Pulsed Neutron Experiments Research Articles

Reply to “Comments on ‘A Pulsed Neutron Experiment with Beryllium by the Use of a Gamma-Ray Flash from an Electron Linear Accelerator’”

"Reply to “Comments on ‘A Pulsed Neutron Experiment with Beryllium by the Use of a Gamma-Ray Flash from an Electron Linear Accelerator’”." Nuclear Science and Engineering, 52(1), pp. 152–153

Comments on “A Pulsed Neutron Experiment with Beryllium by the Use of a Gamma-Ray Flash from an Electron Linear Accelerator”

"Comments on “A Pulsed Neutron Experiment with Beryllium by the Use of a Gamma-Ray Flash from an Electron Linear Accelerator”." Nuclear Science and Engineering, 52(1), p. 152

A two mode high speed time analyzer with a plated wire memory

A 1024 channel high speed time analyzer was made by using a plated wire as a memory element. This time analyzer has two operation modes, TOF mode (add-one mode) and MS mode (multi-scaler or add- N mode), both of which use a 133 MHz crystal oscillator. The channel width of the former mode can be selected from 15 ns to 3.84 μs (9 stages) and that of the latter from 1 μs to 65.536 ms (9 stages). For background counting, the last eight channels have longer channel widths and selective delays. These channel widths and delay times were tested with random pulses from a liquid scintillation counter and a weak radioactive source, and periodic pulses from a pulser. The results agreed satisfactorily with the designed values. The dead time for the TOF mode was found to be about 270 ns and that for the MS mode was about 19 ns in counting and about 250 ns in memory cycle. These values are drastically shorter than previous time analyzers, such as TMC-211. This time analyzer has been applied to fast neutron time-of-flight experiments with an electron linear accelerator, and pulsed neutron experiments in beryllium-oxide piles. In this case, no correction for count losses by dead time of a time analyzer is required.

Effect of Shape of the Assembly on the Decay Constant in Pulsed-Neutron Experiments

Effect of Shape of the Assembly on the Decay Constant in Pulsed-Neutron Experiments

Measurements of Spatially Independent Reactivity in Pulsed-Neutron Experiments

Through the measurement of the kinetic distortion effect, defined as the modal shape and spectral difference between the fundamental prompt- and delayed-neutron modes, a spatial correction factor f...

Conditions of Fast Multiplying Systems for Existence of the Time Eigenvalue of the Fundamental Mode

A few concrete conditions for the existence of the time eigenvalue of fast multiplying systems are derived from the integral transport equation. In order that the real time eigenvalue may exist, there are limitations to the composition and the size of the systems. It may be considered, with very good approximation, that a necessary condition for the existence of the real time eigenvalue is that the infinite multiplication constant is not less then unity. With respect to the size of the system, if half the minimum chord length is not less than three times the inverse of {Σ s (ν)+ νΣ f (ν)}min, the system is not too small for the existence of the real time eigenvalue. These conditions can be applied to the planning and the analysis of pulsed neutron experiments on a fast multiplying system.

A Pulsed Neutron Experiment with Beryllium by the Use of a Gamma-Ray Flash from an Electron Linear Accelerator

A new method of pulsed neutron experimentation is proposed and successfully applied to a beryllium metal system. The present technique utilizes the γ-ray flash from an electron linear accelerator. ...

Conditions of Fast Multiplying Systems for Existence of the Time Eigenvalue of the Fundamental Mode

A few concrete conditions for the existence of the time eigenvalue of fast multiplying systems are derived from the integral transport equation. In order that the real time eigenvalue may exist, there are limitations to the composition and the size of the systems. It may be considered, with very good approximation, that a necessary condition for the existence of the real time eigenvalue is that the infinite multiplication constant is not less then unity. With respect to the size of the system, if half the minimum chord length is not less than three times the inverse of {Σ s (ν)+ νΣ f (ν)}min, the system is not too small for the existence of the real time eigenvalue. These conditions can be applied to the planning and the analysis of pulsed neutron experiments on a fast multiplying system.

A fast time analyzer embodying a high speed plated wire memory

A fast time analyzer operating in a multiscaling mode with 256 channels and 25 ns minimum channel width was constructed by employing the high speed plated wire memory with a 175 ns cycle time for the purpose of its application to pulsed neutron experiments. The characteristic features and details of construction and circuitry of the time analyzer are presented. To test the performance several experiments were carried out. These include measurements of the shapes of the pulsed neutron bursts and measurements of time distributions of thermal neutron capture γ-rays of various foils in a graphite pile.

A modeled theory of pulsed-neutron experiments in fast subcritical assemblies

Abstract The time behavior of a neutron pulse in a fast subcritical assembly is modeled by approximating the spatial dependence by a single diffusion mode and using a simple model of inelastic scattering. This model allows an explicit calculation of the time response of a detector in such a system. Of particular interest is a study of the detector response in those situations in which the flux does not decay in an exponential fashion.

Analysis of Pulsed Neutron Experiment in Beryllium by the Method of Inelastic Scattering Expansion

Pulsed neutron experiments in beryllium have been analyzed by the method of inelastic scattering expansion. Considering the full range of energy, the present method is applied to the calculation of the time dependent spectra within a system as well as at its surface. For obtaining the decay curve of the neutron counting rate, the neutrons are classified according to the number of specified inelastic scatterings that scatter the neutrons over the Bragg cutoff energy. The pseudo mode is, as a principal result, shown to correspond to an eigen solution of the thermal bounded equation. The buckling dependence of the eigenvalue and the eigen spectrum of the thermal bounded equation are studied, and useful approximate expressions are derived. The calculated results are compared with the experiments by Fullwood et al. and other authors.

Analysis of Pulsed Neutron Experiment in Beryllium by the Method of Inelastic Scattering Expansion

Analysis of Pulsed Neutron Experiment in Beryllium by the Method of Inelastic Scattering Expansion

On the theory of pulsed-neutron experiments in polycrystalline moderators

Abstract The transport-theoretical analysis of pulsed-neutron experiments in polycrystalline moderators is performed in the space of functions square summable over infinite ranges in velocity and space variables. The possibility of the existence of discrete eigenvalues of the transport operator below the minimum collision rate is demonstrated.

Reactivity Measurements on Fast Systems with Natural Uranium Metal Blanket by Pulsed Neutron Method

A study has been made on how simple analysis of pulsed neutron experiments could be applied to the measurement of reactivity of fast systems with a blanket of metallic natural uranium. Pulsed neutron experiments have been performed on three fast assemblies of the Fast Critical Assembly at the Japan Atomic Energy Research Institute. The decay constants have been successfully observed even at delayed critical. The energy and spatial higher modes have been also observed. Simple models of Gozani and Simmons-King have been applied to derive the reactivity in dollar units. It has been made clear that the reactivity could be measured by the pulsed neutron method down to —3$, and in a certain case, down to —5$, for fast systems with a core of medium size up to at least about 200 l enclosed in a metallic natural uranium blanket. The establishment of the asymptotic decay has been experimentally investigated. Linearity has been ascertained to hold between the prompt neutron decay constant and the reactivity by the pulsed neutron method and between the reactivities by the pulsed method and by the positive period method down to a few dollars in negative reactivity.

Study of the Use of Pulsed-Neutron Experiments on Multiplying Lattices for the Adjustment of Criticality Codes

Criticality codes are in general adjusted to reproduce measured values of critical bucklings which furnish (k∞ − 1)/M2. The parameter adjusted is k∞, the calculation of leakage being assumed to be ...

Use of repetitive operation analog computers in simulating pulsed neutron experiments

Use of repetitive operation analog computers in simulating pulsed neutron experiments

Reactivity Measurements on Fast Systems with Natural Uranium Metal Blanket by Pulsed Neutron Method

A study has been made on how simple analysis of pulsed neutron experiments could be applied to the measurement of reactivity of fast systems with a blanket of metallic natural uranium. Pulsed neutron experiments have been performed on three fast assemblies of the Fast Critical Assembly at the Japan Atomic Energy Research Institute. The decay constants have been successfully observed even at delayed critical. The energy and spatial higher modes have been also observed. Simple models of Gozani and Simmons-King have been applied to derive the reactivity in dollar units.It has been made clear that the reactivity could be measured by the pulsed neutron method down to -3, and in a certain case, down to -5, for fast systems with a core of medium size up to at least about 200l enclosed in a metallic natural uranium blanket. The establishment of the asymptotic decay has been experimentally investigated. Linearity has been ascertained to hold between the prompt neutron decay constant and the reactivity by the pulsed neutron method and between the reactivities by the pulsed method and by the positive period method down to a few dollars in negative reactivity.

The reduction of time-of-flight errors in pulsed neutron measurements

Calculations and a measurement show that time-of-flight errors in pulsed neutron experiments can be reduced by using a detector whose efficiency decreases at low neutron energies.

Analysis of Pulsed Neutron Experiments in Polycrystalline Media Using a Model Kernel

A detailed investigation of pulsed neutron experiments in thermal, nonmultiplying, polycrystalline moderators is presented. A transport approximation of the spatial dependence of the neutron densit...

A Theory of Pulsed Neutron Experiments in Polycrystalline Media

A Theory of Pulsed Neutron Experiments in Polycrystalline Media