Preliminary Hazard Analysis of the ESS Cryomodules Nuno Elias Cryogenics Engineer Engineering an Integration Support Division Safety review of Spokes and Elliptical Cryomodules, 9 th June 2016

Outline Introduction Hazards related to leaks Hazards Related to thermal events Hazards Related to Sub-system failure Hazards Related to Mechanical failure Hazards Related to Control and Command Hazards Related to Operator 2

Cryomodule 3 CRYOGENICS INSULATION VACUUM INSULATION VACUUM BEAM VACUUM BEAM VACUUM RF CONTROL SYSTEMS CONTROL SYSTEMS TUNING SYSTEM ALIGNMENT SYSTEM SRF CAVITY

The Spokes Cryomodule 4 Donut (left and right side) Pick-up Port Ring (left and right side ) Coupler port

The Spokes Cryomodule 5 4 HPR Ports Coupler port Bellows Helium tank

The Spokes Cryomodule 6 Power coupler double wall cooling C-W transition Cold Tuning System 2-phase manifold Alignment tie rods Power coupler antenna cooling Ceramic disk, 100 mm diameter 400 kW peak power (335 kW nominal) Antenna & window water cooling Outer conductor cooled with SHe Double spoke cavity (3-gaps), MHz,  =0.50 Goal: Eacc = 9 MV/m [Bp= 62 mT ; Ep = 39 MV/m] 4.2 mm (nominal) Niobium thickness Titanium Helium tank and stiffeners Lorentz detuning coeff. : ~-5.5 Hz/(MV/m) 2 Tuning sentivity  f/  z = 130 kHz/mm

The Spokes Cryomodule 7 Length : 2.88 m Diameter: 1.304m

The Spokes CM 8 Cold/warm transition Gate valves Inter-cavity belows Thermal shieldVacuum vessel Prototype cavity Power Coupler interface

Elliptical Cryomodules 9 6-cells medium beta (0,67) cavity Length= mm 6-cells medium beta (0,67) cavity Length= mm 5-cells high beta (0,86) cavity Length= mm 5-cells high beta (0,86) cavity Length= mm MediumHigh Geometrical beta Frequency (MHz) Iris diameter (mm)94120 Maximum surface field in operation (MV/m)45 Nominal Accelerating gradient (MV/m) Nominal Accelerating Voltage (MV)14,318,2 Q 0 at nominal gradient> 5e9 Cavity dynamic heat load (W)4,96,5

Elliptical CM 10 Length : m Diameter: 1.324m

Elliptical Cryomodule Power Coupler Positioning jacks (3 at 120°) Hanging rods Trap door (CTS access) 50K Thermal shield (aluminium) Biphasic He pipe Cavity Positioning optical devices

Elliptical Cryomodule Cavity Spaceframe Access trap Bursting disk Cryogenic valve Door knob and RF wave guide Vacuum vessel (stainless steel) Guide rail and wheel

Hazard Identification Hazard: Potential threat – People – Equipment – Environment Risk: Severity vs. Likelihood of occurrence (event) Minimization of Risk (mitigation): -Measures to minimize occurrence and potential consequences -Measures in case event happens consequences are minimized. 13

Hazards related to leaks Helium Supply Line (HP): – Cavity and Power coupler helium supply (4.5K, 3bar) Vapor Low-pressure Line (VLP): – Low pressure circuit to maintain cavities at 2K, 27 mbar to 1.43 bar) Thermal Shield (TS): – Supply and return lines of the shield circuit (40-50K, bar) Auxiliary Circuits/Media – Purge Line, Safety relief line, Helium guard. – Beam vacuum (BV) – Insulation vacuum (IV) – Ambient air (AIR) – Antenna Cooling water (Water) 14

Go to Document 15 Preliminary Hazard Analysis based on 2013 study: ESS _to be updated_NE_Hazid V3_Protocol_WS6_cryomodules_ docx ESS _to be updated_NE_Hazid V3_Protocol_WS6_cryomodules_ docx Present Study focused in cryomodule operation: Hazard Analysis. pdf

Conclusions A hazard analysis focused on the cryomodule operation is being produced – Various types of hazards have been studied. – Most critical scenarios have been identified and related to sudden beam vacuum loss. Work is on-going, expected input from technical demonstrators tests will add valuable input. 16

Cryomodule Flow and Instrumentation 17

Pressure safety 18 Define the maximum allowable working pressure (PS) used for the design of the vessel and piping – The safety relief devices must be in place to prevent any event from pressurizing the vessel or piping above the MAWP. Evaluate all pressure sources and possible mass flow rates Size the vent line to the relief device – Temperature and pressure of flow stream – Evaluate pressure drop Size the relief device Size downstream ducting, in necessary

Pressure Equipment Directive 19 PS < 0,5bar The equipment is not on the scope of the 97/23/CE directive Article 3-3 The equipment must be designed and manufactured according to workmanlike way. No CE marking Category I The manufacturing must be more documented, especially with internal production control Pre-study: TUV- Nord: Legal QC requirements for pressure equipment Pre-study: TUV- Nord PS=1.04 bar V= 48 l

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Pressure Scale: Safety (1/2) 21 *Safety Relief Line at atmospheric pressure

Pressure Scale: Safety (2/2) 22 *Safety Relief Line at 1.1 bar

Summary of Cryogenic Circuits and Relief Devices Circuit #Operating Pressure Thermal Shield19 to 19.5 bar 4.5 K helium circuit3 bar 2 K helium vessel30 mbar Vacuum vesselClose to 10-6 mbar 23 Circuit #DeviceSet PressureDischarges to Thermal ShieldRelief valve (SV60)24 bargSV Relief Line 4.5 K helium circuitRelief valve (SV02)3 bargSV Relief Line 2 K helium vesselControl valve (CV90)1.5 bara ≈ 0.5 bargSV Relief Line 2 K helium vesselRelief valve (SV90)0.64 bargSV Relief Line 2 K helium vesselBurst Disk (RD90 and RD91)0.99 bargAmbient Vacuum vesselRelief valve (SV70)0.02 bargAmbient

Summary of Cryogenic Circuits and Relief Devices ScenarioCritical heat flux Insulated surfaces with at least 10 layers of MLI0.62 W/cm2 Non-insulated surfaces3.8 W/cm2 24 Circuit #DeviceSet Pressure ScenarioFlow [kg/s] Minimum flow section [mm 2 ] Practical Dimension D[mm] Discharges to Thermal ShieldRelief valve (SV60)24 bargLoss of insulation vacuum SV Relief Line 4.5 K helium circuit Relief valve (SV02)3 bargJT,Filling valve, and PC closed0.092Section of pipe10SV Relief Line 2 K helium vessel Control valve (CV90) 1.5 bara ≈ 0.5 barg Outlet valve closed (Protection of sudden pressure rises) 0.082Kv> 1125SV Relief Line 2 K helium vessel Relief valve (SV90)0.64 bargOutlet valve closed (Protection of sudden pressure rises) SV Relief Line 2 K helium vessel Burst Disk (RD90 and RD91) 0.99 bargBeam vacuum breakage x 100Ambient Vacuum vesselRelief valve (SV70)0.02 bargLoss of insulation vacuum Due to He pipe breakage Ambient [1] Safety Aspects for LHe cryostats and LHe Transport containers, W. Lehmann, G. Zahn, ICEC, 1978, GB. [2] Pressure Protection Against Vacuum Failures on the Cryostats for LEP SC Cavities, G. Cavallari et all, Fourth Workshop on RF Superconductivity, 1989, Japan. [3] Experimental Tests of Fault Conditions During the Cryogenic Operation of a XFEL Prototype Cryomodule, Boeckmann et all, ICEC, 2008, Korea. [4] ISO 21013: Cryogenic vessels - Pressure-relief accessories for cryogenic service > Part 3: Sizing and capacity determination [5] ISO 4126: Safety devices for protection against excessive pressure – (Bursting disc safety devices. Safety valves, etc) Reference: Technical Note – Safety Equipment for the ESS elliptical cryomodules

Helium Low pressure circuit 25 2 bursting disk at each tip + upstream safety relief valve 36° Heat exchanger The circuit is designed to reduce as low as possible the overpressure in case of beam vacuum failure by using a continuous DN100 diameter for the diphasic pipe, large curvatures and 2 DN100 bursting disks at each extremity. A 36° angle is set up for the tank nozzle in order to allow the insertion of the cavity string and the cooling circuit inside the spaceframe To valve box