Helium is a scarce natural resource, used for medical scanning devices, academic low-temperature research and particle detectors. Once released, helium escapes our atmosphere and is lost for future generations. Efficient recovery is therefore important for sustainability. The finite earth depositories of helium also imply an ever growing helium price. Recovery therefore also has an economic incentive. Here we provide information and suggestions for good helium practice - a must read for helium users of our department.
To reduce helium loss, following practice is recommended:
- Figure out when dewars arrive (typically Tuesday and Thursday at 9 am) to UZH and get them connected as soon as possible to a recovery line.
- "Empty" dewars are collected at these delivery times (Tuesday and Thursday at 9 am). Therefore send "empty" dewars to the logistic centre Monday or Wednesday late afternoon.
- Returned dewars should still be more than 10% filled to keep them cold. The evaporation rate of Helium is about 1.5 litres a day.
The first two points optimize the recovery and point three reduces "cost" to re-cool the dewar.
Daily check list
Much helium loss originates from human lapses. Most common points are:
- Helium dewar is left "open" without connection to the recovery system.
- Helium dewar is "closed". Pressure then builds-up and helium is eventually released through the safety valve and therefore lost (forever).
- When pumping on the exhaust line, ensure no air contamination.
- Instruments not connected to the recovery system.
- Contamination of the return line with air or nitrogen. This is very problematic as contaminated Helium cannot be recycled anymore. Therefore, the full balloon of collected Helium is lost in case of a contamination event.
Good to know:
- Switzerland has no natural helium resources, we thus import from Algeria and the US. The sources of Qatar support only Asia.
- Currently, we "pay" about 5 CHF/liter recovered helium and 38 CHF/liter not recovered helium. So not recovered helium is 6 times more expensive.
- In low performing years, we have 20% helium loss. Our mission is to bring losses below 10%. This would earn us a economic saving of more than 25'000 CHF per year. In 2022 we could recover about 93% Helium. Our aim is to get better and reduze the loss to 5%.
Please look also at the information from ETHZ, which describes the actual situation (November 2022). Link (PDF, 926 KB)