Method and device for patrol inspecting and locating a radioactive substance

Patent metadata

Field	Value
Publication number	US-9829601-B2
Application number	US-201214367824-A
Country	US
Kind code	B2
Filing date	Dec 20, 2012
Priority date	Dec 23, 2011
Publication date	Nov 28, 2017
Grant date	Nov 28, 2017

Abstract

A method for patrol inspecting and locating a radioactive substance, comprising: providing a background radioactive intensity value of environment; collecting radioactive intensity values from a inspecting region by a detector at a plurality of sampling points on a patrol inspection route; calculating a radioactive intensity distribution in the inspecting region on basis of the collected radioactive intensity values and the background radioactive intensity value; and determining a position of the radioactive substance on basis of the radioactive intensity distribution. Furthermore, a device for patrol inspecting and locating a radioactive substance comprises: two or more detectors configured to collect radioactive intensity values from a inspecting region around a patrol inspection route, at each of a plurality of sampling points on the patrol inspection route; and a movable carrier configured to carry the detector and to move along the patrol inspection route to pass by the sampling points. The method and device can obtain the position and the radioactive intensity distribution of the radioactive substance within the inspecting region on basis of the multiple-point observation on the patrol inspection route.

First claim

The invention claimed is:

1. A method for patrol inspecting and locating a radioactive substance, comprising:
(a) providing a background radioactive intensity value of an environment;
(b) collecting, at a plurality of sampling points on a patrol inspection route, radioactive intensity values from an inspecting region by a detector carried by a movable carrier passing by the plurality of sampling points on the patrol inspection route;
(c) calculating a radioactive intensity distribution in the inspecting region on a basis of the collected radioactive intensity values and the background radioactive intensity value; and
(d) determining a position of the radioactive substance on a basis of the radioactive intensity distribution,
wherein the method further comprises a step (b2) between the step (b) and the step (c):
determining whether a barrier has had an effect on a radioactive intensity value by determining whether there is a data segment, in which the radioactive intensity values drop abruptly and then increase abruptly, in the sequence of the radioactive intensity values collected at multiple continuous sampling points, and deleting the data segment to eliminate effects of the barrier if it is present.

2. The method for patrol inspecting and locating a radioactive substance according to claim 1 , wherein the method further comprises a step (b1) between the step (b) and the step (c):
determining whether the differences between the collected radioactive intensity values and the background radioactive intensity values are greater than a collecting threshold, and carrying out the step (c) if they are greater than the collecting threshold; otherwise, if they are not greater than the collecting threshold, updating the background radioactive intensity values by a weighted average of the collected radioactive intensity values and the background radioactive intensity values and returning to the step (b) to recollect the radioactive intensity values.

3. The method for patrol inspecting and locating a radioactive substance according to claim 1 , wherein the detector comprises at least two detectors facing towards the inspecting regions in different directions respectively, the detectors being separated by a shielding part from each other.

4. The method for patrol inspecting and locating a radioactive substance according to claim 1 , wherein the radioactive intensity values are represented by counting rate or dose rate.

5. The method for patrol inspecting and locating a radioactive substance according to claim 1 , wherein the step (c) comprises a step (c1):
dividing the inspecting region into a plurality of subregions, providing the detection efficiencies of the detector to the subregions and determining the radioactive intensity of each subregion on basis of the background radioactive intensity and the detection efficiencies.

6. The method for patrol inspecting and locating a radioactive substance according to claim 5 , wherein the number of the subregions is not greater than the number of the sampling points.

7. The method for patrol inspecting and locating a radioactive substance according to claim 5 , wherein the detection efficiencies are calibrated for a certain radiation energy range and/or species of the radioactive substance.

8. The method for patrol inspecting and locating a radioactive substance according to claim 5 , wherein the step (c) further comprises a step (c2):
drawing a map of radioactive intensity distribution in the inspecting region on a basis of the radioactive intensity in each subregion.

9. The method for patrol inspecting and locating a radioactive substance according to claim 5 , wherein the division of the subregions is carried out in one dimension, two dimensions or three dimensions.

10. The method for patrol inspecting and locating a radioactive substance according to claim 5 , wherein the detector is provided on a movable carrier, the collected radioactive intensity value is

c
t

=

b
t

+

∑
m

⁢

⁢

a
m

⁢

Φ
⁡

(

p
m

,

q
t

,

θ
t

)

+

ɛ
t

,

wherein m is the index of the subregions, m=1, . . . , M, M is the total number of the subregions, b t is the background radioactive intensity value, p m is the position of the mth subregion, a m is the radioactive intensity value of the mth subregion, q t is a position of the movable carrier, θ t is a directional angle of the movable carrier, Φ(p m , q t , θ t ) is the detection efficiency of the detector to the position p m if the movable carrier is located in the position q t with the directional angle of θ t , t is the indexes of the collected radioactive intensity values, t=1, . . . , N, N is the total number of the collected radioactive intensity values, ε t is an collecting error.

11. The method for patrol inspecting and locating a radioactive substance according to claim 10 , wherein the step (c1) is performed by sparse decomposition of a vector C on a vector set D, in which the vector C=(c 1 -b 1 , . . . , c N -b N ) T , the vector set D={D m }, D m =(Φ(p m , q 1 , θ 1 ), . . . , Φ(p m , q N , θ N )) T .

12. The method for patrol inspecting and locating a radioactive substance according to claim 11 , wherein the step of determining the radioactive intensity of each subregion further comprises:
(c11) defining a set S of indexes and a residual vector R, and setting an initial value S 0 of the set S as an empty set, an initial value R 0 of the residual vector R as vector C, and an initial value of a m as zero;
(c12) defining a projection of the R 0 on the vector Dm in the vector set D as P m , defining the value of m corresponding to the maximum of Pm as n, then adding n into S 0 to update the set S and updating the residual vector R such that the updated residual vector R is a difference between the vector C and the projection of the vector C on the vector D n ;
(c13) determining whether the norm of the updated residual vector R is less than a residual threshold, and if the norm is less than the residual threshold, a m will be calculated as the projection coefficient of the vector C on the vector D m , in which only if m falls within the updated set S

Assignees

• Nuctech Co Ltd

Inventors

• Wang Qiang
• Zhao Kun
• Ruan Ming

Classifications

• G01T1/00

  Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation (G01T3/00, G01T5/00 take precedence) · CPC title

• G01T1/169 Primary

  Exploration, location of contaminated surface areas · CPC title

• G01T7/00 Primary

  Details of radiation-measuring instruments · CPC title

• G01V5/0008 Primary

  Physics · mapped topic

• G01V5/20 Primary

  Detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects · CPC title