Radiant energy – Invisible radiant energy responsive electric signalling – Semiconductor system
Reexamination Certificate
1998-04-17
2001-02-06
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Semiconductor system
C250S253000
Reexamination Certificate
active
06184531
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to airborne particulate radionuclide collection and analysis.
BACKGROUND OF THE INVENTION
Airborne particulate radionuclide(s) result from natural sources as well as man made sources, for example releases from nuclear power plants, nuclear testing, and weapon detonation. Public health and safety as well as treaty verification have motivated the need for more accurate analysis to identify sources as well as characterize airborne plumes.
Present methods include, for example aircraft mounted filter elements wherein a filter element is placed external to the aircraft while the aircraft is flying thereby filtering that portion of air that passes through the filter element and collecting a sample of the airborne radionuclide(s). The filter with collected sample is returned to a laboratory for gamma spectrometric counting and other analysis. The advantage of this method is that the delay between sample collection and sample counting and analysis permits any radon to decay thereby permitting greater sensitivity to the non-radon radionuclide(s) in the sample. The disadvantage is that by the time the counting and analysis is done, the airborne plume has likely changed significantly so that the analysis no longer characterizes the plume. In addition, delayed laboratory analysis is unable to detect small quantities of some short-lived radionuclides that may be important to treaty verification. Another disadvantage is the limited sensitivity imposed by natural atmospheric radionuclides including radon and radon decay products or daughters. Rn-222 (3.82 d, 10 Bq/m
3
atmospheric concentration) is continuously released from the earth's crust as a decay product of natural uranium. Rn-220 (55 s, 1% of total atmospheric radionuclide concentration) is also continuously released from the earth's crust as a decay product of naturally occurring thorium. Cosmic rays spallate atmospheric nitrogen, oxygen and argon and produce Be-7 (53.28 d). Anthropogenic sources generally contribute less than 1% of the airborne radionuclide concentration in the atmosphere. Present techniques simply lack adequate sensitivity to resolve signals of natural and anthropogenic sources.
Thus, there is a need for a real time analysis of airborne radionuclides so that plume characteristics may be properly identified and known.
SUMMARY OF THE INVENTION
The present invention is an improved apparatus for collecting and analyzing an airborne particulate radionuclide. The apparatus, Real-Time Airborne Radionuclide Analysis and Collection system (RTARAC), has a filter mounted in a housing, the housing having an air inlet upstream of the filter and an air outlet downstream of the filter, wherein an air stream flows therethrough. The air inlet receives the air stream, the filter collects the airborne particulate radionuclide and permits a filtered air stream to pass through the air outlet. The improvement which permits real time counting is a gamma detecting germanium diode mounted downstream of the filter in the filtered air stream. The gamma detecting germanium diode is spaced apart from a downstream side of the filter a minimum distance for a substantially maximum counting detection while permitting substantially free air flow through the filter and uniform particulate radionuclide deposition on the filter.
It is an object of the present invention to provide an improved apparatus for collection and analysis of an airborne particulate radionuclide permitting real time counting and analysis.
The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with accompanying drawings wherein like reference characters refer to like elements.
REFERENCES:
patent: 3555278 (1971-01-01), Schroeder
patent: 4464574 (1984-08-01), Vandrish
patent: 4571492 (1986-02-01), Kane et al.
patent: 4808827 (1989-02-01), Woollman
Perkins Richard W.
Smart John E.
Battelle (Memorial Institute)
Hannaher Constantine
Zimmerman Paul W.
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