Scientists create a lead-free composite shielding material to protect neutrons from gamma radiation

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Schematic diagram of the shielding mechanism for modified nano-composite shielding material. Credit: Huo Zhiping

Dr. Huo Zhipeng and his student Zhao Sheng from the Hefei Institutes of physical science (HFIPS) of the Chinese Academy of Sciences recently developed a lead-free neutron and gamma ray composite shielding material that has high shielding properties and is environmentally friendly. Their results were published in Nuclear Materials and Energy.

The composite, modified-gadolinium oxide/boron carbide/high density polyethylene (Gd2O3/B4C/HDPE), was tested safe and effective to shield neutron and gamma rays through a series of intricate and comprehensive experiments.

Neutron, as an electrically neutral particle, has a strong penetrability and always emits secondary gamma rays during particle collision process. For combined shielding, the scientific and most efficient method of shielding neutron is to use high Z (atomic number), low Z and neutron-absorbing materials simultaneously. The use of lead-containing materials is restricted due to biological toxicities.

Rare earth element gadolinium, usually exists in the form of non-toxic Gd2O3 in nature, has always shown high average thermal neutron absorption, high temperature resistance and good gamma shielding performance.

The researchers studied the shielding mechanism first, and then adopted the coupling agents to modify the surface of Gd2O3 to improve the interfacial compatibility and dispersion of Gd2O3 in the matrix.

“It’s lead-free and poses little threat to the environment and humans,” stated Dr. Huo who has been involved in radiation and environmental protection since years.

He also explained the mechanism of radiation shielding. He also explained how the radiation shielding system worked. Fast neutrons collide inelastically with gadolinium, then collide elastically and with hydrogen until they become thermal nuons.

The experimental results show that the neutron shielding rate of the composite can reach 98% under the condition of 15 cm thickness in CF-252 environment. In cS-137 and CO-60 environments, the gamma shielding rates of the composite are 72% and 60%, respectively, at the same thickness.

Its comprehensive shielding performance surpasses conventional boron–polyethylene collimating protection and is suitable for the neutron spectrum and Gamma spectrum diagnosis system of Experimental Advanced Superconducting Tokamak. According to researchers, it is expected to be a promising radiation-shielding material for neutron/gamma mixed field.

More information:
Zhipeng Huo et al, Surface modified-gadolinium/boron/polyethylene composite with high shielding performance for neutron and gamma-ray, Nuclear Materials and Energy (2021). DOI: 10.1016/j.nme.2021. 101095

Citation:
Scientists invent lead-free composite shielding material for neutrons and gamma-rays (2021, December 23)
retrieved 26 December 2021
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