JP2018179907A - Estimation method of density uneven distribution state and evaluation method of radioactivity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for estimating density unevenly-distributed state of a measurement object stored in a container.SOLUTION: The estimation method, using a detector for detecting a radiant ray, for estimating a density unevenly-distributed state Dt of a measuring object T stored in a container, estimates the density unevenly-distributed state Dt of the measuring object T inside the container on the basis of a first database DB1 and a response result Rt. The first database DB1 includes: disposing an external radiation source C1 outside the container set up in a prescribed density unevenly-distributed state Dn; and, using the external radiation source C1, representing a relationship between a density unevenly-distributed state Dn of the container and detection efficiency En of the detector, obtained by measuring or analyzing the radiation exited from the external radiation source C1 and transmitting through the container. The response result RT includes: disposing an external radiation source C1 outside the container storing a measuring object T; and detecting the radiation exited from the external radiation source C1 and transmitting through the container storing the measuring object T.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method of estimating a density uneven distribution state of an object to be measured and a method of evaluating the radioactivity of the object to be measured.

  Currently, various types of waste are generated along with the decommissioning of nuclear reactor facilities and nuclear fuel handling facilities and repair of facilities. Of these wastes, those possibly contaminated with nuclear fuel are treated as “radioactive waste”. The "radioactive waste" is stored in a waste warehouse or the like at each factory or business site until it is disposed of for disposal, and final disposal such as burying is finally performed.

  However, "radioactive waste" includes substances that are not actually contaminated by nuclear fuel and substances that have extremely low radioactive concentrations of radioactive substances and can ignore human effects. By carrying out the clearance for such wastes, they can be disposed of as general waste, so that not only the amount of radioactive waste is reduced but also wastes after the clearance is renewed Can be used as a resource.

  Therefore, in the case where waste generated at a nuclear reactor facility or a nuclear fuel handling facility is subjected to clearance or disposal, it is necessary to measure the radioactivity of the waste. Methods of measuring the radioactivity of waste include, for example, methods of measuring alpha rays or gamma rays, but since gamma rays have such a high permeation ability that they can only be shielded by a lead plate of about 10 cm in thickness, the waste Can be packed into a container in a certain amount and gamma rays can be measured from the outside of the container. Therefore, the method of measuring gamma rays can measure the radioactivity of the waste more efficiently than the method of measuring alpha rays.

  In Non-Patent Document 1, using a 200 L drum as a container for measuring gamma rays and packing a large amount of waste into this, an example of measuring gamma rays of waste from the outside of the drum with a dedicated passive gamma measuring instrument Is disclosed. In this Non-Patent Document 1, when metal waste is packed in a drum to determine the clearance, it is considered reasonable to perform the measurement unit handled in one measurement with the drum as about 100 kg. There is.

  Furthermore, when calculating the activity concentration of the target nuclide from the measurement result of the gamma ray, a calibration source having the same material and density as the target for which the clearance is to be determined, and whose activity amount has been verified, is disposed in the drum. A calibration test is performed using the product (simulated clearance target), and the radioactivity concentration is calculated from the result of this calibration test, or the radioactivity concentration is evaluated by simulation using a Monte Carlo method or the like. As described above, when the material and the density of the measurement object to be packed in the drum are the same and the contamination distribution and the shape are similar to each other, the measurement result of the gamma ray uniformly packs the target nuclide The amount of radioactivity of can be calculated accurately.

Judging method of clearance in uranium handling facility: 2010, Japan Atomic Energy Society Standard Committee, February 20, 2012

By the way, if 100 kg of iron waste is packed in a 200 L drum (container) for bulk measurement, the specific gravity of iron is 7.8 g / cm ³ , and the volume is about 13000 cm ³ (13 L). Iron will be packed into 200 L drums.

  When packing waste into a container, the density of the lower side increases due to the effect of gravity, or the waste with a small volume gathers downward through the gap of the waste with a large volume, etc. However, it is not always in a state of being uniformly packed in the container. In other words, waste may be unevenly packed in containers (at uneven density).

  At this time, if there is a locally high density waste area in the container, the radiation shielding effect of the waste itself in that area is greater than that in the other areas, so the degree of contamination in that area is It is possible to underestimate the radiation dose (radioactivity, uranium content) to be expressed. For example, the response result of detecting low radiation source intensity at low density (response value) may be the same as the response result of detecting high radiation source intensity at high density (see FIG. 5). It is important to estimate in advance the uneven density distribution state (density distribution) in the container. In the measurement object which is a waste, the uneven distribution of the radiation source and the uneven distribution of the waste density occur respectively. If the information about the uneven distribution of density is selectively extracted and the amount of radioactivity can be estimated based on this information, the accuracy is improved more than the measurement accuracy.

Therefore, the present invention has been made in view of the above problems, and in evaluating the amount of radioactivity of the object to be measured stored in the container prior to the final purpose such as clearance and burying disposal of waste, The purpose is to provide an estimation method for estimating the density uneven distribution state.
Another object of the present invention is to provide an evaluation method for evaluating the radioactivity of an object to be measured stored in a container.

(1) One aspect according to the present invention is a method of estimating a density uneven distribution state of an object to be measured stored in a container using a detector for detecting radiation, which is set to a predetermined density uneven distribution state An external radiation source is disposed outside the container, and the uneven concentration state of the container and the first detection of the detector determined by measuring or analyzing the radiation emitted from the external radiation source and having passed through the container The external radiation source is disposed outside the first database using the external radiation source showing the relationship with efficiency, and the container containing the object to be measured, emitted from the external radiation source, the object to be measured, The concentration uneven distribution state of the object to be measured in the inside of the container is estimated based on the response result of detection by the detector of the radiation which has passed through the container containing the above.
(2) Another aspect according to the present invention is a method of evaluating the radioactivity of a measurement object stored in a container using a detector for detecting radiation, which is the estimation according to the above (1) An internal radiation source is housed inside the container set to the density uneven distribution state of the measurement object estimated by the method and the predetermined density uneven distribution state, the radiation emitted from the internal radiation source and passing through the container And a second database using the internal radiation source indicating the relationship between the uneven density state of the container and the second detection efficiency of the detector obtained by measuring or analyzing the measurement, and the measurement stored in the container The activity of the object to be measured is evaluated on the basis of a response result of detection of radiation emitted from the object and having passed through the container by the detector.
(3) In the aspect of (2), the third detection efficiency of the detector in the density uneven distribution state of the measurement object is determined from the density uneven distribution state of the measurement object and the second database, The activity of the object to be measured may be evaluated based on (3) detection efficiency and the response result.
(4) In the above aspect (2) or (3), the measurement object may contain at least uranium as a radiation source.

According to the present invention, it is possible to provide an estimation method for estimating the uneven density distribution state of the measurement object stored in the container.
Further, according to the present invention, it is possible to provide an evaluation method for evaluating the radioactivity of the measurement object stored in the container.

It is a schematic sectional drawing which shows the gamma ray measuring apparatus used for the estimation method of the density uneven distribution state which concerns on embodiment of this invention, and the evaluation method of radioactivity. It is a flowchart which shows the estimation method of the density uneven distribution state which concerns on embodiment of this invention, and the evaluation method of radioactivity. It is explanatory drawing which shows arrangement | positioning of (a) external radiation source, (b) internal radiation source with respect to a gamma ray detector. It is explanatory drawing which shows the inside of the storage container for gamma ray measurement of (a) uniform density state, (b) hypothetical density uneven distribution state, and (c) actual density uneven distribution state. It is a graph which shows the relationship between radiation source intensity, density, and a response result.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The same components are denoted by the same reference numerals throughout the description of the embodiment.

FIG. 1 is a schematic cross-sectional view showing a gamma ray measurement apparatus 100 used in the estimation method of the uneven density state Dt and the evaluation method of the radioactivity At according to the embodiment of the present invention.
As shown in FIG. 1, the gamma ray measuring apparatus 100 includes a housing 2 surrounding the gamma ray storage container 10, a gamma ray detector 3 for detecting gamma rays, and a rotary table 4 on which the gamma ray storage container 10 is placed. And.

  The housing 2 shields radiation coming from the outside of the gamma ray measurement apparatus 100, and is provided so as to surround the gamma ray measurement storage container 10. That is, the housing 2 eliminates the influence of background radiation so that the gamma ray detector 3 can efficiently detect gamma rays emitted from the measurement object T.

  Moreover, although the housing | casing 2 is carrying out the square box shape in which the opening-closing door was formed in one surfaces, such as a front, if it can enclose the storage container 10 for gamma ray measurement, it will not be limited in particular, May be The top surface, the bottom surface, and the side wall 2a of the housing 2 are formed to a desired thickness using a material that can shield radiation, such as tungsten, lead, and iron.

  The gamma ray detector 3 measures gamma rays emitted from the measurement object T stored in the gamma ray storage container 10, and the sensing unit 3a for detecting gamma rays is located inside the housing 2. A Ge semiconductor detector or a NaI scintillation detector can be employed as the gamma ray detector 3. However, a Ge semiconductor detector is preferable in that it has high resolution and can perform low concentration quantitative measurement for each nuclide. In addition, when employ | adopting to a Ge semiconductor detector, it is good to install the tank which stores liquid nitrogen in the outer side of the housing | casing 2, etc. so that the gamma ray detector 3 can be cooled at the time of measurement.

  The three gamma ray detectors 3 are arranged in the vertical direction of one side wall 2 a of the casing 2, and the sensitive part 3 a of the gamma ray detector 3 is exposed inside the casing 2, It is provided penetrating the side wall 2 a of the housing 2. However, the size and the number of the gamma ray detectors 3 are not limited to this.

  The rotary table 4 mounts the gamma ray storage container 10 and rotates the gamma ray storage container 10 at a predetermined angular velocity (rotational speed) when the gamma ray detector 3 measures gamma rays. By measuring gamma rays while rotating the gamma ray storage container 10, it is possible to make the measurement object T in the circumferential direction of the gamma ray storage container 10 uniform and to make the radiation source uniform. Thereby, the radioactivity concentration can be calculated more accurately from the measured gamma rays. Then, without installing the plurality of gamma ray detectors 3 in the X-axis direction and the Y-axis direction, only by installing the three gamma ray detectors 3 in the vertical direction, measurement objects in the circumferential direction of the gamma ray storage container 10 The measurement which assumed equalization | homogenization of T and equalization | homogenization of a radiation source is possible.

  Here, to describe the measurement object T measured by the gamma ray measurement apparatus 100, the measurement object T may be one that may be contaminated with radioactive material, usually a solid. As this measurement object T, for example, operation, repair, remodeling in nuclear fuel handling facilities such as nuclear power conversion facilities, nuclear fuel conversion facilities, nuclear fuel enrichment facilities and nuclear fuel processing facilities such as nuclear power reactors, experimental reactors and research reactors. And waste materials such as equipment and buildings that are generated as a result of decommissioning.

  The measurement object T may have a high radioactivity concentration treated as a radioactive substance, or has a radioactivity concentration equal to or less than the clearance level, which is a radioactivity concentration removed from handling as a radioactive substance. May be

  Examples of the material of the measurement object T include metals such as carbon steel, stainless steel, copper, and aluminum, but are not particularly limited, and concrete, plastic, or the like may be used. Further, among these materials, the higher the density of the material such as metal, for example, the smaller the volume stored in the gamma ray measurement storage container 10, so it becomes more difficult to pack uniformly so as not to collapse.

  The shape of the measurement object T may be a plate-like object, but is not particularly limited, and may be a simple shape such as a rod, an angular shape, or a spherical shape, or a complex shape having protrusions and curved surfaces. The large measurement object T that can not be stored in the gamma ray measurement storage container 10 may be cut into equal sizes and shapes by cutting and shredding as necessary.

Below, the storage container 10 for gamma ray measurement is demonstrated.
As shown in FIG. 1, the container body of the gamma ray measurement storage container 10 stores a plurality of measurement objects T in an internal space, and has a strength capable of storing, for example, a total of about 100 kg of measurement objects T. Have. The container body is, for example, a cylinder with a bottom and a cylindrical box-shaped container with a disc-like lid closed at the top opening, and a 200 L drum can be adopted. The drum can is inexpensive and has desired strength, and the conveyance jig is full, and it can be rolled and moved in an empty state and has good operability and conveyance.

  Here, an example of an evaluation method for evaluating (measuring) gamma rays emitted from the measurement object T using the gamma ray measuring apparatus 100 will be described. FIG. 2 is a flow chart showing the estimation method of the uneven density state Dt and the evaluation method of the radioactivity At according to the embodiment of the present invention. FIG. 3 is an explanatory view showing the arrangement of (a) an external radiation source C1 and (b) an internal radiation source C2 with respect to the gamma ray detector 3. As shown in FIG. FIG. 4 is an explanatory view showing (a) uniform density state, (b) hypothetical uneven density state Dn (dn), and (c) actual uneven density state Dt inside the gamma ray storage container 10. .

  First of all, the preparation work of a plurality of measurement objects T is large enough to be able to store wastes possibly contaminated with radioactive materials in the nuclear reactor facility or nuclear fuel handling facility in the gamma ray measurement storage container 10 The product is cut into pieces and sorted according to types such as materials and shapes as necessary, and a total of about 100 kg to several hundred kg of measurement units are performed.

  Next, a plurality of measurement objects T are packed into the gamma ray storage container 10 so as to have a uniform density as a whole, and the gaps between the measurement objects T are filled with sand or the like to be measured. Step S1 of measuring T is started.

In step S1, as shown in FIG. 3A, the external radiation source C1 is disposed at a predetermined position outside the gamma ray storage container 10. As shown in FIG. The gamma ray measurement storage container 10 and the external radiation source C1 are surrounded by a housing 2 not shown. Further, when the measurement target T comprises uranium, but an external radiation source C1 may is suitable cobalt -60 (60 ^Co), as long as the radioactive material in the measurement target T can be separated detection (measurement), Other radioactive elements may be used.

  In step S2, radiation emitted from the external radiation source C1 and having passed through the gamma ray storage container 10 is detected by the gamma ray detector 3 to obtain a response result Rt. At this time, the response result Rt under a plurality of conditions may be obtained by changing the position in the vertical direction or horizontal direction of the external radiation source C1 or arranging a plurality thereof.

  In step S3, using the external radiation source C1 showing the relationship between the response result Rt obtained in step S2, the density uneven distribution state Dn of the gamma ray storage container 10, and the first detection efficiency En of the gamma ray detector 3. The density uneven distribution state Dt of the measurement object T in the inside of the gamma ray storage container 10 is estimated based on (1) the database DB1.

  Here, the first database DB1 will be described. In the preparation of the first database DB1, the inside of the gamma ray storage container 10 is filled with a known density uneven distribution state Dn (where n is In each density uneven distribution state Dn, the external radiation source C1 is disposed at a predetermined position outside the gamma ray storage container 10 in each density uneven distribution state Dn, and in the same manner as step S2. The radiation emitted from the external radiation source C1 and having passed through the gamma ray storage container 10 is detected by the gamma ray detector 3 to obtain each response result Rn. At this time, as in step S2, response results Rn under a plurality of conditions may be obtained. The response result Rn can be obtained by actual measurement or numerical analysis.

  Then, from the position of the external radiation source C1 having known radioactivity Ao, the separation distance (and direction) between the external radiation source C1 and the gamma ray detector 3, and the response result Rn of the gamma ray detector 3, each density is unevenly distributed The first detection efficiency En in the state Dn is evaluated to create a first database DB1.

  In step S4, internal radiation indicating the relationship between the density uneven distribution state Dt of the measurement object T obtained in step S3, the density uneven distribution state dn of the gamma ray storage container 10, and the second detection efficiency Fn of the gamma ray detector 3. The third detection efficiency Gt of the gamma ray detector 3 in the density uneven distribution state Dt of the measuring object T is determined from the second database DB2 using the source C2.

  Here, the second database DB2 will be described. In the preparation of the second database DB2, the inside of the gamma ray storage container 10 is made into a known density uneven distribution state dn using a predetermined filling material To, and each density uneven distribution state In dn, the internal radiation source C2 is disposed at a predetermined position inside the gamma ray storage container 10 (see FIG. 3 (b)), and emitted from the internal radiation source C2 and passes through the gamma ray storage container 10 The detected radiation is detected by the gamma ray detector 3 to obtain each response result rn. At this time, as in step S2, response results rn under a plurality of conditions may be obtained. The uneven density state Dn in the first database DB1 and the uneven density state dn in the second database DB2 are preferably equal to each other, but may not be equal. Moreover, this response result rn can be performed by actual measurement or numerical analysis.

  Then, each density is unevenly distributed from the position of the internal radiation source C2 having known radioactivity Ai, the separation distance (and direction) between the internal radiation source C2 and the gamma ray detector 3, and the response result rn of the gamma ray detector 3. The second detection efficiency Fn in the state dn is evaluated to create a second database DB2. The internal radiation source C2 is preferably the same nuclide as the radionuclide possessed by the measurement object T. For example, when the measurement object T is contaminated with uranium, uranium may be used as the internal radiation source C2.

  In step S5, the external radiation source C1 arranged in step S1 is removed, and the external radiation source C1 is not present outside the gamma ray storage container 10.

  In step S6, radiation emitted from the measurement object T and having passed through the gamma ray storage container 10 is detected by the gamma ray detector 3 to obtain a response result rt.

  In step S7, the radioactivity At of the measuring object T is evaluated based on the response result rt obtained in step S6 and the third detection efficiency Gt.

  In this way, the evaluation of the activity At of the measurement object T in step S8 is completed. In addition, at the time of creation of 1st database DB1 and 2nd database DB2 during step S2 and step S6, and the detection of the gamma ray by gamma ray detector 3, the rotation table 4 which mounted the storage container 10 for gamma ray measurement is specified. It may be performed by rotating at an angular velocity. By rotating the storage container 10 for gamma ray measurement and performing estimation or evaluation, uniformity is achieved in the circumferential direction, so the density uneven distribution state Dt in the vertical direction (axial direction) of the storage container 10 for gamma ray measurement or radioactivity At Only can be extracted.

  As described above, in the estimation method of the density uneven distribution state Dt according to the embodiment of the present invention, the density uneven distribution of the measurement object T stored in the gamma ray storage container 10 using the gamma ray detector 3 for detecting radiation An external radiation source C1 is disposed outside the storage container 10 for gamma ray measurement set to a predetermined density uneven distribution state Dn, which is an estimation method of the state Dt, and emitted from the external radiation source C1. Using the external radiation source C1 showing the relationship between the density uneven distribution state Dn of the storage container for gamma ray measurement 10 and the first detection efficiency En of the gamma ray detector 3 determined by measuring or analyzing the radiation that has passed through An external radiation source C1 is disposed outside the database DB1 and the gamma ray storage container 10 containing the measurement object T, and emitted from the external radiation source C1, and the measurement pairs The density uneven distribution state Dt of the measuring object T inside the gamma ray measuring storage container 10 based on the response result Rt in which the radiation that has passed through the gamma ray storage container 10 storing the object T is detected by the gamma ray detector 3 Estimate. Thus, the uneven density distribution state Dt of the measurement object T inside the gamma ray measurement storage container 10 can be estimated easily and appropriately. Further, this estimation method can be referred to as a transmission response method because the density uneven distribution state Dt is estimated by transmitting the radiation of the external radiation source C1 to the measurement object T.

  The evaluation method of radioactivity At according to another embodiment of the present invention is an evaluation method of radioactivity At of the measurement object T stored in the storage container 10 for gamma ray measurement using the gamma ray detector 3 for detecting radiation. The internal radiation source C2 is accommodated inside the storage container 10 for gamma ray measurement set to the density uneven distribution state Dt of the measurement object T estimated by the above estimation method and the predetermined density uneven distribution state dn, and the inside The density uneven distribution state dn of the storage container 10 for gamma ray measurement and the second detection efficiency Fn of the gamma ray detector 3 determined by measuring or analyzing the radiation emitted from the radiation source C2 and passed through the storage container 10 for gamma ray measurement The second database DB2 using the internal radiation source C2 showing the relationship between the two, and the measurement object T stored in the gamma ray storage container 10 for gamma ray storage The radiation which has passed through the 10 and response result rt detected by a gamma ray detector 3, based on, is to evaluate the radioactivity At the measurement target T. As a result, firstly the density uneven distribution state Dt of the measurement object T inside the gamma ray measurement storage container 10 is estimated, and then the activity At of the measurement object T according to the density uneven distribution state Dt is evaluated. You can get a value.

  In the embodiment, the third detection efficiency Gt of the gamma ray detector 3 in the density uneven distribution state Dt of the measurement object T is determined from the density uneven distribution state Dt of the measurement object T and the second database DB2, and the third detection efficiency Gt The radioactivity At of the measurement object T is evaluated based on the response result rt. As a result, it is possible to estimate the density uneven distribution state Dt of the measurement object T inside the gamma ray measurement storage container 10 and accurately evaluate the activity At of the measurement object T according to the density uneven distribution state Dt.

  In the embodiment, the measurement object T contains at least uranium as a radiation source. As a result, it is possible to more accurately and efficiently measure the radioactivity of the waste generated due to the decommissioning of the nuclear reactor facilities and nuclear fuel handling facilities and the repair of the facilities.

(Modified form)
In the above embodiment, the gamma ray storage container 10 has one internal space, but may be provided with sorting means for vertically dividing the internal space into a plurality of regions. At this time, the dividing means may be divided into a state in which the plurality of regions communicate with each other or a state in which the plurality of regions do not communicate with each other. The number of regions is preferably equal to or greater than the number of gamma ray detectors 3.

  Further, in step S5 of the above embodiment, the response result rt may be subtracted from the response result Rt to remove the influence of the radioactive substance in the measurement object T to evaluate the radioactivity At.

  Further, although the gamma ray emitted from the measurement object T is detected by the gamma ray detector 3 in the above embodiment, other radiation may be detected.

  Furthermore, in the above embodiment, the third detection efficiency Gt according to the density uneven distribution state Dt of the measurement object T is obtained for each measurement, and the radioactivity At is evaluated using the obtained third detection efficiency Gt. However, the evaluation of radioactivity At is not necessarily limited to this method. For example, in the case where it is confirmed that the radioactivity At of the measurement object T is less than or equal to a certain reference value, it is not necessary to obtain the third detection efficiency Gt for each measurement. In such a case, as a result of estimating the density uneven distribution state Dt of the measurement object T, if the density uneven distribution state Dt falls within a predetermined range of the density uneven distribution state Du, the density uneven distribution state Du is radiated It is also conceivable to evaluate the activity At of the measurement object T on the safe side based on the influence on performance evaluation and the response result rt of the measurement object T.

  Although the preferred embodiments of the present invention have been described above in detail, the present invention is not limited to the above-described embodiments, and various modifications may be made within the scope of the subject matter of the present invention described in the claims. Changes are possible.

Reference Signs List 2 case, 2a side wall 3 gamma ray detector, 3a sensing unit 4 rotating table 10 storage container 100 gamma ray measuring device DB1 first database, DB2 second database T measurement object, To filling material C1 external radiation source, C2 internal radiation Source At, Ao, Ai Radioactivity Dt, Dn, dn, Du Density uneven distribution state Rt, Rn, rn, rt Response result En 1st detection efficiency, Fn 2nd detection efficiency, Gt 3rd detection efficiency

Claims (4)

What is claimed is: 1. A method of estimating a density uneven distribution state of a measurement object stored in a container using a detector for detecting radiation, the method comprising:
An external radiation source is disposed outside the container set to a predetermined density uneven distribution state, and the density uneven distribution of the container determined by measuring or analyzing the radiation emitted from the external radiation source and having passed through the container A first database using the external radiation source indicating a relationship between a state and a first detection efficiency of the detector;
The external radiation source is disposed outside the container containing the object to be measured, and the detector detects the radiation emitted from the external radiation source and having passed through the container containing the object to be measured. And estimating the uneven distribution state of the object to be measured in the interior of the container on the basis of and. A method for evaluating the radioactivity of a measurement object stored in a container using a detector that detects radiation, comprising:
A density uneven distribution state of the measurement object estimated by the estimation method according to claim 1;
An internal radiation source is housed inside the container set to a predetermined density uneven distribution state, and the density uneven distribution state of the container determined by measuring or analyzing the radiation emitted from the internal radiation source and having passed through the container A second database using the internal radiation source indicating a relationship between the second radiation efficiency and the second detection efficiency of the detector;
The activity of the object to be measured is evaluated on the basis of the result of detection by the detector of the radiation emitted from the object to be measured stored in the container and having passed through the container. Evaluation method of radioactivity. The third detection efficiency of the detector in the density uneven distribution state of the measurement object is determined from the density uneven distribution state of the measurement object and the second database,
The radioactivity of the said measurement object is evaluated based on the said 3rd detection efficiency and the said response result, The evaluation method of the radioactivity of Claim 2 characterized by the above-mentioned. The method for evaluating radioactivity according to claim 2 or 3, wherein the measurement object contains at least uranium as a radiation source.