GB/T 12726.2-2013Nuclear power plants -- Instrumentation important to safety -- Radiation monitoring for accident and post-accident conditions -- Part 2: Equipment for continuous off-line monitoring of radioactivity in gaseous effluents and ventilation air (English PDF)

4.1 Overview

This section applies to all types of equipment in addition to the need to meet the requirements of this part, it must also meet the GB/T 12726.1-2013 provisions in general Requirements, unless otherwise indicated.

4.2 Basic requirements and related functions

Gaseous effluents and ventilation equipment for continuous monitoring of radioactivity in the offline generally used to measure the radioactivity of nuclear engineering plant, such as the reactor building or Fuel processing plant chimney ventilation ducts and activity levels gases path. According to the functional requirements, the device can also be used to measure the discharge Radioactivity into the environment, to detect and identify security barrier (such as. containers, pipes) leaks, as well as provide any information or cause to live Useful information about the release of the plant status.

Radioactive emissions to the environment should theoretically be fully measured, but because of effluents released from halogen and particulate activity during an accident More complex measurements, monitoring is generally considered only an inert gas is sufficient. Thus, the monitor should have detected and measured inert gaseous effluents the ability of the gas activity, such inert gas comprises an inert gas to reach equilibrium just mixed fission products to decay 10d old mixture. can You can require multiple devices to cover the effective range of the measurement required.

Since the measurement is transmitted to a remote for gaseous effluents and ventilation samples continuously, so the detection and measurement devices should be installed in easily accessible places, where the environmental conditions should be consistent with the provisions of this part of the equipment design extreme conditions. This requirement also applies to the required dimension Active parts protected sampling device (pump, flow control instruments).

Other portions (sampling nozzle, transfer line) sampling device may be designed and installed in harsh environments. In this case, e.g.

If the monitor is classified according to IEC 61226, which is part of the monitor should be classified as the same category. If you need to identify, located in harsh environments this part should be part of the sampling device in accordance with those specific environmental conditions environmental qualification.

If required, the system should be displayed at a temperature and pressure conditions at the sampling point and the measured volume of the activity related to values, but to be used by the manufacturer and users agreed. If the measuring device calibration conditions and internal conditions are different, manufacturers and users should also agree on how to correct the measurement.

4.3 Sampling device

4.3.1 Overview

Design of sampling device should refer to ISO 2889:2010 and meet the GB/T 12726.1-2013 the general requirements.

Sampling device generally includes one or more components and functional units.

--- Sampling and exhaust pipes;

--- Gas treatment apparatus (e.g. gas cooling means preventing or indoor condensation gas measurement with a device for removing condensate reheating means, in order to remove the residual gas in the collection device with an external blow Importers wash pipe connection connecting pipe);

--- Measuring chamber;

--- Airborne particulate collection device.

- Aerosol Monitors aerosol filtration unit (filter with fixed or filter);

- Only for iodine and noble gas monitors inlet dust filter;

- iodine monitors iodine zeolite or activated carbon filters or filter cartridges (filter replacement device or a fixed filter);

--- Environmental gamma radiation shielding means and/or compensation device;

--- Separate air pump or central pumping station;

--- Air flow measurement and/or control devices;

Pressure, temperature or humidity measurement and/or control unit (depending on the sampling conditions).

4.3.2 Measurement Technology Requirements

According to the measured nuclides respond air or gas filter to remove radioactive particles and iodine or incorporated volume is known and constant capacity Device. In the latter case, the measuring chamber shall be air flow through type, and should be given its volume and pressure, as well as ease of maintenance or Change detector, which should be easily disassembled, and should ensure that the detector can be accurately mounted on repeating geometrical position.

When the pressure-sensitive measurement techniques, should have the pressure measurements. Instrument calibration should take into account the actual operating pressure conditions as appropriate Amendments. Sampling means acceptable change in pressure and pressure specified by the manufacturer. Should be carefully considered to ensure that the ends of the inlet filter Pressure drop on the measurement chamber pressure is very small.

When measuring the flow of sensitive technology should provide flow measurement devices. Instrument calibration should be considered the actual operating pressure and temperature into Row appropriate amendments. Should consider regulating the flow volume measurement means. It is also desirable to provide a flow control device, the flow of the apparatus the adjustment range is sufficient to withstand changes in air pump can be used with any of the intrinsic properties of the filter. It should be based on the effects of different traffic measurement Value amendment.

If necessary, measure atmospheric humidity to control the adjustment means in order to avoid condensate in the pipeline and the monitor. When the relative humidity is over Crossing the manufacturer's specified value, it should provide an alarm signal.

These tests should be applied to all of the response depends on the traffic flow through the monitoring device known sampling and detection means.

When the device is not sensitive to changes in flow rate, but still need to meet the functional requirements of the sample flow, then shall the manufacturer and user Agreement reached between the simple fluid circuit test and any flow alarm test.

When the device is sensitive to changes in flow rate and the sample flow with the discharge flow variations, it should be agreed between manufacturer and user the appropriate test.

5.4.2 Monitor sampling efficiency

5.4.2.1 Overview

Compared to a particle collection efficiency for each given particle size, the monitor entry and collection filter between collection efficiency provided by the manufacturer, it should not differ more than 10%. If the manufacturer and the user agrees, the actual test by particle simulation test instead.

5.4.2.2 Particle size

In diameter and size range of collection efficiency measurement sampling system used by the particles, by the manufacturer and user agreement, for example. root According to the diameter of the aerosol particles being monitored, given collection efficiency filter media for different sizes of particles and the like.

5.4.2.3 Aerosol type

For aerosol collection efficiency tests There are several different types, such as.

--- Fluorescent tracer particles containing non-radioactive aerosols;

--- Non-radioactive aerosol by a latex or polystyrene spheres constituted;

--- Radioactive aerosol.

5.4.2.4 Test Method

It shall have the right by a median aerodynamic diameter of particles injected into the sampling line inlet air samples collected pipeline efficiency test Experience. Particle size distribution may be more decentralized system have smaller geometric standard deviation. Sampling device should be under standard test conditions (flow rate) jobs.

After sampling device is closed, shall determine the amount of aerosols collected on the sampling media. It should also determine the inlet gas monitor available Sol total. This amount can be measured independently of the amount of aerosol sampling obtained or determined by the following.

--- On the inner surface of the inlet pipe and the amount of aerosols collected on other air circuit upstream media surface collected;

--- Amount of aerosol collected downstream of the collecting medium.

5.4.2.5 Collection efficiency is determined

Monitor the collection efficiency (Em) shall formula (1).

100% (1)

Where.

CM --- amount deposited on the collector medium;

CT --- total aerosol.

If feasible, it is recommended to use another method to determine the total amount of aerosol CT as a means of obtaining verification value. Such methods include Through a variety of equipment and measurement techniques (such as spectrophotometers, particle analyzer and a reference sample, etc.) into the device measuring aerosol concentrations.

If the total amount of material from the inside of the total aerosol sample collected to determine the monitor, then the total amount of aerosol CT (activity, quality or micro Grains) by equation (2) gives.

CT = CM CU CD (2)

Where.

CU --- the amount collected from the upper reaches of the medium air circuit surface collected;

CD --- the amount collected in the collection medium downstream.

5.4.3 Feelings of gas or particle retention

5.4.3.1 Overview

Inert gases or particles remain in the air circuit may affect the measured results. Therefore, to prevent such retention, factory design empty Gas loop should be a reasonable choice of materials and structures.

If the manufacturer and the user agreed to instead of the actual test through simulation tests.

5.4.3.2 Requirements

The volume of activity greater than 10 times the decision threshold for injecting inert gas into the monitor. After injection of the monitor and clean air flushing, gas Retention sensitivity test indicated value should be less than 1% of the maximum reading of the results.

A certain concentration of particles injected into the monitor. After injection of the monitor and clean air flushing, feelings of particle retention test finger Indication should be less than 5% of the maximum reading of the results.

Test Method 5.4.3.3 inert gas During the test, the device will require the design of the chemical form of measurement, which is equal to about 10 times the volume of activity determination threshold inert gas injection probe Measuring device, and at least 10 times the response time of the device in the device.

Of the device does not capture system containing the gas to form a closed loop system, and inject sufficient volume of activity in this system an inert gas is equal to 1000 times the decision thresho...