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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.
J. T. Mihalczo
Nuclear Science and Engineering | Volume 60 | Number 3 | July 1976 | Pages 262-275
Technical Paper | doi.org/10.13182/NSE76-4
Articles are hosted by Taylor and Francis Online.
The effective delayed neutron fraction from fission was determined for an unreflected uranium (93.2 wt% 235U) metal sphere from the ratio of time-correlated counts in a randomly pulsed neutron measurement to those in a Rossi-α measurement. In the randomly pulsed neutron measurements, a 252Cf source was placed in the sphere which contained a fission counter that, because of its location, did not count neutrons directly from the source. Neutrons from spontaneous fission of 252Cf initiated fission chains in the sphere, and the fission counter detected events from the interaction of neutrons from these fission chains with the uranium of the fission counter. A Type I time analyzer was triggered each time a 252Cf nucleus fissioned and recorded the time distribution of neutrons from the fission chains initiated by neutrons from californium at t = 0. The delayed neutron fraction by this method (60.2 ± 0.8 × 10−4) is ∼11% lower than that from other measurements or calculations that are all in agreement. This low value may be due to an improper theoretical formulation for the correction of point kinetics for spatial effects. The value of this correction factor estimated by another theoretical formulation is 30% larger. An 11% larger correction for spatial effects would produce agreement between this measurement and previously measured results.