Polymers in Concrete – The Shielding against Neutron Radiation

Abstract

Concrete has been used as a shield against high-energy photons (gamma) and neutrons since the beginning of use of nuclear reaction in energy, medicine and research. State of knowledge in shielding concrete technology is that while in case of protection against gamma radiation an increase in density caused by change of aggregate type for heavy-weight one is usually an efficient solution, the protection against neutrons is more complex. It is due to the differences in interactions of neutrons with the matter, depending on their kinetic energy and cross-sections for different reactions of the component atoms of the cement paste and the aggregate. The paper presents the results of the project NGS-Concrete - New-Generation Shielding Concrete. The aim is to design the composition of concrete against ionizing radiation, achieved by the use of experiment based on multi-criteria optimization of materials supported by the Monte Carlo simulations. Better concrete is the one that absorbs more thermal neutrons and slows down more fast neutrons at the same time. In the paper both results of Monte Carlo simulations and experimental studies on ordinary and heavyweight concrete containing epoxy polymer additive are presented. Close values of thermal neutron attenuation coefficients proved good accordance between simulation and experiment. The final conclusion is that epoxy resin is an efficient additive for neutron shielding concretes improving its ability to protect mainly against low energy neutrons. In experimental measurement there has not been observed an improvement of fast neutron attenuation due to increase of hydrogen atom content introduced with epoxy.

Influence of Polymer Modification on the Microstructure of Shielding Concrete

“…On the other hand, it was observed that the epoxy dispersion (MPCC2), macrofibers (MF2), and both types of fibers added at the same time caused an increase in HVL from about 5.0% (MPCC2) to 17.0 (MF3); in other words, the thickness of the shield necessary to reduce the radiation by half increased, which means that the shielding effectiveness was weakened. This is not consistent with the results reported in the literature [17][18][19]. Because of the increase in hydrogen content, the addition of polymers to concrete should result in an increase in its effectiveness in shielding against neutron radiation.…”

“…The investigation of the effectiveness of shielding against neutrons was measured using a Pu-Be source and a specially prepared stand that allowed placing 500 mm × 500 mm × 50 mm concrete slabs perpendicularly to the positioning mechanism of the radiation source (Figure 4). The measurements were made according to the individually developed program [18]. The evaluation was based on the half value layer (HVL) expressing the thickness of the absorbing material needed for a reduction in the incident radiation intensity by a factor of two.…”

“…This can be done by modifying the composition of the concrete mix using materials containing hydrogen. One of the milestones in the evolution of shielding technology against neutron radiation was the concept of adding polymers into concrete composites in the form of admixtures (e.g., superplasticizers) and additives (e.g., resins and fibers) [17][18][19]. This enables w/c ratio (water-cement ratio) reduction and improvement of usability properties like tightness, mechanical properties, and chemical resistance without loss of the workability of the fresh concrete mix.…”

Radiation Shielding Properties Prediction of Barite used as Small Aggregate in Mortar

“…That interaction means being completely absorbed or losing energy, which will weaken or destroy the gamma radiation. Therefore, when choosing a shielding material, attention must be paid to the factor of high electron density (electron/cm 3 ), but for high electron density, the number of protons (the Z number) of the atoms should be large, and the density of the shielding material also should be greater (atoms/cm 3 ) [7]. Therefore, the metal element barium (Ba) (Z = 56) in the barium sulfate compound BaSO 4 is suitable for radiation shielding, because it is chemically stable, easy to preserve, pack, and transport, less affected by the surrounding environment, easy to produce, has low cost, it is safe, and easy to use [8,9].…”