| Abstrakt: |
An investigation of safeguards needs in future fast reactor reprocessing plants has been conducted to provide rationale for a new safeguards approach. Ultimately, if nuclear power is to realize its potential in long-term global economic performance, thermal reactors must give way to fast reactors, and once-through fuel cycles must be displaced by reprocessing-recycle. Challenges in safeguarding reprocessing in the fast reactor system are immediately apparent by analogy to the case of large-scale LWR reprocessing. With fast reactors, plutonium throughputs in reprocessing will be increased by up to a factor of 10 or more for a given heavy-metal capacity, due to higher plutonium concentration in the fuel. Even if capacity is reduced (say to 250 MTHM/yr, which was the size used in the last major international study of fast reactor reprocessing some 30 years ago) plutonium throughput will be about 3 times that of a commercial LWR reprocessing plant. The mass throughputs proportionally drive Inventory Difference (ID) and its standard error, which together form the key requirements for material accountancy. Simple models of the head-end portions of representative aqueous and pyroprocess plants have been constructed and analyzed. Our particular interest is in electrochemical reprocessing (the "pyroprocess"), but aqueous plants are modeled too, for comparison. For an 800 MTHM/yr aqueous plant processing LWR fuel of 1.3% Pu content (i.e. spent fuel with ~50 GWd/MTHM burnup), we get an expected result: the plant can meet IAEA accountancy requirements because of (1) the input "accountability tank", and (2) virtual or book inventories done every 20 days or so. For the pyroprocess, it is well known that the absence of a homogeneous measurement point at the head-end is the principal challenge. From our model, a fast reactor pyroprocess plant @ 100 MTHM/yr capacity can meet the IAEA requirement for standard error in ID only with book inventories done every few days, or breakthroughs in the accuracy of nondestructive analysis (NDA) of the input fuel assemblies. Increasingly we believe that success in safeguarding the pyroprocess lies not in refinement of the material accountancy regime, but in defining a safeguards regime that makes full use of the intrinsic properties of the pyroprocess i.e. a U-Pu fuel product that contains the minor actinides and small amounts of fission products. This is the direction of continued research. [ABSTRACT FROM AUTHOR] |
