CN-122017941-A - Pulse neutron generating device for cutting steady neutron radiation and pulse time measuring method

CN122017941ACN 122017941 ACN122017941 ACN 122017941ACN-122017941-A

Abstract

The invention discloses a pulse neutron generating device for cutting steady-state neutron radiation and a pulse time measuring method, comprising a steady-state neutron radiation source device, a shielding structure, a supporting frame, a collimator provided with a conical beam limiting diaphragm, a cutting slide block which is made of neutron absorbing materials and internally provided with a beam limiting hole, a slide block falling stabilizing device, a slide block height adjusting device, a slide block releasing device and a detector positioned at an emergent side, wherein the cutting slide block is made of neutron absorbing materials; the cutting slide block freely falls along a vertical track defined by the falling stabilizing device after being released at a preset height, time cutting is carried out on steady neutron beams passing through the collimator, a reference point is arranged on a supporting frame by the pulse time measuring method, an optoelectronic probe A, an optoelectronic probe B and a timer are arranged near a falling path, the two optoelectronic probes are sequentially shielded in the falling process of the cutting slide block to trigger the timer to start/stop timing, and a time interval recorded by the timer is determined to be the actual pulse width of the pulse neutron radiation.

Inventors

FANG DENGFU
WEI YINGJING
TANG ZHIHUI
ZHANG JIAOYU
SUN BOWEN
DUAN JIAYU
FENG MEI
CUI WEI
CHEN SHUANGQIANG
HUANG ZHENGLIN

Assignees

中国辐射防护研究院

Dates

Publication Date: 20260512
Application Date: 20260109

Claims (7)

1. A pulsed neutron production device that cuts steady-state neutron radiation, comprising: a steady-state neutron radiation source device for generating a steady-state neutron beam; The shielding structure is arranged outside the steady neutron radiation source device and is used for forming a standard radiation field space; a support frame disposed in front of the steady state neutron radiation source device; The collimator is fixed on the supporting frame, is of a cylindrical structure, and is internally provided with a conical beam limiting diaphragm for limiting the emergent direction and the beam spot size of neutron radiation; The cutting slide block is made of neutron absorbing materials, is arranged on the emergent side of the collimator, is internally provided with a penetrating beam limiting hole, and attenuates the neutron dose rate by at least 500 times relative to the unshielded state when the cutting slide block completely blocks the neutron beam; the sliding block falling stabilizing device is connected with the supporting frame and used for limiting the falling track of the cutting sliding block along the vertical direction and stabilizing the posture of the cutting sliding block; the sliding block height adjusting device is connected with the cutting sliding block through a flexible connecting piece and used for lifting the cutting sliding block to a preset height and maintaining the preset height; The slide block release device is matched with the cutting slide block and the slide block height adjusting device and is used for disengaging the cutting slide block from the slide block height adjusting device at a preset height so that the cutting slide block can freely fall along a track defined by the slide block falling stabilizing device under the action of gravity; The detector is arranged on the emergent side of the cutting slide block and is used for measuring the neutron dose rate after passing through the cutting slide block; When the cutting slide block freely falls from a preset height under the action of gravity, the beam limiting hole on the cutting slide block and the beam limiting diaphragm of the collimator move relatively, and the steady neutron beam passing through the collimator is subjected to time cutting, so that pulse neutron radiation with millisecond-order pulse width is formed.
2. The pulsed neutron production device for cutting steady-state neutron radiation according to claim 1, wherein the cutting slide comprises an inner layer and an outer layer, wherein the inner layer is a boron-containing polyethylene shielding layer with the thickness of 15cm and is used for absorbing neutrons, and the outer layer is a steel ladle shell with the thickness of 2cm and is used for enhancing mechanical strength and providing gamma radiation shielding.
3. The pulsed neutron production device of claim 1, wherein the slider drop stabilizing device comprises: The small sliding block is arranged on one side of the cutting sliding block, and a plurality of pulleys are rotatably arranged on the small sliding block; The sliding groove is matched with the small sliding block, the sliding groove is fixed on the supporting frame and made of aluminum alloy material, the section of the sliding groove is concave, the pulley is clamped in the sliding groove and is in sliding connection with the sliding groove, The pulleys of the small slide blocks roll in the sliding grooves, so that the cutting slide blocks are limited and guided in the falling process, the posture of the cutting slide blocks is kept stable, and the falling path of the cutting slide blocks is limited.
4. A pulse time measuring method for measuring pulse time of pulsed neutron radiation generated by the pulsed neutron production device of any of claims 1-3, comprising the steps of: setting a reference point on the support frame, wherein the reference point corresponds to the position of the cutting slide block when the beam limiting hole passes through the initial position of the pulse interval in the falling process; A light triggering timing system is arranged near the falling path of the cutting slide block and comprises an optoelectronic probe A, an optoelectronic probe B and a timer electrically connected with the optoelectronic probe A and the optoelectronic probe B; Lifting the cutting slide block to a preset height, releasing the cutting slide block through a slide block release device, enabling the cutting slide block to freely fall under the action of gravity, and outputting a trigger signal to a timer by the photoelectric probe A to enable the timer to start timing when the cutting slide block shields the light of the photoelectric probe A in the falling process; When the cutting slide block blocks the light of the photoelectric probe B, the photoelectric probe B outputs a stop signal to the timer to stop the timer; And the time interval between the starting triggering time and the stopping triggering time recorded by the timer corresponds to the corresponding relation between the moment when the lower edge of the beam limiting hole of the cutting slide block reaches the reference point and the moment when the upper edge of the beam limiting hole reaches the reference point in the moving process of the cutting slide block, so that the time interval is determined to be the actual pulse width of the pulse neutron radiation.
5. The method of claim 4, wherein the reference point is determined by: lifting the cutting slide block to a position for completely shielding the steady neutron beam, and measuring the neutron dose rate at the moment by using a detector to obtain a measured value M1; adjusting the cutting slide block to enable the center of the beam limiting hole of the cutting slide block to be at the same height as the center of the steady neutron radiation source; Moving the cutting slide block upwards until the neutron dose rate measured by the detector is equal to M1; and taking the corresponding height of the lower edge of the beam limiting hole of the cutting slide block on the supporting frame at the moment as the reference point.
6. The method of claim 4, further comprising the step of theoretically calculating the pulse time: And calculating the theoretical pulse width of the pulse neutron radiation according to the uniform acceleration linear motion relation by taking the pulse interval length, the gravity acceleration and the instantaneous speed of the cutting slide block at the starting point of the pulse interval corresponding to the pulse neutron radiation as parameters, and comparing the theoretical pulse width with the actual pulse width.
7. The method of claim 4, further comprising the step of measuring a pulse neutron dose rate of the pulse neutron radiation produced by the pulse neutron production device: placing a scintillator detector for measuring the dose rate in a standard isotope neutron source metering standard device for calibration to obtain a calibration factor N of the scintillator detector; And placing the sensitive volume of the scintillator detector at the center of the radiation beam of the pulse neutron generating device, releasing the cutting slide blocks under different lifting heights of the cutting slide blocks, respectively measuring corresponding dose rate indication values M, multiplying each indication value M by a calibration factor N to obtain pulse neutron dose rates under different pulse conditions, and combining the pulse neutron dose rates with the actual pulse width to be used for representing the pulse parameters of the pulse neutron radiation field.

Description

Pulse neutron generating device for cutting steady neutron radiation and pulse time measuring method Technical Field The invention relates to the field of ionizing radiation metering, in particular to a pulse neutron generating device for cutting steady-state neutron radiation and a pulse time measuring method. Background A critical incident is an energy release event, typically due to an unexpected occurrence of a self-sustaining or divergent neutron chain reaction, typically at a nuclear fuel plant or nuclear waste reprocessing plant, and most commonly in a nuclear reactor. In critical safety accidents, a large amount of neutron and gamma radiation is usually accompanied, so that workers around the accident site can be subjected to high-dose irradiation, and even a lethal dose is reached. The change of the radiation type is pulse radiation-continuous radiation, and the pulse width of the pulse radiation is in the order of milliseconds, and the radiation type is n/gamma mixed radiation field. The main function of the critical alarm device is to detect radiation generated by a critical accident and to alert personnel. At present, a large number of critical accident alarming devices exist in a nuclear fuel plant and a post-treatment plant, and the requirements are provided in GB/T12787-2020 critical accident alarming devices, after the devices are installed, a detection alarming threshold can detect critical accidents, namely that the total absorption dose of neutron and gamma radiation in free air 2m away from a nuclear reactant is detected to be 0.2Gy within 60 seconds, and the pulse width of pulse radiation used for testing the critical accident alarming devices is 1-3 seconds. However, at present, the corresponding pulse testing device is relatively lacking in China. Disclosure of Invention To achieve the above and other related objects, the present invention discloses a pulsed neutron production device for cutting steady-state neutron radiation, comprising: a steady-state neutron radiation source device for generating a steady-state neutron beam; The shielding structure is arranged outside the steady neutron radiation source device and is used for forming a standard radiation field space; a support frame disposed in front of the steady state neutron radiation source device; The collimator is fixed on the supporting frame, is of a cylindrical structure, and is internally provided with a conical beam limiting diaphragm for limiting the emergent direction and the beam spot size of neutron radiation; The cutting slide block is made of neutron absorbing materials, is arranged on the emergent side of the collimator, is internally provided with a penetrating beam limiting hole, and attenuates the neutron dose rate by at least 500 times relative to the unshielded state when the cutting slide block completely blocks the neutron beam; the sliding block falling stabilizing device is connected with the supporting frame and used for limiting the falling track of the cutting sliding block along the vertical direction and stabilizing the posture of the cutting sliding block; the sliding block height adjusting device is connected with the cutting sliding block through a flexible connecting piece and used for lifting the cutting sliding block to a preset height and maintaining the preset height; The slide block release device is matched with the cutting slide block and the slide block height adjusting device and is used for disengaging the cutting slide block from the slide block height adjusting device at a preset height so that the cutting slide block can freely fall along a track defined by the slide block falling stabilizing device under the action of gravity; The detector is arranged on the emergent side of the cutting slide block and is used for measuring the neutron dose rate after passing through the cutting slide block; When the cutting slide block freely falls from a preset height under the action of gravity, the beam limiting hole on the cutting slide block and the beam limiting diaphragm of the collimator move relatively, and the steady neutron beam passing through the collimator is subjected to time cutting, so that pulse neutron radiation with millisecond-order pulse width is formed. Preferably, the cutting slide block comprises an inner layer and an outer layer, wherein the inner layer is a boron-containing polyethylene shielding layer with the thickness of 15cm and used for absorbing neutrons, and the outer layer is a steel ladle shell with the thickness of 2cm and used for enhancing mechanical strength and providing gamma radiation shielding. Preferably, the slide falling stabilizing device includes: The small sliding block is arranged on one side of the cutting sliding block, and a plurality of pulleys are rotatably arranged on the small sliding block; The sliding groove is matched with the small sliding block, the sliding groove is fixed on the supporting frame and made of aluminum alloy material, the