Table 3 presents comparative data for lead-acid and silver-zinc 

 pressure-compensated battery systems. The lead-acid system is more sensitive 

 to temperature, has a higher initial cost because of the buoyancy material 

 required, has a lower replacement frequency, lower battery cost, has approxi- 

 mately five times the deep discharge cycle life, and is three times as heavy as 

 the silver-zinc system. The effects of many variables will result in considerable 

 variation in the cost of the battery system. 



Nuclear Reactor Energy. There have been many proposals for 

 underwater power systems which produce electrical power from nuclear 

 energy by means of various fluid and conversion systems. Reactor systems 

 are generally classified by their coolant, namely, gas, liquid metal, organic, 

 pressurized water, or boiling water. A comparison of the various systems 

 with the same overall performance characteristics has shown relatively little 

 variation in total weight, space, and cost. Gas-cooled reactors tend to be 

 larger and heavier and require more complex emergency cooling systems than 

 other reactors. They must be designed against water flooding, which causes 

 a nuclear excursion. Their primary application has been for very large, sta- 

 tionary, land power plants. Liquid metal plants are primarily small and 

 lightweight, have a very short life, and are used for space applications. The 

 liquid metals are highly reactive and corrosive in contact with water. Water 

 leakage will probably result in a total plant loss. Although the plant is 

 designed for unmanned operation, shielding must be provided for test opera- 

 tion and maintenance. Boiling water systems eliminate the need for steam 

 operators by using a direct cycle with higher efficiency; however, weight 

 savings are questionable. Primary applications are experimental and are for 

 large land-based stationary power plants. Organic coolants have poor heat 

 transfer characteristics and require more complex systems with increased 

 overall plant weights. 



A pressurized water-cooled reactor was considered the most suitable 

 reactor system for a submerged power plant in the immediate future. The 

 reactor has several advantages. The concept of a pressurized water reactor is 

 well tested and will require a minimum amount of development effort for 

 this application. Besides being a long-life power source, such a reactor is 

 highly reliable and safe. The use of a liquid coolant is most adaptable for 

 providing decay heat removal systems that require no power. In addition, 

 since the coolant retains virtually no radioactivity within a short interval after 

 shutdown, shielding is minimized. The coolant system is readily sealed to 

 minimize loss of coolant and eliminate radioactive carry-over to conversion 

 equipment. The pressurized water coolant provides a fluid which is common 

 to both reactor and conversion systems, thus making for simplicity of 

 design. 



