PASSIVE IN-SITU CHEMICAL SENSOR

• US 20100081206A1
• Filed: 10/01/2008
• Published: 04/01/2010
• Est. Priority Date: 10/01/2008
• Status: Active Grant

• Current Assignee: Consolidated Nuclear Security, Llc
• Original Assignee: Babcock & Wilcox Technical Services Y-12, LLC (Bechtel Group Incorporated)
• Inventors: Morrell, Jonathan S., Ripley, Edward B.
• Granted Patent: US 8,114,677 B2
• Time in Patent Office: Days
• US Class Current: 436/149
• CPC Class Codes: G01N 25/32 using thermoelectric elements

Abstract

A chemical sensor for assessing a chemical of interest. In typical embodiments the chemical sensor includes a first thermocouple and second thermocouple. A reactive component is typically disposed proximal to the second thermal couple, and is selected to react with the chemical of interest and generate a temperature variation that may be detected by a comparison of a temperature sensed by the second thermocouple compared with a concurrent temperature detected by the first thermocouple. Further disclosed is a method for assessing a chemical of interest and a method for identifying a reaction temperature for a chemical of interest in a system.

Claims

1. A chemical sensor for assessing a chemical of interest in a system having an operational temperature that varies over a temperature range, the sensor comprising:

a first thermocouple disposed in the system and configured for exhibiting a first electrical property that varies over the temperature range according to a first calibration curve;

a first detector assembly comprising a second thermocouple and a proximate first reactive component, the first detector assembly disposed adjacent the first thermocouple in the system and wherein the second thermocouple is configured for exhibiting a second electrical property that varies over the temperature range according to a second calibration curve, and wherein the first reactive component undergoes a first chemical reaction correlating to a first maximum temperature variation if the first reactive component is exposed to a first chemical of interest, and wherein the second electrical property changes according to a temperature change caused by the first chemical reaction.

2. The chemical sensor of claim 1 further comprising:

a reader configured to compare the first electrical property and the second electrical property, to use the first calibration curve and the second calibration curve to calculate a first maximum temperature property variation between the first thermocouple and the second thermocouple wherein the first maximum temperature property variation varies according to a third calibration curve associated with the chemical of interest, and to use the first maximum temperature property variation between the first thermocouple and the second thermocouple along with the third calibration curve to indicate the presence of the first chemical of interest.

3. The chemical sensor of claim 2 wherein the reader is further configured for recording time stamped temperature property data for the first thermocouple and the second thermocouple.

4. The chemical sensor of claim 3 wherein the reader is further configured for using the time stamped temperature property data to generate first chemical reaction data based on the time stamped temperature property data associated with the first chemical reaction.

5. The chemical sensor of claim 4 wherein the reader is further configured for analyzing the first chemical reaction data according to an analysis program and generating output data based on an analysis of the first chemical reaction data.

6. The chemical sensor of claim 1 wherein the first reactive component comprises a first chemical substance that yields a product when exposed to the chemical of interest during the first chemical reaction and wherein the product reacts with a second chemical substance in the reactive component, defining a second chemical reaction correlating to a second maximum temperature property variation, wherein the magnitude of the second maximum temperature property variation is greater than the magnitude of the first maximum temperature property variation.

7. The chemical sensor of claim 1 wherein the first reactive component is attached adjacent a first surface along the second thermocouple and wherein the first detector assembly further comprises a second reactive component attached adjacent a second surface along the second thermocouple.

8. The chemical sensor of claim 1 wherein the second thermocouple further comprises a selective barrier attached adjacent the second thermocouple such that the first reactive component is substantially prevented from being exposed to chemicals that are substantially incapable of transporting through the selective barrier.

9. The chemical sensor of claim 2 further comprising:

a calibration assembly comprising a third thermocouple adjacent the first thermocouple and a first non-reactive component proximate the third thermocouple, the third thermocouple configured for generating a third electrical property that varies over the temperature range, wherein the first non-reactive component is selected so as to substantially imitate the heat transfer properties of the first reactive component, wherein the variation of the third electrical property may be compared by the reader to the variation of the first electrical property, and wherein the effect of any difference between the variation of the first electrical property and the variation of the third electrical property may be accounted for during the calculation of the first maximum temperature property variation.

10. A closed system comprising an enclosed structure and the chemical sensor of claim 1 attached to the interior of the enclosed structure.

11. The chemical sensor of claim 1 further comprising:

a second detector assembly comprising a third thermocouple and a proximate second reactive component, the second detector assembly disposed adjacent the first thermocouple in the system and wherein the third thermocouple is configured for generating a third electrical property that varies over the temperature range according to a third calibration curve, and wherein the second reactive component undergoes a second chemical reaction if the second reactive component is exposed to a second chemical of interest, and wherein the third electrical property changes according to a temperature change induced by the second chemical reaction.

12. The chemical sensor of claim 2 further comprising:

a second detector assembly comprising a third thermocouple and a proximate second reactive component, the second detector assembly disposed adjacent the first thermocouple in the system and wherein the third thermocouple is configured for generating a third electrical property that varies over the temperature range according to a third calibration curve, and wherein the second reactive component undergoes a second chemical reaction if the second reactive component is exposed to a second chemical of interest, and wherein the third electrical property changes according to a temperature change induced by the second chemical reaction, the reader configured to compare the first electrical property and the third electrical property, to use the first calibration curve and the third calibration curve to calculate a second maximum temperature property variation between the first thermocouple and the second thermocouple wherein the second maximum temperature property variation varies according to a fourth calibration curve, and to use the second maximum temperature property variation between the first thermocouple and the third thermocouple along with the fourth calibration curve to indicate the presence of the second chemical of interest.

19. A method for assessing a chemical of interest in a system using the chemical sensor of claim 1, the method comprising the steps of:

a. measuring the first electrical property based on the conditions at the first thermocouple;

b. exposing the first reactive component to the chemical of interest at the second thermocouple;

c. measuring the second electrical property based on the conditions at the second thermocouple during a thermal excursion at the second thermocouple caused by the first chemical reaction;

d. comparing the measurement of the first electrical property with the measurement of the second electrical property value; and

e. identifying the chemical of interest based on calibration data and the comparison of the measurement of the first electrical property with the measurement of the second electrical property.

13. A method for assessing a chemical of interest in a system, the method comprising the steps of:

a. measuring a first electrical property value based on the conditions at a reference location within the system;

b. triggering a first chemical reaction by exposing a reactive material to a chemical of interest at an experimental location inside the system;

c. measuring a second electrical property value based on the conditions at the experimental location within the system;

d. comparing the measurement of the first electrical property value with the measurement of the second electrical property value; and

e. identifying the chemical of interest based on calibration data and the comparison of the measurement of the first electrical property value with the measurement of the second electrical property value.

14. The method of claim 13 further comprising the step of:

f. recording a plurality of first electrical property values during a first time period Δ

t₁; and

g. recording a plurality of second electrical property values during a second time period Δ

t₂.

15. The method of claim 14 wherein the second time period Δ

t₂ is substantially identical to the first time period Δ

t₁.

16. The method of claim 13 further comprising the step of:

h. calculating temperature variation deviation data based on a deviation between first temperature variation data associated with the plurality of first electrical property values and second temperature variation data associated with the plurality of second electrical property values, wherein the plurality of first electrical property values are associated with the first temperature variation data based on a first calibration curve, and wherein the plurality of second electrical property values are associated with the second temperature variation data based on a second calibration curve.

17. The method of claim 16 further comprising the step of:

i. calculating quantitative mass data of the chemical of interest based on the generated thermal excursion data and the calculated temperature variation deviation data.

18. The method of claim 16 further comprising the step of:

j. estimating remaining shelf life of an object located in the system based on the calculated quantitative mass data of the chemical of interest and a known relationship between the chemical of interest and the object.

20. A method for identifying a reaction temperature for a chemical of interest in a system, the method comprising the steps of:

a. measuring a plurality of first electrical property values based on the conditions at a reference location within the system;

b. exposing a reactive material to a chemical of interest at an experimental location inside the system;

c. measuring a plurality of second electrical property values based on the conditions at the experimental location within the system;

d. comparing the measured plurality of first electrical property values with the plurality of second electrical property values;

e. measuring the temperature of the system adjacent the reference location and the experimental location; and

f. controlling the temperature of the system so that the measured temperature in the system remains substantially unchanged and is therefore known when measurements are taken of the plurality of first electrical property values and the plurality of second electrical property values.

21. The method of claim 20 further comprising the step of recording the measured temperature of the system.

22. The method of claim 21 further comprising the step of recording the measured temperature of the system in response to a recording signal.

23. The method of claim 21 further comprising the step of recording the measured temperature at regular intervals.

24. The method of claim 21 further comprising the step of calculating the approximate time when a chemical reaction began between the reactive component and the chemical of interest based on a plurality of the recorded measured temperature.

25. The method of claim 22 wherein the recording signal is sent substantially when a chemical reaction begins between the reactive material and the chemical of interest.