US 5,128,539 A · Apparatus having reduced background for measuring radiation activity in aerosol particles

Abstract

Apparatus having reduced background for measuring radiation activity in aerosol particles. A continuous air monitoring sampler is described for use in detecting the presence of alpha-emitting aerosol particles. An inlet fractionating screen has been demonstrated to remove about 95% of freshly formed radon progeny from the aerosol sample, and approximately 33% of partially aged progeny. Addition of an electrical condenser and a modified dichotomous virtual impactor are expected to produce considerable improvement in these numbers, the goal being to enrich the transuranic (TRU) fraction of the aerosols. This offers the possibility of improving the signal-to-noise ratio for the detected alpha-particle energy spectrum in the region of interest for detecting TRU materials associated with aerosols, thereby enhancing the performance of background-compensation algorithms for improving the quality of alarm signals intended to warn personnel of potentially harmful quantities of TRU materials in the ambient air.

Claims14

Dependent claims

An apparatus having reduced background for measuring radioactive emission of aerosol particles having a chosen size in air samples, said apparatus comprising in combination:

a. substantially planar filter means for collecting aerosol particles from air drawn therethrough;
b. substantially planar radioactive emission detection means responsive to the kinetic energy thereof and disposed parallel to and spaced-apart from said filter means for detecting radioactive emissions from aerosol particles located in the vicinity of the surface of said filter means facing said detection means, the surface of said filter means facing said detector means and the surface of said detector means facing said filter means forming a volume;
c. means for establishing flow of the air sample to be investigated through the volume and subsequently through said filter means;
and
d. fractionating screen inlet means disposed upstream from the volume in the air flow and having a mesh size suitable for removing radon progeny particles which interfere with the radioactive emissions from the aerosol particles to be measured.

2 more elements

An apparatus having reduced background for measuring radioactive emission of aerosol particles having a chosen size in air samples, said apparatus comprising in combination:

a. substantially planar filter means for collecting aerosol particles from air drawn therethrough;
b. substantially planar radioactive emission detection means responsive to the kinetic energy thereof and disposed parallel to and spaced-apart from said filter means for detecting radioactive emissions from aerosol particles located in the vicinity of the surface of said filter means facing said detection means, the surface of said filter means facing said detector means and the surface of said detector means facing said filter means forming a volume;
c. means for establishing flow of the air sample to be investigated through the volume and subsequently through said filter means;
d. dichotomous virtual impactor means for further reducing the background of interfering radon progeny aerosol particles, said virtual impactor means being disposed upstream from the volume in the air flow, whereby the air flow is divided into a substantially undeflected air flow and a deflected air flow;
e. fractionating screen means disposed in the deflected air flow for removing aerosol particles having a chosen size therefrom;
and
f. means for returning the resulting filtered air to the undeflected air flow.

4 more elements

Dependencies are inferred from the claim text.

Apparatus having reduced background for measuring radiation activity in aerosol particles

Life of this patent

Apparatus having reduced background for measuring radiation activity in aerosol particles

Life of this patent

Abstract

Claims14