CERN, the European Organization for Nuclear Research, is a laboratory that studies particles and their interactions, but is not concerned with nuclear energy or weaponry. The name is derived from European Council for Nuclear Research, a provisional body founded in 1952 with the mandate of establishing a world-class fundamental physics research organization in Europe. At that time, pure physics research concentrated on understanding the inside of the atomic nucleus and the word ‘nuclear’ in the name reflects this. Very soon, the work at the laboratory went beyond the study of the atomic nucleus and onto sub-nuclear particles and their interactions. As a consequence, the laboratory operated by CERN is commonly referred to as the “European laboratory for particle physics” (“Laboratoire européen pour la physique des particules’) and it is this latter title that really describes the current work of the Organization.
Radiation is the transport of energy through particles or waves, such as X-rays. It occurs, for example, when an unstable atom breaks down to form a stable atom, and releases some of its energy. Rocks, the sun and space all naturally emit ionizing radiation that we can detect on Earth. Artificial ionizing radiation also comes from medical treatment or in small amounts through mining and nuclear power industries. Though safe in small doses, in high doses ionizing radiation can be dangerous as the energy can knock electrons off atoms in living bodies, ionizing and damaging them. The ionizing radiation dose is usually measured in Sieverts (Sv), which is a measure of the effect of radiation on the body.
CERN’s experiments involve colliding beams of particles together or into a stationary target. When this happens some of the particles release radiation or new particles are created. This is very different to radiation from a nuclear power plant where without human intervention the radiation levels could increase exponentially. At CERN radiation only occurs when the particle beam is on, and turning it off stops emissions immediately. Collision events are also very rare; at the LHC each day only 2 nanograms (one millionth of a milligram) of protons will be accelerated and only a small proportion of these will collide. The proton beams can circulate for hours in the collider without being spent totally. It would in fact take millions years to collide 1 gram of protons. Radiation sometimes activates some pieces of components surrounding the collision points, causing them to become radioactive. This small amount of material is well confined and when the accelerator is dismantled it is handled following the appropriate regulations.
CERN typically delivers about 0.01 mSv of effective dose of radiation to someone residing in the local area per year. This is less than 1% of the total annual dose of 3.7 mSv that individuals already receive on average, both naturally, through radioactive elements in soil and rocks or cosmic rays, and artificially through medical procedures, for example, as shown in the chart below. To put this into context, a year of living near CERN is the radiation equivalent of the increased cosmic ray exposure experienced whilst taking a return flight from Geneva to Athens.
This additional radiation dose from CERN is also lower than natural differences between different areas, so that moving to another municipality could raise your annual radiation dose to much more than living near CERN. The Swiss Office Fédéral de la Santé Publique (OFSP) and the French Institut de radioprotection et de sûreté nucléaire (IRSN) have stated that compared with these natural fluctuations, the effect of CERN radiation on the public is negligible.
Most of the radiation produced in collisions will be absorbed by a few solid accelerator components, which may become activated with a range of radionuclides and of those that may impact the effective dose the longest lived is 60Co with a half-life of 5.3 years. This type of radiation cannot escape from the facility so the public are not in any danger. However it must be dealt with following the appropriate radioprotection regulations. Air used for ventilation and water used for cooling may also contain small amounts of radioactive elements. Filters clean the emissions of activated aerosols and all necessary action is taken to prevent these from reaching the environment. Most of the elements have half-lives of just minutes or hours. This means they are radioactive only for a short time. This small amount of emissions is in the form of gamma and beta radiation. Combined with the short radioactive half-lives and their physical and chemical properties, these radionuclides pose a low radiation hazard.
CERN adheres to an internationally recognised radioprotection system that always strives to minimize radiation exposure and, as a consequence, CERN’s emissions remain well below regulatory limits. To check this, 200 various on-line monitoring stations are spread throughout the site and its surroundings, including sensitive gate monitors that measure the radioactivity of each item leaving and entering the site with alarms that prevent any uncontrolled release of radioactive material from CERN to the outside world. Teams of the CERN Safety Commission also take samples of ambient air, soil, river water, groundwater, rainwater, vegetation and agricultural products from the surrounding environment, and carry out thousands of analyses on the samples per year. The limits CERN imposes on exposure of staff and visitors are derived from EU law and all members of personnel working in sensitive areas wear dosimeters that measure their exposure. Shielding is in place throughout the radioactive elements on the site. The fact that accelerator facilities are underground provides an additional natural barrier. Where radioactive materials are stored it is done following the appropriate regulations. CERN teams carry out computer simulations of radiation fields for existing and planned facilities, such as the LHC, so we can anticipate any problems ahead of time. In this way we are able to predict and minimize environmental impacts before the construction of any facility. Recently, the impact studies for the LHC, Super Proton Synchrotron and the CERN Neutrinos To Gran Sasso facility were successfully reviewed by French and Swiss radioprotection government professionals. Of course, we monitor the real levels once programmes go live. The start up of the LHC is not expected to significantly increase the levels of the radiation exposure of the public and the resulting effective doses will stay close to the current levels.
The radioprotection authorities in the CERN host states, the Swiss Office Fédéral de la Santé Publique (OFSP) and the French Autorité de Sûreté Nucléaire (ASN) supported by the Institut de radioprotection et de sûreté nucléaire (IRSN), have carried out a ‘Point Zero’ study aimed at assessing the state of the environment around CERN before the LHC start-up. Based on results obtained over two years, the study report concludes that the radiological impact of CERN on the local environment over its 53 years of activity is negligible. The results of this study also provide a reference point for the future monitoring by the Host States’ authorities to confirm that the public exposure always stays below safe levels. The OFSP and IRSN surveyed the CERN environment in the past and will continue to survey it throughout the operation phase of the LHC. Consequently, the “Point Zero” study was only a start of an international monitoring programme dedicated to the Large Hadron Collider.
The ‘Point Zero’ study is available on the OFSP web site.