CERN has put in place a regulatory framework governing the use of hazardous substances that could cause soil and water pollution. Specific environmental measures have been taken according to the relevant Swiss and French regulations.

The Working Group on the Prevention of Pollution by Liquid Chemical Agents (PoLiChem), which finished its mandate at the end of 2018, recommended CERN-wide actions monitored by CEPS to reduce pollution risks. CERN has already funded and implemented some of the proposed mitigation actions, such as dismantling obsolete equipment, constructing the aforementioned retention basin near Prévessin (see Water and effluents) and replacing an old fuel tank.

In 2020, CERN dismantled the old fuel tank identified as a high-risk case by PoLiChem, which was replaced with a state-of-the-art diesel generator. The project included decontaminating the tank, managing the waste, setting up a temporary tank permitting continuous activity, and designing a new loading and unloading area as well as a sewer network to protect the aquatic environment.

The Large Hadron Collider (LHC) is the largest cryogenic system in the world and one of the coldest places on Earth. The LHC's main magnets operate at a temperature of 1.9 K (-271.3°C), colder than the 2.7 K (-270.5°C) of outer space. The LHC's cryogenic system requires some 130 tonnes of helium to keep the magnets at 1.9 K.

Helium is extracted as a by-product of natural gas production and is not a greenhouse gas. It is supplied to CERN, mainly in liquid state, by means of thermally insulated ISO containers from world-leading industrial gas companies operating in Europe.

The Organization’s total helium inventory at the end of 2020 amounted to 175 tonnes, the majority of which is used for cooling the superconducting magnets of the LHC.

Following the LHC’s initial start-up in 2008, CERN made an effort to reduce its helium needs in terms of compensation for operational losses and equipment conditioning. Annual operational losses were reduced from 30% of the LHC inventory down to 10%. This effort was initiated during Run 1 of the LHC (2008-2013) and completed and stabilised during Run 2 (2015-2019).

Reducing the need for helium when restarting the LHC after long shutdown periods has also been a priority. While the restart phase after the first long shutdown (2013-2014) consumed 21% of the LHC’s helium inventory, CERN succeeded in halving helium consumption to about 11% of the inventory when restarting the LHC after the second long shutdown.

CERN initially concentrated on reducing helium losses related to the LHC, which represents 75% of the total helium inventory at CERN. After this very successful campaign, CERN has also implemented close monitoring of the helium inventory for non-LHC related applications, including test bench facilities and experiments.

Sabrina Schadegg works in CERN’s Environment Group and was involved in developing the CERN Chemical Register for Environment, Health and Safety (CERES).

— What is CERES?

SS: CERES is a new web tool for chemical safety that the Organization launched in 2020. It gives an overview of all liquid, solid and gaseous chemicals present on CERN’s sites. The database includes safety information, the precise location of the chemicals and data on chemical and environmental risk assessments and the mitigation measures in place.

— How is it useful?

SS: CERES has a map view, which is very useful for the Fire and Rescue service during emergency interventions. The map is also useful for assessing the risks within a building or an area. Within the Environmental Protection group, CERES is used to identify environmentally sensitive activities and areas on CERN sites, and allows increased interaction across the departments to improve pollution prevention measures.

Questions regarding this report may be addressed to environment.report@cern.ch.