CN117932267A - Nuclide alarm method, nuclide alarm system and electronic equipment - Google Patents
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Abstract
The invention discloses a nuclide alarm method, a system and electronic equipment, which relate to the radionuclide identification alarm field, wherein the method comprises the following steps: acquiring nuclear detection event sequence information of a ray detector; calculating the time interval of the current detected ray according to the time information of the current detected ray and the last detected ray; calculating a Bayesian factor according to the time interval of the current detected ray; calculating posterior probability according to Bayesian factors and prior probability of full spectrum time intervals; and making a statistical decision according to the posterior probability to determine whether the radionuclide exists. According to the invention, statistical decision is made according to the time-dependent statistics of the radiation signals entering the detector to alarm whether the radionuclide exists or not, the energy is not required, the value range of the time interval is set on the decision function, instead of directly giving a preset time interval parameter, the universality of the method is greatly improved, and the judgment and alarm on whether the radionuclide exists can be more quickly and accurately carried out.
Description
Technical Field
The invention relates to the field of radionuclide identification and alarm, in particular to a radionuclide alarm method, a radionuclide identification and alarm system and electronic equipment.
Background
According to the ITDB database of IAEA, the events of illegal transportation, marketing and malicious use of radioactive materials recorded in the present day are more than 4000. Aiming at illegal transportation detection of radioactive substances in special scenes such as airports, ports, nuclear radiation emergency and the like, the passing time of personnel and goods is usually only tens of seconds at most, so that the required radionuclide alarming algorithm needs to have the performances of small required sample size, high identification speed, high identification precision and the like.
Aiming at the illegal transportation detection alarm of radioactive substances in special scenes such as airports, ports, nuclear radiation emergency and the like, the characteristics of non-static measurement, short detectable time, weak detected signals and the like exist, and new requirements are put forward in the measurement technology:
1-the measurable time is short, typically in the range of sub-seconds to tens of seconds;
the 2-data reliability requirement is high, the requirements on the alarm efficiency and the accuracy are high under the higher confidence level, and the false alarm rate are as low as possible.
The current common nuclide alarm method is based on a gamma energy spectrum analysis technology and a characteristic peak matching technology, and the algorithm mainly comprises background subtraction, filtering smoothing, peak searching and other contents; the qualitative and quantitative judgment of the radioactive material is realized by carrying out Gaussian distribution assumption on the peak shape of the full-energy peak and matching the peak position and statistically analyzing the characteristic gamma rays released by the radioactive material. However, on the one hand, the method needs to collect enough photons to reduce the statistical fluctuation of characteristic peaks, so that certain requirements are imposed on the detection time and the radionuclide radiation release intensity; on the other hand, the characteristic gamma rays are accurately distinguished to identify the characteristic gamma rays, and certain requirements on the energy resolution capability of the detector are needed. In addition, there are detectors based on low energy resolution capability such as plastic scintillators, and the like, and the measurement object is the particle count rate of the scintillation detector, but the identification method mainly depends on classical statistical theory judgment, and has the characteristics of higher detection threshold, poorer sensitivity (generally 2-5 times higher than background count level), and the like.
Disclosure of Invention
The invention aims to provide a nuclide alarm method, a nuclide alarm system and electronic equipment, which can judge and alarm whether radionuclide exists more quickly and accurately.
In order to achieve the above object, the present invention provides the following solutions:
in a first aspect, the present application provides a nuclide alarm method, the method comprising:
Acquiring nuclear detection event sequence information of a ray detector;
calculating the time interval of the current detected ray according to the time information of the current detected ray and the time information of the last detected ray;
Calculating a Bayesian factor according to the time interval of the current detected ray, the time interval probability density function under the original assumption condition and the time interval probability density function under the alternative assumption condition; the original hypothesis is a hypothesis that no radionuclide is present; the alternative hypothesis refers to a hypothesis that a radionuclide is present;
calculating posterior probabilities under the original assumption and the alternative assumption respectively according to the Bayesian factors and the prior probabilities of the full spectrum time interval under the original assumption and the alternative assumption;
and making a statistical decision according to the comparison result of the posterior probability under the original assumption condition and the alarm threshold value, and determining whether the radionuclide exists.
In a second aspect, the present application provides a nuclear species alarm system, the system comprising:
The ray energy time information acquisition module is used for acquiring nuclear detection event sequence information of the ray detector;
the time interval calculation module is used for calculating the time interval of the current detected ray according to the time information of the current detected ray and the time information of the last detected ray;
the Bayesian factor calculation module is used for calculating the Bayesian factor according to the time interval of the current detection ray, the time interval probability density function under the original assumption condition and the time interval probability density function under the alternative assumption condition; the original hypothesis is a hypothesis that no radionuclide is present; the alternative hypothesis refers to a hypothesis that a radionuclide is present;
The posterior probability calculation module is used for calculating posterior probabilities under the original assumption condition and the alternative assumption condition according to the Bayesian factors and the prior probabilities of the full spectrum time intervals under the original assumption condition and the alternative assumption condition respectively;
and the nuclide discriminating module is used for making a statistical decision according to the comparison result of the posterior probability and the alarm threshold under the original assumption condition, and determining whether the radionuclide exists.
In a third aspect, the application provides an electronic device comprising a memory for storing a computer program and a processor for running the computer program to cause the electronic device to perform a nuclear species alarm method as described in any one of the preceding claims.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
The invention provides a nuclide alarm method, a system and electronic equipment, which are used for making a statistical decision according to time-related statistics of a radiation signal entering a detector in the full spectrum range of the detector and rapidly giving an alarm of the existence/non-existence of a radioactive nuclide according to the statistical decision result. The energy is not required; setting a value range of a time interval on a decision function, and not directly giving a preset time interval parameter, so that the universality of the method is greatly improved; the method can realize higher detection sensitivity and lower detection lower limit, and can more quickly judge and alarm whether the radionuclide exists.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic flow chart of a nuclide alarm method according to embodiment 1 of the present invention;
FIG. 2 is a graph and timing diagram of the background provided in example 1 of the present invention;
FIG. 3 is a graph showing the background alarm decision function provided in embodiment 1 of the present invention;
FIG. 4 is a graph and a timing chart of 137 Cs provided in example 1 of the present invention;
FIG. 5 is a schematic diagram of the trend of the alarm decision function of 137 Cs provided in embodiment 1 of the present invention;
fig. 6 is a block diagram of a nuclide alarm system according to embodiment 2 of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide a nuclide alarm method, a nuclide alarm system and electronic equipment, which are based on a gamma spectrometer measurement system capable of detecting gamma rays and outputting ray energy and time information.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Example 1
When gamma rays are incident to the sensitive volume of a gamma ray detector of the measuring system, the measuring system outputs a pair of energy and time data (epsilon, t) of the rays to an upper computer, and the upper computer calculates a decision function and completes statistical deduction based on the pair of energy and time data (epsilon, t) of the incident rays according to the nuclide rapid alarm algorithm provided by the invention, and makes effective deduction on the existence of radionuclides.
As shown in fig. 1, the embodiment provides a specific step of a nuclide rapid alarm method based on energy and time data pairs (epsilon, t):
s1: and acquiring nuclear detection event sequence information of the ray detector, namely acquiring energy-time information of rays detected by the detector.
S2: and calculating the time interval of the current detected ray according to the time information of the current detected ray and the time information of the last detected ray.
When the detector detects a ray, and outputs energy-time information ζ (0)＝(ε(0),τ(0) of the ray), the calculation formula of the time interval Δt:
Δt(0)＝τ(0)-τ(-1)；
Where τ (0) is the measurement time of the current detected ray, τ (-1) is the measurement time of the last detected ray (when the system inputs the first detected ray, τ (-1) takes a value of 0).
S3: calculating a Bayesian factor according to the time interval of the current detected ray, the time interval probability density function under the original assumption condition and the time interval probability density function under the alternative assumption condition; the original hypothesis is a hypothesis that no radionuclide is present; the alternative hypothesis refers to a hypothesis in which the radionuclide is present.
The Bayesian factor has a calculation expression as follows:
In the method, in the process of the invention, Is a Bayesian factor calculated from the time interval Deltat (0) of the current detected ray; g 0(Δt(0)|τ0) and g 1(Δt(0)|τ1) are time interval probability density functions under the original assumption condition M 0 and under the alternative assumption condition M 1, respectively.
Where τ 0 and τ 1 are mathematical expectations of the time intervals under the original assumption and under the alternative assumption, respectively; and τ bkg are the mathematical expectation of the count rate and time interval of the background, respectively, which are reciprocal; τ min is a parameter related to a detection sensitivity lower limit η min under the original assumption, the detection sensitivity lower limit η min is defined as a minimum signal-to-noise ratio η required for making effective judgment and meeting a certain detection performance under the active condition, and the signal-to-noise ratio is a ratio of a full spectrum net count rate to a background count rate. h 1(τ1) is a probability density function under alternative hypothesis/> Where C is the normalized coefficient associated with (τ min,τbkg).
The construction of the time interval probability density function of the original hypothesis and the alternative hypothesis is one of the key points to be protected in the scheme. In this embodiment, with respect to the assumption of the presence or absence of a radionuclide, whether a radionuclide is present is determined based on the time interval difference between the full spectrum time interval obeying the exponential distribution and the background. The probability density of the time interval of the present invention is not limited to the exponential distribution in the example of the present invention, and the specific probability density distribution may be determined according to the actual use scenario.
S4: and calculating posterior probabilities under the original assumption and the alternative assumption respectively according to the Bayesian factors and the prior probabilities of the full spectrum time interval under the original assumption and the alternative assumption.
The expression of the prior probability density function θ (τ) for the full spectrum time interval is:
where θ 0 and θ 1 are the prior probabilities of the full spectrum time interval under the original assumption and the alternative assumption, respectively, and θ 0+θ1 =1. Without any subscript "τ", a parameter of no particular meaning, i.e., a parameter of a time interval exponential distribution of more colloquial meaning (without any limitation), is expressed.
The construction of the prior probability of the time-dependent statistics is one of the key points to be protected in the scheme. In the scheme, the prior probability density function can be selected from an information-free prior probability density function or a conjugate prior probability density function, and is not limited to the information-free prior probability density function; meanwhile, the prior probability initial value can be determined according to actual conditions. In addition, the selection of the time interval value range in the prior probability is related to the background condition and the detector type, and is set according to specific conditions.
The decision function (i.e., posterior probability) can have two construction paths: one is to derive a decision function from the prior probability and the sample probability density function. In the construction process, the decision function is firstly calculated according to the sample probability density function to obtain the Bayesian factor, and then the Bayesian factor is combined and constructed according to the prior probability and the Bayesian factor. The bayesian factor is used as an intermediate parameter and may not be involved in the actual construction process. In the invention, the calculation of the decision function is divided into 2 steps: 1-calculating Bayesian factors, 2-calculating decision functions. The expression "may not participate in the construction process" here means that the above 2 steps may be combined into 1 step, i.e. the first construction path described above.
Whether the calculation is carried out according to the prior probability and the Bayesian factor or directly according to the prior information and the sample information, the construction of the decision function is one of the key points to be protected in the invention. Wherein, the first construction mode is as follows: the calculation formula for directly constructing the decision function directly according to the prior information and the sample information is as follows:
The second construction mode is as follows: the expression of the posterior probability obtained by the joint construction according to the prior probability and the Bayesian factor is as follows:
wherein, And/>The posterior probability calculated according to the time interval of the current detection ray under the original assumption condition and the alternative assumption condition is respectively a decision function of decision.
S5: and updating the prior probability of the full spectrum time interval under the original assumption condition and the alternative assumption condition according to the posterior probability under the original assumption condition and the alternative assumption condition.
S6: and making a statistical decision according to the comparison result of the posterior probability under the original assumption condition and the alarm threshold value, and determining whether the radionuclide exists.
The step S6 specifically comprises the following steps:
(1) Posterior probability under the original assumption Greater than alarm upper threshold/>When this is the case, the decision is made that no radionuclide is present.
(2) Posterior probability under the original assumptionLess than alarm lower threshold/>And if so, determining that the radionuclide exists, and giving an alarm prompt.
(3) Posterior probability under the original assumptionGreater than the alarm lower threshold/>And less than the alarm upper threshold/>And when the next ray is detected, acquiring energy-time information of the ray currently detected by the ray detector by acquiring nuclear detection event sequence information in the step S1, and returning to the step of calculating the time interval of the current detected ray according to the time information of the current detected ray and the time information of the last detected ray.
The magnitude of the threshold is determined by the probability α of making a first type of error (i.e. rejecting M 0 when M 0 is assumed to be true) and the probability β of making a second type of error (i.e. accepting M 0 when M 1 is assumed to be true, also called miss rate or miss rate):
The construction method for finally judging the threshold value when the statistics and the inference of the time correlation statistics are carried out is one of the key points to be protected in the scheme. In the conventional Bayesian method, the relative sizes of the posterior probabilities of the original hypothesis and the alternative hypothesis (and the upper and lower thresholds are 0.5) are generally selected, and when the posterior probabilities of the original hypothesis and the alternative hypothesis are relatively close to each other in statistical decision, an error decision is made with high probability. In this case, the decision function of the time interval sets the upper and lower thresholds as different values, and at the same time, the introduction of decision thresholds for two types of decisions (supporting the original hypothesis and supporting the alternative hypothesis) of the decision function is a protection gist of the present invention, and the selection of the specific value of the threshold can be determined according to the actual use situation.
In this embodiment, the value range of the time interval is set on the prior probability, instead of directly giving a constant value to the time interval parameter, so that the universality of the method is greatly improved. In addition, only the time interval is needed to be measured, whether nuclides exist or not can be judged, the effective alarm is made on whether radionuclides exist or not faster than a spectrum analysis-characteristic peak matching method, and the judging efficiency is higher. The nuclide alarm method of the invention can be used with various types of detectors, including but not limited to scintillator detectors, semiconductor detectors, and the like, with energy resolving power, and plastic scintillators, geiger tubes, and the like, without energy resolving power.
The methods provided in this example are described below using background and 137 Cs, respectively.
A set of 1.5 inch lanthanum bromide detection system is used, background data is collected, and the background count rate of the full spectrum is calibratedAnd background count rate/>, within 46 ROI areas
Since the prior probability has no bias, the initial value of the prior probability is set to be (0.5 ), and the initial values of the prior probabilities of the original hypothesis and the alternative hypothesis can be determined according to practical situations, including but not limited to parameters (0.5 ) in the embodiment of the invention; setting the lower limit of detection sensitivity of the method to be 10%, wherein tau min＝85％·τbkg exists; setting alpha=beta=0.2, and the decision has upper and lower thresholds
The background alarm method comprises the following steps:
The detector detects the first ray, and the time and energy information is (0.045657025, 44)/(time/second, energy/address).
The time interval is calculated by steps S1 and S2: Δt (0) =0.0457
Calculating a bayesian factor from step S3:
Calculating a decision function from step S4:
the prior probability is updated by step S5: θ 0 = 0.5367.
Decision making is made by step S6: due to the decision functionNo decision is made and the arrival of the next ray is continued.
A total measurement of 10 4 ray particles was identified in the example of background, taking about 166 seconds, and the energy spectrum and timing diagram are shown in fig. 2. The algorithm makes effective identification (decision is background) at 6.62 seconds (389 ray sample size), the time-dependent graph of the decision function is shown in fig. 3, the test is repeated 100 times, the false positive rate is lower than 13%, and the result is better than expected (20% of expected).
(II) 137Cs(9.22*103Bq) (the distance between the front end face of the source-detector is 35 cm) (the equivalent dose rate is about 5.52 nGy/h):
The detector detects the first ray, and the time and energy information is (0.030928838, 161)/(time/second, energy/address).
The time interval is calculated by steps S1 and S2: Δt (0) = 0.0309.
Calculating a bayesian factor from step S3:
Calculating a decision function from step S4:
the prior probability is updated by step S5: θ 0 = 0.5188.
Decision making is made by step S6: due to the decision functionNo decision is made and the arrival of the next ray is continued.
After the arrival of the next ray, repeating the steps S1-S4 according to the time and energy information of the ray, and calculating a decision function; step S5 is then repeated based on the decision function, making a decision as to whether a radionuclide is present.
137 In the Cs example, 10 4 ray particles are identified by total measurement, the total spectrum count rate is 64.14s -1 for 154 seconds, and the energy spectrum and the time chart are shown in fig. 4. The nuclide alert algorithm uses 4.20 seconds (276 ray sample size) to make an effective identification (decision as the presence of radionuclide) and the decision function is plotted as a function of time as shown in fig. 5. The test was repeated 100 times with an alarm rate higher than 97% and the result was better than expected (80% expected).
According to two examples, the recognition speed can reach 4.2s under the condition of ultralow signal-to-noise ratio level (1/85% ≡1.18), and the alarm accuracy is higher than 97%, so that the following can be seen: in the practical application scene, the rapid and accurate recognition efficiency and result can be realized.
Example 2
As shown in fig. 6, the present embodiment provides a nuclide alarm system, the system comprising:
The radiation energy time information obtaining module 100 is configured to obtain energy-time information of a radiation currently detected by the radiation detector.
The time interval calculating module 200 is configured to calculate a time interval of the current detected ray according to the time information of the current detected ray and the time information of the last detected ray.
The bayesian factor calculating module 300 is configured to calculate a bayesian factor according to a time interval of the current detected ray, a time interval probability density function under the original assumption and a time interval probability density function under the alternative assumption; the original hypothesis is a hypothesis that no radionuclide is present; the alternative hypothesis refers to a hypothesis in which the radionuclide is present.
The Bayesian factor calculation expression is as follows:
wherein, τ1∈(τmin,τbkg)；
In the method, in the process of the invention,Is a Bayesian factor calculated from the time interval Deltat (0) of the current detected ray; g 0(Δt(0)|τ0) and g 1(Δt(0)|τ1) are time interval probability density functions under the original assumption and under the alternative assumption, respectively; τ 0 and τ 1 are mathematical expectations of the time intervals under the original assumption and under the alternative assumption, respectively; h 1(τ1) is a probability density function under alternative hypothesis/> And τ bkg are the mathematical expectations of the count rate and time interval of the background, respectively; τ min is a parameter related to the lower limit η min of detection sensitivity under the original assumption.
The posterior probability calculation module 400 is configured to calculate posterior probabilities under the original assumption and the alternative assumption according to the bayesian factor and the prior probabilities of the full spectrum time interval under the original assumption and the alternative assumption, respectively.
Wherein, the expression of the posterior probability is:
wherein, And/>The posterior probabilities are calculated according to the time interval of the current detection ray under the original assumption condition and the alternative assumption condition respectively; θ 0 and θ 1 are prior probabilities of full spectrum time intervals under the original assumption and the alternative assumption, respectively.
The nuclide discriminating module 500 is configured to make a statistical decision according to a comparison result of the posterior probability and the alarm threshold under the original assumption condition, and determine whether a radionuclide exists.
Wherein, the nuclide discriminating module specifically includes:
The first judging unit is used for outputting that the current detection ray does not have the radionuclide when the posterior probability under the original assumption condition is larger than the alarm upper limit threshold value.
And the second judging unit is used for outputting the radionuclide existing in the current detection ray and carrying out alarm prompt when the posterior probability under the original assumption condition is smaller than the alarm lower limit threshold value.
And a third judging unit, configured to make no decision and continue to detect the next ray when the posterior probability under the original assumption is greater than the alarm lower limit threshold and less than the alarm upper limit threshold, and when the next ray is detected, acquire the energy-time information of the current detected ray of the ray detector by using the ray energy time information acquiring module 100, and return to execute the step "calculate the time interval of the current detected ray according to the time information of the current detected ray and the time information of the last detected ray" in the time interval calculating module 200.
And the updating unit is used for updating the prior probability of the full spectrum time interval under the original assumption condition and the alternative assumption condition according to the posterior probability under the original assumption condition and the alternative assumption condition after the first discrimination unit or the second discrimination unit or the third discrimination unit makes a decision.
Example 3
The present embodiment provides an electronic device including a memory for storing a computer program and a processor that runs the computer program to cause the electronic device to execute a nuclide alarm method of embodiment 1.
Alternatively, the electronic device may be a server.
In addition, the embodiment of the present invention also provides a computer readable storage medium storing a computer program, which when executed by a processor implements a nuclide alarm method of embodiment 1.
Embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
In this specification, each embodiment is mainly described in the specification as a difference from other embodiments, and the same similar parts between the embodiments are referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.
Claims (9)
1. A nuclear species alarm method, the method comprising:
Acquiring nuclear detection event sequence information of a ray detector;
calculating the time interval of the current detected ray according to the time information of the current detected ray and the time information of the last detected ray;
Calculating a Bayesian factor according to the time interval of the current detected ray, the time interval probability density function under the original assumption condition and the time interval probability density function under the alternative assumption condition; the original hypothesis is a hypothesis that no radionuclide is present; the alternative hypothesis refers to a hypothesis that a radionuclide is present;
calculating posterior probabilities under the original assumption and the alternative assumption respectively according to the Bayesian factors and the prior probabilities of the full spectrum time interval under the original assumption and the alternative assumption;
and making a statistical decision according to the comparison result of the posterior probability under the original assumption condition and the alarm threshold value, and determining whether the radionuclide exists.
2. The nuclear species alarm method of claim 1, wherein the bayesian factor is calculated as:
wherein, τ1∈(τmin,τbkg)；
In the method, in the process of the invention,Is a Bayesian factor calculated from the time interval Deltat (0) of the current detected ray; g 0(Δt(0)|τ0) and g 1(Δt(0)|τ1) are time interval probability density functions under the original assumption and under the alternative assumption, respectively; τ 0 and τ 1 are mathematical expectations of the time intervals under the original assumption and under the alternative assumption, respectively; h 1(τ1) is a probability density function under alternative hypothesis/> And τ bkg are the mathematical expectations of the count rate and time interval of the background, respectively; τ min is a parameter related to the lower limit η min of the detection sensitivity under the assumption of the origin.
3. The nuclear species alarm method of claim 2 wherein the posterior probability is expressed as:
wherein, And/>The posterior probabilities are calculated according to the time interval of the current detection ray under the original assumption condition and the alternative assumption condition respectively; θ 0 and θ 1 are prior probabilities of full spectrum time intervals under the original assumption and the alternative assumption, respectively.
4. The nuclide alarm method of claim 1, wherein the determining whether the radionuclide is present is performed by making a statistical decision based on a comparison of a posterior probability under an original hypothesis with an alarm threshold, and specifically comprises:
When the posterior probability under the original assumption is greater than the alarm upper limit threshold, determining that the radionuclide is not present;
when the posterior probability under the original assumption is smaller than the alarm lower limit threshold, deciding to judge that the radionuclide exists, and carrying out alarm prompt;
when the posterior probability under the original assumption is larger than the alarm lower limit threshold and smaller than the alarm upper limit threshold, no decision is made, the next ray is continuously detected, when the next ray is detected, the energy-time information of the ray currently detected by the ray detector is obtained, and the step of 'calculating the time interval of the current detected ray according to the time information of the current detected ray and the time information of the last detected ray'.
After the decision process is completed, updating the prior probability of the full spectrum time interval under the original assumption condition and the alternative assumption condition according to the posterior probability under the original assumption condition and the alternative assumption condition.
5.A nuclear species alarm system, the system comprising:
The ray energy time information acquisition module is used for acquiring nuclear detection event sequence information of the ray detector;
the time interval calculation module is used for calculating the time interval of the current detected ray according to the time information of the current detected ray and the time information of the last detected ray;
the Bayesian factor calculation module is used for calculating the Bayesian factor according to the time interval of the current detection ray, the time interval probability density function under the original assumption condition and the time interval probability density function under the alternative assumption condition; the original hypothesis is a hypothesis that no radionuclide is present; the alternative hypothesis refers to a hypothesis that a radionuclide is present;
The posterior probability calculation module is used for calculating posterior probabilities under the original assumption condition and the alternative assumption condition according to the Bayesian factors and the prior probabilities of the full spectrum time intervals under the original assumption condition and the alternative assumption condition respectively;
and the nuclide discriminating module is used for making a statistical decision according to the comparison result of the posterior probability and the alarm threshold under the original assumption condition, and determining whether the radionuclide exists.
6. The nuclear species alarm system of claim 5, wherein the bayesian factor is calculated as:
wherein, τ1∈(τmin,τbkg)；
In the method, in the process of the invention,Is a Bayesian factor calculated from the time interval Deltat (0) of the current detected ray; g 0(Δt(0)|τ0) and g 1(Δt(0)|τ1) are time interval probability density functions under the original assumption and under the alternative assumption, respectively; τ 0 and τ 1 are mathematical expectations of the time intervals under the original assumption and under the alternative assumption, respectively; h 1(τ1) is a probability density function under alternative hypothesis/> And τ bkg are the mathematical expectations of the count rate and time interval of the background, respectively; τ min is a parameter related to the lower limit η min of the detection sensitivity under the assumption of the origin.
7. The nuclear species alarm system of claim 6 wherein the posterior probability is expressed as:
wherein, And/>The posterior probabilities are calculated according to the time interval of the current detection ray under the original assumption condition and the alternative assumption condition respectively; θ 0 and θ 1 are prior probabilities of full spectrum time intervals under the original assumption and the alternative assumption, respectively.
8. The nuclear species alarm system of claim 5, wherein the nuclear species discrimination module specifically comprises:
The first judging unit is used for outputting a result that the radionuclide is not present when the posterior probability under the original assumption condition is larger than the alarm upper limit threshold value;
the second judging unit is used for outputting a result that the radionuclide exists when the posterior probability under the original assumption condition is smaller than the alarm lower limit threshold value and carrying out alarm prompt;
The third judging unit is used for making no decision and continuously detecting the next ray when the posterior probability under the original assumption condition is larger than the alarm lower limit threshold and smaller than the alarm upper limit threshold, acquiring the energy-time information of the current detected ray of the ray detector by using the ray energy time information acquisition module when the next ray is detected, and returning to execute the step of 'calculating the time interval of the current detected ray according to the time information of the current detected ray and the time information of the last detected ray' in the time interval calculation module;
and the updating unit is used for updating the prior probability of the full spectrum time interval under the original assumption condition and the alternative assumption condition according to the posterior probability under the original assumption condition and the alternative assumption condition after the first discrimination unit or the second discrimination unit or the third discrimination unit makes a decision.
9. An electronic device comprising a memory and a processor, wherein the memory is configured to store a computer program, the processor running the computer program to cause the electronic device to perform a nuclear species alarm method as claimed in any one of claims 1 to 4.
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