A New Light Weight Structural Material for Nuclear Structures

Technical Report · Thu Jan 14 00:00:00 EST 2016

DOI:https://doi.org/10.2172/1239280· OSTI ID:1239280

Rabiei, Afsaneh ^[1]

---

1. North Carolina State Univ., Raleigh, NC (United States)

Radiation shielding materials are commonly used in nuclear facilities to attenuate the background ionization radiations to a minimum level for creating a safer workplace, meeting regulatory requirements and maintaining high quality performance. The conventional radiation shielding materials have a number of drawbacks: heavy concrete contains a high amount of elements that are not desirable for an effective shielding such as oxygen, silicon, and calcium; a well known limitation of lead is its low machinability and toxicity, which is causing a major environmental concern. Therefore, an effective and environmentally friendly shielding material with increased attenuation and low mass density is desirable. Close-cell composite metal foams (CMFs) and open-cell Al foam with fillers are light-weight candidate materials that we have studied in this project. Close-cell CMFs possess several suitable properties that are unattainable by conventional radiation shielding materials such as low density and high strength for structural applications, high surface area to volume ratio for excellent thermal isolation with an extraordinary energy absorption capability. Open-cell foam is made up of a network of interconnected solid struts, which allows gas or fluid media to pass through it. This unique structure provided a further motive to investigate its application as radiation shields by infiltrating original empty pores with high hydrogen or boron compounds, which are well known for their excellent neutron shielding capability. The resulting open-cell foam with fillers will not only exhibit light weight and high specific surface area, but also possess excellent radiation shielding capability and good processability. In this study, all the foams were investigated for their radiation shielding efficiency in terms of X-ray, gamma ray and neutron. X-ray transmission measurements were carried out on a high-resolution microcomputed tomography (microCT) system. Gamma-emitting sources: 3.0mCi ⁶⁰Co, 1.8mCi ¹³⁷Cs, 13.5mCi ²⁴¹Am, and 5.0mCi ¹³³Ba were used for gamma-ray attenuation analysis. The evaluations of neutron transmission measurements were conducted at the Neutron Powder Diffractometer beam facility at North Carolina State University. The experimental results were verified theoretically through XCOM and Monte Carlo Z-particle Transport Code (MCNP). A mechanical investigation was performed by means of quasi-static compressive testing. Thermal characterizations were carried out through effective thermal conductivity and thermal expansion analyses in terms of high temperature guarded-comparative-longitudinal heat flow technique and thermomechanical analyzer (TMA), respectively. The experimental results were compared with analytical results obtained from, respectively, Brailsford and Major’s model and modified Turner’s model for verification. Flame test was performed in accordance with United States Nuclear Regulatory Commission (USNRC) standard. CMF sample and a 304L stainless steel control sample were subjected to a fully engulfing fire with an average flame temperature of 800°C for a period of 30 minutes. Finite Element Analysis was conducted to secure the credibility of the experimental results. This research indicates the potential of utilizing the light-weight close-cell CMFs and open-cell Al foam with fillers as shielding material replacing current heavy structures with additional advantage of high-energy absorption and excellent thermal characteristics.

• Research Organization: North Carolina State Univ., Raleigh, NC (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 1239280
• Report Number(s): DOE/NEUP-11-3114; 11-3114; TRN: US1600564
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
SHIELDING MATERIALS
STAINLESS STEEL-304L
FOAMS
ALUMINIUM
GAMMA RADIATION
X RADIATION
BARIUM 133
CESIUM 137
COBALT 60
AMERICIUM 241
FINITE ELEMENT METHOD
DENSITY
THERMAL CONDUCTIVITY
TEMPERATURE RANGE 1000-4000 K
FILLERS
HYDROGEN
MONTE CARLO METHOD
SPECIFIC SURFACE AREA
THERMAL EXPANSION
TOMOGRAPHY
NEUTRON TRANSPORT
BORON COMPOUNDS
COMBUSTION PROPERTIES
HEAT FLUX
NUCLEAR FACILITIES
BEAMS
NEUTRONS
EFFICIENCY
FIRES
IONIZATION
TESTING
PHOTON TRANSPORT
ATTENUATION
VERIFICATION