High-range acid-proof I-129 radiation monitoring system and method
Technical Field
The invention belongs to the technical field of nuclear radiation monitoring, and particularly relates to a high-range acid-proof I-129 radiation monitoring system and method.
Background
In the nuclear fuel element post-processing site, after long-term cooling, the radioactive gases in fission products are mainly Kr-85 and I-129, and the half-life of I-129 is as long as 1.57X 107And the product has long-term harm to human bodies and the environment. Therefore, to ensure environmental and operator safety, it is essential to monitor the activity of I-129 in the airborne effluent in the process piping of a nuclear fuel element reprocessing site.
However, due to the low I-129 content of fission gases and the difference in activity between Kr-85 and its activity of at least 106Of the order of magnitude, e.g., a 62GW fuel rod cooled for five years, wherein Kr-85 activity is 7.06X 1012The activity of Bq, I-129 was 3.726X 106Bq, therefore, the effect of Kr-85 must be eliminated when continuously monitoring the activity concentration of I-129 in the nuclear component post-treatment field on-line.
In addition, because the mixed gas contains nitric acid type acidic substances (nitric oxide mono-acid or composite acid), in order to ensure that the radiation monitoring system works stably and reliably for a long time, the radiation monitoring system also has to have acid resistance and corrosion resistance, the I-129 radioactivity is high in front of an iodine absorption tower in a nuclear fuel element post-treatment site, and a high-range acid-proof type I-129 radiation monitoring system applied in front of the iodine absorption tower is also lacked in the prior art.
Disclosure of Invention
The invention aims to solve the technical problem of providing a high-range acid-proof I-129 radiation monitoring system aiming at the defects in the prior art, which has reasonable structural design and convenient realization, can be applied to the I-129 radioactivity monitoring in the iodine absorption tower of the nuclear fuel element post-processing place, effectively improves the acid resistance and the detection range during the I-129 radiation monitoring, has good use effect and is convenient to popularize and use.
In order to solve the technical problems, the invention adopts the technical scheme that: a high-range acid-proof I-129 radiation monitoring system comprises a mounting bracket, wherein a sampling pipeline unit, a sampling detection unit, an on-site radiation processing unit and an electric control unit are arranged on the mounting bracket; the sampling pipeline unit comprises a sampling gas inlet joint, a purge gas inlet joint, a sampling gas outlet joint, a sampling gas inlet pipe, a purge gas inlet pipe and a sampling gas outlet header pipe, and an aerosol filter is arranged at the front end of the sampling gas inlet joint; one end of the sampling gas inlet pipe is connected with a sampling gas inlet joint, the other end of the sampling gas inlet pipe is connected with a sampling detection unit, a first stop valve, a first flowmeter, a first electromagnetic directional valve and a first regulating valve are sequentially arranged on the sampling gas inlet pipe from the sampling gas inlet joint to the sampling detection unit, a first connecting pipe is connected on one section of the sampling gas inlet pipe between the first flowmeter and the first electromagnetic directional valve, one end of the purging gas inlet pipe is connected with the purging gas inlet joint, the other end of the purging gas inlet pipe is connected with the sampling detection unit, a second stop valve, a one-way valve, a second flowmeter, a second electromagnetic directional valve and a second regulating valve are sequentially arranged on the purging gas inlet pipe from the purging gas inlet joint to the sampling detection unit, a second communicating pipe is connected to a section of the purge gas inlet pipe between a second flowmeter and a second electromagnetic directional valve, the first communicating pipe is connected with the second electromagnetic directional valve, the second communicating pipe is connected with the first electromagnetic directional valve, one end of the sampling gas outlet main pipe is connected with a sampling gas outlet joint, the other end of the sampling gas outlet main pipe is connected with a first sampling gas outlet branch pipe and a second sampling gas outlet branch pipe, the first sampling gas outlet branch pipe and the second sampling gas outlet branch pipe are both connected with a sampling detection unit, a third stop valve is arranged on the sampling gas outlet main pipe, a first sampling pump is arranged on the first sampling gas outlet branch pipe, and a second sampling pump is arranged on the second sampling gas outlet branch pipe; the sampling detection unit comprises a shielding chamber, a first iodine sampler and a second iodine sampler are arranged on the side face of the shielding chamber in parallel, a lead stop block is arranged between the first iodine sampler and the second iodine sampler, an electric sliding table is arranged on the bottom face of the shielding chamber, an iodine detector is arranged on the electric sliding table, a sampling gas inlet pipe and a first sampling gas outlet branch pipe are communicated with the first iodine sampler, and a purging gas inlet pipe and a second sampling gas outlet branch pipe are communicated with the second iodine sampler; the end face, close to the iodine detector, of the first iodine sampler is provided with a first carbon fiber end socket, and the end face, close to the iodine detector, of the second iodine sampler is provided with a second carbon fiber end socket.
According to the high-range acid-proof I-129 radiation monitoring system, the electric control unit supplies power to the local radiation processing unit and performs signal transmission with the local radiation processing unit, and transmission signals between the electric control unit and the local radiation processing unit comprise analog quantity, switching quantity and RS485 signals.
In the high-range acid-proof I-129 radiation monitoring system, the sampling gas inlet pipe, the first stop valve, the first flowmeter, the first regulating valve, the first communicating pipe, the second stop valve, the one-way valve, the second flowmeter, the second regulating valve, the second communicating pipe and the third stop valve in the sampling pipeline unit are all made of 316L stainless steel.
In the high-range acid-proof I-129 radiation monitoring system, the valve cores of the first sampling pump and the second sampling pump, and the first stop valve, the first regulating valve, the second stop valve, the one-way valve and the third stop valve in the sampling pipeline unit are all made of polytetrafluoroethylene.
In the high-range acid-proof I-129 radiation monitoring system, the first electromagnetic directional valve and the second electromagnetic directional valve are both two-in one-out electromagnetic directional valves.
In the high-range acid-proof I-129 radiation monitoring system, the first sampling pump and the second sampling pump are acid-proof pumps.
In the high-range acid-proof I-129 radiation monitoring system, the first iodine sampler and the second iodine sampler are arranged at intervals with the iodine detector.
The iodine detector comprises a NaI crystal, a photomultiplier and a signal processing module, wherein a light guide is arranged between the NaI crystal and the photomultiplier, and the photomultiplier receives an optical signal transmitted by the NaI crystal, performs photoelectric conversion and multiplication on the optical signal and transmits the optical signal to the signal processing module.
The high-range acid-proof I-129 radiation monitoring system is characterized in that the NaI crystals have the size
The invention also discloses an I-129 radiation monitoring method, which comprises the following steps:
connecting the sampling gas inlet joint and the sampling gas outlet joint to a main exhaust pipe;
step two, opening the first stop valve, the second stop valve and the third stop valve;
step three, starting the first sampling pump and the second sampling pump;
step four, the sampling detection unit continuously samples the gas in the main exhaust duct, and the specific process is as follows:
step 401, the first electromagnetic directional valve works, the communication between the first electromagnetic directional valve and the second communicating pipe is closed, meanwhile, the second electromagnetic directional valve works, and the communication between the second electromagnetic directional valve and the first communicating pipe is closed;
step 402, under the action of the first sampling pump, gas in the main exhaust pipe enters a first iodine sampler through a sampling gas inlet pipe and is discharged into a sampling gas outlet main pipe through a first sampling gas outlet branch pipe; the iodine detector slides to the first iodine sampler through an electric sliding table to perform I-129 activity detection; simultaneously, blowing and washing the gas into a second iodine sampler through a blowing and washing gas inlet pipe, and blowing and washing the second iodine sampler to remove Kr-85 inert gas in the second iodine sampler; meanwhile, under the action of the second sampling pump, the purge gas enters the second iodine sampler through the purge gas inlet pipe and is discharged into the sampling gas outlet main pipe through the second sampling gas outlet branch pipe;
step 403, time T is elapsed;
404, operating the first electromagnetic directional valve, opening the communication between the first electromagnetic directional valve and the second communicating pipe, and simultaneously operating the second electromagnetic directional valve, opening the communication between the second electromagnetic directional valve and the first communicating pipe;
step 405, under the action of the second sampling pump, gas in the main exhaust pipe enters a second iodine sampler through a second communicating pipe and a purge gas inlet pipe, and is discharged into a sampling gas outlet main pipe through a second sampling gas outlet branch pipe, and the iodine detector slides to the second iodine sampler through an electric sliding table to perform I-129 activity detection; meanwhile, purging gas enters the first iodine sampler through the first communicating pipe and the sampling gas inlet pipe, purging is carried out on the first iodine sampler, and Kr-85 inert gas in the first iodine sampler is removed; meanwhile, under the action of the first sampling pump, the purge gas enters the first iodine sampler through the first communicating pipe and the sampling gas inlet pipe, and is discharged into the sampling gas outlet main pipe through the first sampling gas outlet branch pipe;
and step 406, after the time T, returning to the step 401 to realize continuous radiation monitoring.
Compared with the prior art, the invention has the following advantages:
1. the system of the invention has reasonable structural design and convenient realization.
2. The sampling gas inlet pipe, the first stop valve, the first flowmeter, the first regulating valve, the first communicating pipe, the second stop valve, the one-way valve, the second flowmeter, the second regulating valve, the second communicating pipe and the third stop valve in the sampling pipeline unit are all made of 316L stainless steel, so that the acid resistance and the corrosion resistance are improved.
3. The valve cores of the first sampling pump and the second sampling pump, the first stop valve, the first regulating valve, the second stop valve, the one-way valve and the third stop valve in the sampling pipeline unit are all made of polytetrafluoroethylene, so that the acid resistance and the corrosion resistance are improved.
4. The carbon fiber end sockets are arranged on the sides, close to the iodine detectors, of the first iodine sampler and the second iodine sampler, the carbon fibers can resist nitric acid, meanwhile, the first iodine sampler and the second iodine sampler are arranged at intervals with the iodine detectors, sampling gas is isolated from the iodine detectors, the iodine detectors are not in direct contact with the sampling gas, and an acid-proof effect is achieved.
5. The large-caliber aerosol filter is additionally arranged at the front end of the sampling gas inlet joint, high-outgassing aerosol is filtered to eliminate interference, and high-range I-129 radiation monitoring is realized.
6. According to the invention, the NaI crystal with the thickness of 5mm is designed, so that I-129 low-energy gamma rays can be detected.
7. The invention can be applied to the I-129 radioactivity monitoring in front of the iodine absorption tower in the nuclear fuel element post-processing place, effectively improves the acid resistance and the detection range in the I-129 radiation monitoring process, has good use effect and is convenient to popularize and use.
In conclusion, the system disclosed by the invention is reasonable in structural design and convenient to realize, can be applied to the I-129 radioactivity monitoring in front of the iodine absorption tower in the nuclear fuel element post-processing place, effectively improves the acid resistance and the detection range in the I-129 radiation monitoring process, is good in use effect, and is convenient to popularize and use.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic structural diagram of a sampling probe unit according to the present invention;
FIG. 3 is a schematic diagram of the structure of the iodine detector of the present invention.
Description of reference numerals:
1-a sampled gas inlet connection; 2-purge gas inlet fitting; 3-sampling gas outlet joint;
4, sampling a gas inlet pipe; 5-a purge gas inlet pipe; 6, sampling a gas outlet header pipe;
8-a first stop valve; 9 — a first flow meter; 10-a first electromagnetic directional valve;
11-a first regulating valve; 12-a first communication pipe; 14-a second stop valve;
15-a one-way valve; 16 — a second flow meter; 17-a second electromagnetic directional valve;
18-second regulating valve; 19-a second communicating tube; 21-first sampling gas outlet branch pipe;
22-second sampling gas outlet branch pipe; 23 — a third stop valve; 24 — a first sampling pump;
25-a second sampling pump; 31-a shielded room;
32-first iodine sampler; 33-second iodine sampler; 34-a lead stop;
36-electric slipway; 37-iodine detector; 37-1-NaI crystal;
37-2-photomultiplier tube; 37-3-signal processing module; 37-4-a light guide;
38-a first carbon fiber end socket; 39-second carbon fiber end socket; 40-an aerosol filter;
41, mounting a bracket; 42-in situ radiation treatment unit; 43-electric control unit.
Detailed Description
As shown in FIG. 1, the high-range acid-proof I-129 radiation monitoring system comprises a mounting bracket 41, wherein a sampling pipeline unit, a sampling detection unit, an on-site radiation processing unit 42 and an electric control unit 43 are arranged on the mounting bracket 41; the sampling pipeline unit comprises a sampling gas inlet joint 1, a purge gas inlet joint 2, a sampling gas outlet joint 3, a sampling gas inlet pipe 4, a purge gas inlet pipe 5 and a sampling gas outlet main pipe 6, and an aerosol filter 40 is arranged at the front end of the sampling gas inlet joint 1; the one end and the sampling gas inlet of sample gas intake pipe 4 connect 1, the other end and the sampling detection unit of sample gas intake pipe 4 are connected, sample gas intake pipe 4 is last to have set gradually first stop valve 8, first flowmeter 9, first electromagnetic directional valve 10 and first governing valve 11 from sampling gas inlet joint 1 to the sampling detection unit direction, be located one section between first flowmeter 9 and the first electromagnetic directional valve 10 be connected with first connecting tube 12 on the sample gas intake pipe 4, the one end and the purge gas inlet of purge gas intake pipe 5 connect 2, the other end and the sampling detection unit of purge gas intake pipe 5 are connected, purge gas intake pipe 5 is last to have set gradually second stop valve 14, check valve 15 from purge gas inlet 2 to the sampling detection unit direction, A second communicating pipe 19 is connected to a section of the purge gas inlet pipe 5 between the second flowmeter 16 and the second electromagnetic directional valve 17, the first communicating pipe 12 is connected to the second electromagnetic directional valve 17, the second communicating pipe 19 is connected to the first electromagnetic directional valve 10, one end of the sampling gas outlet header pipe 6 is connected to the sampling gas outlet connector 3, the other end of the sampling gas outlet header pipe 6 is connected to a first sampling gas outlet branch pipe 21 and a second sampling gas outlet branch pipe 22, the first sampling gas outlet branch pipe 21 and the second sampling gas outlet branch pipe 22 are both connected to the sampling detection unit, a third stop valve 23 is arranged on the sampling gas outlet header pipe 6, and a first sampling pump 24 is arranged on the first sampling gas outlet branch pipe 21, a second sampling pump 25 is arranged on the second sampling gas outlet branch pipe 22; as shown in fig. 2, the sampling detection unit includes a shielding chamber 31, a first iodine sampler 32 and a second iodine sampler 33 are arranged in parallel on the side surface of the shielding chamber 31, a lead stopper 34 is arranged between the first iodine sampler 32 and the second iodine sampler 33, an electric sliding table 36 is arranged on the bottom surface of the shielding chamber 31, an iodine detector 37 is arranged on the electric sliding table 36, the sampling gas inlet pipe 4 and the first sampling gas outlet branch pipe 21 are both communicated with the first iodine sampler 32, and the purging gas inlet pipe 5 and the second sampling gas outlet branch pipe 22 are both communicated with the second iodine sampler 33; the end face of the first iodine sampler 32 close to the iodine detector 37 is provided with a first carbon fiber end socket 38, and the end face of the second iodine sampler 33 close to the iodine detector 37 is provided with a second carbon fiber end socket 39.
During specific implementation, a large-caliber aerosol filter is additionally arranged at the front end of the sampling gas inlet joint, and high-outgassing aerosol is filtered to eliminate interference.
During the concrete implementation, the carbon fiber can be resistant to nitric acid, and the acid resistance of the system is improved through the first carbon fiber end socket 38 and the second carbon fiber end socket 39.
In specific implementation, in order to effectively isolate gamma interference of an external environment, the sampling detection unit is arranged in a shielding chamber 31 formed by lead with the thickness of 50mm and stainless steel with the thickness of 20mm, and the attenuation of the gamma background by the shielding chamber 31 with the thickness can reach more than 120 times.
In specific implementation, the iodine detector 37 is mounted on the electric sliding table 36, and the position is switched between the first iodine sampler 32 and the second iodine sampler 33; the iodine detector 37 is spaced to face the first iodine box 32-3 in the first iodine sampler 32 or the second iodine box 33-3 in the second iodine sampler 33 during measurement.
In particular, the lead block 34 is used to isolate the first iodine sampler 32 and the second iodine sampler 33 from interfering with each other.
In this embodiment, the electrical control unit 43 supplies power to the local radiation processing unit 42 and performs signal transmission with the local radiation processing unit 42, and the transmission signal between the electrical control unit 43 and the local radiation processing unit 42 includes an analog quantity, a switching quantity and an RS485 signal.
In particular implementation, the electrical control unit 43 provides power to the in-situ radiation processing unit 42; various types of input/output terminals are provided for a system, including: 2-path 4-20 mA analog quantity output, 4-path switching value output (fault/failure, test/source detection, high value alarm and high value alarm), and 2-path RS485 communication (measurement result and control).
In this embodiment, the sampling gas inlet pipe 4, the first stop valve 8, the first flow meter 9, the first regulating valve 11, the first communicating pipe 12, the second stop valve 14, the check valve 15, the second flow meter 16, the second regulating valve 18, the second communicating pipe 19 and the third stop valve 23 in the sampling pipe unit are all made of 316L stainless steel.
In specific implementation, the stainless steel 316L is resistant to nitric acid.
In this embodiment, the valve cores of the first sampling pump 24 and the second sampling pump 25, and the first stop valve 8, the first regulating valve 11, the second stop valve 14, the check valve 15, and the third stop valve 23 in the sampling pipeline unit are all made of teflon.
In specific implementation, the polytetrafluoroethylene can resist nitric acid.
In this embodiment, the first electromagnetic directional valve 10 and the second electromagnetic directional valve 17 are both two-in one-out electromagnetic directional valves.
In this embodiment, the first sampling pump 24 and the second sampling pump 25 are acid-proof pumps.
In specific implementation, an acid-proof pump is adopted to improve the acid resistance.
In this embodiment, the first iodine sampler 32 and the second iodine sampler 33 are both spaced apart from the iodine detector 37.
During specific implementation, first iodine sampler and second iodine sampler all set up with the iodine detector interval, keep apart sample gas and iodine detector, and the iodine detector does not play the acid-proof effect with sample gas direct contact.
In this embodiment, as shown in fig. 3, the iodine detector 37 includes a NaI crystal 37-1, a photomultiplier 37-2, and a signal processing module 37-3, a light guide 37-4 is disposed between the NaI crystal 37-1 and the photomultiplier 37-2, and the photomultiplier 37-2 receives an optical signal transmitted by the NaI crystal 37-1, performs photoelectric conversion and multiplication on the optical signal, and transmits the optical signal to the signal processing module 37-3.
In this example, the NaI crystals 37-1 have a size of
In specific implementation, I-129 low-energy gamma rays can be detected through 5 mm-thick NaI crystals 37-1.
The invention discloses a high-range acid-proof I-129 radiation monitoring method, which comprises the following steps:
step one, connecting the sampling gas inlet joint 1 and the sampling gas outlet joint 3 to a main exhaust pipe;
step two, opening the first stop valve 8, the second stop valve 14 and the third stop valve 23;
step three, starting the first sampling pump 24 and the second sampling pump 25;
step four, the sampling detection unit continuously samples the gas in the main exhaust duct, and the specific process is as follows:
step 401, the first electromagnetic directional valve 10 works to close the communication between the first electromagnetic directional valve 10 and the second communicating pipe 19, and simultaneously, the second electromagnetic directional valve 17 works to close the communication between the second electromagnetic directional valve 17 and the first communicating pipe 12;
step 402, under the action of the first sampling pump 24, the gas in the main exhaust pipe enters the first iodine sampler 32 through the sampling gas inlet pipe 4, and is discharged into the sampling gas outlet main pipe 6 through the first sampling gas outlet branch pipe 21; the iodine detector 37 slides to the first iodine sampler 32 through the electric sliding table 36 to perform I-129 activity detection; meanwhile, the purge gas enters the second iodine sampler 33 through the purge gas inlet pipe 5, the second iodine sampler 33 is purged, and Kr-85 inert gas in the second iodine sampler 33 is removed; meanwhile, under the action of the second sampling pump 25, the purge gas enters the second iodine sampler 33 through the purge gas inlet pipe 5 and is discharged into the sampling gas outlet main pipe 6 through the second sampling gas outlet branch pipe 22;
step 403, time T is elapsed;
in specific implementation, the value of T is 300 s.
Step 404, the first electromagnetic directional valve 10 works, the communication between the first electromagnetic directional valve 10 and the second communicating pipe 19 is opened, meanwhile, the second electromagnetic directional valve 17 works, and the communication between the second electromagnetic directional valve 17 and the first communicating pipe 12 is opened;
step 405, under the action of the second sampling pump 25, the gas in the main exhaust pipe enters the second iodine sampler 33 through the second communicating pipe 19 and the purge gas inlet pipe 5, and is discharged into the sampling gas outlet main pipe 6 through the second sampling gas outlet branch pipe 22, and the iodine detector 37 slides to the second iodine sampler 33 through the electric sliding table 36 to perform I-129 activity detection; meanwhile, the purge gas enters the first iodine sampler 32 through the first communication pipe 12 and the sampling gas inlet pipe 4, and the first iodine sampler 32 is purged to remove Kr-85 inert gas in the first iodine sampler 32; meanwhile, under the action of the first sampling pump 24, the purge gas enters the first iodine sampler 32 through the first communication pipe 12 and the sampling gas inlet pipe 4, and is discharged into the sampling gas outlet header pipe 6 through the first sampling gas outlet branch pipe 21;
and step 406, after the time T, returning to the step 401 to realize continuous radiation monitoring.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.