A method for measuring the temperature coefficient of reactor moderators under power conditions

Abstract

This invention belongs to the technical field of reactor moderator temperature coefficient measurement methods under power conditions, specifically relating to a method for measuring the reactor moderator temperature coefficient under power conditions. It includes the following steps: Step 1: Confirm or create a reactor xenon imbalance state; Step 2: Set the control rods to manual mode, maintaining constant power and boron concentration; Step 3: Collect reactor power and moderator temperature data to measure the moderator temperature coefficient; Step 4: Calculate xenon toxicity based on power; Step 5: Obtain the Doppler temperature coefficient α under this state according to the design. dop Step 6: Calculate the overall temperature coefficient α ttc The overall temperature coefficient α ttc It equals the negative of the reciprocal of the slope of the rate at which the average temperature of the moderator changes with xenon toxicity; Step 7: Based on α mod =α ttc -α dop Calculation of the temperature coefficient of a moderator. This invention provides a method for measuring the temperature coefficient of a moderator using changes in xenon toxicity. The xenon toxicity calculation is reliable, the measurement time is short, and the measurement error of the temperature coefficient of the moderator can be reduced.

Description

Technical Field

[0001] This invention belongs to the technical field of reactor moderator temperature coefficient measurement methods under power conditions, specifically relating to a method for measuring the reactor moderator temperature coefficient under power conditions. Background Technology

[0002] During the operation of nuclear power plants, the moderator temperature coefficient (MTC) must be measured. The MTC is defined as the change in reactivity caused solely by the moderator for every 1°C change in the average moderator temperature. Currently, common methods include the boron reduction method, the rod insertion method, and the burnup method. However, these methods have various drawbacks, such as large measurement errors or excessively long measurement times, making them unsatisfactory. Accurate measurement of the reactivity coefficient under power conditions has always been a challenge in the industry.

[0003] This invention provides a method for measuring the temperature coefficient of reactor moderators that differs from the above-mentioned method under power conditions, and can solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a method for measuring the temperature coefficient of a reactor moderator under power conditions, which can measure the temperature coefficient of the moderator.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for measuring the temperature coefficient of a reactor moderator under power conditions includes the following steps:

[0007] Step 1: Confirm or create a xenon imbalance state in the reactor;

[0008] Step 2: Set the control rod to manual mode, keep the power constant, and keep the boron concentration constant;

[0009] Step 3: Collect reactor power and moderator temperature data to measure the moderator temperature coefficient;

[0010] Step 4: Calculate xenon toxicity based on power;

[0011] Step 5: Obtain the Doppler temperature coefficient α under this condition according to the design. dop ;

[0012] Step 6: Calculate the total temperature coefficient α according to equation (3). ttc The overall temperature coefficient α ttc It is equal to the negative of the inverse of the slope of the rate at which the average temperature of the moderator changes with xenon toxicity;

[0013]

[0014] Step 7: Based on α mod =α ttc -αdop Calculate the temperature coefficient of the moderator.

[0015] The specific implementation method for step one is to increase the reactor power from low power to high power or decrease it from high power to low power.

[0016] The specific implementation method of step six is ​​as follows: obtain the average reactor temperature during the test through DCS, use the xenon poison calculation result as the X coordinate and the average reactor temperature as the Y coordinate, and calculate the slope during this time period.

[0017] The beneficial effects achieved by this invention are as follows:

[0018] This invention provides a method for measuring the temperature coefficient of a moderator using xenon toxicity changes. The xenon toxicity calculation is reliable, the measurement time is short, and the measurement error of the temperature coefficient of the moderator can be reduced. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments.

[0020] Under power conditions, with constant power, stationary control rods, and constant boron concentration, the reactor reactivity changes caused by xenon imbalance are compensated for by changes in moderator temperature. In the short term, changes in samarium poisoning and burnup are negligible. Based on the reactivity balance equation, we can obtain:

[0021]

[0022] In the formula The rate of change of reactivity introduced by xenon poisoning, α represents the rate of change of temperature of the moderator. ttc The total temperature coefficient is defined as the change in core reactivity caused by the temperature changes of the fuel and moderator for every 1°C change in the average temperature of the moderator. It is equal to the sum of the moderator temperature coefficient and the Doppler temperature coefficient.

[0023] The above equation shows that the temperature change of the moderator is caused by the xenon toxicity change. From the above equation, we can obtain:

[0024]

[0025] That is, the total temperature coefficient is equal to the negative of the ratio of the rate of change of xenon poison to the rate of change of the average temperature of the moderator. Further simplifying the above equation, we get:

[0026]

[0027] From the above formula, we can also obtain that the total temperature coefficient is equal to the negative of the reciprocal of the slope of the moderator's average temperature as a function of xenon poisoning.

[0028] After obtaining the total temperature coefficient in the experiment, the moderator temperature coefficient αmod =α ttc -α dop In the formula α dop is the Doppler temperature coefficient.

[0029] The xenon compensation test method is as follows: Confirm or create a xenon imbalance state, such as increasing or decreasing the power, then keep the power constant, keep the control rod stationary, keep the boron concentration constant, and collect the power and moderator temperature data of the reactor during this period.

[0030] 1. By maintaining constant power, keeping the control rods stationary, and keeping the boron concentration constant while the reactor is in a xenon imbalance state, the power and moderator temperature data of the reactor are collected during this period to measure the moderator temperature coefficient;

[0031] 2. Calculate xenon toxicity based on power;

[0032] 3. Calculate the total temperature coefficient according to equation (2) or (3);

[0033] 4. Obtain the Doppler temperature coefficient α under this condition according to the design. dop ;

[0034] 5. According to α mod =α ttc -α dop Calculate the temperature coefficient of the moderator.

[0035] The technical solution of this invention includes the following steps:

[0036] Step 1: Confirm or create a xenon imbalance state in the reactor, such as:

[0037] Increase the reactor power from low power to high power or decrease it from high power to low power;

[0038] Step 2: Set the control rod to manual mode, keep the power constant, and keep the boron concentration constant;

[0039] Step 3: Obtain the data required for calculation: the temperature and power of the moderator during the experiment;

[0040] Step 4: Calculate xenon toxicity based on power

[0041] Step 5: Obtain the Doppler temperature coefficient α under this condition according to the design. dop , such as α dop = -3 pcm / ℃;

[0042] Step 6: Calculate the total temperature coefficient according to equation (2) or (3);

[0043] The average reactor temperature during the test was obtained using DCS or other means. The xenon toxicity calculation result was used as the X-axis, and the average reactor temperature was used as the Y-axis. The slope of the time period was calculated. A curve showing the change of the average temperature of the moderator with xenon toxicity was obtained. The slope of the curve was 0.00332℃ / pcm. According to Equation (3), the total temperature coefficient can be calculated to be -30.1pcm / ℃.

[0044] Step 7: Based on α mod =α ttc -α dop Calculate the temperature coefficient of the moderator;

[0045] α mod =α ttc -α dop =-30.1-(-3)=-27.1pcm / ℃.

Claims

1. A method for measuring the temperature coefficient of a reactor moderator under power conditions, characterized in that: Includes the following steps: Step 1: Confirm or create a xenon imbalance state in the reactor; Step 2: Set the control rod to manual mode, keep the power constant, and keep the boron concentration constant; Step 3: Collect reactor power and moderator temperature data to measure the moderator temperature coefficient; Step 4: Calculate xenon toxicity based on power; Step 5: Obtain the Doppler temperature coefficient α under this condition according to the design. dop ; Step 6: Calculate the total temperature coefficient α according to equation (2). ttc The overall temperature coefficient α ttc It is equal to the negative of the reciprocal of the slope of the rate at which the average temperature of the moderator changes with xenon toxicity; where The rate of change of reactivity introduced by xenon poisoning, The rate of change of the moderator temperature; Step 7: Based on α mod =α ttc -α dop Calculate the temperature coefficient of the moderator; The specific implementation method for step one is to increase the reactor power from low power to high power or decrease it from high power to low power; The specific implementation method of step six is ​​as follows: obtain the average reactor temperature during the test through DCS, use the xenon poison calculation result as the X coordinate and the average reactor temperature as the Y coordinate, and calculate the slope within the time period of step two.

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