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NRC proposes changes to its rules on nuclear materials
In response to Executive Order 14300, “Ordering the Reform of the Nuclear Regulatory Commission,” the NRC is proposing sweeping changes to its rules governing the use of nuclear materials that are widely used in industry, medicine, and research. The changes would amend NRC regulations for the licensing of nuclear byproduct material, some source material, and some special nuclear material.
As published in the May 18 Federal Register, the NRC is seeking public comment on this proposed rule and draft interim guidance until July 2.
W. Breitung, S. A. Wright
Nuclear Science and Engineering | Volume 105 | Number 4 | August 1990 | Pages 303-318
Technical Paper | doi.org/10.13182/NSE90-A21467
Articles are hosted by Taylor and Francis Online.
Irradiated (U.Pu)-mixed oxide with 5% burnup was heated in the pulsed Annular Core Research Reactor at Sandia National Laboratories. The tests were typical of prompt Bethe-Tait excursions in terms of heating method (nuclear fission), heating period (milliseconds), and temperatures attained (up to 7700 K). Fission products provided high pressures at temperatures at which fresh fuel shows only a negligible vapor pressure. Fission product release became measurable as soon as the temperature exceeded the steady-state irradiation temperature of the fuel sample. The fission product pressures reached 1.3 to 2.5 MPa at 3000 K over solid fuel, and 2.5 to 5 MPa at 4000 K over liquid fuel. The total amount of fission product released corresponded to ∼30 to 75% of the fission gas inventory. The amount of fission product released increased with the fuel heating rate. Under rapid heating, the total pressure over irradiated (U,Pu) oxide is controlled by a suppression mechanism. At any given temperature, the gaseous components (xenon, cesium, and ambient gas) suppress fuel boiling if their pressure pgas is higher than the fresh fuel saturation vapor pressure psat of unirradiated fuel. If psat exceeds pgas, the total pressure is, to a first approximation, equal to Psat. Under millisecond heating, the total pressure from irradiated fuel may be taken as ptot = max(Pgas,Psat).
