........ published in NEWSLETTER # 64
[ PCO Home Page ] [ Table of Contents of NEWSLETTER # 64 ]
........ published in NEWSLETTER # 64
ADVANCED NUCLEAR SYSTEMS CONSUMING EXCESS PLUTONIUM
by Professor E. Merz, Forschungszentrum, Juelich (Germany)
The growing world surplus of separated plutonium from power generation and excess weapon plutonium from disarmament require urgent attention to avoid proliferation of atomic weapons. The technical options for its long-term disposition can be divided into three categories:
1. Indefinite storage arrangements, preferably buried deep underground; applying a so-called multi-barrier approach; 2. Minimized accessibility, in which physical, chemical, or radiological barriers would be created to reduce the plutonium's accessibility for use in weapons, for example, by irradiating the plutonium in reactors or mixing it with high-level wastes;
3. Elimination, in which the plutonium would be made virtually completely inaccessible.
Unless all plutonium is fissioned (category 3), a large amount will remain in some form for a long time, in spent fuel as separated plutonium, or fixed in a matrix such as glass or ceramics. Plutonium contained in spent fuel or, together with high-level radioactive waste, fixed in an inert matrix, makes the storage from self-protecting to a significant degree due to its intense gamma radiation. An advanced approach is required to go beyond the "spent fuel standard" and to further reduce the proliferation risk. Advanced options include almost total burning of plutonium by utilizing special fuel management either in already existing or future advanced reactor types with repeated fuel reprocessing, or in "Accelerator Driven Transmutation Systems (ADS)" with continuous processing.
A modern particle accelerator could provide so many extra neutrons that efficient burning of plutonium as well as minor actinides (Np, Am, Cm) could be accomplished with thermal-energy neutrons, in a system with remarkable engineering and safety advantages. At the outset, this did not appear technically feasible. However, more work is necessary in order to determine whether accelerator driven nuclear energy systems are an economically viable concept.
Achievement of elimination is more costly, complex, and time- consuming than minimizing accessibility to meet the spent fuel standard. Major features dealt with at the workshop (NATO ASI SERIES 1-15) comprise:
- the identification of reactor systems which consume considerable amounts of plutonium; - the assessment of the amounts of radioactive waste products in the different reactor systems as well as the amount and quality of wastes; - the assessment of increased safety performance using futuristic fissioning systems consuming excess plutonium; - necessary additional research, development and demonstration required for advanced nuclear systems.
The workshop concluded that there are several alternative solutions at hand for application and some others may be made available in the future. What is needed now is the promotion of the use of appropriate tools in comparative assessment studies.
Reference books: 1-1, 1-2, 1-4, 1-8, 1-15