ML19253A754
| ML19253A754 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 08/15/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19253A752 | List: |
| References | |
| NUDOCS 7909110163 | |
| Download: ML19253A754 (4) | |
Text
.
pn arc
,o, UNITED STATES
+
5,_
NUCLEAR REGULATORY COMMISSION 3.p% #),f ^,
g WASHINGTON, D. C. 20555
' N] F,./
- e..*
ENVIRONMENTAL IMPACT APPRAISAL BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO MONITORING WATER TEMPERATURES IN WHEELER RESERVOIR FACILITY OPERATING LICENSES DPR-33, DPR-52, AND DPR-68 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNITS NOS. 1, 2 AND 3 00CKETS NOS. 50-269, 50-260 AND 50-296 1.0 Description of Proposed Action By letter dated January 5,1979, the Tennessee Valley Authority (the licensee or TVA) requested changes to the Technical Specifications (Appendix B) appended to Facility Operating Licenses Nos. DPR-33, DPR-52 and DPR-68 for the Browns Ferry Nuclear Plant, Units Nos.1, 2 and 3.
The proposed amendments and revised Technical Specifications would modify the method by which the plant determines compliance with the State of Alabama water temperature standards.
2.0 Background
At present, the state standards require that the maximum temperature outside of the mixing zone must be under 86 F and that the maximum increase in river temperature outside the mixing zone be less than 5 F.
Recently, TVA has been granted a relax-ation of the state standards allowing a maximum temperature of 90 F, but the 5 F increase is still in effect.
The plant discharges heated water through three multiport diffusers located in the old river channel of the Tennessee River in Lake Wheeler adjacent to the site.
The plant may operate once-through, or with the partial or total reliance on mechanical draft cooling towers.
Compliance with state thermal standards is presently determined with a series of monitoring stations upstream and downstream of the discharge. There has been considerable difficulty in measuring a representative upweam temperature so that compliance with the 5'F temperature rise limitation could be determined.
Solar heating of the shallow overbank regions of Wheeler Lake and stratification confuse the upstream thermal measurements, and do not allow true representation of thermal c._,
" "y T 000110l63 *
. modifications from the Browns Ferry discharge. A vivid example of this confusion is that on several occasions, monitoring indicated that the plant was in violation of thermal standards during periods when the plant was shut down and there were no thermal discharges.
Relocation of the monitoring stations has been of only limited help.
These false indications have been responsible for curtailments in power gener-ation during periods of heavy demand.
Direct monitoring of river temperature at the site has proven to be inadequale.
There is no straightforward way to separate the background natural temperature variations from the measurement records to distinguish the true temperature rise induced by the plant. The licensee has instead proposed to use a mathematical simulation of thermal plume dispersion to model the temperature rise and deter-mine compliance. The inputs to the model would be the river flow, plant flow, plant heat rejection, and downstream mixed temperature. The ambient upstream temperature will then be back-calculated iteratively with the model, thereby establishing the temperature rise. River flow would not be measured directly at the site, but will be estimated from the known discharges at the upstream and downstream dams using a flow routing model. The licensee has stated his intention to continually refine the river temperature model in light of operating experience.
This model has been tested and verified through detailed surveillance of the thermal plume at the Browns Ferry site.
In addition, the licensee proposes to reduce the size of the legal mixing zone to a more natural one detennined from the established properties of thermal plume.
3.0 Evaluation and Assessment In assessing the acceptability of the proposed revisions to the monitoring plans, we have reviewed in detail the report from TVA accompanying the letter of July 5,1979 (Ref.1) and a paper describing the modeling of the plume (Ref. 2).
We have also been in contact with members of the staff at TVA and at the Massa-chusetts Institute of Technology concerning the monitoring problems at Browns Ferry for several years.
The proposed compliance system will utilize the following measurements which experience has shown can be measured with much greater accuracy than the parameters presently used to determine compliance:
1.
Mixed temperature: Three monitors will be situated approximately one to two diffuser lengths (1800-3600 feet) downstream of the diffusers. One will be situated at the left side of the navigation channel, one near the right side of the navigation channel, and one between the navigation channel and the right bank. Measurements will be made every 15 minutes at one-meter and two-meter depths at each monitor and transmitted to the plant site.
2.
River Flow:
Cischarges from Guntersville and Wheeler Dams will be transmitted to the plant site at least hourly.
3.
Discharge Temperature: A monitor at the diffuser gate structure will measure the temperature of water entering each diffuser and transmit the data to the plant site.
m.m vuutAc
. 4.
Discharge flow: The number of condenser cooling water pumps in operation and the position (open-closed) of appropriate gate structure will be monitored on site.
These measurements will be received by a dedicated computer which will calculate the following information:
1.
Discharge flow will be computed from the number of condenser cooling water pumps in operation. The position of gate structures will allow detemination of the operating diffusers.
2.
River flow will be computed using an unsteady flow routing model and the previous 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> of Guntersville and Wheeler Dam discharges.
3.
The temperature rise will be computed using the theory of diffuser mixing.
The temperature rise and ambient river temperature will be calculated by an iterative procedure until the difference between successive calculations is small.
4.
The ambient river temperature will be initially calculated as the present downstream temperature less the temperature rise of the previous hour. The ambient river temperature will be recalculated through successive iterative computations of the temperature rise.
5.
The mixed temperature will be calculated using temperature data from the downstream monitor associated with the appropriate operating diffuser. Data at the one-and two-meter depths will be averaged to give temperature at the 1.5-meter (-5-foot) depth. TemperaturcM each monitor will be temporarily averaged using the current temperature and the previous four 15-minute obser-vations.
The river flow, temperature rise, and the mixed and ambient river temperatures will be transmitted to the plant control room. A permanent record will be stored for compliance purposes.
The proposed compliance system is expected to provide a more accurate value of the plar,t-induced tempcrature rise. The math 6ihatical model of ciffuser mixing has been verified to give reascrable predictions of diffuser mixing. Measurements of plant parameters can be readily scanned for accuracy and downstream temperature measurements are expected to be primarily affected by diffuser-induced mixing.
The compliance system will be unaffected by natural temperature variations.
The compliance system will also provide hourly updates to the predictive computer model for cooling modes at Browr.s Ferry. This will permit more accurate forecasting of the effect of plant operation on plant-induced themal effects.
The hourly updates ard forecasts will provide the data the plant needs to take corrective action (i.e., to switch from open cycle to helper mode of operation or from helper to closed cycle) before the state water temperature standards are exceeded.
We conclude that the proposed monitoring will be more reliable than the present system in determining compliance with the 5'F temperature rise standard. The pro-posed model has been adequately field tested at the Browns Ferry site. The state u du,%L3;3 n.3 c ~ -
. water temperature standard was established to insure that there is no signi-ficant impact on the environment from thermal enrichment. While there will be no environmental impact from the proposed action (i.e., approving the amendment request), the proposed action will help to assure that the Browns Ferry plant remains in compliance with state water temperature standards, which, in turn, helps to insure that there is no significant environmental impact associated with plant operation.
4.0 Basis and Conclusion for not Preparing an Enviranmental Imoact Statement We have reviewed this proposed facility modification relative to the requirements set forth in 10 CFR Part 51 and the Council of Environmental Quality's Guidelines, 40 CFR~~1500.6 and have applied, weighted, and balanced the five factors specified by the Nuclear Regulatory Commission in 40 FR 42801 We have determined that the proposed license amendment will not significantly affect the quality of the human environment and that there will be no significant environmental impact attributable to the proposed action other than which has already been predicted and described in the Final Environmental Statement for the facility dated September 1972. Therefore, the staff has found that an environmental impact statement need not be prepared, and that pursuant to 10 CFR 51.5(c), the issuance of a negative declaration to this effect is appropriate.
Dated: August 15, 1979 I
sa s.2 s.i t.
v,
^
. _ References 1.
Ungate, C.
D., " Assessment of Water Temperature Monitoring at the Browns Ferry Nuclear Plant," Report No.WM28-1-67-101, Tennessee Valley Authority, Norris, Tennessee, August 1978.
2.
Almquist, C. W., C. D. Ungate and W. R. Waldrup, " Field and Model Results for Multiport Diffusion Plume," in Verification of Mathematical and Physical Models in Hydraulic Engineering Proceedings, 26th Annual Hydraulic Division in Hydraulic Engineering Conference, August 8-11, 1978, American Society of Civil Engineers.
.*p s
i
{*
g Q 0 J t ='
- ~