Table III-3. Solubility of Oxygen from an Atmosphere of 20.94% 02 And 100% Relative Humidity in Water at Several Temperatures1

1.

Interpolated from values of J. H. Carpenter, Limnol. and Oceanog. 11, 265-77 (1966).

2. Extrapolated from Carpenter's values.

(4)

The Velz report assumed that the condenser intake would be in the Keowee branch with the discharge to the Little River branch. In actuality, the plant flow is in the reverse direction, i.e., intake is from the Little River branch and discharge to the Keowee branch. The estimates given in the Velz report should not be affected by this reversal of condenser flow, since the basis for the study was the total volume and surface of the lake and was independent of the point of discharge of warm water. However, in actual practice the condenser discharge is sufficiently close to the inlet to the hydroelectric plant (about 1800 feet) for potentially all the condenser discharge to pass through the Hartwell backwater during simultaneous operation of the hydroelectric plant and the nuclear plant. This will reduce the impact of the warm water on Lake Keowee, while raising the temperature of the tailrace water about 3°F under normal operating conditions.

Because of the possible discharge of the heated condenser water to the Hartwell Reservoir, a constant monitor must be kept on the temperature of the tailrace water during operation of the hydroelectric station. For normal operation, the dilution factor is so high that the discharge temperature of the water will be well within the South Carolina allowable limit of temperature rise of 3°F. If Lake Keowee is at low level and the hydroelectric station is operated below capacity, the potential exists for the water discharged to Hartwell Reservoir to exceed this limit. In this case, the licensee would have to take the necessary steps to come within the State limit.

In the Velz study it was assumed that the rate of flow of cooling water through the three condensers would be 3800 cubic feet per second, which would result in a temperature rise of 19°F. The study concluded that under expected full heat load and normal climatology the peak water temperatures at the condensers would occur toward the end of August, as follows:

(The above temperatures are calculated; predictions are not this precise.) The calculated monthly averages for a normal year are shown in Table III-2.

The Velz report further assesses the effect of a once-in-20-years adverse climatological combination, resulting in a severe drawdown and heating of the lake.

"The surface water temperature is expected to decline from 103.2°F to 94°F within an area from the source of approximately 1800 acres. At the critical drawdown stage of Lake Keowee the

total reservoir area is 14,600 acres, and hence the affected
area of temperature superelevation above 94°F constitutes 12.3%
of the total reservoir."

In the condenser discharge lines the water would remain at maximum temperature for 2 to 5 minutes. The time of residence is inversely proportional to the pumping rate of cooling water; with only one pump per unit operating, the residence time could be about 12 minutes.

With a full pond, the surface temperature of the lake would probably seldom exceed 94°F at any point. At extreme drawdown, to a surface elevation of 775 feet, surface temperatures could exceed 94°F, as noted in the Velz report. Under the extreme conditions, if we assume a layer of warm water averaging 10 feet thick at maximum drawdown, there would be a twoday lag after discharge from the condenser before enough heat was dissipated to drop the temperature from 103°F to 94°F for any given unit volume of water. According to the Velz report, the warm area would cover about 1800 acres (about 12% of the effective surface area of the lake at 775 feet). It is assumed that warm water would spread more or less uniformly across the surface of the lake from the condenser discharge point.

No drawings showing the temperature profile for the thermal water plume were given in the Velz report. This resulted from the uncertainties of the effects of the water movement caused by the actions of the two hydroelectric plants, at Keowee and Jocassee. The applicant operates a steam plant on Lake Norman (about 100 miles away) of similar capacity which is not affected by unusual water movements. Extrapolation of temperature measurements on Lake Norman to Lake Keowee were made (assuming no effects from operation of the hydroelectric stations) by the applicant. The results appear reasonable and are shown by point indication in Fig. III-5.

(4)

The approach to heat dissipation taken by Velz et al. in estimating the thermal effects on Lake Keowee is based on energy budget relationships. All possible factors were considered, e.g., convection, radiation, evaporation, etc. Natural lake temperatures were estimated and then estimates were made of elevated temperatures and affected areas due to the heat load imposed by the plant.

Assumptions concerning the physical arrangement of the plant and lake were necessary. The basic assumptions made by Velz et al. were:

76-248 O72 17

1.

2.

3.

4.

The discharge of waste heat is into a deep reservoir.

The complete interconnected reservoir is effective in heat
dissipation.

There is no lateral or vertical short-circuiting of flow.

Natural-eddy conductivity is ignored.

5. Heated condenser waters are discharged upon the surface.

6.

An average mixing depth of 10 feet is assumed throughout the
year.

7.

Water is drawn to the condensers from the hypolimnetic layer.

These assumptions are reasonable and are such that the direction of flow through the plant is immaterial, barring abnormal conditions. (Direction of flow assumed by the investigators is the reverse of that put into practice.)

The calculations appear thorough and are in agreement with general approximations that can be made for surface area needed for heat dissipa

tion.

During periods when Lake Jocassee is being pumped up, condenser discharge water is expected to extend several miles up Lake Keowee toward the Jocassee dam. During operation of the hydroelectric plant at Jocassee, a reversed flow will occur. The volume requirements of Jocassee are such that no warm water will reach there during normal operation.

51

2. Radioactive Waste Systems

The operation of a nuclear reactor generates fission products, the bulk of which remain within the cladding of the fuel rods and eventually interfere with (poison) the fission reaction. Thus, when the fuel is only partially depleted, the reactor must be shut down and the spent fuel assemblies removed. These are stored in a pool of water for a period of time to allow for decay of some of the fission-product radioactivity before being shipped in Federally licensed casks to a plant for chemical reprocessing to recover their unused fuel content for future use.

Small fractions of the gaseous and liquid radioactive materials produced during reactor operation enter the primary coolant system. The coolant system is processed by the radioactive waste (radwaste) system to control the level of radioactivity and the chemical composition of the coolant. The radwaste system is designed to protect plant personnel and the public from exposure to radioactive effluents in accordance with the Commission's regulations set forth in 10 CFR Parts 20 and 50. The system includes equipment to collect, store, process and treat wastes as required and to monitor and dispose of liquid, solid, and gaseous radioactive wastes. It is designed to process and remove radioactive wastes from the Plant adequately and safely when activation and fission product concentrations in the reactor coolant are within design values.

Based upon experience with other pressurized water nuclear power plants similar to Oconee, the annual average release of radioactivity in the Oconee effluents is not anticipated to exceed the values presented in Table III-4.

The basic source of radioactive liquid wastes is the reactor coolant. During operation, the coolant accumulates some fission products that have "leaked" from the nuclear fuel and some activation products that are either formed when neutrons are absorbed by the coolant or by the products of corrosion of structural material and fuel cladding. A less important source of radioactive liquid waste is the fuel element storage pools which can contain contaminated fuel and components.

The reactor coolant is continuously processed to provide chemical control for the reactor and to remove radioactivity from the system. The Chemical and Volume Control Systems are used in conjunction with auxiliary liquid radwaste systems to remove radioactive material by evaporation, by demineralization, or by retention for radioactive decay prior to discharge in low concentrations as a plant effluent. Table III-5 lists the sources of radioactive liquid wastes which are processed by the radwaste system. Figure III-10 showe a schematic diagram of the liquid radwaste system.