Method for detecting a moving radioactive source and associated device

Patent metadata

Field	Value
Publication number	US-9739893-B2
Application number	US-201414761466-A
Country	US
Kind code	B2
Filing date	Jan 21, 2014
Priority date	Jan 23, 2013
Publication date	Aug 22, 2017
Grant date	Aug 22, 2017

Abstract

A method for detecting a radioactive source moving on a linear path substantially parallel to an alignment of N detectors. The method includes: forming N×N t pulse counting values M i,t (i=1, 2, . . . , N and t=1, 2, . . . , N t ) from N×N t detection signals delivered by the N detectors in the form of a succession over time of N t sets of N signals simultaneously detected by the N detectors over a same duration Δt, a pulse counting value representing a number of pulses detected by a detector over a duration Δt; and computing, using a computer: a set of N t correlation products R t , a static mean R of the N×N t counting values, a correlation condition for each correlation product R t .

First claim

What is claimed is:

1. A method for detecting a radioactive source moving on a linear path substantially parallel to an alignment of N detectors, N being an integer equal to or greater than 2, the method comprising:
simultaneously detecting N signals by N detectors;
delivering N×N t detection signals from the N detectors in the form of a succession over time of N t sets of the N signals simultaneously detected by the detector over a duration Δt, N t being significantly greater than N, a pulse counting value representing a number of pulses detected by a detector over a duration Δt;
forming N×N t pulse counting values M i,t (i=1, 2, . . . , N and t=1, 2, . . . , N t ) from the N×N t detection signals;
computing, using a computer:
a set of N R correlation products R z so that:
R z =Π i=1 N M i,[(N−i)z+1] ( z= 1,2, . . . , N R )

with N R being an integer equal to

N
t

-
1

N
-
1

,

a statistical mean R of the N t products Π i=1 N M i,t such that:

R
_

=

1

N
t

⁢

∑

t
=
1

N
t

⁢

⁢

∏

i
=
1

N

⁢

⁢

M

i
,
t

a standard deviation σ( R ) of the N t products Π i=1 N M i,t , and
a correlation condition for each correlation product R z ; and

determining that a radioactive source moved in front of the detectors if R z ≧ R +K 2 σ( R ), K 2 being a scalar, or
determining that no radioactive source moved in front of the detectors if R z < R +K 2 σ( R ).

2. The method according to claim 1 , the method further comprising computing, by the computer, a speed V of the radioactive source as soon as a radioactive source is determined to have moved in front of the detectors, such that:
V=d /( T×Δt ),
where d is a distance separating two neighbouring detectors and T is a rank t of a set of N pulse counting values for which the correlation product R Z is maximum.

3. The method according to claim 1 , the method further comprising computing, by the computer, an intensity I of the radioactive source as soon as a radioactive source is determined to have moved in front of the detectors, such that:

I
=

1
N

⁢

∑

i
=
1

N

⁢

⁢

M

i
,

(

N
-
i

)

⁢
T

+
1

-

1

N
×

N
t

⁢

∑

t
=
1

N
t

⁢

⁢

[

∑

i
=
1

N

⁢

⁢

M

i
,
t

]

.

4. The method according to claim 1 , further comprising smoothing the pulse counting values before computing.

5. A device for detecting a radioactive source moving over a substantially linear path, the device comprising:
N detectors (D i , i=1, 2, . . . , N) substantially aligned parallel to the linear path of the radioactive source, N being an integer equal to or greater than 2, the N detectors simultaneously delivering N detection signals over duration Δt,
N processing circuits (T i , i=1, 2, . . . , N) connected to the N detectors, each processing circuit being configured to deliver an electronic signal corresponding to a detection signal delivered by a different detector,
N counting circuits (K i , i=1, 2, . . . , N) connected to the N processing circuits, each counting circuit being configured to count, during N t successive counting durations Δt, a number of electronic pulses delivered by a diff

Assignees

• Commissariat L Energie Atomique Et Aux Energies Alternatives
• Commissariat A L'Energie Atomigue Et Aux Energies Alternatives

Inventors

• Coulon Romain
• Kondrasovs Vladimir
• Boudergui Karim
• Bakkali Mounir
• Normand Stéphane

Classifications

• G01V5/0075

  Physics · mapped topic

• G01T1/16 Primary

  Measuring radiation intensity (G01T1/29 takes precedence {; self-powered detectors G01T3/006; using an ionisation chamber filled with a liquid or solid, e.g. frozen liquid, dielectric G01T3/008}) · CPC title

• G01T7/08

  Means for conveying samples received · CPC title

• G01V5/26 Primary

  Passive interrogation, i.e. by measuring radiation emitted by objects or goods · CPC title