Progress on the Cold Powering failure modes document

Progress on the Cold Powering failure modes document – Edms 2303664 HL-LHC Cold Powering failure modes WG mtg#8: 20 May 2020 N. Grada on behalf of the HL-LHC Safety Project Office

Latest updates § § § Scope of the document changed to “cryogenic and electrical hazards” “m”- system : added a statement saying that the description of the FM is the same but the dynamics of the release and the resulting dimension of safety devices will be different from the “x” system. Added that the rated valve of DFH would open before DFX in case of power cut, to keep link as cold as possible (as per VG proposal) 2

To be clarified before circulation of V 1. 0 § DFX § Volume remains unchanged? (401. 8 L? ) No permanent fillers? § Overheating > 10 min autonomy > and after? (to prevent resistive heating of splices). @Yann, the 35 g/s would be relieved by BD or RV? § @Paul -> is an icing of safety device because of bad outgassing a realistic event? 3

To be clarified before circulation of V 1. 0 § DSHx functional and technical specification? (Demo 2? ) § DSHx Drawings? § Mtg#7 > sc link buffer volume? N. Grada 4

To be clarified before circulation of V 1. 0 § DFHx § Technical spec? § Obstruction of recovery line: rated valve alone? If yes, wrt Yann’s calculation (10 g/s), will move this in the “minor failure mode” section N. Grada 5

General questions § Are there voltage taps along the cables? § Does an undetected quench lead to an arc? § Functional specification of String Test: who should add VG’s proposal for the rated valve in this doc? Action for the working group? Next steps § Aggregate all data available at the time of writing and circulate a version 1. 0 CERN-wide (after comments & approval from the WG members) § Create a new version once the “m-system” design is fixed N. Grada 6