ESS elliptical cryomodule ESS CRYOMODULE FOR ELLIPTICAL CAVITIES SAFETY REVIEW LUND June 9th, 2016 Unité mixte de recherche CNRS-IN2P3 Université Paris-Sud 11 91406 Orsay cedex Tél. : +33 1 69 15 73 40 Fax : +33 1 69 15 64 70 http://ipnweb.in2p3.fr

ESS elliptical cryomodule

ESS elliptical cryomodule

Circuits - characteristics Temperature (K) Pressure (bara) Volume (l) Control valve Safety device Thermal shield 40 - 50 19 - 19,5 3 CV60 (Kv 0.8m3/h) SV60 (24barg) Helium inlet 4.5 1 CV03 (Kv 2.8) SV02 (3barg) Couplers 1.3 Cooling down 1.5 CV02 (Kv 0.2) Filling 2 - 4.5 CV01 (Kv 0.04) Low pressure 2 0.030 – 1.43 219 (Diph. pipe half filled) CV04 (Kv 71) RD90 / RD91 (0.99barg) CV91 (1.5bara) SV90 (0.64barg) Vacuum 300 K SV70 (0.02 bar)

Helium distribution Jumper VLP circuit (8l) Rupture disk & safety valves Jumper VLP circuit (8l) JT valve CV01 Exchanger Rupture disk & purge valve + pressure gauges Cooling down valve (CV02) Diphasic pipe (27l) Helium tank (48l) Coupler circuit (1,3l) Filling line (1l) Thermal shield circuit (3l) Cooling down circuit (1.5l)

cavities Medium beta High beta Ø neck 80mm Øext tank 418mm Internal volume: 48l

Cryogenic interfaces Rupture disk CV01 & safety valves Jumper connections Vacuum safety valve CV02 Rupture disk & purge valve & press. gauges He coupler outlet (x4)

Vacuum vessel : safety device Minimum flow section (mm²) Set pressure (barg) 11200 0.02 Considered worst scenario: Rupture of 2K phase separator liquid helium fills the vacuum vessel liquid helium mass : 30 kg Volume of vessel : 6.3 m3 helium mass flow : 4.1 kg/s (1.04 bara, 4.76 K) Diameter of relief valve SV70 : 200 mm

Thermal shield : Safety devices Minimum flow section (mm²) Set pressure (barg) 34 24 Considered worst scenario: loss of insulation vacuum air fully condensates onto the CM thermal shield surface covered with 30 MLI considered heat power density : 1.5 kW/m² thermal shield (~24 m²): 36 kW helium mass flow : 0.1 kg/s (25 bara, 66K) Diameter of relief valve SV60 : 10 mm

Cooling down and coupler circuits A relief valve SV90 associated with a control valve CV90 (1.5 bara) Minimum flow section (mm²) Set pressure (barg) 340 0.64 Considered worst scenario: HP He supply: 3 bara, 5 K Valves CV01, CV02, CV03 fully opened (at kv max) Valve CV04 closed helium mass flow : 0.082 kg/s (1.74 bara, 4.85 K) Diameter of relief valve SV90 : 25 mm Kv of CV 90 : 11

Low pressure line

Safety strategy for the low pressure circuits Operating constraints: maximal allowable pressure of cavities is about 2 bar, pressure required by the cryogenic plant is 1.43 bar, 1.43 bar is close of the opening pressure of the safety valves, the pressure margin between the operating pressure and safety device is low. Safety strategy: Two burst disks (RD90 – RD91) designed for accidental scenarios, a safety valve (SV90) designed for abnormal operation and to avoid the bursting of RD90 or RD91, a control valve (CV90) designed to limit the pressure at a level lower than the opening pressure of SV90.

2 K vessel : safety devices FAILURE SCENARIOS (JP THERMEAU, Safety equipments for helium circuits) scenarios Circuit Area (m²) heat flux (kW/m²) Heat load (kW) Mass flow (kg/s) Failure of the insulation vacuum Helium vessel 4 x 1.53  6.2 (10 MLI layers) 38 2 Failure of the beam vacuum Cavity 4 x 1.81 (air on cavity wall) 275 14.5 Failure of insulation and beam vacuum Vessel + cavity 312 16.4 7.25 Kg/s per bursting disk Most credible & critical Reference for the sizing of the safety devices Unlikely Minimum rupture disk diameter: 88mm Maximum He volume to be evacuated: 200l (about 30 Kg)

Dimensions updated by Witzenmann on 2016/04/07 Bursting disk Ø97mm Dimensions updated by Witzenmann on 2016/04/07 Ø90mm

Summary Pressure drop in the main line : > 3%PS, Name Minimum flow section (mm²) Practical diameter (mm) Set pressure (barg) SV60 34 10 24 SV02 Section of pipe 3 SV90 340 25 0.64 CV90 kv > 11 1.5 bara RD90 - RD91 5300 100 0.99 SV70 11200 200 0.02 Pressure drop in the main line : > 3%PS, no risk to damage the cavities. The pressure margins between the burst disks and the safety valves are very low (100 to 200 mbar).

Pressure equipment directive Breakdown of each circuit in elementary sections to check the product Ps x V and the compliance to the Pressure Equipment Directive. Each section is considered as a separate vessel.

Pressure equipment directive 1.04 48 Aim: remain in 3.3 category Volume of the largest circuit vessel: the cavity helium tank

Mechanical behaviour of the cavities under pressure Pressure test scenario: Cavity fully constrained Pressure in the tank Beam vacuum carried out The maximum pressure allowable is 2.60 bar for 50 MPa VM (worst scenario) 3.64 bar for 70 MPa VM (best scenario) Max. pressure (test at 1,25 Pmax): 2,6 barg Maximum working gauge pressure: 2,6/1,25 = 2,08 barg Maximum Ps: 2,08-1,013=1,067 barg This value is very close to the limit of 1,04barg needed to stay in PED chapter 3.3 (Andrea BIGNAMI, INFN LASA - PDR, LASA, 19 May 2016)

Safety devices operating range ABSOLUTE PRESSURE GAUGE PRESSURE Pmax = 2.14 bar Maximum pressure = 1.1 PS = 1.14 barg 2.04 bar PS = MAWP = 1.04 barg Rupture disk outlet to the atmosphere at 1 bara Bursting area of the rupture disk Bursting pressure = 0.99 barg ±0.05bar 1.94 bar 0.94 barg Pressure margin ~ 0.2 bar Max. pressure when the relief valve is open: 1.1 x 0.67 ~ 0.74 barg 1.74 bar Opening area of the relief valve 1.05 Pset ~ 0.67 barg Safety valve outlet to SV relief line at 1 bara Set pressure = 0.64 barg ± 5% 0.95 Pset ~ 0.61 barg 1.55 bar Min. pressure to allow the closing of the relief valve: 0.9 x 0.61 ~ 0.55 barg 1.5 bar PLC Control valve ~ 0.5 barg 1.43 bar Min./Max. operating pressure of the cryogenic plant: ~ 0.43 barg (cooling down phase) Operating pressure area 30 mbar Pressure operation at 2K

Safety devices operating range ABSOLUTE PRESSURE GAUGE PRESSURE Pmax = 2.14 bar Maximum pressure = 1.1 PS = 1.14 barg 2.04 bar PS = MAWP = 1.04 barg Rupture disk outlet to the atmosphere at 1 bara Bursting area of the rupture disk Bursting pressure = 0.99 barg ±0.05bar 1.94 bar 0.94 barg Pressure margin ~ 0.1 bar Max. pressure when the relief valve is open: 1.1 x 0.67 ~ 0.74 barg (% outlet circuit) 1.84 bar Opening area of the relief valve 1.05 Pset ~ 0.67 barg (% outlet circuit) Safety valve outlet to SV relief line at 1.1 bara Set pressure = 0.64 barg ± 5% (% outlet circuit) 0.95 Pset ~ 0.61 barg (% outlet circuit) 1.65 bar Min. pressure to allow the closing of the relief valve: 0.9 x 0.61 ~ 0.55 barg (% outlet circuit) 1.5 bar PLC Control valve ~ 0.5 barg 1.43 bar Min./Max. operating pressure of the cryogenic plant: ~ 0.43 barg Operating pressure area 30 mbar Pressure operation at 2K

Safety devices operating range ABSOLUTE PRESSURE GAUGE PRESSURE Increase of the Ps value, if exhaust line > Patm Pmax > 2.14 bar Maximum pressure = 1.1 PS PS = MAWP > 1.04 barg >2.04 bar 1.04 barg (% outlet circuit) Rupture disk outlet to exhaust line > 1 bara Bursting area of the rupture disk Bursting pressure = 0.99 barg ±0.05bar (% outlet circuit) >1.94 bar 0.94 barg (% outlet circuit) Pressure margin > 0.1 bar Max. pressure when the relief valve is open: 1.1 x 0.67 ~ 0.74 barg (% outlet circuit) 1.84 bar Opening area of the relief valve 1.05 Pset ~ 0.67 barg (% outlet circuit) Safety valve outlet to SV relief line at 1.1 bara Set pressure = 0.64 barg ± 5% (% outlet circuit) 0.95 Pset ~ 0.61 barg (% outlet circuit) 1.65 bar Min. pressure to allow the closing of the relief valve: 0.9 x 0.61 ~ 0.55 barg (% outlet circuit) 1.5 bar PLC Control valve ~ 0.5 barg 1.43 bar Min./Max. operating pressure of the cryogenic plant: ~ 0.43 barg Operating pressure area 30 mbar Pressure operation at 2K

Remaining issues Value of Ps to remain in PED 3.3 category Value of Ps to avoid any yielding of the cavities Impact of the helium discharge of one cryomodule on the other disks: increase of the bursting pressure Exhaust line at atmospheric pressure? (lost of the helium?)

ESS elliptical cryomodule Thank you for your attention