Continuous monitoring radon detector

• US 20040232345A1
• Filed: 03/31/2003
• Published: 11/25/2004
• Est. Priority Date: 03/31/2003
• Status: Abandoned Application

• Current Assignee: University of Guelph
• Original Assignee: University of Guelph
• Inventors: Simpson, John J., Jagam, Pillalamarri
• Application Number:
  US10/401,593
• Publication Number:
  US 20040232345A1
• Time in Patent Office: Days
• US Class Current: 250/370.02
• CPC Class Codes: G01T 1/178 for measuring specific activity in the presence of other radioactive substances, e.g. natural, in the air or in liquids such as rain water

Abstract

A device for the continuous monitoring in situ of radon concentration in ambient air, and the simultaneous measurement of working level (WL) values of the radon daughters in ambient air. The device comprises an electrical field formed of two hemispherical walls facing each other with a gap therebetween allowing ambient air to diffuse through. The area between the walls is considered a “sensitive volume”. A positively-charged photodiode is disposed in communication with the sensitive volume for the detection of alpha emissions from radon or radon progeny electrically isolated within said electrical field.

Claims

1. A device for detection of radon or radon daughters in ambient air comprising:

a) an electrical field comprising two hemispherical walls facing each other, with a gap therebetween through which ambient air diffuses, said walls forming a sensitive volume; and

b) a positively-charged photodiode in communication with said sensitive volume for the detection of alpha emissions from radon or radon progeny electrically isolated within said electrical field.

2. The device of claim 1 wherein the hemispherical walls comprise food preparation bowls.

3. The device of claim 1 wherein said hemispherical walls comprise hemispherical steel round-bottomed deep fryers.

4. The device of claim 1 wherein said gap is from 1 to 6 mm between said two hemispherical walls.

5. The device of claim 4 wherein said gap is about 1.5 mm.

6. The device of claim 1 additionally comprising a light shielding means surrounds said gap to partially exclude light from the sensitive volume.

7. The device of claim 1 wherein the sensitive volume is from 1 L to 400 L

8. The device of claim 7 wherein the sensitive volume is selected from the group consisting of about 11 L, 60 L, and 208 L.

9. The device of claim 1 wherein said hemispherical walls comprise aluminum tubing supporting an aluminized polyester film on all sides.

10. The device of claim 9 wherein said tubing has a diameter of approximately 0.5 inch.

11. The device of claim 10 wherein said sensitive volume is up to about 1000 L.

12. The device of claim 1 wherein said photodiode is a positive-intrinsic-negative (PiN) diode.

13. The device of claim 12 wherein said PiN diode is operated in a reverse bias mode.

14. The device of claim 1 wherein said alpha emissions are emitted from daughters generated from the decay of radon (²²²Rn) or thoron (²²⁰Rn).

15. The device of claim 14 wherein said daughters are ²¹⁸Po, ²¹⁴Bi, or ²¹⁴Po emitting energetic alpha particle radiation at 6003 keV, 6020 keV, and 7687 keV respectively.

16. The device of claim 14 wherein said daughters are generated from decay of thoron and are ²¹⁶Po or ²¹²Po, emitting energetic alpha particle radiation at 6778 keV and 8785 keV, respectively.

17. A method for computing concentration of radon in ambient air comprising evaluating relative ratio of radon daughters ²¹⁸Po and ²¹⁴Po in the sensitive volume of a device according to claim 1.

18. A system for detection of radon or radon daughter concentrations in ambient air comprising:

a) the device of claim 1;

a) a battery box in communication with said positively charged photodiode;

b) signal conditioning means for receiving and manipulating a signal from said positively charged photodiode; and

d) a computer to receive a manipulated signal from the signal condition means to display a radon or radon daughter concentration.