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 pow^er 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; ajid 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 



