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Nanocrystalline optically-based neutron irradiation history sensor

a technology of neutron irradiation history and nanocrystalline materials, applied in the field of neutron detection, can solve the problems of increasing the cost of scintillators in which sup>6/sup>li is used, increasing the size, increasing the cost, and increasing the risk of compromising the mission

Active Publication Date: 2014-03-06
STC UNM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention is about a method and sensor for detecting neutrons using a new method that involves the transmutation of certain materials. The invention takes advantage of the unique optical properties of these materials to determine the relative fractions of different elements. This allows for the creation of a forensic record of previous neutron exposure. The detection is done using nanocrystals, which can be embedded in a transparent polymer or ceramic material, making the sensor both mechanically robust and sensitive to neutA particular advantage of this invention is that no enrichment of a specific isotope is required, as the natural abundance of a certain isotope allows for its use without enrichment.

Problems solved by technology

Boron-loaded scintillators are also used, although they encounter the challenge of discriminating between gamma rays backgrounds and gamma rays due to neutrons.
This requires enrichment of 6Li isotope, and increases the cost of the scintillators in which 6Li is embedded.
The thermal neutron cross-section for the 3He(n,p) reaction is 5330 barns, but its natural abundance of only 0.0001% results in even higher cost than 6Li.
A further problem with all of these neutron detection methods is the need for active electronics to detect the particle emitted from the nucleus that has absorbed a neutron, increasing size, cost, and danger of compromising the mission if used for clandestine activities.

Method used

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  • Nanocrystalline optically-based neutron irradiation history sensor
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  • Nanocrystalline optically-based neutron irradiation history sensor

Examples

Experimental program
Comparison scheme
Effect test

example 1

A. Synthesis of Dysprosium Oxide Dy2O3 Nanocrystals

[0045]In a three-neck flask, 2 mmol of dysprosium (III) nitrate hexahydrate are added to 40 mL of diethylene glycol (DEG), and after that 6 mmol of NaOH is added to the flask. The mixture is then refluxed open to air at 210° C. for 30 minutes. As the solution is cooled, 1.6 mmol of oleic acid mixed with 20 mL of DEG are added to the flask. The obtained nanocrystals are then washed by centrifuging 5 mL of the solution in 10 mL of toluene 3 times and collecting the toluene mixture as the product.

B. Characterization of Dysprosium Oxide Dy2O3 Nanocrystals

[0046]Dy2O3 NCs are obtained as spherical nanoparticles 25 to 50 nm in diameter shown in the bright-field TEM image of FIG. 9.

example 2

A. Synthesis of Dysprosium Fluoride DyF3 Nanocrystals

[0047]In an argon-filled glovebox, a mixture of 35 mL of anhydrous methanol with 3 mmol of ammonium fluoride is prepared in a three-neck flask, and the flask is sealed before removal. Then inside the glovebox, a 20 mL syringe is prepared, containing 2 mL of anhydrous methanol mixed with 1.3 mmol of dysprosium (III) nitrate hexahydrate. The flask is set up on the Schlenk line and a flow of argon in the flask is started. Next, the flask is brought to 60° C. and the solution from the syringe is added to the flask. The mixture in the flask is allowed to soak for 2 hours, and then 0.50 mL of oleic acid is added to the flask. The solution is centrifuged twice at 10,000 rpm in methanol. The obtained nanocrystals are collected by removing the supernatant and by dispersing it in 20 mL of toluene.

B. Characterization of Dysprosium Fluoride DyF3 Nanocrystals

[0048]DyF3 NCs are obtained as nanorods ˜100 nm to 200 nm long and ˜40 nm to 50 nm i...

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Abstract

A neutron irradiation history sensor and detection method for detection of thermal neutrons exploit transmutation of 164Dy into 165Ho and 166Er and significant differences in optical properties of Dy, Ho, and Er in order to enable detection of relative fractions of Dy, Ho, and Er and thus the degree and timing of prior thermal neutron exposure that has occurred, providing a tamper-proof forensic record of the prior thermal neutron exposure. The irradiation history sensor and detection method advantageously employ Dy-containing nanocrytals (NCs) residing in a transparent host.

Description

RELATED APPLICATION[0001]This application claims benefits and priority of provisional application Ser. No. 61 / 463,885 filed Feb. 24, 2011, the entire disclosure of which is incorporated herein by reference.FIELD OF THE INVENTION[0002]This invention relates generally to neutron detection and, more specifically, to a method and sensor for detection of thermal neutrons which exploit optical detection of the transmutation of 164Dy to 165Ho and 166Er in response to neutron irradiation.BACKGROUND OF THE INVENTION[0003]Standard detectors of slow neutrons rely on the 10B(n,α), 6Li(n,α), or 3He(n,p) reactions. The thermal neutron cross-section for the 10B(n,α) reaction is 3840 barns, and the natural abundance of 10B is 19.8%. The most common detector based on the boron reaction is a BF3 gas tube. Boron-loaded scintillators are also used, although they encounter the challenge of discriminating between gamma rays backgrounds and gamma rays due to neutrons. The thermal neutron cross-section for...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G01T3/08
CPCG01T3/00
Inventor WITHERS, NATHAN J.OSINSKI, MAREK A.SMOLYAKOV, GENNADY A.
Owner STC UNM