阅读说明：本技术 一种定位破损燃料组件的方法 (Method for positioning damaged fuel assembly ) 是由 叶刘锁 潘泽飞 杨晓强 刘健 王伟 姜宇 马旭东 金涛 于 2020-06-05 设计创作，主要内容包括：本发明涉及核电领域,尤其涉及一种定位破损燃料组件的方法。所述定位破损燃料组件的方法为：调整机组功率至40％～60％额定水平,控制棒的棒位在70％～75％堆芯高度；下插1个控制棒,监测所述控制棒位置区域内对应燃料组件的功率下降情况,并且实时监测一回路冷却剂系统管道中的裂变产物活度,绘制碘活度曲线,确定所述功率下降期间,是否出现碘活度的峰值；若出现碘活度的峰值,判定所述控制棒位置区域内存在破损燃料组件；若未出现碘活度的峰值,判定所述控制棒位置区域内的燃料组件完好；重复上述步骤,继续判定其他位置燃料组件的破损情况。所述方法,实现压水堆核电机组在功率运行期间定位破损燃料组件的位置,甄别效率高。(The invention relates to the field of nuclear power, in particular to a method for positioning a damaged fuel assembly. The method for positioning the broken fuel assembly comprises the following steps: adjusting the power of the unit to 40-60% of rated level, and the rod position of the control rod is 70-75% of the height of the reactor core; inserting 1 control rod downwards, monitoring the power reduction condition of a corresponding fuel assembly in the control rod position area, monitoring the activity of fission products in a primary loop coolant system pipeline in real time, drawing an iodine activity curve, and determining whether the peak value of the iodine activity occurs during the power reduction period; if the peak value of the iodine activity occurs, judging that a damaged fuel assembly exists in the control rod position area; if the peak value of the iodine activity does not occur, judging that the fuel assembly in the control rod position area is intact; and repeating the steps, and continuously judging the damage condition of the fuel assemblies at other positions. The method realizes the positioning of the damaged fuel assembly of the pressurized water reactor nuclear power unit during the power operation, and has high screening efficiency.)

1. A method of locating a broken fuel assembly, comprising the steps of:

step S1: adjusting the power of the unit to 40-60% of rated level, and the rod position of the control rod is 70-75% of the height of the reactor core; inserting 1 control rod at any position downwards, monitoring the power reduction condition of a corresponding fuel assembly in the control rod position area, monitoring the activity of fission products in a primary loop coolant system pipeline in real time, drawing an iodine activity curve, and determining whether a peak value of the iodine activity occurs during the power reduction period;

step S2: if the peak value of the iodine activity occurs, judging that a damaged fuel assembly exists in the control rod position area;

if the peak value of the iodine activity does not appear, judging that the corresponding fuel assembly in the control rod position area is intact;

step S3: repeating the steps S1-S2, and continuing to judge the damage condition of the fuel assemblies at other positions; until the determination of the fuel assemblies for all positions is completed.

2. The method of locating a broken fuel assembly of claim 1, wherein said step S1 further comprises: raising the rod position of the control rod and raising the power of the corresponding fuel assembly within the control rod position region to a nominal level; and monitoring the power rise condition of the corresponding fuel assembly in the control rod position area, monitoring the activity of the fission products in a loop coolant system pipeline in real time, drawing an inert gas activity curve, and determining whether the peak value of the inert gas activity occurs during the power lifting period.

3. The method of locating a broken fuel assembly of claim 2, wherein said step S2: if the peak value of the iodine activity and the peak value of the inert gas activity occur, judging that a damaged fuel assembly exists in the control rod position area;

and if the peak value of the iodine activity and the peak value of the inert gas activity do not occur, judging that the corresponding fuel assembly in the control rod position area is intact.

4. The method of locating a broken fuel assembly as set forth in claim 1, wherein in step S1, a core measurement system is used to detect a power drop condition of the corresponding fuel assembly in the control rod position region.

5. The method of locating a damaged fuel assembly according to claim 1, wherein fission product activity in the primary coolant system tubes is monitored in real time using an online detection and analysis system.

6. The method of locating a broken fuel assembly of claim 1, wherein in step S1, the power of the assembly is adjusted to a nominal level of 40% -55%.

7. The method of locating a broken fuel assembly of claim 4, wherein in step S1, the power of the assembly is adjusted to 50% of the rated level.

8. The method of positioning a broken fuel assembly of claim 1, wherein the control rods are positioned at 75% of the core height.

Technical Field

The invention relates to the field of nuclear power, in particular to a method for positioning a damaged fuel assembly.

Background

The integrity of the fuel assembly, which serves as the first safety barrier of the nuclear power plant, is directly related to the safety, reliability and economy of the nuclear power plant. Although the reliability of the fuel assembly used by the current commercial nuclear power generating unit is greatly improved along with the development of nuclear power technology, the phenomenon that the fuel assembly is damaged is continuously increased in the actual operation process of the reactor, particularly along with the large-scale development of the nuclear power generating unit.

At present, on each in-service nuclear power generating unit at home and abroad, a method for checking whether a damaged fuel assembly exists in a reactor core during power operation is mature, but the position of the damaged fuel assembly in the reactor core is still difficult to realize during power operation. The general method of finding out the position of the damaged fuel assembly is to use the pool edge sipping and leaking method after the unit is stopped, check one by one, consume a large amount of manpower, material resources and construction period, and have larger radiation risk and industrial safety risk.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the method for positioning the damaged fuel assembly is high in screening efficiency and safety.

The invention provides a method for positioning a damaged fuel assembly, which comprises the following steps:

step S1: adjusting the power of the unit to 40-60% of rated level, and the rod position of the control rod is 70-75% of the height of the reactor core; inserting 1 control rod at any position downwards, monitoring the power reduction condition of a corresponding fuel assembly in the control rod position area, monitoring the activity of fission products in a primary loop coolant system pipeline in real time, drawing an iodine activity curve, and determining whether a peak value of the iodine activity occurs during the power reduction period;

step S2: if the peak value of the iodine activity occurs, judging that a damaged fuel assembly exists in the control rod position area;

if the peak value of the iodine activity does not appear, judging that the corresponding fuel assembly in the control rod position area is intact;

step S3: repeating the steps S1-S2, and continuing to judge the damage condition of the fuel assemblies at other positions; until the determination of the fuel assemblies for all positions is completed.

Preferably, the step S1 further includes: raising the rod position of the control rod and raising the power of the corresponding fuel assembly within the control rod position region to a nominal level; and monitoring the power rise condition of the corresponding fuel assembly in the control rod position area, monitoring the activity of the fission products in a loop coolant system pipeline in real time, drawing an inert gas activity curve, and determining whether the peak value of the inert gas activity occurs during the power lifting period. .

Preferably, the step S2: if the peak value of the iodine activity and the peak value of the inert gas activity occur, judging that a damaged fuel assembly exists in the control rod position area;

and if the peak value of the iodine activity and the peak value of the inert gas activity do not occur, judging that the corresponding fuel assembly in the control rod position area is intact.

Preferably, in step S1, the core measurement system is used to detect a power drop of the corresponding fuel assembly in the control rod position region.

Preferably, the fission product activity in the primary coolant system tubes is monitored in real time using an on-line detection and analysis system.

Preferably, in step S1, the power of the unit is adjusted to 40% to 55% of the rated level.

Preferably, in step S1, the power of the unit is adjusted to 50% of the rated level.

Preferably, the control rods are positioned at 75% of the core height.

Compared with the prior art, the method for positioning the damaged fuel assembly can realize the positioning of the damaged fuel assembly in the power operation period of the pressurized water reactor nuclear power unit, thereby improving the discrimination efficiency of the damaged fuel assembly, reducing the difficulty of the detection of the damaged fuel assembly, saving the cost and having high safety.

Drawings

FIG. 1 is a flow chart illustrating a method of locating a broken fuel assembly according to the present invention;

FIG. 2 is a layout diagram of a nuclear power generating unit core measurement system according to embodiment 1 of the present invention;

FIG. 3 is a diagram showing the arrangement of a control cluster of the nuclear power plant according to embodiment 1 of the present invention;

FIG. 4 is a graph showing the activity of iodine peaks during the power-down period of the fuel assembly in example 1 of the present invention;

in FIGS. 2 and 3, reference numerals 01 to 42 denote core coordinate positions.

Detailed Description

For a further understanding of the invention, embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are included merely to further illustrate features and advantages of the invention, and are not intended to limit the invention.

An embodiment of the present invention discloses a method of locating a damaged fuel assembly, with particular reference to fig. 1, comprising the steps of:

step S1: adjusting the power of the unit to 40-60% of rated level, and the rod position of the control rod is 70-75% of the height of the reactor core; inserting 1 control rod at any position downwards, monitoring the power reduction condition of a corresponding fuel assembly in the control rod position area, monitoring the activity of fission products in a primary loop coolant system pipeline in real time, drawing an iodine activity curve, and determining whether a peak value of the iodine activity occurs during the power reduction period;

step S2: if the peak value of the iodine activity occurs, judging that a damaged fuel assembly exists in the control rod position area;

if the peak value of the iodine activity does not appear, judging that the corresponding fuel assembly in the control rod position area is intact;

step S3: repeating the steps S1-S2, and continuing to judge the damage condition of the fuel assemblies at other positions; until the determination of the fuel assemblies for all positions is completed.

The method for positioning the damaged fuel assembly realizes the positioning of the damaged fuel assembly through the disturbance of the reactor core power distribution, thereby realizing the positioning of the damaged fuel assembly during the power operation of a pressurized water reactor nuclear power unit and improving the screening efficiency of the damaged fuel assembly.

During the power operation of a nuclear power unit, the power of the fuel assemblies at the local position of the reactor core is changed, the pressure in the fuel assemblies is changed, iodine, inert gas and the like generated by fission in the fuel assemblies enter a primary loop coolant through the damaged position, and whether the damaged fuel assemblies exist at the position can be discriminated by monitoring the change trend of radioactive fission products.

In accordance with the present invention, the method of locating a broken fuel assembly is described in detail below:

step S1: adjusting the power of the unit to 40-60% of rated level, and the rod position of the control rod is 70-75% of the height of the reactor core; inserting 1 control rod at any position downwards, monitoring the power reduction condition of the corresponding fuel assembly in the control rod position area, monitoring the activity of fission products in a primary loop coolant system pipeline in real time, drawing an iodine activity curve, and determining whether the peak value of the iodine activity occurs during the power reduction period.

When the power of the unit and the rod position of the control rod are adjusted, the power distribution distortion of the reactor core can not cause the generation of related protection actions in the process of inserting the control rod at a local position, and the rod position of the control rod is in the limit range specified by the safe operation of the unit.

Preferably, the power of the unit is adjusted to 40% -55% of the rated level; more preferably, the unit power is adjusted to 50% of the rated level.

Preferably, a core measurement system is utilized to detect a power drop condition of the corresponding fuel assembly within the control rod position region.

Preferably, the fission product activity in the primary coolant system tubes is monitored in real time using an on-line detection and analysis system.

In order to improve the positioning accuracy, preferably, after the step S1 determines whether an iodine activity peak occurs during the power down period, the method further includes:

raising the rod position of the control rod and raising the power of the corresponding fuel assembly within the control rod position region to a nominal level; and monitoring the power rise condition of the corresponding fuel assembly in the control rod position area, monitoring the activity of the fission products in a loop coolant system pipeline in real time, drawing an inert gas activity curve, and determining whether the peak value of the inert gas activity occurs during the power lifting period. .

Preferably, a core measurement system is utilized to detect a power rise condition of the corresponding fuel assembly within the control rod position region.

Preferably, the fission product activity in the primary coolant system tubes is monitored in real time using an on-line detection and analysis system.

Step S2: if the peak value of the iodine activity occurs, judging that a damaged fuel assembly exists in the control rod position area;

and if the peak value of the iodine activity does not occur, judging that the corresponding fuel assembly in the control rod position area is intact.

If it is determined in the previous step that the activity peak of the inert gas occurs, the determination criteria in step S2 are:

if the peak value of the iodine activity and the peak value of the inert gas activity occur, judging that a damaged fuel assembly exists in the control rod position area;

and if the peak value of the iodine activity and the peak value of the inert gas activity do not occur, judging that the corresponding fuel assembly in the control rod position area is intact.

Step S3: after the judgment is finished, repeating the steps S1-S2, and continuously judging the damage conditions of the fuel assemblies at other positions; until the determination of the fuel assemblies for all positions is completed.

In the case of intact fuel assemblies, the iodine activity should be maintained within a plateau range in the primary coolant system tubes. Thus, in the present invention, the peak of iodine activity refers to: fluctuations above normal were found during monitoring.

Also, in the case of intact fuel assemblies, the inert gas activity in the primary coolant system tubes should be maintained within a plateau range. Thus, in the present invention, the peak value of the inert gas activity refers to: fluctuations above normal were found during monitoring.

For further understanding of the present invention, the method for positioning a damaged fuel assembly provided by the present invention is described in detail below with reference to the following examples, and the scope of the present invention is not limited by the following examples.