Gamma ray shielding

Control rod with fuel follower Aluminum reflector element Gamma ray shield plate... 

A thin coat of gadolinium in the interior of the outside surfaces will be enough to block neutrons. Gamma ray shielding will require classical shielding. 

The sixth component of the system is the shield, which protects materials and workers from radiation, especially neutrons and gamma rays. 

The nuclear reactor also must be shielded against the emission of radioactive material to the external environment. Suitable radiation controls include both thermal and biological shielding systems. Radiation from alpha particles (a rays) and beta particles ((3 rays) has little penetrating power, but gamma rays have deep penetration properties. Neutron radiation is, however, the primary area of risk. Typically, extremely thick concrete walls are used as a neutron absorber, but lead-lined concrete and special concretes are also used. 

This metal chamber serves to shield the plates from outside electric fields and to contain the air or other gas. Gamma rays have very little trouble in penetrating the metal walls of the chamber. Beta particles and alpha particles, however, are stopped by the metal wall. For alpha and beta particles to be detected, some means must be provided for a thin wall or "window." This window must be thin enough for the alpha and beta particles to penetrate. However, a window of almost any thickness will prevent an alpha particle from entering the chamber. 

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. 

Medical X-Ray and Gamma-Ray Protection for Energies Up to 10 MeV— Structural Shielding Design and Evaluation (1970). [Superseded by NCRP Report No. 49]... 

When lead, which is very soft, is freshly cut, it has shiny blue-white sheen, which soon oxidizes into its familiar gray color. Lead is extremely malleable and ductile and can be worked into a variety of shapes. It can be formed into sheets, pipes, buckshot, wires, and powder. Although lead is a poor conductor of electricity, its high density makes it an excellent shield for protection from radiation, including X-rays and gamma rays. 

Once radioactive decay starts, it continues until all the atoms have reached a stable state. The radioisotope can only be shielded to prevent exposure to the radiation. The most common applications of gamma rays are sterilization of single-use medical supplies, elimination of organisms from pharmaceuticals, microbial reduction in and on consumer products, cancer treatment, and processing of polymers (cross-linking, polymerization, degradation etc.). 

SC 1-5 Uncertainty in Risk Estimates SC 1-6 Basis for the Linearity Assumption SC 1-7 Information Needed to Make Radiation Protection Recommendations for Travel Beyond Low-Earth Orbit SC 9 Structural Shielding Design and Evaluation for Medical Use of X Rays and Gamma Rays of Energies Up to 10 MeV SC 46 Operational Radiation Safety... 

The distributions of americium on the fissure surfaces were then quantitatively determined by scanning the face of each fissure with a Nal scintillation crystal through a 0.3 cm slit in lead shielding. The 59 keV gamma ray emitted by Am was monitored. Histograms of the americium distributions on the fissure surfaces were produced and are presented in Figures 5, 7, and 9. 

---