JPH01287493A - Waste water monitor - Google Patents

Abstract

PURPOSE:To automatically determine a radioactivity value by measuring the electrical pulses generated after radiations are detected by a scintillator in the plural measurement regions defined by the upper and lower limits of a pulse height analyzer. CONSTITUTION:A waste liquid sample transported by a pump from a waste liquid storage tank and the liquid scintillator sent from a storage vessel are automatically injected into a vessel 1 existing in a measurement position. Many photons are generated by radiation energy in a prepd. sample 2 which is the mixture composed of the waste liquid sample and the liquid scintillator. The photons are made incident to two pieces of photoelectron multipliers 3 and are converted to the electrical pulses. The pulses enter a simultaneous counter circuit 4 where noises are removed from the pulses. Only the pulses which are signals are sent to the ensuing stage. On the other hand, the pulses increases in pulse height by a SAM circuit 5 are passed through a gate 6 and are introduced into an automatic efficiency tracer device consisting of an AD converter 7 and a memory mechanism 8, by which the radioactivity concn. is automatically determined.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to radiation monitoring.

[Prior art]

It is regulated that used radioactive waste fluid generated in facilities handling radioactive materials must be stored in a storage tank and discharged into general sewage after confirming that the radioactivity of the waste fluid is below the permissible concentration. In the case of wastewater, measurements are usually carried out using wastewater monitors, but conventional wastewater monitors can only obtain measurement results based on counts of radioactive waste liquid.

[Problem that the invention seeks to solve]

A major drawback of conventional wastewater monitors is that counting efficiency cannot be determined, so measurement results can only be obtained in terms of count rate (cpm), and required radioactivity values cannot be obtained.

When draining water, it is necessary to determine the radioactivity concentration in the waste liquid, but conventional wastewater monitors are unable to satisfy this requirement, creating a problem. The reason such defective wastewater monitors have been in use for many years is that no solution to this shortcoming has been found.

[Failure to solve the problem]

Automatic Efficiency Tracer Technology for Wastewater Monitoring (Reference: Patent Application No. 59-028678: 62-254555: Kako Shikawa, et al.: Int.
J, Appl, Radia.

IaotoMol, 35, 463 (1984))
By applying , the value of the total radioactivity of the woodcutter's radioactive substances present in the measurement sample can be easily obtained. By introducing automatic efficiency tracer technology into the wastewater monitor, radioactivity 11[ of the waste liquid was automatically determined, and one problem was solved.

〔Example〕

The waste liquid sample transported by a pump from the waste liquid storage tank and the liquid scintillator sent from the storage container are placed in the container l at the measurement position.
automatically injected into the In the prepared sample 2, which is a mixture of a waste liquid sample and a liquid scintillator, a large number of photons are generated by radiation energy, and each photon enters two photomultiplier tubes 3 and is converted into an electrical pulse. The signal enters the Noxys 11 coincidence circuit 4, where noise is removed and only the pulse signal is sent to the next stage. On the other hand
The increased pulse wave height (by the V system circuit 5) is transmitted to the automatic efficiency tracer device through the Ruska T gate 6.

The automatic efficiency tracer device consists of a Nockles wave height analyzer and a data processing device 9, but the Nockles wave height analyzer further consists of an AD converter 7 and a memory mechanism 8. The pulse wave height is converted into a clock pulse number, which is a digital quantity. In other words, the clock pulse for AD conversion is sent to the next stage memory mechanism 8.
at a channel number equal to the number of clock pulses, and the radiation spectrum shown in FIG. 2 is formed.

FIG. 2 shows the spectrum 10 of the standard sample and the spectrum 11'Y of the measurement sample (waste liquid sample) whose radioactivity is to be determined. Here, the lower limit of the measurement area is defined as tLII-Li, and the upper limit is defined as Lu. Each measurement area YL1~Lu, L
, ~Lu, --.-Li-Lu. In these measurement regions, the counting efficiency of the standard sample is expressed as E, , and
E, ,...Ki, these values are obtained simultaneously, and the net counting rate t of the measurement sample after subtracting the background is n, e''*...ni, respectively.

These values can also be obtained at the same time. The following quadratic regression equation is determined from the relationship between E and n obtained.

n = &E'' + bE 10e α) Here, a, b, and c are constants.

In the formula, the counting rate at 100% counting efficiency is:
In other words, it means the radioactivity of the measurement sample. This is because if a counting efficiency value of 100- is obtained for the standard sample,
Under the same measurement conditions, the measurement sample also has a low counting efficiency.
% value, that is, the radioactivity value will be determined.

The 70-chart of the software of the data processing device built into this drainage monitor is shown in Figure 3.
The explanation of each step is as follows.

Sl: L, NLu, L, 〜Lu・-・Li〜
Define the LuLu chisel measurement area. In addition, the number of decays dpm of the standard sample is 4 people.

S: Measure the standard sample for 1 minute.

S: Calculate the counting efficiency E, , E, . . . Ei from the ratio of the standard sample's counting rate cpm and dpm.

S4 Measure the two pack ground.

S-haze: Measure the measurement sample.

S@: Subtract those of the pack ground from the counting rate of each area of the measurement sample.

S: Read the net counting rate "J + "*...ni y2.

S: Determine the quadratic regression equation that represents the relationship between E and n.

The dpm is determined from the value of n at E=100% in this regression equation.

S: Determine the radioactivity concentration by dividing the dpm value 'k (Z22XIO') x the measurement sample volume.

Although various radionuclides are mixed in the measurement sample, even in such cases, the radioactivity concentration is automatically determined in exactly the same way as in the case of a sample of a single nuclide, and only one type of standard sample is used. Dimensions.

FIG. 1 shows an example in which a prepared sample 2, which is a mixture of a radioactive waste liquid and a liquid scintillator, is measured in a stationary state in a container l. However, this is not necessarily a static state; instead, it is a flow type system designed to take measurements while the sample is flowing through a pipe installed between both photomultiplier tubes 3. You can also take it.

However, whichever method is adopted, automatic efficient tracer technology is essential in order to automatically determine the radioactivity values of all radionuclides present in the measurement sample.

〔Effect of the invention〕

Facilities that handle unsealed radioactive materials are regulated to discharge water into general sewage after confirming that the radioactivity of used radioactive materials is below the permissible level. However, when conventional wastewater monitors are used, measurement results are obtained only as counted values, and the necessary radioactivity level cannot be obtained. Under such conditions, radioactive waste liquid with a concentration higher than the permissible level may be discharged into general sewage, which is a problem.

However, when the drainage monitor of the present invention is used, the radioactivity of the waste liquid sample is automatically obtained and it can be confirmed that the concentration is above the permissible concentration.
Environmental safety is guaranteed even when water is released.

In general, even when α-emitters, pure β-emitters, and β-r emitters are mixed in the measurement sample, if one monitor is used, the total radioactivity value in the sample is automatically determined and complete monitoring is possible. It is possible. but.

This is not possible with other existing radiation measurement techniques.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a drainage monitor according to the present invention. FIG. 2 is a principle diagram of the automatic efficiency tracer technology, and FIG. 3 is a flowchart of the data processing device. l... Container, 2... Prepared sample, 3... Photomultiplier tube. 4... Coincidence circuit, 5... Sum circuit, 6... Gate. 7...AD converter, 8...memory mechanism, 9...
Data processing device, 10... Spectrum of standard sample, 1
1... Spectrum of the measurement sample. Patent applicant Nippon Science Co., Ltd. Representative Hiroshi Ishikawa Figure 1 Figure 2 Channel number

Claims (1)

[Claims] The electrical pulses generated after the radiation is detected by the scintillator are measured in multiple measurement regions defined by the lower and upper limits of the pulse height analyzer, and each counting efficiency and each measurement region obtained simultaneously for the standard sample are calculated. , for the measurement sample whose radioactivity is to be determined, calculate the counting rate obtained simultaneously in each measurement area that is the same as for the standard sample, and from the data group consisting of each counting efficiency and each counting rate, calculate the counting rate of the data processing device. A method for measuring radioactivity in a wastewater monitor, in which a regression equation expressing the relationship between counting efficiency and counting rate is determined using a method, and the counting rate at 100% counting efficiency is determined as the radioactivity of a measurement sample from this regression equation.