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

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.