JPH0720247A - Method and equipment for measuring radiation and monitoring nuclide continuously - Google Patents

Abstract

PURPOSE:To allow high sensitivity continuous determination of the concentration of nuclide, dose and variation thereof in the early stage without prolonging the measuring time by determining the radiation information within an arbitrary measuring time width continuously based on the spectral data for at least one section corresponding to the measuring time width. CONSTITUTION:Radiation energy is detected 4 continuously for a measuring time t0 (minimum unit time for detecting the variation) which can be split into a plurality of sections. It is then amplified 5 and subjected to A/D conversion 6 before being recorded in a data recording memory 7. When the radioactive spectral data for L adjacent measuring sections(time t0) is added for each channel to obtain one spectral data, the adjacent L sections are shifted by one data to the next measuring section thus shifting the time axis by the unit time t0. Consequently, the data (shown by black points) can be obtained every unit time t0 while handling data for t0xL time interval and since the concentration variation curve 3 connecting the data points is approximate to an actual concentration variation curve 1, high sensitivity measurement can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation measuring device for monitoring a continuous nuclide used in a nuclear power plant or the like.

[0002]

2. Description of the Related Art At present, all radiation monitors used in commercial light water reactors (nuclear power plants) employ the gross γ-ray method, and although radiation counting information can be obtained,
The current situation is that energy information is not available.

This is sufficient for ordinary applications, but in the future, particularly high-resolution semiconductor detectors such as Ge detectors that can obtain energy and nuclide information will be used as a high-level monitoring method using a γ-ray monitor. By adopting the continuous nuclide monitor system used, it is possible to detect and detect abnormal signs early and to operate and maintain the nuclear power plant safely.

Further, even in a fast breeder reactor which will be put to practical use in the future, adoption of a nuclide monitor device using a Ge detector as a fuel damage detection system is being considered. Currently, such a γ-ray spectrometer has already been put to practical use as a nuclide analyzer, and it is necessary to measure sampled samples, etc. in a container, or in some cases chemical-treated samples, etc. It is installed in the analysis room.

Therefore, the measured and calculated radioactivity concentration of the nuclide is the concentration at the time of sampling, and it was not possible to continuously monitor it. For this reason, attempts are being made to install a measuring device at the measurement site and perform measurement for continuous monitoring, but there are various problems with the conventional measurement.

The characteristic curve diagram of FIG. 6 shows the continuous spectrum measurement by the conventional method. Now, focusing on the radioactivity concentration of a specific nuclide, as shown in FIG. Think That is, the actual change in the concentration of the radionuclide radioactivity shown by the concentration change curve 1 shows a slight increasing tendency at time t ₁ and eventually returns to the original level. Further, at time t ₂ , a larger increase than before is shown, but it is assumed that the fluctuation returns to the original level after a while.

On the other hand, in the radiation spectrum measurement, the average radioactivity concentration during the measurement time is calculated by repeating the data collection in the measurement section for a fixed time and analyzing the data after the end of each measurement. In FIG. 6, 1 to 4 are shown as the measurement sections, the values calculated after the measurement are shown by white circles, and the concentration change of the radioactivity of the nuclide is shown by the concentration change curve 2 of the one-dot chain line connecting them.

In this example, since the fluctuation from the time t ₁ is small and the measurement section 1 and the measurement section 2 are spread over, the measurement section 1 and the measurement section 2 are not measured. , The change from the previous quantification result is very small, and may not be detected depending on the time width and magnitude of the change.

Next, at time t ₂ , if there is a larger fluctuation than in the previous example, there is a possibility that the data in the measurement section 3 will show a larger sign than before. However,
Probably, it is expected that the radioactivity concentration level will return to the original level in the next measurement section 4, and in the end, there is only a possibility that it can be confirmed from the result of the measurement section 3 that the radioactivity concentration slightly increased.

This situation changes depending on the degree of fluctuation of the radioactivity concentration and the relationship between the time width and the measurement time.
Usually, if you measure for a long time to improve statistical accuracy,
Since the averaging interval becomes larger by that amount, it becomes difficult to capture the change itself. This is similar to the principle of general arithmetic mean.

Therefore, in a count rate meter used in a general radiation monitor or the like, various methods such as a count rate calculation method by a variable measurement time for making the statistical error constant and a method of judging a sudden change from the statistical error are available. Considering that it has been adopted, it cannot be said that it is appropriate to directly adopt this conventional spectrum measurement method as a nuclide monitor device.

That is, detailed information on the time-averaged nuclide composition and the like can be obtained only by installing a conventional γ-ray spectrometer and a nuclide analyzer in the vicinity of the object to be measured and performing so-called “in-situ” measurement. However, it is difficult to clearly detect changes in the radioactivity concentration and the radiation dose, and even if it could be detected, a large delay time is involved depending on the timing. I had to say that it was lacking.

[0013]

A conventional radiation monitor for a nuclear power plant always gives count rate information, and detects an abnormality by a change with time of the count rate information. on the other hand,
When considering the introduction of a nuclide monitor device by energy spectrum measurement using a high-purity Ge detector or the like, in the conventional so-called time-averaged spectrum measurement method, time-averaged data from the start to the end of measurement Only collection is repeated one after another.

For example, even if the concentration of a certain nuclide fluctuates in the time span that extends over the i-th measurement and the i + 1-th measurement,
In some cases, it may not be possible to detect it due to the relationship between the fluctuation time width, the degree of change, and the measurement time, or even if it can be detected, it will become clear after the i + 1-th measurement that is considerably delayed from the time when the change phenomenon occurred. .

On the other hand, in the case of adopting the method of repeating the measurement divided into short time intervals, there is no problem in the long time measurement, and it is necessary to save the data necessary for switching and to initialize the memory. The ratio of the time to the measurement time increases, and this becomes a missing time that cannot be ignored. Furthermore, in such a short measurement, it is expected that the statistical accuracy of each data itself is low, and there is a possibility that accurate processing cannot be performed only by the short time measurement.

For this reason, in a continuous nuclide monitoring device for a nuclear power plant, there is a method of continuous and accurate measurement of an energy spectrum, and the data is cut out by arbitrarily changing the time width of interest on a continuous time axis. There has been a demand for a measurement means and a measuring device equipped with these data processing means.

An object of the present invention is to provide a radiation measuring method and apparatus for a continuous nuclide monitor which stores the detected radiation energy spectrum and divides by switching to continuously measure.

[0018]

In order to achieve this object, a radiation measuring method for a continuous nuclide monitor according to the invention of claim 1 is continuous in time and can be divided into a plurality of intervals. Measure the energy spectrum of radiation,
It is characterized in that spectral data for one or more sections corresponding to an arbitrary time width is taken out, and information on the radiation dose, radioactivity concentration, nuclide, etc. in the time width is continuously obtained from this data.

In the radiation measuring apparatus for continuous nuclide monitoring according to the second aspect of the present invention, the radiation detecting means and its output are used as electric signals in order to continuously obtain information on the radiation dose, activity concentration, nuclides and the like. An amplification means and an AD conversion means for performing analog-digital conversion (hereinafter referred to as AD conversion) of the output signal are provided.

Further, the memory capacity is an even number (m) times more than the capacity required for recording one spectrum data, and the number of bits required for digital conversion of the peak value (voltage value) of the radiation pulse is increased. Further, log (m) / log (2) bits are introduced as upper bits, and this is added to the AD conversion means as an offset of the digital value at the time of AD conversion result, and the memory area to be used is designated by this value. Thus, it is characterized by comprising data recording memory means for switching the memory and data processing means for rapidly saving the memory contents of the area which is not being recorded and preparing for the next measurement.

In the radiation measuring apparatus for continuous nuclide monitoring according to the third aspect of the present invention, the radiation detecting means and its output are used as electric signals in order to continuously obtain information on the radiation dose, activity concentration, nuclides and the like. The amplifying means, the AD converting means for performing AD conversion of the output signal, the memory capacity which is an integer (n) times or more the capacity required for recording one spectrum data, and the memory control function for the memory address for recording are provided. Is composed of a data recording memory means which is switched by a signal given from the outside, and a data processing means which quickly saves the memory contents of an area which is not being recorded and prepares for the next measurement.

In the radiation measuring device for continuous nuclide monitoring according to the fourth aspect of the present invention, the radiation detecting means and its output are used as electric signals in order to continuously obtain information on the radiation dose, the radioactivity concentration and the nuclide. Amplifying means, AD converting means for performing AD conversion of the output signal, and a plurality of data recording memory means having a capacity necessary for recording at least one of the spectrum data are provided, and these are provided for each measurement. Data processing means for switching data alternately and recording data, and saving data of the recorded and unused data recording memory means while the other data recording memory means is in use to prepare for the next recording. It is characterized by consisting of.

[0023]

According to the first aspect of the present invention, the energy spectrum of radiation is measured and stored at a measurement time that can be continuously divided into a plurality of sections, and the spectrum of one or more sections corresponding to an arbitrary time width is stored. It is taken out as data, and information such as radiation dose, radioactivity concentration and nuclide in that time range is continuously obtained from this data.

According to a second aspect of the present invention, the radiation input signal detected by the radiation detecting means is converted into an electric signal by the amplifying means,
This signal is AD-converted by the AD conversion means and input to the data recording memory means having a memory capacity that is an even number (m) times the capacity required for recording one spectrum data.

In the data recording memory means, log (m) / log is set as an upper bit to the number of bits required for digitally converting the crest value (voltage value) of the radiation pulse.
(2) A bit area is introduced, and this is added by the AD conversion means as an offset of the digital value at the time of AD conversion result to specify the memory area and switch the memory.

The memory contents of the area which is not being recorded are saved in the data processing means to prepare for the next measurement, and after being recorded in the mth area, the recording is repeated from the first area to infinite. Obtain data continuously for a number of times.

According to a third aspect of the present invention, the radiation input signal detected by the radiation detecting means is converted into an electric signal by the amplifying means,
This signal is AD-converted by the AD conversion means and input to the data recording memory means having a memory capacity which is an integer (n) times or more of the capacity required for recording one spectrum data.

In the data recording memory means, the address of the memory for recording is switched by a signal externally given to the memory control function. The memory contents of the area which is not being recorded are saved to the data processing means to prepare for the next measurement, and after being recorded in the nth area, the recording is repeated from the first area to the infinite number of times continuously. To get the data.

According to a fourth aspect of the invention, the radiation input signal detected by the radiation detecting means is converted into an electric signal by the amplifying means,
This signal is AD-converted by the AD conversion means, and at the same time, the signals are alternately switched and input to a plurality of data recording memory means having a memory capacity necessary for recording at least one of the spectrum data.

By the way, the data in the data recording memory means that has been recorded and is not in use is saved in the data processing means while another data recording memory means is in use to prepare for the next recording. Data is continuously acquired an infinite number of times without missing measurement.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. According to the first embodiment of the present invention, as shown in the characteristic curve diagram of FIG. 1, the minimum time unit for detecting a change depends on the dose of the object to be measured, but this is assumed to be time t ₀ . In the present invention, it is necessary to sequentially repeat the measurement in the cycle of the time t ₀ and sequentially save from the memory area where the measurement is completed to the data processing means.

In addition, since there is a possibility that the data in only the t ₀ section is insufficient in statistical accuracy, the spectrum data for a plurality of adjacent L measurement sections are added for each channel to form one spectrum data. . The spectrum data thus obtained corresponds to the section average measurement data for t ₀ × L time obtained in the final section used for integration,
It can be said that it is equivalent to the measurement by the conventional method.

However, if the previously adopted L adjacent sections are shifted by one data and detected in the next measurement section, the section average data is handled, but the time axis is shifted by t _0. Will be done. This allows
While handling the data for t ₀ × L time, the information is obtained every t ₀ time as shown by the black dots, and the concentration change curve 3 obtained by connecting this information is the same as the actual concentration change curve 1. Will be done.

A time chart showing the relationship between the change in nuclide concentration and the measuring method shown in FIG. 2 will be described in comparison with the conventional example. Here, assuming that the measurement time of the conventional method is T ₀ and the measurement time of the present invention is T ₁ , the relationship of T ₀ = 5 × T ₁ is established. In addition, in the present invention, continuous measurement without missing is performed as compared with the conventional method.

Now, a certain nuclide shows a constant radioactivity concentration, which increases stepwise at time t ₁ and decreases stepwise again at times t ₂ and t ₃ to settle to a constant value. Assume a pattern. Here, [t ₁ ,
The change in the [t ₃ ] section is called pattern 1, and the change in the [t ₁ , t ₂ ] section is called pattern 2.

In the case of pattern 1, considering the time when the first measurement by the conventional method is finished, the time t ₁ when the nuclide concentration increases occurs after about 4/5 of the measurement time T ₀ has already passed. Since there is, about 1/5 of the concentration increase
Is a value that is added to the previous concentration quantitative value.

At this time, whether or not this change is detected depends on the relative intensities of the previous quantitative value and ⅕ of the change in concentration and the statistical accuracy of each. On the other hand, in the present invention, the data is integrated by going back 5 sections at each end of each measuring time T _{1 and} the quantification is performed from the data.

Therefore, as shown in FIG. 2, in the fifth measurement, the conditions are the same as in the case of the conventional method, but as the sixth and seventh measurements are performed, the nuclide concentration increase in all five sections is increased. The ratio of minutes, that is, the ratio of information after the change becomes large. Therefore, as a matter of course, the detection probability of the concentration increasing phenomenon increases with the progress of each of the sixth, seventh, and eighth measurements.

However, in the conventional method, when the detection cannot be performed in the first measurement, the determination cannot be performed at least until the end of the next measurement (corresponding to the end of the tenth measurement of the present invention), and thus there is no possibility of detection. In comparison with this, the present invention has a possibility that detection can be performed without waiting for the end of the 10th measurement, and has an effect that early detection can be achieved as compared with the conventional method.

Next, the pattern 2 will be described. In this case, it is assumed that the nuclide concentration change occurs in a time width shorter than that of the previous pattern 1, the concentration increased stepwise at time t ₁ shows a constant value, and immediately returns to the original level at time t ₂ . In the example of FIG. 2, this [t ₁ , t ₂ ] is represented as about 1.5 times T ₁ time at most. In this case as well, whether or not it can be detected by each measurement method depends on the relative intensity of the concentration, the measurement time, the statistical error, etc., as in the previous case. Therefore, the relative comparison between the respective measurement methods will be described.

In the conventional measuring method, when the first measurement is completed, as in the case of the above-mentioned pattern 1, the density increment
Approximately / 5 is the degree at which the added concentration is obtained. In the next measurement, the conditions were even worse, and
Only about 10 is added.

However, according to the measurement of the present invention, 5
At the end of the second measurement, the same conditions as the conventional method are used, but
When the second measurement is completed, 1.5 / 5 will be added, and the detection probability is high because it contains more information of the change phenomenon than the conventional method. Therefore, although it is not detected by the conventional method, there are many cases in which it can be detected by the present invention.

The second embodiment relates to claim 2, and as shown in the block diagram of FIG. 3, a radiation detecting means 4 for detecting the incident radiation and an amplifying means 5 for outputting the output as an electric signal. AD conversion means 6 for performing AD conversion of the output signal is provided.

Further, the AD converter means 6 is provided with a peak value (voltage value) of a radiation pulse by providing a memory capacity which is an even number (m) times as large as a capacity required for recording one spectrum data.
Introduce log (m) / log (2) bits as the higher order bits to the number of bits required for digital conversion by, and add this as an offset of the digital value at the time of AD conversion result. It is composed of a data recording memory means 7 for switching the memory by designating a memory area to be used, and a data processing means 8 for quickly saving the memory contents of an area which is not being recorded and preparing for the next measurement.

Next, the operation of the above configuration will be described. After the spectrum data detected by the radiation detecting means 4 and inputted to the data recording memory means 7 via the amplifying means 5 and the AD converting means 6 is recorded in the m-th area,
It is equivalent to using m memory for data recording capable of recording one spectrum data in a quasi manner by re-recording from the first area, and the data is continuously obtained for an infinite number of times. .

Therefore, the energy spectrum of the radiation is measured at a measurement time which is continuous in time and can be divided into a plurality of sections, and the spectrum data for one section or more corresponding to an arbitrary time width is taken out. Information such as radiation dose, activity concentration, and nuclides in that time range can be obtained from the data.

With this configuration, the offset is added to the most significant bit of the digital output of the AD conversion result at each measurement, and the AD conversion means 6 performs AD conversion with an offset of zero at the first measurement. Since the result is output and the offset bit is incremented by 1 when the next measurement is started, assuming that the number of bits required for the net conversion is k bits, an offset of 2 to the power of k is applied.

The value of 2 raised to the power of k is equal to the number of channels of spectrum data, or the value of what is called conversion gain. Therefore, the measurement of the next section is 2 k
An AD conversion value with a power offset is obtained. Further, since the offset bit is further incremented by +1 in the measurement of the next section, an offset of 2 times the kth power is applied.

The result of this AD conversion is used as a relative address value of the data recording memory means 7, and the data is recorded by incrementing the memory content indicated by the address by one. If the offset bit overflows, it will start from offset zero again. During this time, the necessary data in the memory has been saved in the data processing means 8.

As for the offset value switching timing information, necessary information is input to the AD conversion means 6 by using the clock of the data processing means 8 or the data recording memory means 7, the clock of the AD conversion means 6 or the like. To do.

The third embodiment relates to claim 3, and the configuration and effect thereof are almost the same as those in the block diagram of FIG. 3, and the radiation detecting means 4, the amplifying means 5 for outputting the output as an electric signal, The AD control means 6 for performing AD conversion of this output signal and the memory capacity which is an integer (n) times or more of the capacity required for recording one spectrum data are provided, and the memory control device externally stores the memory address for recording. It is composed of a data recording memory means 7 which is switched by a signal given from the data processing means 8 and a data processing means 8 which quickly saves the memory contents of an area which is not being recorded.

As a result, after the spectrum data is recorded in the data recording memory means 7 in the n-th area, one spectrum data is pseudo-recorded in a circular manner so as to be recorded again from the first area. This is equivalent to the use of n memory means for data recording capable of storing data, and data can be obtained continuously infinitely.

According to the third embodiment, the offset is directly added to the AD conversion result in order to switch the memory address in the second embodiment. However, in the direct memory addressing, the data recording memory It is also possible to switch the memory area by adding an offset on the control circuit side.

The switching timing in this case is
It is of course possible to use the clock inside the data recording memory means 7, but in addition to this, the information transmission from the AD conversion means 6, the data processing means 8 and the like can also be performed by an additional circuit required.

The fourth embodiment relates to claim 4, and as shown in the block diagram of FIG. 4, the radiation detecting means 4 and the amplifying means 5, the AD converting means 6 for AD converting the output signal, and the spectrum. A plurality of data recording memory means 7 having a capacity necessary for recording at least one data is provided.

Further, these are alternately switched for each measurement to record data, and the data of the recorded and unused data recording memory means 7 is changed to the other data recording memory means 7.
The data processing means 8 is configured to save the data while it is in use. With the above configuration, the saved data is prepared for the next recording so that the measurement is not lost in time and the data is continuously obtained an infinite number of times, which enables continuous spectrum measurement without any missing data. .

As an application example, as shown in the block diagram of FIG. 3, a radiation detecting means 4 for detecting incident radiation, an amplifying means 5 for outputting the output as an electric signal, and an AD for the output signal. It is composed of an AD conversion means 6 for performing conversion and further a data processing means 8, and its operation and effect are the same as those of the above-mentioned third and fourth embodiments, but in any case, it is necessary to record the spectrum data. By allocating a part of the memory held by the data processing means 8 to such a memory, the configuration can be simplified.

Further, a method of adding all the data measured or recorded at every time t ₀ , or the data intervals of adjacent intervals while checking the count of the portion of interest and calculating the number of intervals satisfying the statistical accuracy as variable Alternatively, if there is already a large change in the addition process, it is also effective to use means such as calculation as the addition up to the section immediately before the addition. Further, a high-purity Ge detector is adopted for detecting radiation. Can be continuously cooled by an electric type or a liquid nitrogen cooling device to obtain stable characteristics with high resolution.

These cases will be shown in the following embodiment section. (1) A radiation measuring device for continuous nuclide monitor, wherein a part of the memory held by the data processing means 7 is used as a memory for recording the spectrum data and switching the spectrum data.

(2) The spectral data for each designated unit time interval is transferred from the data recording memory means, which is the primary storage device, to the secondary storage device, and the spectral data is recorded and stored by writing, and at any time. Data processing function that obtains one or more spectrum data corresponding to minutes by adding the previous spectrum data for each unit time, and obtains information such as radiation dose, radionuclide, radioactivity by nuclide and total radioactivity A radiation measuring apparatus for a continuous nuclide monitor, comprising:

(3) In particular, the data processing means is provided with a continuous arbitrary constant constant spectrum addition and calculation processing function for each unit time, and moves the processing target section by a fixed number on the time axis with time. A radiation measuring device for continuous nuclide monitoring, which is characterized in that

(4) The data processing means selects a section in which the total count or the net count value of the portion corresponding to the photoelectric peak of the specific nuclide of interest has a constant statistic, particularly in any continuous section. A radiation measuring apparatus for continuous nuclide monitor, which is provided with a function of performing a calculation process on the data in this section.

(5) Radiation for continuous nuclide monitoring, characterized in that a high-purity Ge detector is used as the radiation detecting means and is continuously cooled by electric cooling or liquid nitrogen cooling with a liquid nitrogen evaporation prevention device. measuring device.

[0064]

As described above, according to the present invention, a continuous nuclide monitor using a nuclide analyzer or a radiation spectrometer in a nuclear power plant or the like enables the nuclide concentration, the dose, and the change thereof to be measured earlier without increasing the time. Since high-sensitivity and continuous quantification and detection are performed, there is an effect that the operation and management of equipment such as a nuclear power plant can be maintained more safely.

[Brief description of drawings]

FIG. 1 is a characteristic curve diagram of a radiation measuring method according to a first embodiment of the present invention.

FIG. 2 is a time chart showing the relationship between the change in nuclide concentration and the measuring method according to the first embodiment of the present invention.

FIG. 3 is a block configuration diagram of a radiation measuring apparatus according to second and third embodiments of the present invention.

FIG. 4 is a block configuration diagram of a radiation measuring apparatus according to a fourth embodiment of the present invention.

FIG. 5 is a block configuration diagram of a radiation measuring apparatus according to an application example of the invention.

FIG. 6 is a characteristic curve diagram of conventional continuous spectrum measurement.

[Explanation of symbols]

1 ... Actual concentration change curve, 2 ... Conventional concentration change curve, 3 ... Inventive measurement concentration change curve, 4 ... Radiation detection means, 5 ... Amplification means, 6 ... AD conversion means, 7 ... Data recording memory Means, 8 ... Data processing means.

Claims (4)

[Claims] 1. An energy spectrum of radiation is measured at a measurement time that is temporally continuous and can be divided into a plurality of sections, and spectrum data for one or more sections corresponding to an arbitrary time width is extracted and A radiation measuring method for a continuous nuclide monitor, characterized in that information such as a radiation dose, a radioactivity concentration and a nuclide in the time width is continuously obtained from the data. 2. A radiation detecting means, an amplifying means for converting the output into an electric signal, and an analog digital for converting the output signal into an analog signal in order to continuously obtain information on the radiation dose, the radioactivity concentration, the nuclide and the like. The conversion means and the memory capacity that is an even number (m) times larger than the capacity required for recording one spectrum data are provided, and the number of bits required for digitally converting the crest value (voltage value) of the pulse of radiation is further higher. Log (m) / log (2) as bits
Data recording memory means for switching the memory by introducing a bit portion, adding this to the analog-digital converting means as an offset of a digital value at the time of AD conversion result, and designating a memory area to be used by this value, A radiation measuring apparatus for a continuous nuclide monitor, comprising a data processing means for rapidly saving the memory contents of an area which is not being recorded and preparing for the next measurement. 3. A radiation detecting means, an amplifying means for converting the output into an electric signal, and an analog digital for converting the output signal into an analog signal in order to continuously obtain information on the radiation dose, the radioactivity concentration, the nuclide and the like. A memory means for recording data, which comprises a converting means and a memory capacity which is an integer (n) times or more the capacity required for recording one spectrum data and which switches the address of the memory for recording by a signal externally applied to the memory control function. And a data processing means for quickly saving the memory contents of the area not being recorded to the data processing means to prepare for the next measurement. 4. A radiation detecting means, an amplifying means for converting the output into an electric signal, and an analog digital for converting the output signal into an analog signal in order to continuously obtain information on the radiation dose, the radioactivity concentration, the nuclide and the like. A plurality of conversion means and a plurality of data recording memory means having a capacity necessary for recording at least one of the spectral data are provided, and these are alternately switched for each measurement to record the data. Radiation measurement for continuous nuclide monitoring, comprising data processing means for saving the data of the unused data recording memory means while another data recording memory means is in use to prepare for the next recording. apparatus.