Notes

1. DOE is used to include its predecessor Government organizations, i.e., the U.S. Army Corps of Engineers Manhattan Engineer District, the Atomic Energy Commission (AEC) and The Energy Research and Development Administration (ERDA).
2. Throughout this report metric tons (MT) and kilograms (kg) are used as the measure of the amounts of plutonium. One metric ton is 2,205 pounds, and one kilogram is approximately 2.2 pounds.
3. The combined plutonium inventory of 99.5 MT is 0.1 MT less than its two component elements due to rounding to the nearest tenth of a metric ton.
4. The acquisition and removal numbers are understated by 0.1 MT of plutonium due to transactions that remain classified for national security reasons, and to rounding of numbers.
5. Special nuclear material is defined in the Atomic Energy Act and includes plutonium and enriched uranium.
6. Isotopes are different forms of the same chemical element that differ only by the number of neutrons in the nucleus. Most elements have more than one naturally occurring isotope. Many more isotopes have been produced in nuclear reactors and scientific laboratories.
7. Half-life is the time it takes for one-half of any given number of unstable atoms to decay. Each isotope has a specific half-life.
8. Plutonium-238 has a Pu-238 content of greater than 10 percent by weight of the total plutonium.
9. Plutonium-242 has a Pu-242 content of 20 percent or greater by weight of the total plutonium.
10. The acquisition and removal numbers are understated by 0.1 MT of plutonium due to transactions that remain classified for national security reasons, and to rounding of numbers.
11. The combined Hanford and Savannah River plutonium production figure is 0.1 MT less than the two subtotals due to rounding to the nearest tenth of a metric ton.
12. The combined plutonium inventory figure is 0.1 MT less than the two subtotals due to rounding to the nearest tenth of a metric ton.
13. Includes power reactor grade plutonium
14. Ibid.
15. Cumulative production since 1945
16. Adjustment to previous years' production to reflect the difference between theoretical calculations of plutonium produced in the reactors and the measured value of plutonium recovered in the chemical separations plants.
17. Ibid.
18. Adjustment to previous years production to reflect the difference between theoretical calculations of plutonium produced in the reactors and the measured value of plutonium recovered in the chemical separations plants.
19. The material from Nuclear Fuels Services, Erwin, Tennessee, was in the form of liquid residues generated during the fabrication of reactor fuel for the Southwest Experimental Fast Oxide Reactor (SEFOR).
20. The total is 0.1 MT less than the two subtotals due to rounding to the nearest tenth of a metric ton.
21. This quantity is cumulative for the years prior to 1959.
22. Plutonium materials remaining in process tanks, piping, drains, ventilation ducts or other locations.
23. This quantity is cumulative for the years prior to 1969
24. Plutonium decay is the spontaneous emission of alpha or beta particles resulting in the change of the element plutonium to other elements.
25. This quantity is cumulative for the years prior to 1969.
26. A negative number is an increase to the inventory.
27. Nuclear Nonproliferation Treaty
28. Inventory differences are defined as the difference between the actual physical inventory and the estimated inventory. Additional information on the relationship between waste and inventory differences can be found in the Report on Strategic Special Nuclear Material Inventory Differences, ERDA, 77-68, August 1977, and the periodic updates published through 1992.