JPS5937480A - Analyzing method for secular change of wave height distribution - Google Patents

Abstract

PURPOSE:To find physical half life from measurement results and to specify a nuclear species name easily, by taking simultaneous measurements of changes in the intensity of radiation of various energies emitted from radiation nuclear species with time by energy levels. CONSTITUTION:A sequence representing an energy distribution in the (i)th fine interval among pulses to radiation in respective fine time intervals and fine energy intervals is denoted as Ai, and a sequence representing a secular change in energy level in the (j)th fine energy interval is denoted as Bj. One column of the sequence Ai specifies the energies of radiations by the longitudinal axis of R1-R5 indicating sharp peaks atop, and the intensity of the radiation by the horizontal axis indicating the height of sharp peak. Then, the physical half life of, for example, the radiation R1 is found by the sequence Bj. Thus, pieces of information on the sequences Ai and Bj of the individual radiations R1-R5 are processed to specify the nucelar species of the measured radiations.

Description

[Detailed description of the invention] The present invention relates to a method for analyzing changes in wave height distribution over time.

More specifically, when the radiation to be measured contains multiple radionuclides whose nuclide names are unknown, the temporal changes in the intensity of radiation of various energies emitted from these radionuclides can be simultaneously measured for each energy level. In general, in the analysis of radioactive nuclides, how to use the nuclide of a radioactive substance whose nuclide is unknown, regarding the method of determining the half-life from the measurement result and identifying the name of the corresponding nuclide through measurement.

It is necessary to know the characteristics of the radiation that generates the nuclide, and there are 9 types of radiation characteristics, including energy, half-life, etc.8 To identify the type of radiation, change the detector. placing a shield between the radiation source and the detector;
Alternatively, it is possible to determine the nuclide by applying an electric field, etc.Also, to identify the energy of radiation, a detector whose output depends on the energy of the radiation, such as a scintillation detector or germanium detector, is used. A method of determining the pulse height distribution of the electrical pulses of this detector using this method is widely used. but.

In many cases, it is not possible to identify the nuclide that emits radiation just by knowing the energy of the radiation.This is because there are nuclides that emit radiation with energy levels that are close to each other.
. Even in this case, if the half-life of the radiation is measured by determining the attenuation of the intensity of the radiation over time using the fact that the half-life of the radiation differs, it becomes possible to identify the nuclide of the radiation.

However, such nuclide analysis is not always easy.

For example, in cooling water or radioactive waste liquid at a nuclear power plant, there are many types of nuclides, the radiation intensity of some nuclides is low, and the half-life of other nuclides is short compared to the measurement time. If the length is short, analysis of nuclides becomes difficult.

One of the reasons is that in such cases, the method of identifying the nuclide by measuring its half-life is not often used.

In order to simultaneously determine the attenuation of radiation containing multiple nuclides, wave height analysis must be repeated at certain measurement time intervals, but nuclides with short half-lives can be analyzed within a single measurement time. This is because it will be attenuated and will not be detected in the trench first-order measurement.

Current methods for measuring the radiation energy and half-life described above include the following:

In a so-called multi-channel analyzer that divides the wave height of an input pulse into many sections and measures them simultaneously, the number of each channel (memory) depends on the radiation energy and is set, for example, to the first order.

1 channel - 18~20 Memorize the number of KeV gamma ray pulses 2 channels - 20~2? ! Memorize the number of γ-ray pulses of KeV 3 channels - Store the number of γ-ray pulses of 22 to 24 KeV Using this method, the maximum number of channels is 60, and the number of pulses is proportional to the wave height. A counting circuit that usually uses a combination of a KAD conversion device and an electronic computer, and usually uses a single-channel analyzer to measure half-life, and calculates the temporal change in the number of radiation particles in a range that has a specific energy. Or, when using a multi-channel analyzer, each channel is set to correspond to time, for example, as in the 9th order. The energy to be measured is 65
When increasing from 0 KeV to 680 KeV, the first order is obtained.

1 channel - memorize the number of gamma ray pulses from 0 to 2 seconds 2 channels - memorize the number of gamma ray pulses of 2 to 4 seconds Channel 3 - Memorization of the number of gamma ray pulses of 4 to 6 seconds According to the method for analyzing changes in wave height distribution over time according to the present invention.

Eliminates the shortcomings of conventional wave height analysis methods and simultaneously measures different radiation energies and different radiation half-lives.
Unknown nuclide groups can be identified.

In the method of the present invention, channels (memories) ij
It is divided into a matrix of a x b (a + b are both integers), and there are b sets of 8 channels for pulse height distribution, and the pulse height distribution data of the input pulse during a certain minute time 61 is the first one. stored in a channels of 1
The same wave height distribution data during the next minute time Δ is the second a
stored in channels. Thereafter, by repeating this operation, it is possible to obtain changes over time in the wave height distribution data for group b of Δ.

An embodiment of the method of the invention will now be described.

The memory is divided into ka pieces x b groups, and the minute time interval Δt is 2.
It is expressed as follows as the number nij of radiation having each energy at each time when the same energy interval is 2 KeV.

KeV KeV KeV
KeVθ~22~44~6...2(b-
1) ~ 2b Konotoki, sequence Ai = (nl II ”
i2 + n i! """ n 1 bl represents the energy distribution of radiation in the i-th minute time interval Δt, and the sequence Bj=(nlj.

n2j+nsj...nBj) is the temporal change ta% of the radiation at the j-th energy level.

The energy distribution of radiation 1 [one row of the number sequence selection is shown in FIG. In Figure 1, the energy of the radiation is specified by the horizontal axis of radiation R, , R2, R8, R, and R1, which have sharp peaks at the tips, and the energy of the radiation is specified by the vertical axis, which shows the height of the sharp peak. The strength of is determined. Next, for example, the half-life of the radiation R1 is determined in the sequence Bj showing the change over time of the energy rail. In this way 9 individual radiations R1vB!・・・・・・
- The nuclide of the radiation to be measured can be specified by performing matrix data processing on the information on the horse number sequence Ai and number sequence B1 using, for example, an electronic computer.

According to the method of the present invention, it is based on the fact that each radionuclide emits radiation having a specific energy, and furthermore, its half-life is specified.

By processing both pieces of information together, it is possible to easily identify the nuclide of the radiation to be measured from among a large number of peaks.

It goes without saying that it is possible to identify nuclides with extremely short half-lives by selecting minute time intervals such that the half-life is not smaller than the minute time interval.

[Brief explanation of the drawing]

FIG. 1 is a curve showing the energy distribution of radiation, with radiation energy b'fr on the horizontal axis and radiation intensity nib on the vertical axis. In the figure

Claims (1)

[Claims] A number sequence AI representing the energy distribution 'fr in the first minute time interval among the number of pulses 1'l+j generated by the detector for the radiation for each minute time interval and every minute energy interval of the radiation to be measured, A method for analyzing changes in wave height distribution over time, which consists of obtaining information regarding the number sequence Bj that represents the change in energy level over time in the @jth minute energy interval, and obtaining the half-life that corresponds to the number sequence Bj of the radiation that corresponds to the number sequence Ai. .