Application of REPAS Methodology to Assess the Reliability of Passive Safety Systems

Table 5

Design and critical parameters case c.

Parameter ID	Description		Unit	Nominal value	Range	Discrete initial value
						and associated probabilities
LP	Linear power of electrically heated rod		W/m	30𝑒^6	0–30𝑒^6	—
						1.0
P1	Initial Pressure of the loop		bar	5	1–10	1 3 5 8 10
						0.02 0.13 0.7 0.1 0.05
T2	Temperature of the SS fluid at the cooler inlet		K	303	295–350	295 303 325 350
						0.18 0.65 0.15 0.02
HL1	Heat losses from the test section (TS). % of TS power		%	0.2	0–4.5	0.0 0.2 1.0 4.5
						0.1 0.69 0.15 0.06
HL2	Heat losses from the loop w/o (TS). % of TS power		%	3	0–20	0.0 3 10 20
						0.1 0.69 0.15 0.06
L1	Total length of the loop		m	21	12–34	12 21 28 34
						0.05 0.69 0.14 0.12
LV	Loop volume (change of the pre-heater tank)		m^3	0.09	0.07–0.2	0.07 0.09 0.12 0.2
						0.05 0.65 0.18 0.12
PV	Volume of PRZ		m^3	0.06	0.03–0.12	0.03 0.06 0.09 0.12
						0.05 0.65 0.18 0.12
PN	Noding of the PRZ		—	N	N1-N2	N1 N N2
						0.1 0.8 0.1
PP	Position of the PRZ	Upstream the cooler (U)	—	U	U–D	U D
		Downstream the cooler (D)				0.85 0.15
K1	Local pressure drop coefficient (K) at the inlet of the TS		—	0.2	0–1.2	0.0 0.2 0.4 1.2
						0.05 0.53 0.3 0.12
K2	K factor at the outlets of the TS		—	0.6	0-1	0.0 0.6 0.8 1.2
						0.05 0.53 0.22 0.2
TK	Sum of the K factors, w/o TS inlet and outlet		—	7.5	3–25	3 7.5 15 25
						0.05 0.55 0.22 0.18
EI	Electrical Insulation in the heater	AL2O3 (A)	—	A	A-B	A B
		Boron nitride (B)				0.85 0.15
CIT	Thickness of cooler tubes		mm	2	1–3	1 2 3
						0.05 0.65 0.3
CT	Cooler tubes		—	Cu	Cu–SS	Cu SS
						0.85 0.15
E2	Equivalent diameter of secondary side of the cooler		mm	10	7–20	7 10 20
						0.25 0.7 0.05
E1	TS Equivalent diameter (coolant passage)		mm	8	5–12	5 7 8 12
						0.05 0.3 0.55 0.1
AR	Ratio of Heater heat transfer area to cooler heat transfer area		—	0.18	0.05–0.37	0.05 0.12 0.18 0.37
						0.05 0.3 0.6 0.05
PD	Axial power distribution	Uniform (U)	—	U	C–S	C U S
		Cosine (C)				0.1 0.65 0.25
		Semi cosine (S)
CO	Orientation of the cooler	Vertical (V)	—	H	I–V	I H V
		Horizontal (H)				0.08 0.65 0.27
		Inclined (I)
MF2	Secondary side mass flow rate		Kg/s	1.2	0.4–1.8	0.4 1.2 0.8 1.8
						0.05 0.55 0.23 0.17
P2	Secondary side pressure		bar	1	1–10	1 5 10
						0.6 0.3 0.2
LS	Presence of U-pipe or loop seal in the cold part of the loop		—	No	Yes-No	Y N
						0.2 0.8
D1	Riser diameter		mm	25	25–100	25 50 75 100
						0.55 0.25 0.15 0.05
D2	Down comer diameter		mm	25	25–75	25 50 75
						0.55 0.25 0.2
PC	PRZ Connection	Direct (D)	—	S	D–S	S D
		Surge Line (S)				0.8 0.2
G1	Non-condensable gas mass fraction at the inlet of cooler piping		—	0	0–1	0.0 0.05 0.2 0.5 0.8
						0.58 0.3 0.1 0.01 0.01
G2	Non-condensable gas mass fraction inside the TS		—	0	0–1	0.0 0.05 0.3 0.5 0.8
						0.58 0.3 0.1 0.01 0.01
UL	Undetected leakage		Kg/s	0	0–1𝑒^−2	0.0 0.1𝑒^−5 0.1𝑒^−3 0.1𝑒^−2
						0.65 0.25 0.09 0.01