Figure of Merit for Chlorine Measurement in Reinforced Concrete Using {sup 252}Cf-Based Nondestructive Testing Method
The objective of this study is to design, fabricate, and evaluate a portable system for nondestructive determination of chloride concentration in reinforced portland cement concrete (PCC) structures. The need for such an instrument arises from the massive deterioration of the reinforced PCC, which has been used to construct a major part of the highway infrastructure. This deterioration of PCC is due to corrosion of the reinforcing steel, which is greatly promoted by the chloride ions. The sources of chloride include deicing salts, set accelerator, and seawater, either in the form of concrete-mixing water or as airborne droplets from ocean spray. The system consists of a high-purity germanium detector for gamma-ray detection and a portable {sup 252}Cf neutron source. Tradeoffs in the design of the neutron source include data quality, operational efficiency, and radiation safety. The number of photons detected in the germanium detector is directly proportional to the neutron source strength and the chloride nuclei concentration in the sample under testing. Therefore, assuming a uniform distribution of chloride, the figure of merit of the number of photons detected in the detector can be expressed as F = C/SN, where C = number of (6111) keV gamma rays detected per second, N = concentration of chloride nuclei, and S = neutron source strength (n/s). Under the assumption that the neutron source strength is fixed, the figure of merit in this case can have at least two uses. One is to optimize the thermalization efficiency of the neutron moderator. The second is to evaluate how effective the detector configuration is in detecting the gamma rays generated in the concrete. Using the figure-of-merit approach, it is possible to find an optimum size of moderator. This is important for a portable system. Other variables such as source/detector separation or detector gamma-ray shielding can also be evaluated.
- Research Organization:
- Federal Highway Administration, McLean, VA (US)
- Sponsoring Organization:
- none (US)
- OSTI ID:
- 786885
- Report Number(s):
- ISSN 0003-018X; CODEN TANSAO; ISSN 0003-018X; CODEN TANSAO; TRN: US0109364
- Resource Relation:
- Conference: 2000 International Conference on Nuclear Science and Technology: Supporting Sustainable Development Worldwide (2000 ANS Winter Meeting), Washington, DC (US), 11/12/2000--11/16/2000; Other Information: Transactions of the American Nuclear Society, Volume 83; PBD: 12 Nov 2000
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
CHLORIDES
GE SEMICONDUCTOR DETECTORS
NEUTRON SOURCES
NONDESTRUCTIVE TESTING
PORTLAND CEMENT
REINFORCED CONCRETE
CORROSION PROTECTION
CALIFORNIUM 252
PORTABLE EQUIPMENT
DESIGN
GAMMA DETECTION
NONDESTRUCTIVE ANALYSIS
HIGH-PURITY GE DETECTORS
CONCENTRATION RATIO