CERN collision course

Transcription

1 The underground centre straddling France and Switzerland is home to the 27 km tunnel containing the Large Hadron Collider and some very particular hazards. Article date: Thursday, May 18, :45 Case study Do you know what antimatter is and understand how it is produced? No? Neither, it seems, did bestselling author Dan Brown when he put it at the centre of the plot of his 2000 blockbuster thriller Angels & Demons. The story centres on a secret scientific society known as the Illuminati, which steals 0.25 g of antimatter created by scientists at CERN the European Organisation for Nuclear Research. It plans to use the highly-volatile substance to wipe out the Vatican by causing the antimatter to annihilate itself by colliding with matter. It s a great plot, spoiled only by the fact that the difficulty of creating antimatter makes the whole thing impossible. The amount they managed to get hold of in the story would take CERN scientists something like 250 million years, working only on that, to produce! exclaims Simon Baird, head of health, safety and environment at CERN. The vast complex straddles the Swiss/French border just outside Geneva and houses the Large Hadron Collider (LHC), the world s largest particle accelerator which sits in a 27 km tunnel. Physicists and engineers at CERN use it and other accelerators to make the basic constituents of matter fundamental particles smash together at close to the speed of light. Detectors then observe and record the results of these collisions, giving the scientists an insight into the fundamental laws of nature. Page 1 of 8

2 Or, as Baird puts it: What we do here is try to determine why particles do what they do and why nature favours matter what we and everything in the universe are made of over antimatter, in order to discover why we are here. Simple as that. The reality confounds scientific theory, which suggests that matter and antimatter should have been produced in equal quantities in a Big Bang 13.7 billion years ago and then, almost immediately should have annihilated each other which is why we should not exist. CERN is attempting to fill in these huge gaps in the quantum world. Baird took over the OSH role in January 2016, after 35 years as a physicist, working mainly on the accelerators. He made the move at the request of CERN s director-general, Fabiola Gianotti. She had ideas of what she wanted to do, which struck a chord with me, he says. So I took the job, and I m very glad I did. Baird s department reports directly to the director-general and comprises some 230 people. Operationally, they are responsible for radiation protection matters, general safety and the fire and rescue services, and they organise and carry out safety training. Each individual operational department is responsible for looking after their own safety, says Baird, but we will inspect and help them design safe systems. Ensuring they are safe is their responsibility, though. Each department has a dedicated safety officer. There are also many specialised officers for specific risks. On the larger experiments there will be a group leader for safety matters usually a safety professional hired by the experiment team. Finding the right person for that job makes all the difference, says Baird. Closed circuit When the LHC s beam hits the target and particles fly out, ionising radiation is produced. This causes residual radiation, even when the beam is turned off. Baird and his team have experts who will ensure that the dose received by staff intervening in zones where ionising radiation is present will be as low as reasonably achievable. Baird says this can be realised by optimising the way you work, Page 2 of 8

3 waiting until levels go down, or using more people, so individual exposures are lower. Anyone who enters a radiation area must wear a dosimeter. The worst scenario Baird s staff have to envisage is a major release of radioactive material, or a serious fire: The combination of radiation and fire can cause the release of radioactive smoke, and that is probably foremost in people s imagination of what could go catastrophically wrong at CERN. However, we do have a closed ventilation system to prevent the external release of smoke. The potential effects of a serious fire in an underground area are so high that CERN has its own fire department, with about 60 staff. All calls are received and dispatched from the fire safety control room, which also monitors where people are carrying out risky activities, so they can direct the response if there is an incident. According to fire officer Rui Samoës, the service receives, on average, eight emergency callouts a day everything from stuck lifts upwards. There are one or two significant fires a year, while smaller fire incidents average ten a month. The CERN alarm monitoring system monitors the 8,000 fire detectors and 800 gas detectors. It s a double system, with two banks of monitors, in case one fails. False alarms are frequent two or three a day but they are always taken seriously, according to Samoës. The site also has 6,000 fire extinguishers, which must be maintained. You start to understand it and get to know all the facilities and where they are after about two-and-a-half years on the job, says Samoës. Evacuation drills are held every year in the high-risk zones, less often in the rest of the centre. Evacuating the tunnels is a particularly delicate operation. Contrary to standard practice, the LHC staff are supposed to use the lifts in an emergency, because the shafts are designated safe zones. Baird explains: In the LHC, there are eight access points, so you could be 2 km from the nearest evacuation exit. Therefore, we are extra careful about the equipment that goes into the tunnels to minimise the opportunity for fire. There has been a fire in the tunnel of the Proton Synchrotron [CERN s original flagship accelerator] but it was near the surface and it was easy to evacuate. Both the LHC and the Super Proton Synchrotron [SPS the second-largest accelerator on the site] have experienced flooding and gas alarms. Pedal problem Page 3 of 8

4 CERN s more conventional risks are much like those at any other large industrial site, encompassing electricity, gas and compressed-air systems. Confined-space work is obviously an issue, as is work at height some of the caverns housing the detectors are up to 25m high. Surprisingly, one of Baird s biggest concerns is commuting incidents in 2015, 79 were logged, almost two-thirds of them involving cyclists. In the summer especially, many of our people come to work on bikes, he says, and they can also be rented on site. So we give out helmets and reflective gear, and run safe-cycling campaigns around the site. Everyone accepts the as low as reasonably achievable principle for the high-hazard stuff but we need to get the same acceptance for getting to, from and around work. To rent a bike at CERN, staff must now complete a road-traffic bike-riding e-learning course. With the smaller experiments especially, people come from all sorts of places where safety constraints might not be so stringent Safety in the workshops where the experiments are constructed and maintained is also high on Baird s list of priorities because there are, as he points out, always lots of people building stuff. A key challenge is the fact that most of the experimental physicists on site are not fully employed by CERN they are known as CERN users, or associated members of personnel, and come from scientific institutes worldwide, staying for varying lengths of time. (The total working population of CERN comprises 2,300 employees, 1,400 associated members of personnel, 3,500 contractors and some 12,500 users.) Page 4 of 8

5 As Baird explains: With the smaller experiments especially, people come from all sorts of places Page 5 of 8

6 where safety constraints might not be so stringent. Also, they are eager to get on with their work, so the pressure to cut safety corners is high. The people here are highly specialised and take a huge amount of pride in what they do. Getting things switched on on time, for example, is very important to them but what is important to me is getting it switched on on time safely. When new experiments are proposed, we will generally get involved to look at the safety aspects at the research stage, when the decision is made on whether to proceed, says Baird. We look at the likely impacts of what they want to do, and whether they can do it safely. At the project stage conceptual and technological design safety has to be involved. We will risk assess the radiological aspects, use of pressure vessels and so on. We have turned down projects before or told them how to do it differently to improve safety. Experiments have also been stopped for safety reasons. While they are ongoing, we will check to see that things are being done as they are supposed to be. This approach works well for the larger projects at CERN the LHC experiments, for example, have been going on for more than 20 years and involve many thousands of people but some of the smaller ones can be, as Baird puts it, a bit Heath Robinson, run by just a few people from a university for maybe six months. In these cases, he says, we have to inspect their equipment to make sure it s safe, even though it s unlikely it will have CE marking or the like, because it s so specialised. We will also make sure they are not using unsuitable materials for example, PVC is not allowed anywhere. All CERN installations are monitored by the CERN control centre (CCC). This is a huge, high-ceilinged room divided into four separate console areas: one dedicated to technical infrastructure controlling electricity, water, vacuum and cryogenic systems and industrial control (as would be found in any factory or plant), and the other three to the accelerators. When IOSH Magazine visited, the accelerators and detectors were being switched back on after winter maintenance, during which they can be shut down for between six and 15 weeks. The LHC runs for three years, then is turned off for two years, and then back on again, Baird explains. But there will be shorter stops within that for mechanical maintenance. This is carried out in winter because electricity is more expensive then, so we save by shutting down the machines. When the beams are running, concerns relate to the beam itself, such as electrical and cryogenic risks the effects on matter at very low temperatures. There are software-controlled systems to protect the machines, so if something does go wrong with the monitoring system, the collider beam would be dumped. In essence, this is to protect the machine from itself. In this case, the control team can call on experts who are obliged to arrive within an hour at any time. During shutdowns, the concern shifts to people because they will be in the tunnels welding or carrying out repairs. It is important to co-ordinate who is doing what and ensure everyone understands the hazards. Permits to work are strictly enforced. To do any work, you need to submit a request to the co-ordination team, which plans and authorises it, says Baird. Your request has to outline whether the work impacts anything else, how you are going to go about it, what services you need. For example, if you are going to be welding you will need to alert the control guys and the fire brigade. The access system will authorise you to go in to do that job and that job only for that particular period. If you are not on the list for that activity, you won t get access to the work area when you turn up. Dual liability Access to the tunnels is controlled by safety interlocks, and all people who go in are counted back out again. Light-beam guards interact with the control system and there is also an analogue relay control to determine nobody is inside when they shouldn t be. According to Baird, the failure rate is no more than one in 10,000. The system has to be extremely reliable, as it would be catastrophic from a reputational point of view if it were to fail. Page 6 of 8

7 But if an incident did occur, which authorities would be responsible for investigating it? After all, CERN sits across the border of two countries one of which is in the EU and the other isn t. Which country would have to send in its safety regulator, or law enforcers if, say, there was a fatality? They would definitely come and investigate, states Baird, but because CERN is an international organisation, it is independent of national authorities. The two host states can t impose rules or inspect us unannounced, but CERN follows high safety standards and collaborates with both host states, so they can feel comfortable that things are running safely on site. If there is a work-related death, this is reported to the host-state authorities. If we are required to give evidence for an investigation, those authorities have to ask the relevant host-state government to ask us to do so. In my role, I am immune from prosecution by the host states but, in the case of a serious accident, this immunity can and would be lifted. In terms of regulation, whose rules do they follow? We self-regulate but we don t do so vastly differently from how it is done in Switzerland, France or the EU. In general, we tend to follow EU rules and standards. In any case, the measures we take and standards we operate to are generally stricter than those that apply in Switzerland or France. For example, the maximum personal radiation dosage levels allowed for radiation workers at CERN are lower than those in the host states. So, could a health and safety professional who doesn t understand experimental physics do this job? Baird thinks it would be difficult but not impossible. Even though my background is in physics I still have to listen to the experts in the organisation and take into account their views and requirements same as anyone in a health and safety role would. I have to say, though, the biggest challenge is managing people. There are a lot of very intelligent, focused people at CERN. Those guys you see on the TV comedy The Big Bang Theory those types of people really do exist, and most of them work right here. Topic : Fire [1] Emergency planning [2] Personal protective equipment [3] Electricity [4] Page 7 of 8

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