Method for measuring drop time of a control rod cluster integrated with a rod position measurement device

1 . A method for measuring drop time of a nuclear reactor control rod cluster integrated with a rod position measurement device, wherein the method is used to measure the drop time of the nuclear reactor control rod cluster, and comprises:

S1, monitoring a voltage Ua of coils in Group A to capture a rod cluster drop signal;

S2, searching a point (tmax, Vmax) with a maximum drop speed;

S3, retroactively calculating, from tmax, an end of a time period T4 when the nuclear reactor control rod cluster starts to drop;

S4, retroactively searching, from a minimum value point of a drop reference signal DROPref, a start of the time T4 period when the drop reference signal DROPref drops from a maximum value to 33% of the maximum value;

S5, determining, from tmax forward, a time point t1 when a drop speed of the nuclear reactor control rod cluster is lower than 0;

S6, calculating an end of a time period T6 when the drop speed of the nuclear reactor control rod cluster is 0;

S7, searching an end of a time period T5 based on a change in the drop speed of the nuclear reactor control rod cluster;

S8, calculating a time point t2 when the drop speed returns to 0 after t1;

S9, calculating a time point t3 when the drop speed returns to 0 after t2;

S10, calculating a time point t4 when the drop speed returns to 0 after t3; and

S11, performing calculation on results obtained in S1 to S10 to obtain calculation results, and saving and outputting the analysis result calculation results in a form of file;

wherein S2 comprises:

S2.1, performing digital filtering on a voltage Up of a primary coil to obtain a second filtered voltage;

S2.2, transforming a waveform of the second filtered voltage into broken lines and removing outlier points on the broken lines;

S2.3, calculating a second median sequence;

S2.4, searching among the second median sequence a point P1, wherein absolute values of the point P1 and preceding three points of the point P1 exceed 0.5;

S2.5, if a value of P1 is negative, inverting the second median sequence;

S2.6, searching backward, from P1, a point P0 with a value smaller than or equal to 0, and searching forward, from P1, a point P2 with a value smaller than or equal to 0; and

S2.7, calculating a maximal value among a section between P0 and P2 to obtain Pmax (tmax, Vmax);

wherein S7 comprises:

S7.1, retroactively searching, from t1, a point P05 with an amplitude greater than 50% of Vmax;

S7.2, retroactively searching, from t1, a point P075 with an amplitude greater than 75% of Vmax;

S7.3, determining a horizontal line Line1 passing through Pmax (tmax, Vmax);

S7.4, determining a straight line Line2 passing through P05 and P075; and

S7.5, determining a point where Line1 intersects with Line2, wherein a time point corresponding to the point is an end of the time period T5.

2 . The method according to claim 1 , wherein S1 comprises:

S1.1, performing digital filtering on the voltage Ua of the coils in Group A to obtain a first filtered voltage;

S1.2, transforming a waveform of the first filtered voltage into broken lines and removing outlier points on the broken lines;

S1.3, calculating a first median sequence of a result of $1.2;

S1.4, searching a first minimal value point P2 (tmin, Vmin) of the first median sequence;

S1.5, searching backward, from the first minimal value point, a median point P1 with a value smaller than Vmin/2;

S1.6, determining a point P0 where a line connecting the first minimal value point P2 and the median point P1 intersects with a 0-axis; and

S1.7, if a slope of a line connecting P0 and P2, a time difference between P0 and P2, and an amplitude difference between P0 and P2 are within predetermined ranges respectively, determining that the nuclear reactor control rod cluster starts to drop.

3 . The method according to claim 1 , wherein S3 comprises:

retroactively searching, from tmax, a point P04 with an amplitude smaller than 0.4*Vmax, retroactively searching, from tmax, a point P02 with an amplitude smaller than 0.2*Vmax, and determining an end of the time period where a line connecting P04 and P02 intersects with a 0-axis.

4 . The method according to claim 3 , wherein S4 comprises:

obtaining a subsequence of a value sequence corresponding to the drop reference signal DROPref before tmax, determining a minimum value point and a maximum value point of the subsequence, and searching backward, from the minimum value point, a point with a value greater than 33% of a maximum value of the subsequence.

5 . The method according to claim 4 , wherein S5 comprises:

searching, among the second median sequence and from tmax, a point with a value smaller than 0, and setting a time point corresponding to the point to be t6.

6 . The method according to claim 5 , wherein S6 comprises:

determining a point where a line connecting a point corresponding to t1 and a point corresponding to (t1-1) inserts with the 0-axis as an end t1 of the time period T6.

7 . The method according to claim 1 , wherein S11 comprises:

S11.1, calculating the time period T4 by subtracting the start of T4 from the end of T4, calculating the time period T5 by subtracting the end of T4 from the end of T5, and calculating the time period T6 by subtracting the end of T5 from the end of T6;

S11.2, verifying that T4, T5, T6 are within a threshold range;

S11.3, verifying positivity of t2, t3 and t4; and

S11.4: saving and outputting calculation results in the form of file.

8 . The method according to claim 2 , wherein S3 comprises:

retroactively searching, from tmax, a point P04 with an amplitude smaller than 0.4*Vmax, retroactively searching, from tmax, a point P02 with an amplitude smaller than 0.2*Vmax, and determining an end of the time period T4 where a line connecting P04 and P02 intersects with a 0-axis.

9 . The method according to claim 8 , wherein S4 comprises:

obtaining a subsequence of a value sequence corresponding to the drop reference signal DROPref before tmax, determining a minimum value point and a maximum value point of the subsequence, and searching backward, from the minimum value point, a point with a value greater than 33% of a maximum value of the subsequence.

10 . The method according to claim 9 , wherein S5 comprises:

searching, among the second median sequence and from tmax, a point with a value smaller than 0, and setting a time point corresponding to the point to be t1.

11 . The method according to claim 10 , wherein S6 comprises:

determining a point where a line connecting a point corresponding to t1 and a point corresponding to (t1-1) inserts with the 0-axis as an end t1 of the time period T6.

12 . The method according to claim 1 , wherein S11 comprises:

S11.1, calculating the time period T4 by subtracting the start of T4 from the end of T4, calculating the time period T5 by subtracting the end of T4 from the end of T5, and calculating the time period T6 by subtracting the end of T5 from the end of T6;

S11.2, verifying that T4, T5, T6 are within a threshold range;

S11.3, verifying positivity of t2, t3 and t4; and

S11.4: saving and outputting the calculation results in the form of file.