Award Date

1-1-2008

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Committee Member

Robert F. Boehm

Number of Pages

157

Abstract

In the recently completed RACE Project of the AFCI, accelerator-driven subcritical systems (ADS) experiments were conducted to develop technology of coupling accelerators to nuclear reactors. In these experiments electron accelerators induced photon-neutron reactions in heavy-metal targets to initiate fission reactions in ADS. Although the Idaho State University (ISU) RACE ADS was constructed only to develop measurement techniques for advanced experiments, many reactor kinetics experiments were conducted there. In the research reported in this dissertation, a method was developed to calculate kinetics parameters for measurement and calculation of the reactivity of ADS, a safety parameter that is necessary for control and monitoring of power production; Reactivity is measured in units of fraction of delayed versus prompt neutron from fission, a quantity that cannot be directly measured in far-subcritical reactors such as the ISU RACE configuration. A new technique is reported herein to calculate it accurately and to predict kinetic behavior of a far-subcritical ADS. Experiments conducted at ISU are first described and experimental data are presented before development of the kinetic theory used in the new computational method; Because of the complexity of the ISU ADS, the Monte-Carlo method as applied in the MCNP code is most suitable for modeling reactor kinetics. However, the standard method of calculating the delayed neutron fraction produces inaccurate values. A new method was developed and used herein to evaluate actual experiments. An advantage of this method is that its efficiency is independent of the fission yield of delayed neutrons, which makes it suitable for fuel with a minor actinide component (e.g. transmutation fuels). The implementation of this method is based on a correlated sampling technique which allows the accurate evaluation of delayed and prompt neutrons. The validity of the obtained results is indicated by good agreement between experimental data and simulated responses of neutron detectors. The accuracy (0.2% uncertainty) of the calculated effective delayed neutron fraction, together with the exponential decay of neutron population in the reactor, allows the estimation of the mean neutron generation time to be performed with acceptable uncertainty (1.5%). Because the multiplication constant is a standard result with MCNP, the difference between dynamic reactivity (which is measured in the experiment) and static reactivity is clearly shown.

Keywords

Accelerator; Advanced; Advanced Fuel Cycle Initiative; Coupling; Cycle; Experiments; Fuel; Initiative; Neutron Fraction; Race; Reactor; Reactor Physics; Reactor-accelerator Coupling Experiments

Controlled Subject

Mechanical engineering; Nuclear engineering; Nuclear physics

File Format

pdf

File Size

2805.76 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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