Analytical and Experimental Comparison of the Velocity of a Supersonic Projectile in the Soft Recovery System

In order to compare numerical analyses made by Song and Kim needed for predicting gas and water filling with experimental results we conducted an experiment to recover a test projectile (43.7 kg with a 155 mm diameter) at a velocity of 775 m/s in a soft recovery system with a length of 179 m using pressurized gas and filled water. The soft recovery system consisting of a series of pressure tubes had a diaphragm, piston, and water plug for filling the pressurized gas and water. We installed a continuous wave Doppler radar system for velocity measurements of the test projectile travelling in the pressure tubes and pressure transducers for measuring the pressure in the soft recovery system. Continuous wave Doppler radar has the advantage of achieving real-time measurements of the velocity of a test projectile. The velocity-time curve of the test projectile, measured using the continuous wave Doppler radar, and the pressure profile were compared with the numerical analysis results. The experiment results show good agreement with the numerical analysis results based on the one-dimensional Euler equation with an HLL Riemann solver.

244Cm contributions to the alpha source term of CANDU reactors

In this report the expected rate of buildup of 244Cm in a CANDU neutron flux is evaluated and used to explain cases of high 244Cm in alpha-active samples from Bruce and Pickering Units. It is demonstrated that 244Cm is enriched on the surface of irradiated pressure tubes where it is associated with Zr/Nb activation products. It is further shown, using 94Nb as a fluence monitor, that the 244Cm/(239Pu + 240Pu) ratio for Bruce and Pickering irradiated pressure tube deposits exhibits a power law = 0.0042 (Fluence)3.1982. For non-pressure tube samples, such as feeder pipes, steam generator deposits and PHTS cruds, it is observed that Zr/Nb activation products are also associated with elevated 244Cm activities. Thus, based on the data presented in this report, the inference is that all CANDU Units may be expected to exhibit significant levels of 244Cm activity on PHTS surfaces, both in and out-of-core, with 244Cm/(239Pu + 240Pu) ratios significantly greater than one.

A simplified analysis of the Chernobyl accident

We show with simplified numerical models, that for the kind of RBMK operated in Chernobyl: The core was unstable due to its large size and to its weak power counter-reaction coefficient, so that the power of the reactor was not easy to control even with an automatic system. Xenon oscillations could easily be activated. When there was xenon poisoning in the upper half of the core, the safety rods were designed in such a way that, at least initially, they were increasing (and not decreasing) the core reactivity. This reactivity increase has been sufficient to lead to a very high pressure increase in a significant amount of liquid water in the fuel channels thus inducing a strong propagating shock wave leading to a failure of half the pressure tubes at their junction with the drum separators. The depressurization phase (flash evaporation) following this failure has produced, after one second, a significant decrease of the water density in half the pressure tubes and then a strong reactivity accident due to the positive void effect reactivity coefficient. We evaluate the fission energy released by the accident

Deuterium Ingress at the Rolled Joints in CANDU Reactors: Where Does it Comefrom and How Can It be Reduced?

Simple, small-scale, experiments demonstrate the high deuterium concentrations found in the zirconium pressure tubes at CANDU rolled joints comes from the initial as-received protium in stainless-steel end fittings exchanging with deuterium before being gettered by the zirconium. We propose to reduce the concentration of hydrogen isotopes at the ends of pressure tubes in heavy-water nuclear reactors with yttrium getters placed in the outer regions of the stainless-steel end fittings away from the heat-transport heavy water. Simple, small-scale, experiments demonstrate the operating principle showing that yttrium can getter hydrogen isotopes from the zirconium through the stainless steel.