Now that I have discussed natural radiation levels, existing regula­tions, and design objectives, attention can be directed toward radioactive waste disposal systems themselves. They are, in general, provided to collect potentially radioactive wastes, process them, and discharge them in a safe and economical manner.

Gaseous Waste System. In arriving at the design of the gaseous waste system which has been used as a standard for many years, designers in­cluded several factors in order to meet General Electric’s design objec­tives. For example, assume that a nuclear power plant without these design features released enough radioactivity over a year to result in a whole — body gamma dose of 500 mrem (the aec limit) to a man standing at the power plant site boundary. From this assumed beginning, the design of the gaseous waste system was improved by adding a holdup capacity which delays the release of the material for a specified period of time and allows much of the radioactivity to decay before release. This equipment addition reduced the assumed 500 mrem to about 50. A stack about 300 feet high and twice as high as any nearby structure was then also added, further reducing the off-site effect by another factor of about 10. This brought the design close to the design objective of 5 mrem/yr. In other words, there is a design that not only meets today’s regulations, but further minimizes radioactive release and meets a design objective well below the federal limit.

What are the principal sources of radiation which result in these small off-site doses? In a nuclear power plant the process of producing steam creates some waste materials in the form of gas. About 90 per cent of this gaseous waste consists of oxygen and hydrogen, which are not radioactive. Most of the remaining 10 per cent consists of nitrogen, which is not radioactive either. A small portion, however, consists of some radio­active nitrogen and oxygen and various forms of krypton and xenon, a fraction of which are radioactive.

In a conventional bwr plant the steam, with its small percentage of radioactive gas, goes through the turbine and into the condenser. In the condenser the steam is converted back into water and the water is returned to the reactor in a closed process system. Some of the radioactivity stays with the condensate. The remaining air (including the radioactive gases) is drawn out of the condenser to create a near vacuum. These gaseous wastes are then passed into a delaying storage system which reduces the radioactivity in oxygen and nitrogen to minor amounts; the amounts of radioactivity in the xenon and krypton are also reduced. Next, the wastes are passed through a filter, which removes any solid radioactive particles. The gases are then dispersed to the environs through a stack or vent pipe which is generally about twice the height of the nearby buildings.

These gases, before passage out of the stack, are monitored continu­ously to measure at all times the amounts being emitted. The monitoring equipment is provided with automatic alarms to tell whenever the emis­sion is reaching preset limits.

Liquid Waste System. The actual facts about the radioactivity of liquid wastes from a nuclear power plant are perhaps even more reassuring than are the facts about wastes released to the atmosphere. But in this case, too, the facts are easier to accept if one knows what the wastes con­sist of and how they get into the water — and if one considers the question in some meaningful perspective.

Radioactive liquid wastes originate with a number of planned opera­tions within the power plant. The wastes are kept separated enough to achieve the best treatment method and to recover as much water as prac­tical for re-use in the plant. More than 80 per cent of the liquid wastes are thus recovered and reused — therefore, never released from the plant.

The essential purpose of the liquid radioactive waste system is to remove radioactive material from the waste water. This is achieved by filtration, ion exchange, and in some cases evaporation. These treatment methods essentially move the radioactive materials from the liquid (water) to a solid or concentrated form.

Some of the liquid wastes contain impurities which make them un­suitable for reuse in the plant, which requires very high purity water. Such wastes include those from the plant laundry, chemical laboratory,

and floor drains. The amounts of radioactivity in these are small, con­tribute only a small increment to natural background radioactivity, and so are planned for environmental discharge. Before such discharge, how­ever, each batch (tankful) is analyzed to determine that it does meet the required criteria for discharge. Wastes not meeting such criteria are re­turned for reprocessing. Thus, no discharges are made which are not well within allowable conditions. Any water which is discharged is mixed with the effluent cooling water at a rate to ensure good dispersion.

Monitors on the waste discharge line provide continuous information about the concentrations in the liquid waste. Further, samples of the dis­charge are routinely collected from the canal and analyzed to give a composite of all activity discharged from the plant.

Solid Waste System. The solid waste system collects the radioactive solids resulting from processing of liquid wastes and from water purifying in the plant. Most of the radioactive material present in wastes leaves the plant via this route. All of these materials are encased in steel barrels and stored temporarily within the plant facilities. When a sufficient number of barrels accumulate, they are shipped to an AEC-approved site.

Therefore, with respect to the systems which handle the gaseous, liquid, and solid waste, there is a demanding design basis, a conservative approach to allowable releases, and finally a condition in which the de­signers have been provided a safe design. Systems were added to far exceed the effort necessary to just meet existing regulations. Liquid and solid release are completed under controlled operations.