Results of Research to Evaluate Solid Plutonium Nitrate as a Safe Shipping Form

Abstract

The results of the research described indicate that the compound Pu(NO/sub 3/)/sub 4/.XH/sub 2/O is a viable material for consideration as a solid shipping form. It meets the criteria set forth to define a suitable solid form of plutonium. Several plutonium compounds were considered for study as a shipping form before selecting Pu(NO/sub 3/)/sub 4/.XH/sub 2/O as having the most desirable characteristics. It is reasonably easy to prepare on a kilogram scale with relatively simple equipment using vacuum evaporation techniques. Plutonium nitrate does begin to thermally decompose at about 100/sup 0/C; however, proper equipment design and instrumentation can overcome this problem. Although Pu(NO/sub 3/)/sub 4/.XH/sub 2/O does produce some radiolytic gases, such as oxygen and nitrogen, an explosive mixture is not produced as only minor amounts of hydrogen are formed except during extended storage. Excessive pressurization in the shipping mode should not be a problem if the transport container is not closed for protracted periods of time. However, some form of thermal insulation would be required to prevent decomposition of the compound and to preclude over-pressurization during a fire. Plutonium nitrate has been found to be completely soluble in nitric acid even after storage for extended periods of time. Aftermore » the equivalent of 25 years of storage time of first-cycle reactor-grade plutonium from a radiation damage standpoint, Pu(NO/sub 3/)/sub 4/.XH/sub 2/O prepared from 85 percent /sup 238/Pu was found to be completely soluble in 4M HNO/sub 3/. Plutonium nitrate was also found to be soluble in water, but it rapidly converted to plutonium polymer.« less