The Investigation of Nonavailability of Passive Safety Systems Effects on Small Break LOCA Sequence in AP1000 Using RELAP5 MOD 4.0

Table 1

Actuation set-points and time delay assumption considered for AP1000 LOCA [4].

System/function	Actuation set-points	Time delay (sec)
Reactor trip	12.41 MPa	2
“S” signal generation	11.72 MPa	2
SG feedwater valves start closing	After reactor trip signal	3.2
Main steam isolation valves start closing	After “S” signal	4.8
Reactor coolant pumps trip	After “S” signal	6
PRHRS isolation valve opens	After “S” signal	0
CMT actuation	After “S” signal	0
Accumulator actuation	4.83 MPa	0
ADS-1 actuation	After CMT water volume reduces to 67.5%	20
ADS-2 actuation	70 s after ADS-1 actuation	30
ADS-3 actuation	120 s after ADS-2 actuation	30
ADS-4a actuation	20.0% liquid volume fraction in CMT	2
ADS-4b actuation	60 s after ADS-4a actuation	2
IRWST injection	Pressure < 89.6 kPa + containment pressure	2