GB 9136-1988 Technical regulations for radioactive waste gas treatment systems of light water reactor nuclear power plants
Some standard content:
National Standards of the People's Republic of China
Radioactivity of Light Water Reactor Nuclear Power Plants
Technical Regulations for Heating Treatment Systems
The technical rules about gaseousradioactive waste processing system for light water reactor plants1Theme content and scope of application|| tt||GB 9136-88
This standard specifies the minimum technical requirements for the design, construction and operation of radioactive waste gas treatment systems for light water reactor nuclear power plants (hereinafter referred to as this system).
This standard is applicable to the design, construction and operation of radioactive exhaust gas treatment systems of light water reactor nuclear power plants. Radioactive exhaust gas treatment systems of similar reactors can also be used as a reference.
The starting point of the boiling water reactor radioactive waste gas treatment system in this standard is the discharge point of the main condenser degassing equipment, the main condenser mechanical vacuum pump and the turbine steam gland seal exhaust device: the radioactive waste gas treatment system of the pressurized water reactor The starting point is the discharge points of relevant components, equipment and systems set up to remove radioactive gases from the reactor coolant, as well as the discharge points of the equipment exhaust gas collection system. The end points of these systems are the air flow inlets of the power plant exhaust system.
2 Reference Standards
GB6249 Nuclear Power Plant Environmental Radiation Protection Regulations HAF0200 Nuclear Power Plant Design Safety Regulations
3 Terminology
3.1 Covering Gas
Under a certain pressure , filling the liquid storage tank space with inert gas to prevent leakage of air. 3.2 Low-temperature time absorption system
is a processing device that uses an adsorbent to separate (adsorb) and retain decayed radioactive gases at low temperatures. 3.3 Low-temperature distillation device
Equipment that uses low-temperature distillation to separate rare gases from waste gas. 3.4 High-efficiency particulate air filter (referred to as high-efficiency filter) - a disposable dry filter with a minimum filtration efficiency of 99.97% for particles with a particle size of 0.3 μm (made by the DOP method) efficiency test).
3.5 compounder
A device that performs controllable catalytic compound reaction of hydrogen and oxygen through catalytic heating method. 3.6 Must, should and can
"Must" indicates a necessary condition and is a mandatory requirement; "should" indicates a recommendation or suggestion; "can" indicates permission, which is neither a requirement nor a suggestion. The radioactive waste gas treatment system must be designed, constructed and operated in accordance with the requirements specified in this standard, and does not necessarily adopt the recommendations approved by the National Environmental Protection Agency on 1988-05-25 and implemented on 1988-09-01
.
4 Objectives
GB9136-88
This standard specifies a series of requirements to enable the radioactive waste gas treatment system to achieve the safety objectives, design objectives and operational objectives in this chapter.
4.1 Safety Objectives
4.1.1 In the design, construction and operation of this system, when radioactive materials are released into the environment, the radiation exposure to professional workers of the nuclear power plant and the public must be kept within reasonable limits. to the lowest possible level. 4.1.2 It should be ensured that under all operating conditions, the dose equivalents received by professional workers of nuclear power plants and the public do not exceed the corresponding limits specified by the country.
4.2 Design objectives and operating standards
4.2.1 The system should be able to safely process, store and discharge various radioactive waste gases from nuclear power plants. 4.2.2 The concentration and annual emissions of radioactive substances in the exhaust gas processed by this system must not exceed the management target value specified by the competent department.
5 Sources of Radioactive Waste Gas
The source and quantity of radioactive waste gas are related to the type of power reactor and its operating conditions. Whether it is damage to reactor fuel elements or radioactive gases generated by activation of the core area, they will be partially dissolved in the cooling water of the reactor loop and discharged with the leakage of cooling water or steam. These gases may contain inert gases (isotopes of Kr and , particles and atmosphere. The amount of atmosphere released is related to the amount of water vapor discharged. Since the amount of water vapor discharged from the radioactive waste gas system is very small, the amount of atmosphere released with the system has little impact on the environment.
Table 1 and Table 3 list the expected amount and design basis amount of radioactive gas before treatment, which can be used to estimate the annual emission of radioactive gas, the accident release amount of radioactive waste gas treatment system, determine shielding requirements and develop equipment (or component) environmental requirements. Table 1 The expected amount of iodine-131, inert gas and design basis amount of radioactive activity before pressurized water reactor radioactive exhaust gas treatment 1》
Exhaust gas source
Exhaust gas treatment system"
No With volume control
system degassing storage
system
for volume control
box degassing adsorption or
volume reduction system|| tt||For volume control
Adsorption of system degassing
or volume reduction system
Erotic gas
Expected amount
1.41×105 (3.80×10)
9.25×1016(2.50×10°)
1.18×101(3.20X×10)
Design basis quantity”
Expected quantity| |tt||Ying181
Bg/a(Ci/a)
Design reference quantity
Exhaust gas source
Air ejector exhaust 3
Without volume control
Storage of system degassing
System
Adsorption for volume control
box degassing or
Volume reduction system| |tt||Used for volume control
Adsorption of system degassing
or volume reduction system
Exhaust of sewage expansion vessel
No condensation|tt ||Total evaporation of purified water
U-shaped tube steam
Generator
Perto-evaporation treatment of purified
of condensed water
U-shaped tube steam generator
generator
GB9136—88
continued table 1
radioactive activity\
inert gas
Expected volume
9.62×1012(260)
2.07X1012(56)
1. 07X1012(29)
Design basis volume 5)
Expected Amount
Iodine-a
1.00×10°(0.027)
6.66X10°(0.18)
3.15×109(0.085)
Note: 1) All data are based on a single stack power of 3400MW (thermal). Bq/a(Ci/a)
Design basis quantity
9.62X100(2.6)
6.29X101(17)
3.00×1011(8.1)||tt ||2) The expected activity is calculated based on the American Nuclear Society standard ANS-18.1/N237 & Radioactive Source Term under Normal Operation of Light Water Reactors. 3) The expected value of the coolant leakage rate from the primary circuit to the secondary circuit is 45kg/d, and the design basis value is 550kg/d. 4) Not suitable for single-pass steam generators. 5) The design reference amount of inert gas is based on 1% fuel element damage rate and rated reactor thermal power. Table 2 Design basis air intake quantity of pressurized water reactor radioactive exhaust gas treatment system
Exhaust gas source
Volume control box
Continuous purge and degassing
Gap purge and degassing|| tt||Degassing tower (degasser)
Boron recovery degassing tower gap exhaust)
Composition of the volume control system downdraft degasser (continuous exhaust)
H
HN or mixed gas
H2
H2
m\/h
Normal range
1.19~~2.382||tt| |0~6.80
0.43~2.28
0.51~1.36
L/s
Quantity
Annual base
m3/a
0.3~0.6
0~2
0.11~~0.6
0.13~0.36
85003
85
100
4200
Exhaust gas source
Reactor coolant drain tank
With control fluid Position intermittent exhaust
Variable liquid level exhaust
Pressure regulator pressure box\
Fuel inspection
Note: 1) During shutdown and degassing, Change to 100% nitrogen GB9136-88
Continued Table 2
Composition
H2, N2 or mixed gas
H2, Nz or mixed gas
N
Nwww.bzxz.net
m\/h
number
normal range
0~8.50
0~8.50
0 ~68
6.80
L/s
0～2
0～2
0~20
-2||tt ||Quantity
2) Determined by the maximum gas flow into the recombiner of 20L/s compressor capacity and the maximum hydrogen concentration in the recombiner exhaust of 4%, 3) based on a start-up and shutdown operation.
4) For some nuclear power plants, this item is not available. Table 3. Expected amount of iodine-131, inert gas and design basis amount of radioactive activity before treatment of boiling water reactor radioactive exhaust gas\
Exhaust gas source
Main condenser exhaust
Gland Sealed exhaust
When using primary circuit steam
When using clean steam
Mechanical vacuum pump exhaust
Expected amount
Erotic gas"||tt ||Design basis quantity
5.55×106(1.5×10)
5.55×10(1.5×10)
Xel8$1.30X10/3(350)
Note : 1) Based on a single reactor power of 3400MW (thermal). 2) A mixture of radioactive gas isotopes. 3) The expected amount is after 30 minutes of decay. Do not use "
expected amount
. Iodine-181
year row child
m/a
6
340
60
Bq/a(Ci/a)
Design basis quantity
1.85×10(5.0)
7.40×10*(0.02)
1.11×10*(0.03)
4) Use 1.11×10Bq/s (3.0×10°uCi/s) (continuous 30d) as the design reference quantity. Table 4 Boiling Water Reactor Radioactive Exhaust Gas Treatment System Design Baseline Air Inlet Volume Exhaust Gas Source
Main Condenser Exhaust System
Gland Sealing Exhaust System
Mechanical Vacuum Pump Exhaust System||tt ||When initially vacuuming and exhausting
Restarting during operation or
When using
Composition
H2+02
Air leakage||tt ||Initial air
Water vapor
Steam and air
Air
Air+H+
Note: 1) Air leakage amount, according to each set The condenser is considered to be 17m2/h. 2) Consider according to the technical regulations of air injectors. m*/h
0.10/MW (thermal)
511)
4252)
Normal flow
9.25×1011(25)||tt ||L/s
0.03MW (thermal)
14
120
Saturation value under system design conditions
According to the two conditions of the turbine gap Conditions
The flow rate is based on the rated capacity of the pump, the total volume is based on the condenser volume, and normal operation is considered to be 40 hours per year
5.1 Source of radioactive waste gas from pressurized water reactors
GB 9136-88||tt| |There are several sources of exhaust gas in the pressurized water reactor radioactive exhaust gas treatment system, some of which are intermittent and some are continuous. Tables 1 and 2 show the design basis values ??and expected values ??for each exhaust gas source. 5.1.1 Volume control box
The hydrogen concentration in the reactor coolant system is controlled by adding hydrogen to the volume control box. There are radioactive gases in the reactor coolant, and different concentrations of radioactive gases will also accumulate in the gas space of the volume control box. These gases can be continuously purged or periodically vented to an exhaust gas treatment system.
5.1.2 Reactor coolant drain tank
The reactor coolant drain tank is used to collect the effluent from the primary loop coolant controlled leakage system. Gas accumulates in the reactor coolant drain tank and is discharged through the exhaust port to the radioactive waste gas treatment system. The concentration of radioactivity in this gas source varies widely. 5.1.3 Degassing tower
The degassing tower (or degasser) is used to remove dissolved gases from the liquid and discharge them to the radioactive waste gas treatment system. The flow rate and radioactivity concentration of the gas source are related to the system design
5.1.4 Covering gas
Covering gas is used to fill the upper space of the storage tank (such as volume control box, drain box, etc.) to prevent leakage into the air to limit the oxygen concentration in the water or prevent it from forming explosive gas with hydrogen.
5.1.5 Pressure regulator pressure relief box
The radioactive gas discharged from the pressure regulator pressure relief valve is discharged to the exhaust gas treatment system through the pressure stabilizer pressure relief box. 5.1.6 Other
exhaust gases such as fuel inspection should be sent to the radioactive waste gas treatment system. 5.1.7 Air ejector exhaust
The main condenser air ejector exhaust is composed of air and water vapor. When a steam generator tube leaks, the water vapor may contain radioactive material. This gas source is generally not processed by radioactive waste gas treatment systems. 5.1.8 Steam generator blowdown expansion vessel exhaust During the operation of the nuclear power plant, the flash steam discharged from the steam generator blowdown expansion vessel may contain radioactive gases, radioactive iodine and particulate radioactive substances, and usually returns to the secondary loop system. . 5.1.9 Equipment exhaust gas gathering system
The exhaust from equipment storing radioactive liquids may be piped to a separate gas collection system. This exhaust may contain radioactive inert gases, radionuclides and radioactive particles. 5.2 Boiling water reactor radioactive exhaust gas sources
Table 3 and Table 4 show the design basis values ??and expected values ??of each gas source. 5.2.1 Main condenser exhaust
The main condenser exhaust consists of hydrogen and oxygen produced by radiolysis of reactor water, air, water vapor, radioactive gas fission products and activation products leaking into the main condenser.
5.2.2 Gland seal exhaust
The gland seal exhaust includes the air sucked into the turbine seal and the non-condensable gas in the seal steam. If main steam is used as a seal, the seal exhaust will carry inert gases, gas activation products, and radioactive iodine and particulates. If clean steam is used as the seal, the amount of radioactivity in the seal exhaust is negligible. The amount of steam and air entering the gland sealing system can be considered as twice the air leakage amount of the sealing gap given in the turbine manual. If main steam is used as the sealing steam, the amount of sealing steam is about 0.1% of the main steam flow. Therefore, the feed amount of radioactive materials under design basis conditions is also 0.1% of the main steam. The amount of radioactive material vented by the gland seal is shown in Table 2. If clean steam is used as a seal, the amount of steam is as mentioned above, but the content of radioactive substances is the amount of fluorine contained in the steam condensate. Other radioactive materials in the condensate can be ignored. 5.2.3 Mechanical vacuum pump system exhaust
GB9136-88
The mechanical vacuum pump used to drain the main condenser will also discharge a small amount of radioactive materials into the environment. The composition and quantity of the discharged radionuclides are consistent with Decay time after shutdown.
The air discharge volume and exhaust rate depend on the condenser volume, mechanical vacuum pump capacity, and vacuum degree related to time and temperature. The design reference values ??are shown in Table 3 and Table 4.
6 System requirements
6.1 Process design of pressurized water reactor exhaust gas treatment system The source and quantity of pressurized water reactor exhaust gas are shown in Table 1 and Table 2.Usually, these waste gases are combined and treated. There can be many processes to achieve the "operation target". Figures 1 to 4 show four typical processes, three of which use box storage methods and one uses activated carbon adsorption method. In Figures 2 and 3, a combiner is used, which can combine hydrogen in the exhaust gas with external oxidation to synthesize water. This can not only reduce the amount of exhaust gas (or the storage volume of the decay box), but also increase the storage decay time and degassing of the reactor coolant. There are two methods: one is to continuously purge with hydrogen to remove the fission product gas in the volume control box; the other is to use a degassing tower installed on the coolant purification circuit to continuously remove the fission gas. to the exhaust system
degassing tower
volume control box
coolant sulfur water tank
fuel inspection
volume control box
supply Hydrogen
Supply nitrogen
Evaporator exhaust
Drain box exhaust
Pressure regulator pressure relief box exhaust
Buffer tank||tt| | Compressor | | tt |
To the exhaust system
Decommissioning decay box
Press
Preheater
Oxygenation
Will||tt ||Filter
To the exhaust system
Filter
Cooler
To the volume control system
or filter treatment system||tt ||Return (for dilution)
Figure 2 Leshui reactor exhaust gas volume reduction-storage treatment system decay box used for degassing of volume control box
Volume control box
Dehydration tower
Coolant drain tank
Pressure regulator pressure relief tank
Fuel inspection
Buffer tank
Condenser
To waste disposal System
GB 9136--88
Compressor
Nitrogen internal circulation composite system
Compressor
(for circulation): ||tt| |Combiner
Transformer
Preheating dew
(if necessary)
Additional photon
To the exhaust system
Filter
Figure 3 PWR exhaust gas volume reduction-storage and treatment system used for degassing of the chemical volume control system 6.1.1 Pressurized storage and treatment system
Figure 1 is a storage tank without a recombiner A schematic process for treating radioactive waste gas. The storage system first collects radioactive waste gas containing hydrogen and fluorine in a buffer tank, and then compresses it and stores it in a decay box. After the exhaust gas decays for a period of time and is sampled and analyzed, it is returned to circulation or emitted after monitoring.
6.1.1.1 Process requirements
The pressurized storage and treatment system must have the following process characteristics: a. It can transfer waste gas from one storage tank to another busy storage tank. manage. It can detect the formation and accumulation of potentially explosive mixtures of hydrogen and oxygen and generate an alarm signal. Able to sample the gas in the storage tank.
c.
dt
can purge each storage tank with an inert gas. The exhaust gas can be analyzed before discharge and monitored during discharge. e.
6.1.1.2 Process design methods that can be adopted
The following measures can be taken to design the pressurized storage and treatment system: a.
Radioactive waste gas should be filtered by a high-efficiency filter before being discharged . b.
The blowing air is sent to the monitoring discharge port through a closed pipeline system. The system should be equipped with at least three gas decay chambers. c.
d Emit gas under conditions that ensure it does not cause combustion. 6.1.2 Composite volume reduction system
There are several processes that use a composite device to react hydrogen in the exhaust gas with external oxygen. Figures 2 and 3 are two of them. 6.1.2.1 Volume reduction-storage treatment system for degassing of volume control boxes Figure 2 shows a schematic process with a recombination device for continuous purging operation of a volume control box. During normal operation of the reactor, hydrogen purge is used to bring the exhaust gas in the volume control box into the closed loop exhaust gas treatment system. During shutdowns, hydrogen purging is continued to reduce the radioactivity concentration in the primary coolant. But before shutting down, nitrogen is purged to eliminate hydrogen in the coolant. This process is a closed loop of nitrogen circulation. It can ensure that the mixed concentration of hydrogen and added oxygen is diluted to the low oxygen explosion range. It can also remove hydrogen through the hydrogen-oxygen compound method to reduce the risk of explosion and the volume of waste gas. Finally, Exhaust gas storage decay is performed to reduce its radioactivity. 6.1.2.2 Volume reduction-storage treatment system for degassing of chemical volume control system Figure 3 shows an inter-European operation composite volume reduction treatment process for degassing of reactor chemical volume control system. After the decay boxes are filled one by one, the gas in the box is sent to the composite system of nitrogen internal circulation in turn, and the exhaust gas returns to the buffer tank. In order to reduce the gas storage volume and explosion risk, this system is equipped with a compressor and a compounder. During operation, the hydrogen and oxygen content in the gas in the decay box is first analyzed, and then the waste gas is sent to the combiner for processing. The gas entering the recombiner must be diluted with internal circulating nitrogen to keep the hydrogen at a low concentration. After preheating and adding oxygen in stoichiometric amounts, the mixed gas undergoes hydrogen-oxygen recombination with the help of a catalyst bed. After the water vapor is separated through the condenser, the remaining gas (mainly nitrogen and inert gas) returns to the buffer tank. This operation is continued until the pressure in the gas supply decay box drops to a predetermined low value. The exhaust gas of the combiner is injected into another gas decay box. The other compressor is not used for exhaust gas compression, but is only used for circulating nitrogen and supplying the gas in the decay box. After analysis, monitor emissions under favorable weather conditions. 6.1.2.3 Process requirements
The composite volume reduction treatment system must have the following process characteristics: a.
b.
c.| |tt||d.
e.
f.
g.
h.
t.
No. tt||Can adequately handle the exhaust gases discharged during shutdown, start-up and normal operation. Under all operating conditions, the hydrogen and oxygen concentrations in the entire system should be kept outside the explosion range to ensure that they are not in the catalyst bed. Condensation water is generated inside. It can combine hydrogen and oxygen to reduce the risk of explosion. The storage capacity required for decay can be provided by allowing the exhaust gas to be transferred from one decay box to another. The gas inside is discharged through the monitoring outlet after sampling. The entire system can be purged with a quiet gas. For storage systems that are not designed to be explosion-proof, the formation of potentially explosive gas mixtures must be detected and an alarm can be issued. Before being discharged to the environment, radioactive waste gas must be filtered by a high-efficiency filter. k. The waste gas can be monitored before being discharged. The following measures can be adopted to design the composite volume reduction system: a.
Control the oxygen concentration (or remove hydrogen) with the help of a suitable diluent to keep the hydrogen concentration low. Use reliable equipment with anti-explosion capability to perform the hydrogen-oxygen catalytic composite reaction. b.
c.
Control the humidity of the gas by cooling and separating moisture. Use steam heating to preheat if oxygen is added in the later stage of the system and the possibility of fire due to electrical failure can also be used. .
Preheating by electric heating.
The purge gas is sent to the monitoring exhaust port for discharge e.
The gas is discharged without causing combustion. . f.
to the exhaust system
volume control box
degassing tower
coolant water tank
pressure regulator pressure box|| tt||Fuel inspection
Dryer
Adsorber
To abdominal fluid treatment system
Return to volume control box
Filter
Compressor
Figure 4 Pressurized water reactor exhaust gas adsorption treatment system
6.1.3 Adsorption treatment system
Figure 4 shows an adsorption treatment process, which can handle the desorption of the chemical volume control system Gas tower exhaust, volume control box purge gas and anaerobic tank exhaust. These hydrogen-based exhaust gases are first demixed, then retained and decayed by the activated carbon adsorption bed, and then discharged to the environment or returned for recycling. If the exhaust gas returns to the volume control box, it must also be compressed. 6.1.3.1 Process requirements
The adsorption treatment system must have the following process characteristics: GB9136-88
can remove moisture in the exhaust gas to meet the humidity requirements of the adsorbent. a.
b.
c.
warning signal.
d.
The carbon adsorbent bed can provide sufficient residence time to meet the "objectives" of Chapter 4. Adsorption systems that are not designed to be explosion-proof must be able to detect the formation and accumulation of potentially explosive gas mixtures, and must be able to issue an alarm and purge the entire system with an inert gas. 6.1.3.2. Process design methods that can be adopted
a.
b.
e.
use cooling, desiccant drying or low-temperature precipitation to control the humidity of the exhaust gas. Activated carbon adsorption can be used as the main method of retention decay. Use high-efficiency filters to filter radioactive particles. The purge gas is sent to the monitoring exhaust port for discharge through a closed pipeline system. During normal operation, the dryer regenerates without venting to the atmosphere. 6.1.3.3 Activated carbon adsorption bed retention time
The carbon adsorption retention time must be determined according to the decontamination coefficient required in Chapter 4 "Targets". The adsorption process relationship is shown in the following formula: T=edM/F
where: T-
Kd -
M -
F
average band retention Time, $;
dynamic adsorption coefficient, cm/g;
adsorbent weight, 8
gas flow rate, cm/s.
The above parameters are all operating condition values. The dynamic adsorption coefficient values ??of nitrogen and xenon are related to the type of activated carbon, relative humidity, temperature, pressure and other influencing factors. Therefore, when designing the adsorption bed, the type, quantity and system operating conditions of the carbon used must be selected to meet the design basis requirements. Residence time.
6.2 Process design of boiling water reactor exhaust gas treatment system to exhaust system
Gu heater
Dilution steam
(if necessary)
Air ejector| |tt||Main cooler
Mechanical vacuum pump
Gland seal exhaust
Combiner
Condenser
To heat trap||tt| |Condenser
To heat trap
Decay box
Dryer
or
Condenser
Adsorber
Filter
To heat trap or liquid handling system
Main cooler air ejector exhaust system
To exhaust system
Fan
Decay (If radioactive)
Gland sealing and vacuum exhaust system
Figure 5 Boiling water reactor exhaust gas treatment system
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