JP2005134246A - Tritium sampler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tritium sampler capable of reducing the error of evaluation for radiation of tritium and also improving workability. <P>SOLUTION: The tritium sampler for collecting the tritium at the measurement of radiation concentration of the tritium in the gaseous waste comprises: the mean water vapor concentration measurement means 4, 5, 14, for prescribed period in the sampling interval of sampling air by sampling the air containing the tritium; the mean water vapor concentration calculation means 14 for calculating the water vapor concentration for each prescribed period during the sampling interval; the mean water vapor concentration memory means 14a; the mean water vapor concentration memory and display means 15, 16: and the tritium collection means 6-9 for collecting the tritium in the phase of water by compressing the sample air during the sampling interval and cooling it so as to condense the tritium containing water vapor into the form of water. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tritium sampler used when measuring the radioactivity concentration of tritium contained in gas waste discharged from an exhaust stack in a light water reactor facility such as a nuclear power plant.

Since tritium is present in the form of water vapor (THO, T ₂ O) in gaseous waste mainly composed of air, a tritium sampler employing a cooling condensation method is mainly used in nuclear power plants. On the other hand, “Guidelines for the measurement of radioactive materials released at light water reactor facilities for power generation” states that a thermometer and a hygrometer must be installed in the case of the cooling condensation method. In the case of the cooling condensation method, the tritium concentration of the condensed sample water is measured using a liquid scintillation counting device or the like at a frequency of at least once a month, using a part of the obtained water sample as a measurement sample. It is said. Furthermore, the tritium emission radioactivity is calculated from the measured tritium concentration of water (the radioactivity concentration of the condensed sample water) as follows.

C = _Cw * W * H * 10 ^<-2 > (Bq / cm ^{< 3} >) ... (1)
However, _Cw : Radioactivity concentration of condensed sample water (Bq / g)
W: Average saturated water vapor density during the sampling period (g / cm ³ )
H: Average relative humidity during the sampling period (%)

  Conventionally, the average saturated water vapor density during the sampling period is obtained by visually reading the average temperature from the temperature record for one month of the recorder and comparing the saturated water vapor pressure corresponding to the average temperature with the table of JIS-Z8806. It was. Similarly, the average relative humidity was visually determined from the relative humidity record for one month of the recorder.

  Since the relative humidity varies greatly depending on the temperature even if the water vapor density in the air is constant, there is a drawback that reading error is large when reading the average relative humidity from the record of the recorder. In order to improve this, a method of measuring the dew point with a lithium chloride dew point meter was introduced. In this case, the average dew point is visually read from a recorder, and the saturated water vapor pressure corresponding to the average dew point is similarly obtained by collating with the table of JIS-Z8806 (see, for example, Patent Document 1).

JP 2001-330695 A

In the apparatus as described above, when the water vapor density in the air is constant, the dew point does not change even if the temperature changes. Read error was improved. However, since one month of recording paper is used to visually read the average temperature and average humidity in the case of thermometers and hygrometers, and the average dew point in the case of dew point meters, there is an error in reading the average value. There is a problem that it takes time to collect and read the data.
In addition, due to clogging of the filter, there is a difference between the pressure at the sampling point and the pressure at the water vapor density measurement point of the tritium sampler. there were.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a tritium sampler that can reduce the error in evaluating the released radioactivity of tritium and that has improved workability.

  The present invention relates to a tritium sampler used to collect tritium when measuring the radioactive concentration of tritium contained in gaseous waste, and samples the air containing tritium during the sampling period of the sampling air. Means for measuring the water vapor density for each predetermined period, means for calculating an average water vapor density of the water vapor density obtained for each predetermined period during the sampling period, means for storing the average water vapor density, and the average A means for recording and displaying the water vapor density, and a tritium collecting means for condensing the water vapor containing tritium by pressurizing and cooling the sampling air during the sampling period and collecting the tritium in the form of water. The tritium sampler is characterized by

  Since the tritium sampler of the present invention calculates and records and displays the average water vapor density during the sampling period based on the water vapor density, it can reduce errors in the evaluation of the released radioactivity of tritium and improve workability.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a tritium sampler according to Embodiment 1 of the present invention. In the figure, an intake nozzle 1 sucks air as gas waste sampled from an exhaust pipe (not shown) in a light water reactor facility such as a nuclear power plant, and an inlet valve 2 shuts off the intake air. The air filter 3 removes particulate matter from the sampled air. The thermometer 4 and the hygrometer 5 respectively measure the temperature and humidity of the sampled air, and the compressor 6 samples and pressurizes the air from the exhaust pipe.

  The cooling device 7 cools the pressurized air, condenses water vapor, and collects sample water. The auto drain 8 automatically discharges when the sample water accumulates to a predetermined level, and the poly container 9 accumulates the discharged sample water for the sample collection period. The pressurized air pressure gauge 10 measures the pressure of the pressurized air, and the pressure adjustment valve 11 adjusts the pressure of the pressurized air to a predetermined value while looking at the instructions of the pressurized air pressure gauge 10, and the exhaust nozzle 12 Exhausts sampled air as gas waste to the exhaust stack. The control circuit 13 controls the compressor 6 and the cooling device 7. The sequencer 14 is a control unit that operates according to a program configured by a computer or the like, and is connected to a recorder 15 and an operation display device 16 having an input function and a display function.

  The sequencer 14 receives operation data of the compressor 6 and the cooling device 7 from the operation display device 16 and outputs the operation data to the control circuit 13 as a start / stop signal. The sequencer 14 calculates the water vapor density from the temperature measurement value obtained as the temperature signal of the thermometer 4 and the relative humidity signal of the hygrometer 5 and the relative humidity measurement value, and based on the water vapor density, the average water vapor during the sampling period is calculated. The density is calculated and output to the recorder 15 and the operation display device 16. The recorder 15 records the temperature, relative humidity, and average water vapor density of the sampling air based on the measurement value output from the sequencer 14. The operation display device 16 includes an operation screen and a display screen, and starts and stops the compressor 6 and the cooling device 7 by selecting the operation screen and operating the displayed buttons. The operation screen also displays the operating states of the compressor 6 and the cooling device 7. By selecting the display screen, for example, the temperature, relative humidity, and average water vapor density of the sampling air are displayed.

  The memory 14a of the sequencer stores a table of saturated water vapor pressure with respect to temperature, and the saturated water vapor pressure at that temperature is obtained by comparing the sampling air temperature with the table. The water vapor density corresponding to the saturated water vapor can be calculated from the following equation, for example.

_{Wh n = (H n /100)×{0.000804/(1+0.00366T n} )} × (e n / P n) ··· (2)
However, Wh _n : Water vapor density of sampling air (g / cm ³ )
H _n : Relative humidity of sampling air (%)
T _n : temperature of sampling air (° C.)
e _{n: T} saturated water vapor pressure at _n ℃ _{P n:} (same units as _{e n)} the pressure of the sampling air
* Normally, _Pn is atmospheric pressure (standard pressure: fixed value). The water vapor density Wh corresponds to W × H in the above equation (1).

FIG. 2 is a flowchart showing a procedure for calculating the average water vapor density in the sequencer 14. In step S01 every fixed cycle inputting a temperature T _n and the relative humidity H _n of the sampling air. In step S02, the water vapor density (amount) Wh _n is calculated based on the calculation formula (2). Step S03 In calculates an integrated steam density (amount) ΣWh _i sampling periods to overwrite the value and the accumulated number of times n in the memory 14a. In step S04, the average water vapor density (amount) Wh _av = (ΣWh _i ) / n is calculated, overwritten in the memory 14a, and output to the recorder 15 and the operation display device 16.

  FIG. 3 shows an example of a display screen of the operation display device 16, and a “sample collection start” button (not shown) is touched at the start of sampling. Then the start date is displayed. Normally, the temperature and relative humidity of the sampling air, the average water vapor density during the sampling period, and the sampling start date and time are displayed. When the sample collection is completed, the plastic container 9 is replaced with a new one, and a “sample collection end” button (not shown) is touched to display the end date and time. These dates and times are managed by a timer by a program in the sequencer 14, for example. Further, the temperature, relative humidity, average water vapor density, sampling start and end date / time shown in FIG. 3 are stored in the memory 14a as needed.

  FIG. 4 is a diagram schematically showing an example of daily changes in temperature, humidity, and average water vapor density in the recorder 15, where a is the temperature, b is the relative humidity, and c is the average water vapor density from the start of sampling. In the case of fine weather, the temperature a changes by about 5 to 10 ° C., and the relative humidity changes by 20 to 30% due to the influence, whereas there is almost no daily change in the average water vapor density c.

At the end of the sampling period, the average water vapor density displayed on the operation display device 16 is recorded, and the sample water for one month in the plastic container is brought back, and a liquid scintillation counter is used for a part of the sample water in the analysis room. use measuring tritium (radioactive) concentration C _w of the sample water, based on the record of the measurement results and the average water vapor density Wh _av (= equivalent to an average of the (1) formula (W × H)) The tritium (radioactivity) concentration C of the sample air is calculated by the above equation (1). Therefore, the troublesome work of reading the recording paper from the site and reading the average temperature and the average relative humidity during the sampling period in the analysis room is eliminated, and the calculation of the average water vapor density is not required, so that the work can be saved.

  Note that the sequencer 14 may be a control unit including the input valve 2, the pressure adjustment valve 11, and the like as illustrated.

Embodiment 2. FIG.
FIG. 5 is a block diagram showing a configuration of a tritium sampler according to Embodiment 2 of the present invention. In the figure, the same or corresponding parts as those in the above embodiment are indicated by the same reference numerals. The sampling air pressure gauge 17 measures the pressure of sampling air. When the air filter 3 becomes clogged, the indication of the sampling air pressure gauge 17 makes a difference with respect to the pressure at the sampling point of the source flow. The sampling point is generally atmospheric pressure, and the difference is the pressure loss of the air filter 3 and the pressure loss of the piping. Since the pressure loss of the pipe is small, the influence on the average water vapor density is negligibly small. However, the influence of the pressure loss due to the clogging of the air filter 3 may be about 15%, for example.

  Since the average water vapor density is evaluated as that at the sampling point, it is desirable to correct the pressure when the pressure loss of the air filter 3 is large. Moreover, since the pressure loss of the air filter 3 changes every moment, it is desirable to correct each time the water vapor density is calculated. The sampling air pressure gauge 17 is installed for this pressure correction, and the measured sampling air pressure value is input to the sequencer 14 and correction calculation is executed by the following equation.

Whp _n = Wh _n × (P ₀ / P _n ) (g / cm ³ ) (3)
However, Whp _n : Water vapor density of the sampling air after correction (g / cm ³ )
Wh _n : Water vapor density of sampling air (g / cm ³ )
P _n : Sampling air pressure P ₀ : Standard state pressure (fixed value) (same unit as P _n )

FIG. 6 is a flowchart showing a calculation procedure for the pressure correction of the water vapor density in the sequencer 14. In step S011, the temperature T _{n of the} sampling air, the relative humidity H _n and the pressure P _n are input at regular intervals. Based on in step S021 equation (3) calculating a water vapor density (amount) WHP _n. In step S031, the integrated water vapor density (amount) ΣWhp _i during the sampling period is calculated, and the value and the integrated number n are overwritten in the memory 14a. In step S041, the average water vapor density (amount) Whp _av = (ΣWhp _i ) / n is calculated, overwritten on the memory 14a, and output to the recorder 15 and the operation display device 16.

  Thus, by adding a pressure correction term to the calculation of the water vapor density, the error in the evaluation of the released radioactivity of tritium can be reduced.

Embodiment 3 FIG.
FIG. 7 is a flowchart showing a calculation procedure of tritium collection abnormality alarm output in the sequencer 14 of the tritium sampler according to the third embodiment of the present invention. For example, after step S04 of FIG. 2 of the first embodiment, in step S05, the pressure P of the pressurized air from the pressurized air pressure gauge 10 and the cooling temperature Tc from the cooling device 7 are input. In step S06, if the AND condition of allowable pressure lower limit value ≦ pressure P of pressurized air ≦ allowable pressure upper limit value and allowable temperature lower limit value ≦ cooling temperature Tc ≦ allowable temperature upper limit value is satisfied, the process returns to step S01 in FIG. If the condition is not satisfied, a tritium collection abnormality alarm is output to the monitoring device 19 via the recorder 15, the operation display device 16, or the transmission cable 18 shown in FIG. In addition, the allowable pressure lower limit value and the upper limit value of the pressure P of the pressurized air and the allowable temperature lower limit value and the upper limit value of the cooling temperature Tc are respectively stored in advance in the memory 14a of the sequencer 14, for example.

  When the pressure P of the pressurized air is smaller than the allowable pressure lower limit value, the amount of allowable water vapor that can be contained per unit volume increases, so that even if the cooling temperature is constant, the collection efficiency of the sample water is reduced. Traceability becomes a problem. Further, when the pressure P of the pressurized air is larger than the allowable pressure upper limit value, the flow rate of the sample ring air is lowered, and similarly the traceability of the sample water becomes a problem. Further, when the cooling temperature Tc is lower than the allowable temperature lower limit value, ice is generated by supercooling and the air passage is closed. Such a state requires a long time for recovery, and causes a problem of missing for a long time (unmeasurable). When the cooling temperature Tc is higher than the allowable temperature upper limit value, the collection efficiency of the sample water is lowered. Conventionally, the pressure of the pressurized air and the cooling temperature have been carefully checked during regular patrols. By detecting an abnormality in the pressure of the pressurized air and an abnormality in the cooling temperature and outputting an alarm, maintenance workability can be improved and a missing side can be prevented in advance by early abnormality detection.

  In the above description, the case where this function is added to the first embodiment is described. However, step S05 in FIG. 7 is started after step S041 in FIG. 6 in the second embodiment, and the steps after steps S06 and S07 are performed. It is also possible to return to step S011 in step 6, and the same effect can be obtained.

Embodiment 4 FIG.
FIG. 8 is a block diagram showing a configuration of a tritium sampler according to Embodiment 4 of the present invention. In FIG. 8, the sequencer 14 is connected to a monitoring device 19 for remotely monitoring a tritium sampler in the field by a transmission cable 18 for transmitting data. The sequencer 14 stores the start date / time and end date / time of sampling and the average water vapor density in the memory 14a. For example, the data can be easily obtained by accessing the sequencer 14 from the analysis room in which the monitoring device 19 is provided. Improves workability in calculating tritium release radioactivity. In addition, since desired operation parameters can be viewed from the analysis room, it is possible to save labor such as reducing the number of regular patrols.

As described above, the tritium sampler of the present invention calculates and records and displays the average water vapor density during the sampling period based on the water vapor density, so that it is possible to reduce the error in evaluating the released radioactivity of tritium and improve the workability. .
In addition, since the pressure of the water vapor density is corrected by measuring the pressure of the sampled air, the error in the evaluation of the released radioactivity of tritium can be reduced.
In addition, the pressure of the pressurized air and the cooling temperature are measured, and the tritium collection function is diagnosed based on the measured values, so that inspection items in periodic inspections can be reduced, and inspection workability is improved. improves.
In addition, the start date and end date and time of the previous sampling and the average water vapor density were memorized, so that the operation state of the sampler could be monitored remotely, and the data could be obtained remotely. Workability is improved.

It is a block diagram which shows the structure of the tritium sampler concerning Embodiment 1 of this invention. It is a flowchart which shows the calculation procedure of the average water vapor density in the sequencer of the tritium sampler concerning Embodiment 1 of this invention. It is a figure which shows the example of a display screen of the operation display apparatus of the tritium sampler concerning this invention. It is the figure which represented typically the example of the daily change of the temperature in the tritium sampler recorder concerning this invention, humidity, and an average water vapor density. It is a block diagram which shows the structure of the tritium sampler concerning Embodiment 2 of this invention. It is a flowchart which shows the calculation procedure of the pressure correction of the water vapor density in the sequencer of the tritium sampler concerning Embodiment 2 of this invention. It is a flowchart which shows the calculation procedure of the tritium collection abnormality alarm output of the tritium sampler concerning Embodiment 3 of this invention. It is a block diagram which shows the structure of the tritium sampler concerning Embodiment 4 of this invention.

Explanation of symbols

  1 Intake nozzle, 2 Inlet valve, 3 Air filter, 4 Thermometer, 5 Hygrometer, 6 Compressor, 7 Cooling device, 8 Auto drain, 9 Poly container, 10 Pressurized air pressure gauge, 11 Pressure adjusting valve, 12 Exhaust nozzle , 13 control circuit, 14 sequencer, 14a memory, 15 recorder, 16 operation display device, 17 sampling air pressure gauge, 18 transmission cable, 19 monitoring device.

Claims (5)

A tritium sampler used to collect tritium when measuring the radioactive concentration of tritium contained in gaseous waste,
Means for sampling the air containing tritium and measuring the water vapor density at predetermined intervals during the sampling period of the sampling air;
Means for calculating an average water vapor density of the water vapor density obtained at predetermined intervals during the collection period;
Means for storing the average water vapor density;
Means for recording and displaying the average water vapor density;
Tritium collecting means for compressing and further cooling the sampling air during the sampling period to condense water vapor containing tritium and collect tritium in the form of water;
A tritium sampler characterized by comprising: The storage means stores a table indicating a relationship of saturated water vapor pressure to the temperature of the sampling air;
The means for measuring the water vapor density comprises means for measuring the temperature and relative humidity of the sampling air, and the saturation obtained by the table at the measured sampling air temperature, relative humidity, and the measured sampling air temperature. Means for determining the water vapor density of the sampling air based on the ratio of the water vapor pressure to the atmospheric pressure,
The tritium sampler according to claim 1.   The means for measuring the water vapor density includes means for measuring a pressure before pressurizing the sampling air, and means for correcting the water vapor density by a ratio of the measured pressure to a predetermined standard state pressure. The tritium sampler according to claim 1 or 2, further comprising: The storage means further stores an upper limit value and a lower limit value of the pressure of pressurized air and the cooling temperature in the tritium collection means,
Means for measuring the pressure of the pressurized air and the cooling temperature in the tritium collecting means;
Means for generating an alarm when at least one of the measured pressure of the pressurized air and the cooling temperature is not in a range between the respective upper limit value and lower limit value;
The tritium sampler according to any one of claims 1 to 3, further comprising: Means for designating the start and end of the sampling air sampling period;
The storage means further stores a start date and an end date and time of designated sampling for the calculated average water vapor density;
The tritium sampler according to any one of claims 1 to 4, further comprising a remote monitoring unit capable of remotely monitoring the tritium sampler and accessing the storage unit.

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