Gamma-shielding effect

Gallium-71 NMR, 329,332-34,336-37,340 Gamma shielding effect, 355 Gauge invariant atomic orbitals, 32 Geochemistry, 374... 

It Is recommended that a suitable programme to carry out the above testing be commissioned. The effects on gamma shielding and volume of waste should also be assessed. 

As eq>ected, a lead reflector around the array In-ereues keff when compared to a water reflector. The magnitude et ttis effect Is seen by comparing cases 1 and 4, 2 and S, 3 ai 6. Since lead is a typical gamma shielding material for spent-fuel shipping casks, this effect adll have to be considered for most casks. 

Also shown in the core map is a radial reflector assumed to consist of a 50 volume % HT9-50 volume % Pb mixture. The steel shroud surrounding the core is also represented by this region. A steel containing reflector is necessary to reduce the fast neutron fluence at the reactor vessel (lead is a superior gamma shield, but has a low effectiveness in shielding invessel structures from fast neutrons.) Flowing lead in the downcomer between the shroud and the reactor vessel is also modelled in the neutronics analysis. 

As mentioned before, the LBE cooled long-life small fast reactor shows better performance for neutron economy, bum-up reactivity swing and void coefficient due to a larger elastic scattering cross section. The LBE also exhibits a better shielding effect against neutrons and gamma rays, which facilitates a reduction of the total reactor size. 

Radiation-Density Gauges Gamma radiation may be used to measure the density of material inside a pipe or process vessel. The equipment is basically the same as for level measurement, except that here the pipe or vessel must be filled over the effective, irradiated sample volume. The source is mounted on one side of the pipe or vessel and the detector on the other side with appropriate safety radiation shielding surrounding the installation. Cesium 137 is used as the radi-... 

When using an ionization chamber for detecting neutrons, beta particles can be prevented from entering the chamber by walls thick enough to shield out all of the beta particles. Gamma rays cannot be shielded from the detector therefore, they always contribute to the total current read by the ammeter. This effect is not desired because the detector responds not only to neutrons, but also to gamma rays. Several ways are available to minimize this problem. 

The use of a moderator will also allow us to locate the positron source far enough from the trap to allow adequate shielding and minimze the effects of the decay gammas so that we will be able to use a 100 mCi source of 22Na. This is a 102 increase compared to the TJW experiment. A possible geometry of the source, traps and moderator is illustrated in Fig. 1. 

Holmium in the form of HooO, powder was sealed in quartz ampoules (5 mg/ampoule), which were cold welded in an aluminium container for irradiation in the core of PARR-1 at a thermal flux of 1 x 10 n-cm -s for 1,10, 24 or 48 h. To work out the effect of shielding on the activation yield, 10,20 and 40 mg of Ho were also irradiated. Irradiated targets were dissolved in 5M HCl and evaporated to dryness. The residue was dissolved in physiological sahne solution and diluted to a specified volume for labelhng studies. The long hved radionuchdic impurity Ho was also measured using gamma spectrometry. 

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