1. Vacuum tank relief for Super-FRS long multiplet cryostat CrYogenic Department in Common System (CSCY) GSI, Darmstadt Yu Xiang

2. Scenarios of Insulation vacuum accidents: Loss to Helium or to Air Insulation vacuum volume [m³]6,9 Volume of helium vessel [m³] 1,5 Volume of liquid helium in LHe vessel [m³] mass of liquid helium in LHe vessel [kg] 1,3162,5 Volume of gas helium in LHe vessel [m³] mass of gas helium in LHe vessel [kg] 0,24,06 Scenarios of Insulation vacuum accidentsLoss to heliumLoss to air report for TESLA Test Facility at DESY 1995LEP report 1989BNL report 1992BNL report 1993 average heat flux between 300 K vacuum vessel and gas helium (calculation) measured heat flux into helium vessel [kW/m²] measured heat flux [kW/m²] Q1 = 2.0 [kW/m²]Q2 = 1.5 [kW/m²]Q2 = 0.6 [kW/m²]Q3 = 1.7 [kW/m²] Q3 Q2 Q1 Inner surface of vacuum tank A1 = 47,2 [m²] Outer surface of helium vessel A2 = 40 [m²] Heating power from vacuum tank [kW] heating power from gas helium to helium vessel [kW] Q1 x A1 = 94,4Q2 x A2 = 60,0

3. Scenarios of Insulation vacuum accidents: Loss to Helium Q2 Q1 LEP report 1989 Pressure in helium tank > 2 bara Assumption : P_helium_tank = 2.5 bara during helium release to vacuum tank. Helium heat input per gram ejected for typical pressure; 2.5 bar ~4 bar 13 [J/g] Fundamentals of Cryomodule Design Tom Peterson, Fermilab 22 July 2011 P [bar]T [K]Latent / V*dHdV|P 25,212,8 [J/g] 2,55,3514,1 [J/g]

4. Scenarios of Insulation vacuum accidents: Loss to Helium Q2 Q1 Calculation model: Gas helium in vacuum tank is warmed up by Q = Q1 x A1 - Q2 x A2 = 94.4 – 60.0 = 34.4 kW; Helium heat input per gram ejected for typical pressure; 2.5 bar ~4 bar 13 [J/g] Liquid /SHe helium in helium tank is evaporated by Q2 x A2 = 60 kW; Discharge rate of liquid /SHe helium from helium tank is determined by, Release rate = Q2 x A2 /(Latent for LHe or equivalent specific heat for SHe) = 60 [kW] / 12.8 [kJ/kg] = 4.688 kg/s; Heating power from vacuum tank [kW] heating power from gas helium to helium vessel [kW] Q1 x A1 = 94,4Q2 x A2 = 60,0

5. Helium pressure and temperature in vacuum vessel under Loss to Helium

7. Size of relief valve vs. venting temperature The minumum size of the vacuum tank relief for long multiplet is about 350 mm in diameter

8. Conservative assumption: choked flow occurs at relief device The size of the vacuum tank relief in the calculation is 350 mm in diameter

9. Choked flow vs. size of the hole C = 0.7 (assumed) For the flow rate of 4.6 kg/s at choked conditions, the size of the hole on the LHe vessel is around 40 to 50 mm in diameter

10. Maximum inner diameter, 80 mm (5000 mm²) Minimum inner diameter, 25 mm (510 mm² =0.34 mm²/litre x 1500 litres) The sizes for insulation vacuum relief seems too small according to EN 13458-2:2002 European Standards (DIN/BS EN 13458) The size of the Vacuum tank relief device we chosen is much larger than the European Standards (DIN/BS EN 13458) requires.

11. The size of the vacuum tank relief device is about 350 mm in diamter, which is much larger than the Euqropen Standards (DIN/BS EN 13458) requires. ~ 350 mm