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RP aspects for He cooling system
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Europe/Zurich
892/1-B09 (CERN)
RP aspects for He cooling system
He-cooling system overview and H-3 risks
· Overview of He cooling system was given, which will include several HEPA filters and chemical getters, but no charcoal filters as it could pollute the high purity system
· Chemical getters
o 2% of overall flow rate circulated through them
o Permanently trap H2O, O2, CO2, H2 and sulfur compounds with very high efficiency
· H-3 permeation through SS304L pipes was evaluated
o Conservative assumptions: all H3 produced in W target passes to He, permeation mechanism is driven diffusion (p^0.5 dependence, rather than p), zero outside partial pressure
o H-3 concentration in circuit was estimated to be of 322 pptV -> to be translated to Bq (Action/Claudia)
o Permeation rate of 1.18E-15 mol/s for 30 deg and 1.36E-11 mol/s for 200 deg. Action/Claudia to ask Rui for max. target temperature (see input from Mike below). Action/Francesco to provide fractions for the following compartments: BDF target area, transfer to surface building, CV room). Action/Fabrice/Pavol/James to translate to Bq/year and evaluate the impact
o Piping until heat exchanger will have double wall with vacuum in between
o Gas getters act equally on HT, T2 and HTO
o In view of high He purity (1 ppm impurity, probably bake-out of target/pipes, vacuum before He filling, getters) not much HTO formation is expected in the system
Outgassing estimations for W-BDF
· Radionuclide inventory of W target is based on simulations and was sorted according to their LA contribution, but total activities are available in the Excel file
· Outgassing of radionuclides was estimated based on the conservative assumption of air instead of He environment
· From the most relevant radionuclides (LA based), 57 have potential to form volatile species, however some under conditions that might not be fulfilled during BDF operation (e.g. as temperature not reached). Action/Claudia to get max. operational temperatures of W target from Rui
· Action/Claudia/Serdar to produce an updated list with activities expected to be volatile based on the operational temperatures and evaluate impact to personnel that could be present indoor
· Action/Pavol/James to evaluate worst case environmental impact of released volatile species
· Action/Fabrice to investigate potential measurements that can be performed during the 2026 BDF prototype test once the updated list of volatile radionuclides is available
· Many of the volatile radionuclides would have a high affinity to metals and could therefore either stick to the W or then to the stainless-steel pipes. Action/Francesco to share paper about Gd-148 contamination on stainless steel, which was impossible to remove below 200 C. Gd-148 would also not be volatile by itself, but only if combined with Iodine, which is why the effective contribution is expected to be small
· To be seen in the future if exhaust pipes of ventilation system are to be equipped with charcoal filters to trap Iodine
Input from Mike concerning target temperatures provided after the meeting:
- Current goal to keep the target surfaces below ~400°C to prevent oxidation (temperature limit based on EDMS 2648378 & other literature), resulting in a max temperature in the bulk around 450°C
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