The safety of a reactor, of course, depends to a great extent on the use to which the reactor is put. In general a power station is less likely to give trouble than a moving power source. It is not probable that nuclear locomotives will ever be safe. In nuclear ships more room is available and more room permits more safety measures. But even so the safety of nuclear motors in ships will have to be considered particularly carefully because ships will have accidents in harbors. Between the urgent need for progress and the absolute necessity of safety it is difficult to keep a sense of balance and one can easily make the mistake of being unnecessarily cautious. Such unnecessary caution was probably exercised when the Committee on Reactor Safeguards considered the earthquake hazard of the Brookhaven reactor on Long Island. A seismologist, who is a Jesuit Father, was asked to tell the committee[15] of the possibilities and probabilities of an earthquake on Long Island. The chairman[16] of the committee subjected the expert to a long and detailed questioning. After half an hour the Committee on Reactor Safeguards ran out of questions. But the Jesuit Father had not given any signs of running out of answers. The session being at an end the expert, looking the chairman of the committee firmly in the eye and in a more authoritative voice than he had yet used, said, “Mr. Chairman, I can assure you on the highest authority that there will be no major earthquakes on Long Island in the next fifty years.” CHAPTER XVIII By-products of Nuclear Reactors Nuclear reactors generate energy with the help of nuclear fission. Every time a fission occurs we are left with radioactive by-products. It is most important to prevent the uncontrolled escape of these fission products from the reactor. Fortunately the dangerous products can be retained in the reactor—if the machine has been constructed and operated with reasonable care. In the end, however, the burnt or partly burnt uranium charge will have to be removed from the reactor and fresh charge, fresh fuel will have to be added. What will become of the fission products at this time? During protracted operation of a reactor most of the short-lived fission products decay. Those with longer lives accumulate. The discharge of the reactor is strongly radioactive, and it will remain radioactive for many years. One certainly must not dispose of this radioactive waste in a careless manner. There are, however, many ways in which one can store such waste with reasonable safety. One can deposit the radioactive material in well-built underground tanks. One can concentrate the activity, imprison it in concrete blocks, and deposit it at the bottom of the ocean. If one is very much worried he might even put the radioactivity in rockets and let it decay harmlessly in outer space. These procedures will cost money and will add to the expense of nuclear energy.