JP5540321B2 - Radioactivity measurement method, biomass degree measurement method, neutron fluence measurement method, absolute radioactivity measurement method using a cryogenic microcalorimeter - Google Patents

Description

  The present invention relates to a radioactivity measurement method using a cryogenic microcalorimeter, and more particularly to a radiation measurement technique applicable to biomass degree measurement, neutron fluence measurement, and radioactivity absolute measurement.

  Bioplastics and biofuels produced by immobilizing carbon dioxide in the modern atmosphere by photosynthesis of plants without using fossil fuels such as oil to reduce carbon dioxide emissions for the purpose of suppressing global warming In order to ensure the reliability of biomass-derived products, it is identified whether the products are derived from current biomass or fossil fuels such as petroleum, and further mixed. For products produced in this way, a method for measuring the proportion of biomass raw material used is required.

  Natural radioactive carbon 14 originates from cosmic rays, and is generated by interaction of radiation such as nitrogen and neutrons in the upper atmosphere. Therefore, fossil fuels such as petroleum that are not easily affected by cosmic rays contain almost no carbon 14 with a half-life of 5730 years, but absorb carbon dioxide in the atmosphere and absorb it. Since the biomass-derived material contains carbon 14, the amount of carbon 14 in the product is measured to calculate the ratio of the biomass-derived material in the product (Non-Patent Document). 1).

  As a method for measuring carbon 14 derived from biomass in a product, there are a method using a liquid scintillation counter (LSC) and a method using an accelerator mass spectrometer (AMS). The liquid scintillation counter mixes a liquid sample containing carbon 14 with a liquid scintillator, converts β-ray energy emitted from the carbon 14 into light with the liquid scintillator, and detects the light with a photodetector to detect carbon 14. This is a device for measuring β-rays. In the accelerator mass spectrometry, carbon in a sample to be measured is purified to graphite, a part of the graphite sample is evaporated at an atomic level, and the atoms that have become ions are accelerated to perform mass analysis. This is a method of directly counting the number of atoms.

  In addition, there is a need to evaluate and reduce the medical exposure of patients and medical workers due to leaked neutrons of accelerators that have been introduced for medical use in recent years, and accurate thermal neutron fluence evaluation is required. . As a method for measuring thermal neutron fluence, there is an activated foil method. This is because gold foil and other metal foils are exposed to thermal neutrons, and the radioactivity generated by thermal neutron activation is measured with a 4πβ-γ simultaneous measurement device, Ge semiconductor detector, etc. (See Non-Patent Document 2).

  Further, the 4πβ-γ simultaneous measurement method is mainly used as the radioactivity absolute measurement method. This is because β-rays emitted from a radiation source are measured with a β counter such as a proportional counter, a plastic scintillator, or a liquid scintillation measuring device, and at the same time, γ-rays emitted from the radiation source are detected by a NaI scintillator or a Ge semiconductor. It is measured using a γ counter such as a vessel, and is measured using a β-ray count rate, a γ-ray count rate, and a β-ray and γ-ray simultaneous count rate (see Non-Patent Document 3). Here, absolute measurement is possible even with α rays, Auger electrons, and characteristic X rays instead of β rays.

  On the other hand, the cryogenic calorimeter uses the fact that when radiation is incident on the radiation absorber, the energy of the radiation is converted into heat, the temperature of the detector rises, and the resistance value of the superconductor changes. A superconducting radiation detector (refer to Patent Documents 1 and 2) called a superconducting transition edge detector for detecting radiation, or a magnetic calorimeter (Non-patent Document 4) or a thermistor that reads a temperature rise as a change in magnetization. There are detectors used. It has been used mainly as a detector for radiation that is a photon such as X-rays and gamma rays (see Patent Documents 4 and 5). Moreover, it is beginning to be used as a detector for particles such as α rays and β rays (see Non-Patent Document 4).

  When detecting radiation with a cryogenic microcalorimeter, radiation is irradiated from the outside of the radiation detection device and the temperature rises due to radiation entering the cryogenic microcalorimeter itself or the absorber, or in the absorber There is a method in which a radiation source is sealed and a temperature rise event due to radiation energy applied to the absorber is utilized. When measuring radioactivity with a cryogenic microcalorimeter, in order to absorb radiation efficiently, two metal plates are used, a radioactive solution is dropped on one metal plate and dried, and then another A sheet of metal plate is covered and is thermally connected to the cryogenic microcalorimeter as an absorber. A high detection efficiency and a low background that cannot be realized by other detectors are realized (see Non-Patent Document 4).

JP 2001-289954 A JP-A-2005-3411

Masao Kunioka, Measurement method of biomass carbon 14 content by accelerator mass spectrometry, RADIOISOTOPES, 58, 767-799, 2009 GRENN F. KNOLL (translated by Ichiro Kimura and Eiji Sakai) Radiation Measurement Handbook 2nd Edition, Nikkan Kogyo Shimbun, 1982 Particle Counting in Radioactivity Measurement, ICRU REPORT 52, 1994 M. Loidl, et al. First measurement of the beta spectrum of 241Pu with a cryogenic detector, Applied Radiation and Isotopes, 68, 1454-1458, 2010

  In measuring the degree of biomass, the liquid scintillation counter can measure only (1) liquid samples, and (2) colored samples such as biofuels have low detection efficiency due to quenching in which light is absorbed by colored substances, and accuracy There are problems such as difficult to measure well. Further, (3) since the abundance of carbon 14 contained in biomass carbon is extremely small, it is only possible to obtain a carbon 14 count rate that is equal to or less than the background count rate, thereby improving measurement accuracy. It is difficult.

  Accelerator mass spectrometry can accurately measure a small amount of carbon 14, but the introduction of an accelerator mass spectrometer requires more than 5 billion yen including facility development. It is difficult to deal with a wide range of measurement samples. Furthermore, in order to perform accelerator mass spectrometry, the sample must be chemically purified to graphite, and the pretreatment is complicated.

  In the thermal neutron fluence measurement by the activation foil method, the detection efficiency is low due to the self-absorption of radiation by the gold foil, and it is difficult to measure the radioactivity accurately and obtain the thermal neutron fluence.

  For 4πβ-γ simultaneous measurement, the detection efficiency of the β counter is limited to about 30% to 90% depending on the nuclide, and conversion electrons and γ rays are also detected by the β counter, and these corrections deteriorate the measurement accuracy. It was.

  On the other hand, the radioactivity measurement by a conventional cryogenic microcalorimeter can be applied only to a radiation source having almost no thickness, and a sample having a thickness on the order of several tens of μm to cm, such as the sample for measuring the degree of biomass. As for, radioactivity could not be measured. Moreover, since it was the measurement using only one cryogenic microcalorimeter, the absolute radioactivity measurement by simultaneous measurement was not able to be performed.

  The present invention has been made to solve the above-mentioned conventional problems, and utilizes the characteristics of the cryogenic microcalorimeter, that is, the high detection efficiency and low background that cannot be realized by other detectors, and the measurement sample. Is processed into a structure suitable for measurement with a cryogenic microcalorimeter, thereby improving the radiation detection efficiency and improving the heat conduction characteristics of the measurement sample. The first problem is to be able to perform on a sample having a thickness of cm order.

  Thereby, in the measurement of the biomass degree, the β-ray derived from carbon 14 is efficiently measured with a very low background, so that the measurement accuracy is comparable to that of the accelerator mass spectrometry and the percentage of the accelerator mass spectrometer is 100%. The second task is to enable measurement of the degree of biomass at an introduction price of 1 or less.

  Furthermore, by measuring the radiation emitted from radioactive materials such as metal foil activated by thermal neutrons with high detection efficiency that cannot be achieved by other radiation detectors, it will be possible to accurately measure thermal neutron fluence. Is the third issue.

  In addition, it is possible to detect alpha rays, beta rays, particles such as Auger electrons, or characteristic X-rays with high detection efficiency that cannot be realized with other detectors, and simultaneously detect γ rays, so that it can be realized with other radioactivity absolute measurement devices. A fourth problem is to enable absolute radioactivity measurement with inaccurate measurement accuracy.

  A sample with radiation generation is layered with a radiation absorbing layer made of a radiation absorbing material or mixed with a radiation absorbing material, so that part or all of the radiation energy emitted from the measuring sample is contained in the measuring sample. Form a structure that can be imparted. Measurements are made by bringing a radiation-generating sample with a radiation-absorbing layer or containing a radiation-absorbing material inside into contact with the radiation absorber of the cryogenic microcalorimeter or the cryogenic microcalorimeter with absorber. When the radionuclide in the sample decays, some or all of the energy of the emitted radiation can be transferred to the cryogenic microcalorimeter as heat with very high probability. Thereby, particles such as α rays, β rays, Auger electrons, conversion electrons, etc. can be detected with very high efficiency. In addition, by adding a gamma ray detector such as a cryogenic microcalorimeter for gamma ray detection, it is possible to perform absolute radioactivity measurement by enabling simultaneous counting.

  Here, the radiation absorbing material is a metal element-containing solution, a non-metal element-containing solution, a metal element-containing paste, a non-metal element-containing paste, a metal element-containing powder, a non-metal element-containing powder, a metal element-containing film, or a non-metal element. It can be either a contained film or a metal foil.

  Further, the radiation absorbing material can be an adhesive.

  Here, the radiation absorbing material comprising any one of a metal element-containing solution, a non-metal element-containing solution, a metal element-containing paste, a non-metal element-containing paste, a metal element-containing powder, and a non-metal element-containing powder is dried or sintered. Can be stratified or solidified.

  Further, the radiation absorbing material may be a metal element or a non-metal element, which can be stratified by vapor deposition.

  Further, the radiation absorbing material may be a film containing a metal element, a film containing a non-metal element, or a metal foil, and may be laminated by sticking or fusing it to the surface of a solid sample.

  The radiation absorbing material may be a film containing a metal element, a film containing a non-metal element, or a metal foil, whereby a container is formed, and a powder sample is placed therein and melted to form a layer. .

  The radiation absorbing material can be a resin material.

  The radiation absorbing material may be silver, a solution containing silver, a paste containing silver, a film containing silver, or a silver foil.

  The radiation absorbing material may be gold, a solution containing gold, a paste containing gold, a film containing gold, or a gold foil.

  The radiation absorbing material may be copper, a solution containing copper, a paste containing copper, a film containing copper, or a copper foil.

  The radiation absorbing material may be nickel, a solution containing nickel, a paste containing nickel, a film containing nickel, or a nickel foil.

  The radiation absorbing material may be carbon, a solution containing carbon, a paste containing carbon, or a film containing carbon.

  The radiation absorbing material can be a material containing polyvinyl alcohol.

  The radiation absorbing material can be a material containing alpha cyanoacrylate.

  The radiation absorbing material can be a conductive ink.

  In the present invention, the cryogenic microcalorimeter can be a superconducting radiation detector.

  The cryogenic microcalorimeter can be a magnetic calorimeter.

  The cryogenic microcalorimeter can be a radiation detector using a thermistor.

  The present invention also provides a biomass degree measuring method characterized by measuring β-rays derived from carbon 14 by any one of the methods described above.

  Moreover, the neutron fluence measurement method characterized by measuring the radiation emitted from the radioactive material activated by the thermal neutron by any one of the methods described above.

  In addition, it provides a method for absolute measurement of radioactivity characterized by detecting particles such as α rays, β rays, Auger electrons, or characteristic X-rays and simultaneously detecting γ rays by any one of the methods described above. is there.

  According to the present invention, it is possible to measure radioactivity with a high detection efficiency that cannot be realized by a conventional method, on a sample having a thickness of several tens of μm to several cm and having a large self-absorption.

  In measuring the degree of biomass, measurement of β-rays derived from carbon 14 with a very low background and high detection efficiency enables measurement accuracy comparable to that of accelerator mass spectrometry. The spread of inexpensive and high-precision measurement devices can ensure that the product is derived from biomass. Thereby, it can contribute to the suppression of global warming and the safety and security of life.

  Also, by measuring the radiation emitted from the radioactive material such as metal foil activated by thermal neutrons with high detection efficiency that cannot be realized by other radiation detectors, the thermal neutron fluence can be accurately measured. This makes it possible to more accurately measure the distribution of leaked neutron fluences in accelerators, which have been introduced for medical use in recent years, and provide a basis for evaluating and reducing the medical exposure of patients and healthcare professionals. It becomes possible to acquire information precisely.

  In addition, it is possible to detect alpha rays, beta rays, particles such as Auger electrons, or characteristic X-rays with high detection efficiency that cannot be realized with other detectors, and simultaneously detect γ rays, so that it can be realized with other radioactivity absolute measurement devices. It becomes possible to perform absolute radioactivity measurement with inaccurate measurement accuracy, so that the basic technology of radioactivity measurement can be advanced and a new radioactivity standard can be established.

(A) a sample provided with a radiation absorbing layer on the surface, (b) a sample mixed with a radiation absorbing material, (c) a sample provided with a radiation absorbing layer inside, (d) a radiation absorbing layer used in the present invention Sectional view showing an example of a sample prepared on the surface and mixed with radiation absorbing material inside The block diagram of embodiment of the radioactivity measuring apparatus provided with the cryogenic microcalorimeter for measuring the radioactivity of the said sample by this invention Block diagram showing a basic configuration example of a superconducting radiation detector as an example of a cryogenic microcalorimeter 1 is a block diagram of an embodiment of an absolute radioactivity measuring apparatus equipped with a cryogenic microcalorimeter for measuring the radioactivity of the sample shown in FIG. 1 according to the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a case where (a) a surface or (c) a radiation absorbing layer 102 is provided, (b) a radiation absorbing material 104 is mixed inside, or (d) a radiation absorbing layer 102 is processed according to the present invention. Is a cross-sectional view of a sample 100 in which a radiation absorbing material 104 is mixed. The sample 100 has radioactivity and generates radiation.

  Here, in order to form the radiation absorbing layer 102 on the sample 100 that generates radiation or to mix the radiation absorbing material 104, the following method can be used.

  In the case of a solid sample such as plastic or graphite, the radiation absorbing layer 102 can be formed by applying an adhesive containing polyvinyl alcohol, alpha cyanoacrylate, or the like over the entire surface of the sample. Alternatively, the radiation absorbing layer 102 can be formed by depositing metal on the surface. Alternatively, the layer can be formed by applying a solution containing metal or a paste containing metal to the entire surface by a technique such as spin coating. A conductive ink containing metal may be applied to the front surface of the sample using an ink jet printer and dried or sintered. Alternatively, a film or foil may be attached to at least one surface of the sample, and may be fused in some cases.

  In the case of a solid sample such as diamond, the radiation absorbing layer 102 can be formed by depositing metal on the surface. Alternatively, the layer can be formed by applying a solution containing metal or a paste containing metal to the entire surface of the sample by a technique such as spin coating. A conductive ink containing metal may be applied to the front surface of the sample using an ink jet printer or the like, and dried or sintered. Alternatively, a film or foil may be attached to at least one surface of the sample, and may be fused in some cases.

In the case of powder samples such as plastic, graphite, diamond, etc., conductive ink or a material in which a metal powder is dispersed in a binder is used as a mixture, mixed into the powder sample, dried, and optionally sintered, A measurement sample mixed with the absorbent 104 can be obtained.
In the case where the powder sample can be melted, it is possible to form a sample in which the radiation absorbing layer 102 is formed by forming a container with a film or foil, putting the powder sample therein, and melting it. Alternatively, the radiation absorbing layer 102 can be provided inside the measurement sample by arranging a film or foil in a layer form in the powder sample and sintering. Further, the radiation absorbing layer 102 as described above may be formed on these samples. At this time, the radiation absorbing material 104 to be mixed with the sample and the radiation absorbing material constituting the radiation absorbing layer 102 should be the same, increasing the amount of the absorbent, or having different characteristics as another. Can do. The same applies to the radiation absorbing layer 102 inside the sample and the radiation absorbing layer 102 on the sample surface.

  When a metal foil such as gold is a sample, the radiation absorbing layer 102 can be formed by depositing metal on the surface. Alternatively, the layer can be formed by applying a solution containing metal or a paste containing metal to the entire surface by a technique such as spin coating. A conductive ink containing metal may be applied to the front surface of the sample using an ink jet printer and dried or sintered. Alternatively, a film or foil may be attached or fused to at least one surface of the metal foil sample.

  In the case of a sample in which a radioactive solution is dropped on a metal plate and dried, the radiation absorbing layer 102 is formed on the sample by applying a material that is a radiation absorber such as resin or conductive ink and seals the sample. Can be stratified. FIG. 2 is a block diagram for measuring radioactivity of a sample having radiation generated by a cryogenic microcalorimeter. Here, reference numeral 110 denotes a cryogenic microcalorimeter or a cryogenic microcalorimeter with an absorber (hereinafter referred to as a cryogenic microcalorimeter), which is radiation, particularly particles such as α rays, β rays, Auger electrons, conversion electrons, etc. Is sensitive to. Sensitivity can be imparted to characteristic X-rays. The cryogenic microcalorimeter 110 is in thermal contact with the radiation absorbing layer 102 of the sample 100 or the sample 100 itself.

  The cryogenic microcalorimeter 110 has an absorber 112 that absorbs radiation energy and converts it into heat, as shown in FIG. 3 as a basic configuration example of a cryogenic microcalorimeter composed of a superconducting radiation detector, A superconducting transition edge sensor (TES) 114 having three states of a superconducting state, a normal conducting state, and an intermediate transition state depending on temperature may be configured so as to be in thermal contact with the heat bath 118. In this case, the energy of the radiation is converted into an electrical signal by utilizing a steep temperature-resistance change in the superconducting transition state. In some cases, the radiation is directly incident on the TES 114, converted into heat inside the TES 114, and converted into an electrical signal. In this method, in the sample 100, the energy of radiation is converted into heat by the absorber 112 and the TES 114 in some cases. In FIG. 2, reference numeral 120 denotes a reading device that drives the cryogenic microcalorimeter 110 and reads a weak signal output from the cryogenic microcalorimeter 110, and outputs a radiation-derived signal to the counting / control device 140. send. Reference numeral 130 denotes a refrigerator that keeps the cryogenic microcalorimeter 110 and the reading device 120 at a low temperature so that they can operate. Reference numeral 140 denotes a counting / control device that controls the cryogenic microcalorimeter 110 and the reading device 120 and counts signals sent from the reading device 120. A computer 150 controls the counting / control device 140 and the refrigerator 130 and acquires a count value from the counting / control device 140. Reference numeral 160 denotes a display that displays data related to control and counting. Reference numeral 170 denotes an input device that inputs data to the computer 150 and controls the computer 150.

  If the radionuclide in the sample undergoes alpha decay, beta decay, or EC decay and γ rays are emitted at the same time, radiation can be achieved by adding a cryogenic microcalorimeter or other gamma ray detector 115 that detects γ rays. An absolute measuring device can be configured. This is shown in FIG.

  FIG. 4 is a block diagram of absolute radioactivity measurement of a sample having radiation generated by a cryogenic microcalorimeter. Here, reference numeral 100 denotes a sample which is processed and provided with the radiation absorbing layer 102 or mixed with the radiation absorbing material 104, has radioactivity, and undergoes α decay, β decay, EC decay and generates γ rays. Reference numeral 110 denotes a cryogenic microcalorimeter, which has sensitivity to radiation, particularly particles such as α rays, β rays, Auger electrons, and conversion electrons. Sensitivity can be imparted to characteristic X-rays. Reference numeral 115 denotes a cryogenic microcalorimeter or other γ-ray detector, which is particularly sensitive to γ-rays. The cryogenic microcalorimeter 110 is in thermal contact with the sample 100. Reference numerals 120 and 125 denote readout devices that drive the cryogenic microcalorimeter 110, the cryogenic microcalorimeter, or other γ-ray detector 115, as well as the cryogenic microcalorimeter 110, the cryogenic microcalorimeter, or other γ. A weak signal output from the line detector 115 is read, and a radiation-derived signal is sent to the counting / control device 140. Reference numeral 130 denotes a refrigerator that keeps the cryogenic microcalorimeter 110, the cryogenic microcalorimeter or other γ-ray detector 115, and the reading devices 120 and 125 at a low temperature. Reference numeral 140 denotes a counting / control device that controls the cryogenic microcalorimeter 110, the cryogenic microcalorimeter or other γ-ray detector 115, and the reading devices 120 and 125, and signals sent from the reading devices 120 and 125. Count. The following is the same as in FIG. 2, and 150 is a computer that controls the counting / control device 140 and the refrigerator 130 and obtains a count value from the counting / control device 140. Reference numeral 160 denotes a display that displays data related to control and counting. Reference numeral 170 denotes an input device that inputs data to the computer 150 and controls the computer 150.

  By obtaining the counting of α rays, β rays, Auger electrons, etc. and the counting of γ rays, and the simultaneous counting of α rays, β rays, Auger electrons, etc., and γ rays with the counting / control device 140, the radiation absorbing layer It is possible to calculate the absolute radioactivity value of the sample 100 provided with 102 or the radiation absorbing material 104 mixed.

  Alpha cyanoacrylate was applied to the entire surface of the bioplastic with a brush to form a radiation absorbing layer. This was brought into thermal contact with the absorber 112 of the cryogenic microcalorimeter 110, and β rays derived from carbon 14 released from the bioplastic were counted. The radioactivity of the bioplastic was obtained from the counted value, and the biomass degree of this bioplastic could be calculated.

  The bioplastic powder was mixed with conductive ink, dried and then sintered. This was brought into thermal contact with the absorber 112 of the cryogenic microcalorimeter 110, and β rays derived from carbon 14 released from the bioplastic were counted. The radioactivity of the bioplastic was obtained from the counted value, and the biomass degree of this bioplastic could be calculated.

  In order to measure the spatial distribution of the fluence of neutrons leaking from the accelerator for radiopharmaceutical production, a gold foil was placed in the accelerator chamber for a certain period. The activated gold foil was collected, a conductive ink containing silver was applied to the entire surface of the gold foil with a spin coater, and sintered in an electric furnace to form the radiation absorbing layer 102. This was brought into thermal contact with the absorber 112 of the cryogenic microcalorimeter 110, and β rays emitted from the radioactive gold isotope in the gold foil were counted. From this, the activation amount of the gold foil was calculated, and the neutron fluence could be calculated based on the activation amount.

  In order to obtain the absolute value of radioactivity of the cerium-139 radioactive solution, a part of the radioactive solution was dropped on a gold foil and dried, and a resin ink was applied thereon with an inkjet printer. This is brought into thermal contact with the absorber 112 of the cryogenic microcalorimeter 110, the Auger electrons and X-rays are detected by the contacting cryogenic microcalorimeter 110, and the cryogenic microcalorimeter that is not in contact is detected. Alternatively, γ rays were detected by another γ ray detector 115, and Auger electrons, X rays and γ rays were counted simultaneously. From the obtained count value, the radioactivity absolute value of the cerium-139 radioactive solution could be calculated.

  In the above embodiment, a brush, a spin coater, an ink jet printer, and an electric furnace are used to form the radiation absorbing layer 102 on the sample. However, other means may be used. As the sample, bioplastic, gold foil, and cerium 139 were used. However, the sample that generates radiation and the type of radiation are not limited to the above embodiment. The cryogenic microcalorimeter is not limited to a superconducting radiation detector.

  It can be used to measure the degree of biomass of a biomass product, to measure the spatial distribution of leaked neutron fluences at an accelerator facility, and to assign a radioactivity value by absolute radioactivity measurement to a radioactive solution.

DESCRIPTION OF SYMBOLS 100 ... Radiation generation sample which provided the radiation absorption layer or mixed the radiation absorption material 110 ... Cryogenic micro calorimeter 115 ... Cryogenic micro calorimeter or other gamma ray detector 120, 125 ... Reading apparatus 130 ... Refrigerator 140 ... Counting / controlling device 150 ... Calculator 160 ... Display 170 ... Input device

Claims (24)

A radiation absorbing layer is added to the radiation generating sample using a stratified material made of a radiation absorbing material,
Thermally contacting the radiation generating sample with the absorber of the cryogenic microcalorimeter or the cryogenic microcalorimeter with an absorber improves the detection efficiency of the radiation and improves the heat conduction characteristics of the sample. Radioactivity measurement method using a cryogenic microcalorimeter. A radiation absorbing material is mixed with the radiation generating sample,
Thermally contacting the radiation generating sample with the absorber of the cryogenic microcalorimeter or the cryogenic microcalorimeter with an absorber improves the detection efficiency of the radiation and improves the heat conduction characteristics of the sample. Radioactivity measurement method using a cryogenic microcalorimeter.   Radiation measurement using a cryogenic microcalorimeter according to claim 2, wherein a radiation absorbing layer is added to the radiation generating sample mixed with the radiation absorbing material using a layered material made of a radiation absorbing material. Method.   The radiation absorbing material is a metal element-containing solution, a non-metal element-containing solution, a metal element-containing paste, a non-metal element-containing paste, a metal element-containing powder, a non-metal element-containing powder, a metal element-containing film, a non-metal element-containing film, The radioactivity measurement method using the cryogenic microcalorimeter according to any one of claims 1 to 3, wherein the radioactivity is any one of metal foils.   The radioactivity measurement method using a cryogenic microcalorimeter according to any one of claims 1 to 3, wherein the radiation absorbing material is an adhesive.   The radiation absorbing material comprising any one of a metal element-containing solution, a non-metal element-containing solution, a metal element-containing paste, a non-metal element-containing paste, a metal element-containing powder, and a non-metal element-containing powder is stratified by drying or sintering. Alternatively, the radioactivity measurement method using the cryogenic microcalorimeter according to claim 4, wherein the radioactivity is solidified.   The radioactivity measurement method using a cryogenic microcalorimeter according to claim 1 or 3, wherein the radiation absorbing material is a metallic element or a nonmetallic element, and is formed by vapor deposition.   2. The radiation absorbing material is a film containing a metal element, a film containing a non-metal element, or a metal foil, and is laminated by pasting or fusing it to the surface of a solid sample. Or the radioactivity measuring method using the cryogenic microcalorimeter of 3.   The radiation absorbing material is a film containing a metal element, a film containing a non-metal element, or a metal foil, whereby a container is formed, and a powder sample is put therein and melted to form a layer. A radioactivity measurement method using the cryogenic microcalorimeter according to claim 1 or 3.   The radioactivity measurement method using a cryogenic microcalorimeter according to any one of claims 1 to 3, wherein the radiation absorbing material is a resin material.   The cryogenic microcalorimeter according to any one of claims 1 to 3, wherein the radiation absorbing material is silver, a solution containing silver, a paste containing silver, a film containing silver, or a silver foil. Radioactivity measurement method.   The cryogenic microcalorimeter according to any one of claims 1 to 3, wherein the radiation absorbing material is gold or a solution containing gold, a paste containing gold, a film containing gold, or a gold foil. Radioactivity measurement method.   The cryogenic microcalorimeter according to any one of claims 1 to 3, wherein the radiation absorbing material is copper, a solution containing copper, a paste containing copper, a film containing copper, or a copper foil. Radioactivity measurement method.   The cryogenic microcalorimeter according to any one of claims 1 to 3, wherein the radiation absorbing material is nickel, a solution containing nickel, a paste containing nickel, a film containing nickel, or a nickel foil. Radioactivity measurement method.   4. The radioactivity using a cryogenic microcalorimeter according to claim 1, wherein the radiation absorbing material is carbon, a solution containing carbon, a paste containing carbon, or a film containing carbon. Measuring method.   The radioactivity measurement method using the cryogenic microcalorimeter according to claim 1, wherein the radiation absorbing material is a material containing polyvinyl alcohol.   The radioactivity measurement method using a cryogenic microcalorimeter according to claim 1, wherein the radiation absorbing material is a material containing alpha cyanoacrylate.   The radioactivity measurement method using a cryogenic microcalorimeter according to claim 1, wherein the radiation absorbing material is a conductive ink.   The radioactivity measurement method using the cryogenic microcalorimeter according to any one of claims 1 to 18, wherein the cryogenic microcalorimeter is a superconducting radiation detector.   The radioactivity measurement method using the cryogenic microcalorimeter according to any one of claims 1 to 18, wherein the cryogenic microcalorimeter is a magnetic calorimeter.   The radioactivity measurement method using a cryogenic microcalorimeter according to any one of claims 1 to 18, wherein the cryogenic microcalorimeter is a radiation detector using a thermistor.   The biomass degree measuring method characterized by measuring the beta ray derived from carbon-14 by the method in any one of Claims 1 thru | or 21.   A neutron fluence measurement method, comprising: measuring radiation emitted from a radioactive material activated by thermal neutrons by the method according to any one of claims 1 to 21.   An absolute radioactivity measurement method comprising detecting particles such as α rays and β rays and simultaneously detecting γ rays by the method according to any one of claims 1 to 21.

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