170 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1946 
shield can be devised. This means that there is no reason to hope that 
atomic power units for normal uses can be built that will weigh less 
than perhaps 50 tons. Driving motor cars or airplanes of ordinary 
size by atomic power must thus be counted out. 
Prominent among the advantages of atomic power are the extraor- 
dinarily low rate of fuel consumption and consequent low cost of fuel, 
the wide flexibility and easy control of the rate at which power is de- 
veloped, and the complete absence at the power plant of smoke or 
noxious fumes. With regard to fuel consumption, when completely 
consumed, the fission energy available from a pound of uranium is 
equivalent to the energy obtained from burning over a thousand tons 
of coal. With the prewar price of uranium oxide at roughly $3 per 
pound and of coal at $3 per ton, this would mean the economical use of 
uranium as fuel if only one part in a thousand of its available energy 
isused. Actually we should expect the first plants built for producing 
atomic power to be considerably more efficient than this in their use of 
the fission energy which would mean a substantial cost advantage in 
favor of uranium. One must consider also, however, the need to 
purify and fabricate the uranium into the desired form. For certain 
types of power plants under consideration, some separated U-—235 is 
required and this is expensive. Attempting to consider all such 
factors, it appears that the fuel cost of the atomic power plant of the 
future will nevertheless be small as compared with the corresponding 
fuel cost of a coal-burning plant. 
In considering the economic aspects there are, however, many other 
factors. It is not really possible for these to be explored until we have 
actual experience with atomic power plants. First is the capital cost. 
Clearly, if one must charge against the capital cost what is spent in 
research and development, this cost is very high indeed. If, however, 
one looks down the line to a billion dollar a year national industry 
based on atomic power, the Nation can afford a considerable investment 
in the research and development required to bring this industry into 
being. When this development is completed, it appears not unlikely 
that the cost of building and maintaining a large-scale atomic power 
plant may compare favorably with that of a coal-consuming plant of 
the same capacity. 
Much remains to be learned, however, regarding the metallurgical 
and other technical problems involved in constructing a successful 
plant to transform fission energy efliciently into high-temperature 
heat. The materials to be used may be expensive. The designs are, 
nevertheless, essentially simple. An inherent advantage of the atomic 
power unit is that the heat sources, i. e., the uranium blocks, can readily 
be maintained at any desired temperature regardless of how rapidly 
the heat is being removed. This means that a relatively small-size 
