Data: Japan’s Separated Plutonium Inventory (as at 2005)

The data released this year (see tables below) is more detailed than in the past, though similar data was belatedly released last year in response to inquiries by CNIC and Diet Member Nobuto Hosaka.

Of particular interest is the material unaccounted for (MUF). The figures shown here are very low. Indeed, the positive figure for JAEA’s Tokai reprocessing facility means that the balance books show 0.6 kg more plutonium than there should be. MUF is an indication of the limits of the plutonium accounting system, and given that the measurements for the other categories are not 100% accurate, positive MUF figures such as this are quite possible. The plutonium in the retained waste (stored within the material balance area) and the measured discard (disposed of in such a way that it is not suitable for further nuclear use) could conceivably be plus or minus several percent compared to the figures shown here. (No response was ever received to CNIC’s inquiry about the accuracy of these measurements.)

However, the most significant thing about the data released this year is that we can expect similar detailed information next year. We look forward to seeing a detailed breakdown of the plutonium accounting for the active tests at the Rokkasho reprocessing plant.