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BRIEF DESCRIPTION OF A NUCLEAR SHIP REACTOR AND ITS OPERATION In this report, consideration has been given primarily to current American practice in the design and operation of water-cooled nuclear reactor systems. There is to date considerable actual operating experi- ence with systems of both the pressurized water and the boiling water type. (Descriptions of these are given in technical manuals covering the Shippingport Atomic Power Station, Shippingport, Pennsylvania, the Army Package Power Reactor at Fort Belvoir, Virginia, the Experi- mental Boiling Water Reactor at the Argonne National Laboratory, Lemont, Illinois, and the Vallecitos Boiling Water Reactor, Vallecitos, California.) Design and operation: A nuclear reactor for ship propulsion re- places conventional boilers fired by fossil fuel. Thermal energy re- moved by the reactor coolant serves to form steam, either directly or indirectly, to drive the ship's propulsion equipment. Most of the other principal and auxiliary equipment associated with the power cycle is very similar to that used in the conventional marine power system. In the typical reactor, light water serves as a neutron moderating medium, as well as the heat transfer fluid. The uranium is fabricated in the form of plates or pins, within a cladding, and assembled as con- veniently handled fuel elements to form the reactor core. At start-up the excess volume created by thermal expansion of water in some types of systems is displaced as the reactor is brought up to operating tem- perature. This volume must necessarily be replaced when the reactor is shut down, to assure that the system will be completely filled. This excess volume from thermal expansion is one of the types of waste with which this report is concerned. As later described, this water contains relatively low concentrations of radioactive corrosion products and may, under some circumstances, also contain a certain variable concentration of fission products. The removal of these ma- terials is generally accomplished by the use of a by-pass purification system through which a portion of the primary coolant is continuously circulated. Additional sources of liquid radioactive wastes include: operational leakage from various components of the primary and auxiliary systems; sampling and laboratory wastes, and those due to equipment decontam- ination; and shower and laundry wastes associated with the reactor plant. The effluents are collected into holding tanks for storage, decay, and analysis before being either transferred to shore facilities, treated aboard ship, or directly disposed of through controlled discharge over- board. Shipboard reactors are generally designed to operate continuously for two to three years on a single loading of fuel ranging up to several thousand kilograms of uranium, depending on the degree of its enrich- ment. Refueling will be programmed insofar as possible to coincide
