Sensitivity analysis of a passive decay heat removal system under a post-loss of coolant accident condition

Figures & data

Figure 1. Schematic representation of one loop of the GFR passive decay heat removal system [4].

Table 1. Geometric parameter of the system [4].

Section	Hydraulic diameter (m)	Flow area (m^2)	Length (m)	ΔZ* (m)	K loss coefficient	Roughness (m)
1	0.6	7.2571	7.7	−5.3	1	4.5 × 10^−5
2	7.4	43.008	1	0.5	0	4.5 × 10^−5
3	0.0145	1.65 × 10^−4	1	1	0.5	1.0 × 10^−5
4	0.0145	1.65 × 10^−4	1.7	1.7	0.25	1.0 × 10^−5
5	0.0145	1.65 × 10^−4	1	1	1	1.0 × 10^−5
6	7.4	43.0	3	3	0	4.5 × 10^−5
7	5.4	22.9	6	6	0.1	4.5 × 10^−5
8	0.8	50.3	4	0	1.23	4.5 × 10^−5
9	1	2.24	2	2	0	4.5 × 10^−5
10	1.6364	5.4	1.5	1.5	0.1	4.5 × 10^−5
11	0.15	1.35	1.25	−0.5	0.23	4.5 × 10^−5
12	0.003055	9.81	0.3	−0.3	1.23	1.0 × 10^−5
13	0.15	1.35	1.25	−0.2	1	4.5 × 10^−5
14	1.526	8.2	1	−1	0	4.5 × 10^−5
15	1	3.76	3	−3	13.23	4.5 × 10^−5
16	1.526	8.20	1	−1	0	4.5 × 10^−5
17	0.25	0.363	3	0	1	4.5 × 10^−5
18	2.0253	2.29	5.4	−5.4	0.5	4.5 × 10^−5
Notes: *It refers to the change in height from the beginning to the end of the section in question. “−” signal represents that the height of the end of a section is lower than the height of the beginning of this section.

Table 2. Uncertain parameters in the GFR passive decay heat removal system.

	Parameter	Mean value	Standard deviation (% of the mean value)
Parameter uncertainty	X 1 (power level (MW))	12.0	1
	X 2 (system pressure (kPa))	1650	7.5
	X 3 (cooler wall temperature (°C))	90	5
Model uncertainty (ε)	X 4 (Nusselt number in the forced convection regime)	1	5
	X 5 (Nusselt number in the mixed convection regime)	1	15
	X 6 (Nusselt number in the free convection regime)	1	7.5
	X 7 (friction factor in the forced convection regime)	1	1
	X 8 (friction factor in the mixed convection regime)	1	10
	X 9 (friction factor in the free convection regime)	1	1.5

Figure 2. The PDF of the helium gas temperature at the outlet of the hot channel.

Figure 3. The PDF of the helium gas temperature at the outlet of the average channel.

Table 3. Contributions of uncertain input parameters to the uncertainty of the model output Y ₁.

Parameter	Contributions to the uncertainty of Y 1 based on Si (%)		Contributions to the uncertainty of Y 1 based on STi (%)
	Ratio	Ranking	Ratio	Ranking
X 1 (core power)	0.6%	5	1.7%	5
X 2 (system pressure)	73.3%	1	80.4%	1
X 3 (cooler wall temperature)	3.8%	4	4.5%	4
X 4 (Nu number, forced)	0.03%	7	1.7%	6
X 5 (Nu number, mixed)	4.9%	3	5.7%	3
X 6 (Nu number, free)	0.2%	6	1.6%	7
X 7 (friction factor, forced)	0.004%	9	1.5%	9
X 8 (friction factor, mixed)	7.6%	2	9.2%	2
X 9 (friction factor, free)	0.01%	8	1.5%	8

Figure 4. The contributions ratios of the nine uncertain input parameters to the uncertainty of the helium gas temperature at the outlet of the hot channel.

Table 4. Contributions of uncertain input parameters to the uncertainty of the model output Y ₂.

Parameter	Contributions to the uncertainty of Y 1 based on Si (%)		Contributions to the uncertainty of Y 2 based on STi (%)
	Ratio	Ranking	Ratio	Ranking
X 1 (core power)	0.93%	5	1.7%	5
X 2 (system pressure)	72.4%	1	75.8%	1
X 3 (cooler wall temperature)	7.2%	3	7.4%	3
X 4 (Nu number, forced)	0.007%	7	0.9%	6
X 5 (Nu number, mixed)	8.3%	2	9.2%	2
X 6 (Nu number, free)	0.1%	6	0.9%	8
X 7 (friction factor, forced)	0.004%	8	0.9%	9
X 8 (friction factor, mixed)	4.8%	4	5.8%	4
X 9 (friction factor, free)	0.003%	9	0.9%	7

Figure 5. The contribution ratios of the nine uncertain input parameters to the uncertainty of the helium gas temperature at the outlet of the average channel.