NAVAL REACTORS

HEU De-Enrichment. Highly enriched uranium (HEU), initially enriched to >93% U, for use in research, naval reactors, and nuclear weapons, may be de-enriched and fabricated into fuel for civihan nuclear reactors. An estimate of the world inventory of highly enriched uranium in the nuclear weapons states is provided in Table 6 (34). 

The amount of HEU that becomes avadable for civdian use through the 1990s and into the twenty-first century depends on the number of warheads removed from nuclear arsenals and the amount of HEU in the weapons complex that is already outside of the warheads, ie, materials stockpdes and spent naval reactor fuels. An illustrative example of the potential amounts of weapons-grade materials released from dismanded nuclear weapons is presented in Table 7 (36). Using the data in Table 7, a reduction in the number of warheads in nuclear arsenals of the United States and Russia to 5000 warheads for each country results in a surplus of 1140 t of HEU. This inventory of HEU is equivalent to 205,200 t of natural uranium metal, or approximately 3.5 times the 1993 annual demand for natural uranium equivalent. 

An improved solvent extraction process, PUREX, utilizes an organic mixture of tributyl phosphate solvent dissolved in a hydrocarbon diluent, typically dodecane. This was used at Savannah River, Georgia, ca 1955 and Hanford, Washington, ca 1956. Waste volumes were reduced by using recoverable nitric acid as the salting agent. A hybrid REDOX/PUREX process was developed in Idaho Falls, Idaho, ca 1956 to reprocess high bum-up, fuUy enriched (97% u) uranium fuel from naval reactors. Other separations processes have been developed. The desirable features are compared in Table 1. 

Spent fuel can be stored or disposed of intact, in a once-through mode of operation, practiced by the U.S. commercial nuclear power industry. Alternatively, spent fuel can be reprocessed, ie, treated to separate the uranium, plutonium, and fission products, for re-use of the fuels (see Nuclear REACTORS, CHEMICAL reprocessing). In the United States reprocessing is carried out only for fuel from naval reactors. In the nuclear programs of some other countries, especially France and Japan, reprocessing is routine. 

Uranium-235 Enrichment. The enrichment of uranium is expressed as the weight percent of in uranium. For natural uranium the enrichment level is 0.72%. Many appHcations of uranium requite enrichment levels above 0.72%, such as nuclear reactor fuel (56,57). Normally for lightwater nuclear reactors (LWR), the 0.72% natural abundance of is enriched to 2—5% (9,58). There are special cases such as materials-testing reactors, high flux isotope reactors, compact naval reactors, or nuclear weapons where enrichment of 96—97% is used. 

Ei ty-flve percent of the zirconium used in the first land-based prototype of a submarine reactor was made by the hot-wire process. In 1952, the hot-wire process for zirconium was superseded by the lower-cost KroU process. However, the hot-wire process is still used to produce hafnium for control rods in U.S. naval reactors. 

Uranium metal is very dense and heavy. When it is depleted (DU), uranium is used by the military as shielding to protect Army tanks, and also in parts of bullets and missiles. The military also uses enriched uranium to power nuclear propelled Navy ships and submarines, and in nuclear weapons. Fuel used tor Naval reactors is typically highly enriched in U-235 (the exact values are classified information). In nuclear weapons uranium is also highly enriched, usually over 90% (again, the exact values are classified information). 

In many situations, the yield strength is used to identify the allowable stress to which a material can be subjected. For components that have to withstand high pressures, such as those used in pressurized water reactors (PWRs), this criterion is not adequate. To cover these situations, the maximum shear stress theory of failure has been incorporated into the ASME (The American Society of Mechanical Engineers) Boiler and Pressure Vessel Code, Section m. Rules for Construction of Nuclear Pressure Vessels. The maximum shear stress theory of failure was originally proposed for use in the U S. Naval Reactor Program for PWRs. It will not be discussed in this text. 

I State in lieu of this Order. Also excluded from the provisions of this Order are naval reactor... 

Thomas, D.E. Hayes, E.T. (i960) The Metallurgy of Hafnium. Naval Reactors, Division of Reactor Development, US Atomic Energy Commission. 

These cultural norms implied that an engineer s task was to prove the shuttle was not safe rather than to prove that it was safe. Tetrault compared NASA to the naval reactors program, which enjoys a long history of successfiil nuclear submarine missions... 

H.G. Rickover, L.D. Geiger, and B. Lustman. 1975. History of the Development of Zirconium Alloys for Use in Nuclear Reactors, U.S. Energy Research and Development Administration, Division of Naval Reactors, TID-26740, Washington, DC U.S. Government Printing Office. 

Belle, J., Berman, R.M., 1984. Thorium Dioxide Properties and Nuclear Applications. Naval Reactors Office, United State Department of Energy, Government Printing Office, Washington, DC, USA. 

I. Cohen, et al.. Silver and silver-hased alloys, in W.K. Anderson, J.S. Theilacker (Eds.), Neutron Absorber Materials for Reactor Control, Naval Reactor Handbooks, USAEC, 1962. 

Subject Documentation of Naval Reactors Papers and Presentations for the Space Technology and Applications International Forum (STAIF) 2006... 

The intent of the papers and presentations is to provide future space reactor developers an overview of the Naval Reactors program work on Project Prometheus and direct them to the more complete documentation that will be stored in the Office of Scientific and Technology Information (OSTI) Database. The reference above summarizes the Project Prometheus development work. 

John Ashcroft and Curtis Eshelman Naval Reactors Prime Contractor Team... 

April 2004 DOE Secretary Commissioned Naval Reactors and its National Laboratories to Design, Build and Operationally Support Civilian Space Reactor. 

Keywords Space Reactors, Nuclear Electric Propulsion, Direct Gas Brayton, Prometheus, Naval Reactors Program... 

This paper summarizes the work completed and future work recommendations of the Naval Reactors Prime Contractor Team (NRPCT) as part of the NASA Prometheus space reactor development project. The majority of the work undertaken was focused on a reactor system suitable to a deep space nuclear electric propulsion (NEP) system, with the Jupiter Icy Moons Orbiter (JIMO) as the first mission. 

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