarily for navigation reasons.
The nain impetus for redesigning the diffuser system was the strong recoamenda-tion by the U.S. Corps of Engineers that the orginally-designed submerged nultiport diffuser would present an obstacle to maintenance dredging of the river (Ref. 2). The applicant also feared that the small ports in the submerged diffuser would tend to collect sedinent and Asiatic clans, and clog during periods of inoperation. The newly designed submerged jet discharge would alleviate these two problems in addition to being sinpler and cheaper.
The applicant perfomed a design study of the thermal performance of the proposed shoreline discharge diffuser. A wide range of effluent release conditions, pipe diameters, discharge angles and ambient river temperatures and flows was considered. The Hirst mathematical model of jet diffusion was used to simulate the dispersion of the themal effluent (Ref. 3). The Hirst model is a well accepted nodel of submerged jet dispersion (Ref. 4) and is appropriate for the present study.
The Hirst model is an integral jet model which considers jet dispersion in a stagnant or unifornly noving infinite body of water. The designer of the model must be cognizant of the boundary conditions of the prototype which would limit the validity of the model.
In the Vogtle case, the low-flow depth of the river erricr >
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i in the area of the site ranges fron about nine (9) to fifteen (15) feet.
Interference of the jet with the surface or bottom of the river would decrease the dispersion in the vertical direction, and therefore, the
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nodel would overestinate the degree of dispersion. Therefore, close attention had to be paid to the spatial relationship of the jet and the river surface or botton.
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Table 1 presents the applicant's analyses of jet dispersion for a 24-inch pipe angled 20 degrees from the perpendicular and for the nininun river flow-4 rate of 5800 cfs. The cases chosen cover nomal operation of the plant for Units 1 cnd 2 with and without plant dilution flow and for extrenes of ambient a
i river temperature.
i The applicant speculated that the five (5) degrees Fahrenheit (F) isothem in-case 7a would be slightly larger than that stated in Table 1 because of some i
interference with the river. surface - although there would still be lateral dispersion. The two (2) F isothern, being larger, would be more greatly in error, particularly in cases la, 2a, 4a and 7a. Since lateral dispersion would not be affected by vertical interference, the applicant placed an arbitrary correction factor of 150 percent on the volume within the five (5) F isotherm-4 to account for diminished vertical dispersion for. the worst cases of interference.
The staff considers this to be a reasonable and conservative correction.
The staff has independently reviewed the applicant's analysis for several cases. We have relied on the Shirazi-Davis nomograms for submerged jet discharges (Ref. 5). The Shirazi-Davis nomograms are based on somewhat different jet nodels and field data than used by the applicant.
The graphical technique was expedient, but has the drawback that it was only I
applicable in this case for stagnant water, whereas the present case is that of a uniform ambient flow. The Shirazi-Davis ~ nonograns can be used cautiously, however, if the following two factors are considered:
1.
A noving flow will cause the jet to be bent in the downstrean direction.
Therefore, the length of the jet should be the measure along its centerline;-
1 and 2.
Dispersion in a flowing body of water will generally be greater than dispersion in a stagnant body of water, providing that there is no interference of the jet with the near shore.
The applicant's cases 2a and 7a were chosen for the staff's comparison calculations. Table 2 shows key conparisons of the applicant's and staff's results. The nodels agree reasonably well. The applicant's results appear to be slightly nore conservative.
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JAN 2 91982 The staff concludes that the applicant's analysis of the themal plumes associated with the revised diffuser design has been accurately performed and interpreted.
The staff bases its conclusion on its experience with jet diffuser designs and models and an independent appraisal of the jet dispersion for two of the cases evaluated by the applicant.
Biology Construction of the originally proposed diffuser system would have resulted in permanent alteration of about 800 feet (ft) of the river botton and in temporary siltation effects during dredging for diffuser placement (FES-CP, Sec.10.3.2).
Construction of the nee design will result in less impact on the benthic connunity because less river bottom area will be disrupted and less suspended sediments will be introduced to the water column. The river bottom is characterized as an inhospitable habitat for benthic and perphytic organisms because the substrate consists of shifting sands; thus, construction of either of the discharge designs would not have caused significant impacts.
Operational effects of the discharge on aquatic biota are similar in type except that the plume from the subnerqcd single-port design is nearer the shoreline and nay, under certain operating nodes, reach the river bottom and surface.
Inpinge-nent of the plune on the river bottom could cause some localized scouring and disruption of the benthic community. As noted above, the shifting sand substrate is rather inhospitable as a habitat for benthic organisrs; thus, the impact of localized botton scour is judged to be neo';igible. The applicant has predicted that the benthic area affected would extend along the jet centerline trajectory For starting about 25 ft from the discharge port to a distance of about 30 ft.
this sane operating node, the plune is predicted to become visible at the water surface at a distance of about 30 ft from the discharge port. Because of the orientation of the discharge port, the plume is not expected to inpinge on the shoreline; thus, tha movement of migratory fish species along the Georgia side of the river will nct be completely blocked; the zone of passage along the Georgia side is less for the new discharge design than for the original diffuser design.
The river width unaffected by the discharce mixing zone is larger for the new design; therefore, the potential for blockage of fish micratory pathways is less than previously assessed.
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- Conclusion On the basis of the foregoing analysis, we conclude that there will be no environmental impact due to construction and operation greater than those already predicted and described in the Commission's Final Environnental i
Statement _ for the Construction Pemit, issued in !! arch 1974. Furthermore, based on our previous conclusions that the requested acendment does not involve a significant increase in the probability or consequences of accidents previously considered nor a significant decrease in safety nargins.we find that this amendment does not involve a significant hazards consideration. The issuance of Amendnent No. 3 to Construction Pemits CPPR-108 and CPPR-109 wil not be inimical to the common defense and security or the health and safety of the public. Having made these conclusions, the Commission has further concluded that no envircnnental inpact statenent for the proposed action need be prepared and that a negative declaration to this effect is appropriate.
l Date of Issuance: JAN 2 91982 4
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Tabi'.e 2 - Comparison of Applicant's and Staff's Jet Analysis A/
CANT STAFF U)
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W(3) g (4) gk L(2) g(3)
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(1)'Differen~ce between' di'scha'rge temperature and anbient river temperature '
(2) Length of 5*F isothcrm along center line (3) Maximum width of 5*F isothenn (4) Length of 2?F isotherm along center line (5) Maximum width of 2'F isotherm References 1.
C. S. Chiou, "Vogtie Nucicar Plant Units 1 and 2 Wastewater Effluent Discharge Structure Plume An'alysis," Attachment 2, letter to D. Eisenhut-from W. Ehrensperger, Georgfa Power Company, dated May 1,1981.
2.
Letter to Mr. T. F. Byerly, Georgia Power Company, from Steven Oswald, Dept. of the Army, Corps of ' Engineers, Savannah GA, dated November 14, 1930, Attachment 1, to above let,ter.
3.
T.'A. Hirst, " Analysis of Round,' Turbulent Jets Discharged to Flowing Stratified Ambients," ORNL-46MI, Oe.k RidgeINational Laboratory, June 1971.
'4.
B. A. Benedict, J. L. Anderson, E. L. Yandell Jr. '" Analytical Mo' elitag d
of. Thermal Discharges," AHL/ES.-18,.. Argonne.Nationa1.Laboratorie.s. Ap.r.il,-1974.
5 M. A. Shirazi, L. R. Davis, Ucrkbook of Thennal Plume Prediction, Vo'1.1 i
- Submerged Discharges,". EPA-R2-72-005a, U.S. Environmental Protection Agency, August 1972.
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