ESS Cryogenic System Design Philipp Arnold Section Leader Cryogenics www.europeanspallationsource.se 6th Internation Workshop on Cryogenic Operations November 10-12, 2014

View of the Southwest in 2025 Max IV – a national research facility, under construction, opens up in 2015 Science City – a new part of town Lund (113 500) Malmö (309 000) Copenhagen (1 200 000)  MAX IV - Linac comprising 43 cryomodules in baseline design, called optimus+ ; contingency space for 57 CMs Rotating thungsten target with two cold moderators cooled with supercritical 17K hydrogen Neutron instrument halls, comprising consumers of smaller quantities of LHe and LN2  ESS

Outline System Overview Cryogenic Design Choices Plant and process arrangement Cryomodule cooling at 2K ACCP plant staging LN2 pre-cooling Helium storage Heat recovery Control system Procurement and Tender Evaluation

(1) ESS Cryogenic System Pure Helium Gas Storage 1 Standalone Helium Purifier Helium Recovery System Pure Helium Gas Storage 2 Target Moderator Cryoplant Accelerator Cryoplant 20 m3 LHe Tank 5 m3 LHe Tank Test & Instrument Cryoplant Target Distribution System Test Stand Distribution System ACCP: 3kW @ 2K, 11kW @ 40K, 270 l/h Liquefaction  special plant, power consumption in MW range, big industrial compressors, sophisticated CC system TICP: 76W @ 2K, 420W @ 40K, 6 l/h Liquefaction  plant well in the standard range TMCP: 25kW @ 16-19K  very large again, some challenges but not terribly sophisticated process, compared to ACCP Large and sophisticated cryo-distribution system for all plants and their consumers LHe Mobile Dewars Cryogenic Distribution System LN2 Storage Tanks Hydrogen Circulation Box LN2 Mobile Dewars Instruments & Experiments Cryomodule Test Stand Hydrogen Moderator Cryomodules

(2.1) Plant and process arrangement 1 coldbox building, 1 compressor building, 1 plant per job Highest space and CAPEX savings Schedule, budgeting and technical requirements Maintainability Combination of warm and cold sub-atmospheric compression for ACCP High flexibility for load adaption Optimal overall efficiency Only warm sub-atmospheric compression for TICP Natural decision for split in three cryoplants due to very different operation ranges and schedules All plants at one space, start-up control room next door

(2.2) Cryomodule cooling at 2K Production of 2 K helium in 2 K heat exchanger and a sub-sequent Joule-Thomson valve in each of the cryomodule–valve box assemblies Heat load on CDS only on 4.5K, not 2K helium independent warm-up / maintenance / cool-down of single cryomodules while the rest of the system is maintained in cold condition One VBX per CM, all welded jumper connection Vacuum barrier separating CM vacuum from CDS

(2.3) ACCP plant staging Two sets of flow parts for cold rotating equipment turbine expanders cold turbo compressors Variable frequency drive(s) in the warm LP compressor system Stepwise upgrading of linac with CMs  ACCP long time well under max load In case not all margins are needed later adaption possible Acceptance testing: first with 2nd set of flow parts for full load, then 1st set for stage 1 load

WITHOUT LN2 PRE-COOLING TICP WITH LN2 PRE-COOLING CM testing: “constant level liquefaction w/o internal freeze- out purification” Liquefaction for LHe consumers: “rising level liquefaction w/ internal purification”  Turbo-expanders can be optimized to perform efficiently in both operation Much better plant fit with easy adapting when higher rate needed (switch pre-cooling on) ACCP WITHOUT LN2 PRE-COOLING ~80% of the load is at 2K  with cold compression translated to 4-20K refrigeration ~20 tons of cold mass max do not impose tough cool-down requirements No substantial CAPEX impact Downsides of LN2 usage like dependency on regular supply and increased traffic at ESS more severe 1st CM testing w/ LN2, 2nd Liquefaction for Neutron Instruments w/o LN2 LN2 usage makes most sense for liquefaction, less in refrigeration LN2 usage also helps for cool-down Thermal anchor point @ 80K for adsorber beds more important in systems with less turbines

(2.5) Helium Storage Helium inventory in CMs and CDS ~ 2 tons during normal operation 20 m3 LHe tank as second fill Speed up re-cool-down Facilitate helium management in transient modes 16 x 60 m3 warm tanks Store helium when accelerator warm A little more required for warm parts of ACCP and higher helium inventory during 4.5K standby mode / cool-down 3 Low design pressure of helium vessels in CMs  relief valves only for small flow  for bigger accidents burst disk  high helium loss LHe tank used also for helium management in off-design operation cases, e.g. parts of the linac have to be warmed up 2 1

(2.6) Heat Recovery 25C Middle temperature Return 37C Middle temperature Supply 27C 25C He to fine oil removal Compr. motor 39C 83C High temperature Return 32C 27C Middle temperature Return He from cold box 90C 85C Helium compressor Helium cooler No elevated oil or helium temperatures out of compressor suppliers specs Dedicated cooling water circuit for cryoplant (quality constraints of available cooling water in the building) Slow temperature control on cooling water side, fast temperature control on oil side Cooler design state of the art e.g. for Kaeser compressors Cooling function has priority over heat recovery return Clean up with rumors from last ICEC – no, we don’t intend to destroy our compressors right after first start-up, crack oil, reduce lifetime etc. Quite straight-forward approach Small dT on warm end side of the coolers with PFHX instead tube/shell HX Closed secondary loop with own pumps Oil vessel 90C 85C 32C 27C Oil cooler

(2.7) Control System Functional split between local PLCs and EPICS IOC Safe operation even in case the EPICS IOC shuts down ACCP control system is compatible with the other linac control Advantages of an open control system Deterministic control loops Time critical and internal functions Safety functions Supervisory controls High level batch operations HMI incl. local SCADA Alarm handling Data archiving

(3) How do we get what we want? Procurement procedures open, restricted, negotiated, competitive dialogue Scope split clear interfaces (also during different phases of installation) complex systems (rather one integrator) vs. simple systems Small yet relevant qualitative part in the tender evaluation verifiable with proposal Thorough acceptance testing Possibly incentive part for consumption Sincere and transparent procurement process For complex projects with many unknowns and long duration don’t do open bid but rather a negotiated procedure to find the best solution together with industry Think thoroughly about where to split scopes – what must be managed for acceptance testing, what should be procured separately (obvious example: tanks) Try to quantify quality in order to make offers comparable; the cheaper isn’t always the best but the most expansive also not Bonus malus system to make bidders aware of importance of power consumption, motivate for optimized process but not too optimistic for sales – the requested has to be proven Most important point; even for in-kind equipment free and unprejudiced competition, allow most market possible with few suppliers Thank you for your attention