Nuclear Structural Engineering最新文献

The boundary value problem concerned with the state of stress in two normally intersecting circular cylindrical shells subjected to internal pressure is formulated. The differential equations of the two shells are solved for a small ratio of radii ($\text{ϱ}{}_0\text{R}\text{<}\text{1}\text{3}$) subject to edge conditions along the intersection curve and at the ends of the cylinders. The numerical results will be published in a later paper.

General features of a MOSEL (MOlten Salt ExperimentaL) reactor concept and a schematic flow diagram are given.

A number of core designs appear capable of satisfying the requirements of such reactor. Interacting parameters which need to be evaluated as a function of operating conditions are permissible temperature distribution, stresses, nuclear performance, and fabrication possibility as a function of core design. In general it appears that plate type design facilitate low friction of structural material, achievement of modular units, and fuel flow control. Tube-type designs appear advantageous relative to stress considerations and high fuel power density.

The absolute magnitude, and the variations in form, of the fast neutron spectrum during deep penetration (0.8 – 1.1 m) in massive shields of water, ordinary and magnetite concrete have been studied by using threshold detectors (In(n, n′), S(n, p), Al(n, α)). The results have been compared with predictions by two rigorous (NIOBE, Moments method) and two non-rigorous (multigroup removal-diffusion) shielding codes (NRN, RASH D).

The absolute results predicted were in general within 50% of the measured ones, ie. showed as good or better accuracy than thermal and epithermal flux predictions in the same small-reactor configurations. No difference in accuracy was found between the rigorous and non-rigorous methods.

The changes in the relative form of the spectrum (indicated by variations in the (Al/S) and (In/S) reaction rate ratios and amounting to factors up to 3–4 during a one metre penetration in water) were rather accurately (within 10–30%) predicted by all of the methods.

The photonuclear excitation of the 335 keV level used for detecting the In(n, n′) reaction was found to distort completely the In results in water at penetrations > 50 cm.

An experimental program was carried out to determine the effect of small weld cracks on the fatigue strength of steel pipe. Direct and bending load tests of both innate and artificial flaws were carried out with special hydrostatic pressurization and vibratory fatigue machines. Values of notch sensitivity of the base, weld and heat affected zone materials were found to be similar, ranging between 0.1 and 0.2. The results showed that no appreciable reduction in specimen life occurred when small (to 4% wall thickness) cracks were tested in the presence of ordinary manufacturing discontinuities such as surface roughness and weld notches.

A semi-empirical method for computing the influence of small pipe wall cracks on pipe life is suggested and compared with the test results.

Some problems in the construction of cooling medium inlet and outlet nozzle rings of nuclear reactor pressure vessels are discussed. The factors affecting the stress concentration factor in this part of the vessel have been identified theoretically and experimentally. It has been determined that the stress concentration factor depends on the form of the hole in the vessel shell, on the number of holes made on the periphery of the vessel, on the curvature and wall thickness of the vessel shell, on the reinforcement of the hole of the nozzle to the vessel.

A general method is presented for finding lower and upper bounds on the collapse pressure for a plastic-rigid vessel composed of intersecting cylindrical and spherical shells obeying Tresca's yield condition and associated flow rule. Depending upon the ratio $\text{(}\text{t}\text{d}\text{)/(}\text{T}\text{D}\text{)}$ different types of solutions are generated. The solutions are presented in terms of generalized stresses and may be used in conjunction with any choice of yield surface of the form Φ(N_ϕ,N_θ,M_ϕ) = C².

The 105-N building, which houses the world's largest power reactor, is a highly specialized structure of reinforced concrete and steel. The secondary shielding walls, which surround the reactor and its coolant system, are 4 to $\text{5}\text{built1}\text{2}$ feet thick; the ceilings $\text{1}\text{built1}\text{2}$ to $\text{2}\text{built1}\text{2}$ feet thick. These walls are designed to reduce radiation levels to safe human tolerance during normal reactor operation and to function as a low pressure confiner during an emergency. Interior surfaces are covered with an elastomeric coating consisting of 15 mils of neoprene and 5 mils of (white) hypalon. In addition to normal dead and live loads, the structure is designed to resist: 1) a temperature differential of 40°F, 2) an internal pressure of 5 psig or a vacuum of 2 psig, and 3) seismic loads associated with a ground acceleration of 0.2 gravity. Criteria used in the detail design of the 105-N building are reproduced in this paper.

This reports the results of a testing program and study to find low-activation shielding materials for nuclear reactor environmental test chambers. Economic trade-offs associated with low-activation shielding materials are considered. Activation dose rates in existing test chambers are compared with study results.

This paper outlines a simple method to determine the elastic stress-concentration factor of radial reinforced outlets from spherical vessels subjected to internal pressure.

The computed values of the stress-concentration factor are compared with the results of photoelastic tests, showing good agreement, ordinarily within 10% or less.