Edward Naessens

Non-Destructive In-Situ Method And Apparatus For Determining Radionuclide Depth In Media

Application

#6518579 Feb 11, 2003

Filed

Jun 11, 1999

Inventor

Edward P. Naessens (West Point, NY)

Appl. No.

09/330660

Assignee

Rensselaer Polytechnic Institute (Troy, NY)

International Classification

G01T 100

U.S. Classification

250393

Abstract

A non-destructive method and apparatus which is based on in-situ gamma spectroscopy is used to determine the depth of radiological contamination in media such as concrete. An algorithm, Gamma Penetration Depth Unfolding Algorithm (GPDUA), uses point kernel techniques to predict the depth of contamination based on the results of uncollided peak information from the in-situ gamma spectroscopy. The invention is better, faster, safer, and/cheaper than the current practice in decontamination and decommissioning of facilities that are slow, rough and unsafe. The invention uses a priori knowledge of the contaminant source distribution. The applicable radiological contaminants of interest are any isotopes that emit two or more gamma rays per disintegration or isotopes that emit a single gamma ray but have gamma-emitting progeny in secular equilibrium with its parent (e. g. , Co, U, and Cs to name a few). The predicted depths from the GPDUA algorithm using Monte Carlo N-Particle Transport Code (MCNP) simulations and laboratory experiments using Co have consistently produced predicted depths within 20% of the actual or known depth.

Claim

What is claimed is: 1. An apparatus for a non-destructive determination of an unknown depth of a radiological contamination having a depth distribution in a building medium, the building medium having a known attenuation coefficient, the radiological contamination being of a type which emits gamma radiation with at least two gamma rays of different energies per disintegration or a single gamma ray with at least one gamma-emitting progeny of different energies, but at an unknown rate, the apparatus comprising: collimator means for collimating the gamma radiation emitted from the contamination and at the surface of the medium; detector means having a gamma ray counting surface associated with the collimator means for simultaneously counting the collimated gamma radiation including the two gamma rays of different energies from the collimator means; computing means operatively connected to the detector means for applying a gamma penetration depth unfolding algorithm to the two gamma rays simultaneously counted using a data differentiation technique with a point kernel implementation to iterate the depth of the contamination; and a computer connected to the detector means and containing the computing means as a computer program. 2. An apparatus according to claim 1, wherein the computer is a portable computer, the apparatus being portable. 3. An apparatus according to claim 1, wherein the collimator means comprises a lead collimator having bore with an aperture for facing a surface of the building medium for receiving gamma radiation from the contamination, the detector means being at an end of the bore opposite from the aperture. 4.