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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.
Susumu Naito, Makoto Takemura, Shungo Sakurai, Mikio Izumi, Yasushi Goto, Yoshiji Karino
Nuclear Science and Engineering | Volume 166 | Number 2 | October 2010 | Pages 107-117
Technical Paper | doi.org/10.13182/NSE09-99
Articles are hosted by Taylor and Francis Online.
To simplify in-core instrumentation in a next-generation boiling water reactor (BWR), we study an ex-core nuclear instrumentation system. As a first step of this study, we focused on ex-core local power monitoring, which is especially difficult because neutrons inside a core cannot fly out of a reactor pressure vessel (RPV) due to shielding of fuel, water, etc., except when they are generated in the outer edges of the core. To resolve this, we created a local power monitoring method with neutron streaming pipes (NSPs). An NSP is a gas-filled pipe of size comparable to an instrumentation tube of an existing BWR. NSPs are axially inserted into the core. In-core neutrons are transported to the RPV through NSPs. The neutrons transmitted through the RPV are monitored with ex-core neutron sensors. We analytically evaluated the applicability of this NSP method for an advanced BWR (ABWR) with a three-dimensional BWR core simulator and the MCNP5 code. The ex-core neutron flux through the NSP was highly proportional to local power (1.0% of the residual standard deviation). The flux amount and the linearity gave feasible specifications for the ex-core neutron sensor in typical operation modes (pulse, Campbell, and current modes). Therefore, the NSP method is applicable to an ABWR.
