NUCLEAR POWER FOR PEACEFUL PURPOSES — SMYTH 193 



by the radiation present, and, finally, that the replacement of parts 

 is difficult or impossible because of the health dangers involved. In 

 a power-producing reactor, the temperature should be as high as possi- 

 ble so that the heat energy removed can be converted efficiently into 

 useful power. This is a real difficulty as we shall see later on and is 

 one point where the Hanford designers had a considerable advantage. 



CONTROL 



Wlien the first reactors were designed, the question of control was 

 a very critical one. No one knew very certainW whether it would be 

 possible to prevent the reactor from running a^vay with itself. We 

 do not w^ant to have a reactor heat up to the point where it will melt 

 and destroy itself. We wish to avoid this for two reasons : first, we 

 do not want to lose the reactor; and second, we do not want to spew 

 radioactive material all over the countryside. By now we have had 

 enough experience to relieve our concern about essential difficulties of 

 control. We are perfectly sure that we can build a reactor which we 

 can control. In fact, as I shall mention later, some types of reactor 

 are self-controlling. There does remain, however, a problem of con- 

 venience, efficiency, and cost in designing the proper controls to start, 

 stop, or maintain at a desired operating level the nuclear chain 

 reaction. 



CHEMICAL PROCESSING OF FUEL 



Ideally, we would like to put into a nuclear reactor a certain amount 

 of uranium and leave it there until all the uranium had been con- 

 verted into heat energy and fission products. If that were possible, 

 we would be concerned with chemical processing only in preparing 

 the fuel. Unfortunately, the difficulties both of neutron economy as 

 affected by the growth of fission products and of the corrosion or 

 radiation damage of structural materials or fuel elements make it quit© 

 out of the question to consume more than a fraction of a nuclear 

 charge in any known design of reactor. After a certain length of 

 time — and one of the problems in the design of reactors is to make 

 that length of time as great as possible — it is necessary to remove the 

 fuel. It is too valuable to throw away, since it will probably still 

 contain some 90 percent or more of the fissionable material. Conse- 

 quently, we have to reprocess it chemically, separating out the fission 

 products and refabricating the uranium into new fuel elements. This 

 turns out to be one of the most costly processes in the whole business 

 of operating a reactor for power. 



I believe it is possible that the nuclear power industry will stand or 

 fall economically depending on the success which chemists and chemi- 

 cal engineers have in developing cheap processes for purifying and 

 refabricating nuclear fuel. 



