The authors propose a system for diagnosing the state of operation of nuclear reactors.The system comprises the block TWODIS, EST and MEMORY.
The signals received from a number of detectors in the reactor are led sequentially into the block TWODIS. The input signals are analyzed statistically, to identify the actual state of operation with one of several reference modes prescribed beforehand. The algorithm used here for the identifying operation is based on the linear discriminant function.
When TWODIS identifies the state of the reactor with one of the abnormal reference modes, the disturbance estimating block EST set to work. This block statistically analyzes the signals depicting past history retrieved from MEMORY, and estimates the quantitative characteristics of the abnormality source (disturbance). Laguerre function expansion and multiple regression analyses are used in EST.
As a numerical example, a single channel model sodium coolant fast reactor is represented by a reactor simulator, in which only the coolant outlet temperature and the coolant flow rate are chosen as state variables to be detected.
The reference modes of reactor operating state prescribed for the identifying operation by TWODIS are; (1) Normal state, (2) Increasing power density, and (3) Decreasing flow rate.The EST estimates the magnitude and time constant of the causative disturbance.
Trial experiments made with simulated disturbances prove the practicality of the proposed diagnostic system.

View full abstract

Slightly pressurized water (p_sat=1.26.0bar) was flashed into steam void by step decom-pression to atmospheric pressure, using a shock tube type device with vertical test section, made of stainless steel pipe about 2m long, with an inner diameter of 40mm. The transient pressure depression below saturation and the time constant of pressure recovery to the satu-ration were measured, based on the observed transient pressure response signals. The transient pressure curve could be approximated by the expression p(t)=p_min+(p_sat-p_min)(1-e^-t/τ) for the period immediately following step decompression. This time constant τ represents the effective relaxation time of thermodynamic nonequilibrium.
Defining the term decompression ratio ε as the ratio of the excess transient depression below saturation pressure to the difference between saturation and atmospheric pressure, i.e., ε=(p_sat-p_min)/(p_sat-p_fin), the dependence of ε on the vertical position along the test column z and p_sat was found to follow approximately the empirical formula ε=exp[-β'{(p_sat/p_fin) -1}(z+z₀)], where β' was evaluated to be 0.43m^-1. Correspondingly, the attenuation constant β=-(-1/ε)•dε/dz=β'{(p_sat/p_fin)-1}. The time constant τ was found to range between 10 300msec, with a tendency to increase with decreasing saturation pressure determined by the measured water temperature. The value of τ showed little dependence on the position of observation along the test section. The expression 1/τ=βV (V being the propagation velocity of pressure waves) indicates a hyperbolic relation between τ and p_sat. This relation roughly agreed with experimental data.

View full abstract

The large and complicated system that is the Purex process is decomposed into units pos-sessing common functions. Then, using the concentration plofile determined by linear search, the inputs, the outputs and the concentration profiles of all the individual units can be deter-mined systematically. Using this approach, Powell's method and multilevel control theory is applied to the Purex process design problem, which is thereby reduced to a problem of optimi-zation. Numerical calculations are carried out, resulting in optimal process variables well within the range of practicability. These process variables are calculated without taking into consider-ation such relevant but difficult factors as criticality and the instability of Pu solutions. These factors could, however be accounted for by adding appropriate penalty terms to the performance index. The computer program devised for the present calculations is given the code name POSER (Program for Optimization of Solvent Extraction Process).

View full abstract

Loss by deposition of aerosol particles in an air sampling pipe causes error in the esti-mation of aerosol concentration in the atmosphere.
For a horizontal pipe, the deposition fraction for laminar flow can be estimated by equations of deposition governed by gravity settling and diffusion. For turbulent flow, there are two methods available-one using the equation by Yoshioka et al. to express deposition velocity, the other being the "extrapolation method" proposed by the present authors.
The present paper examines the validity of the two methods, with particular reference to the contribution of gravity settling to the deposition, and the effect of roughness of the pipe wall on the deposition from turbulent flow.
The deposition fraction in a horizontal straight metal pipe can be estimated with deviation from experimental values not exceeding a factor of 2, throughout the whole region covered by the study, extending over both laminar and turbulent ranges. Use of a suitable friction factor to account for the roughness of the pipe wall gives a reasonable value of deposition fraction in the turbulent region. The deposition from turbulent flow is mainly governed by gravity settling when the Reynolds number is not very large (Re ?? 10⁴).

View full abstract