Simulation of backscatter imaging
Frequently during remodeling or modifications of existing buildings, it is necessary to know that exact location of various utility lines (such as water or sewer and electrical conduit) before drilling holes in floors and walls. In many cases conventional radiography or metal detectors may be used to map out the lines, but occasionally a one-sided inspection is required deep within concrete or brick. The purpose of this work was to explore the feasibility of using the backscattered radiation from a high-energy bremsstrahlung beam to detect the existence of a void in construction material. If the focal point of the detector collimator is centered on the void, the backscattered signal should be slightly different than from adjacent regions. By using the MCNP (Monte Carlo Neutron Photon) code to simulate the inspection, we can identify fundamental limitations of the technique as well as estimate design parameters of a practical system. This will reduce the time, effort, and expense for any subsequent experimental program to develop the technique. Our basic approach to the simulation was to keep the geometry as simple as possible but still realistic. The radiation source was a simulated 6-MeV bremsstrahling spectrum from a commercially available linac that is relatively small, portable, and can produce an output of 300 rad/min at 1 m. All shielding is assumed to be tungsten. The object being inspected is assumed to be a semi-infinite slab of homogenized concrete. Our concrete'' has the correct proportions of elements and the correct density, but none of the inhomogeneities caused by sand and aggregate in real concrete. The errors caused by this assumption will be discussed later. The nominal void we are trying to detect is air-filled sphere, 2.54 cm in diameter. We also assumed that the maximum depth of the void would be 45.72 cm. 2 refs.
- Research Organization:
- Los Alamos National Lab., NM (United States)
- Sponsoring Organization:
- USDOD; Department of Defense, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 5322349
- Report Number(s):
- LA-12277-MS; ON: DE92010927
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
CONCRETES
VOIDS
GAMMA RADIOGRAPHY
COMPUTERIZED SIMULATION
DETECTION
BACKSCATTERING
BREMSSTRAHLUNG
MONTE CARLO METHOD
BUILDING MATERIALS
ELECTROMAGNETIC RADIATION
INDUSTRIAL RADIOGRAPHY
MATERIALS
RADIATIONS
SCATTERING
SIMULATION
440101* - Radiation Instrumentation- General Detectors or Monitors & Radiometric Instruments
990200 - Mathematics & Computers