Performance evaluation of a new signal processing system design to improve CANDU SDS1 trip response during large break LOCA events

Figures & data

Figure 1. Design procedure of the new signal processing system to improve CANDU SDS1 trip response during LLOCA events.

Figure 2. Schematic representation of the trip logic based on the new signal processing algorithm.

Figure 3. Design of the new signal processing system and its comparison to the existing system for LLOCA events.

Table 1. The algorithm of converting reactor power to log amplifier voltage output.

Reactor power (% FP)	Log of reactor power	Log amplifier output (V)
below 0.0000001	←7	<0.5
0.0000001	−7	0.5
0.000001	−6	0.9
0.00001	−5	1.3
0.0001	−4	1.7
0.001	−3	2.1
0.01	−2	2.5
0.1	−1	2.9
1	0	3.3
10	1	3.7
100	2	4.1
200	2.3	4.22
1000	3	4.5

Figure 4. Schematic diagram of the new trip setpoint designation.

Figure 5. Transfer function chart of new signal processing system for LLOCA event.

Table 2. Simulation results about the trip time regarding the existing and new signal processing systems.

	Trip time (millisecond)
		The new system
Initial power level (%FP)	The existing system	(F2–F1)/F1	(F3–F1)/F1	“AND”	Spurious trips in the new system
100	225.6	118.3	101	118.3	NO
80	225.4	117.7	100.6	117.7	NO
50	224.9	116.2	99.5	116.2	NO
30	223.9	113.4	97.2	113.4	NO

Table 3. Sensitivity analysis to the trip performance of the new signal processing system at low reactor power levels.

	Trip time (millisecond)
		The new system
Initial power level (%FP)	The existing system	(F2–F1)/F1	(F3–F1)/F1	“AND”	Spurious trips in the new system
20	222.8	110^1	90.8^1	110^1	Yes^1
10	218.8	73.8^1	37.2^1	73.8^1	Yes^1

1: Two spurious trips happen in the steady state period.

Table 4. Sensitivity analysis to the trip performance of the new signal processing system at low reactor power levels (noise amplitude is half of its original).

	Trip time (millisecond)
		The new system
Initial power level (%FP)	The existing system	(F2–F1)/F1	(F3–F1)/F1	“AND”	Spurious trips in the new system
20	224.5	113.6	97	113.6	NO
10	222.8	108.5	74.5	108.5	NO

Figure 6. Estimation of the reactor peak power decrease during the LLOCA event caused by the new signal processing system.