EDMS No. xxxxxxx v.1
ORGANISATION EUROPEENNE POUR LA RECHERCHE NUCLEAIRE
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH
Laboratoire Européen pour la Physique des Particules
European Laboratory for Par ticle Physics
16th May 2013
CERN Neutrino Facility – environmental impact
Near and far detector buildings
Authors: List
Abstract
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EDMS No. xxxxxxx v.1
Document history
Version
1
Date
04/03/2011
Major changes / comments
Creation.
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EDMS No. xxxxxxx v.1
Contents
1 Brief description of the facilities ....................................................................................................... 4
2 Construction phase ............................................................................................................................ 4
2.1 Transport nuisances ........................................................................................................... 4
3 Operation Phase ................................................................................................................................ 4
3.1 Commissioning ................................................................................................................. 4
3.2 Use of cryogenic liquids.................................................................................................... 5
3.3 Accidental release of Argon in large quantities ................................................................ 5
3.4 Cryogenic services ............................................................................................................ 5
3.4.1 Cooling........................................................................................................................ 5
3.4.2 Noise ........................................................................................................................... 6
3.4.3 Lubricants ................................................................................................................... 6
3.5 Ionizing radiation .............................................................................................................. 6
3.5.1 Neutrinos ..................................................................................................................... 6
3.5.2 Testing and calibration muon beams .......................................................................... 6
3.5.3 Greenhouse gases ........................................................................................................ 6
3.5.4 Gases depleting ozone layer........................................................................................ 6
4 Dismantling phase ............................................................................................................................. 6
5 Conclusion ........................................................................................................................................ 7
6 References ......................................................................................................................................... 8
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1 Brief description of the facilities
The neutrinos generated in the primary area from muons and kaons will be detected and
studied in two experimental areas equipped with several large detectors filled with liquid argon
(LAr):
1. The near detector facility will be at a distance of about 460 m from the secondary
beam complex. The experimental hall EHN1 will be extended towards the NE and
house three detectors: ICARUS-150T (225 t of LAr), Nessie Near muon spectrometer
and a LAGUNA prototype (XXX t of LAr);
2. The far detector facility will be placed at a distance of about 1600 m from the
secondary beam complex. A new building will be constructed that will house two
detectors: ICARUS-600T (760 t of LAr) and NESSiE muon spectrometer.
All detectors will be embedded in deep trenches together with compressors and argon
liquefiers. Liquid argon will be stored in closed basins avoiding gas overpressure and losses.
Missing: Alternative locations, justification for this site.
Missing: Description of the current site and its usage.
2 Construction phase
The near detector facility will be at a distance of 50–100 m from the site fence in an extension
to the existing EHN1 building. The far detector facility will be constructed on an external parcel
(120m x 66m) connected to the north-eastern border of the Prevessin site, for which an access road
will be constructed through the CERN site to the south side of the new building. All services will be
brought to the detector facilities from the inner part of the CERN site. The emplacement is on an
existing track that will be displaced around the new security fence.
2.1 Transport nuisances
The far construction site will be accessed from the CERN side through the main Prevessin site
entrance, respecting the maximum number of trucks per day allowed. No field roads outside the site
will be used.
(n.b. In construction phase the work site will need space to excavate around the building, is
the proposed distance sufficient for deep excavation? The perimeter fence and replacement road
will need to be established at the time of excavation. N.b. The gas hazard only requires a few
meters.)
3 Operation Phase
3.1 Commissioning
Some detectors will use liquid argon as their detection medium, the quantities involved will
be several hundreds of tons.
Argon is a common industrial gas, used in welding, food processing, window insulation and
in many other applications. It is chemically inert but is a simple asphyxiant causing suffocation by
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displacing the oxygen in air. In gaseous phase it is heavier than air so it has the tendency to fill
zones placed below the terrain around. It has neither colour nor odour and hence it cannot be
detected by human senses even at concentrations causing serious oxygen deficiency leading to
death. Even though no leaks will be tolerated, the safe use of this gas requires the simple safety
measures (ref Air Liquide MSDS Argon) of assuring good ventilation and avoiding any
accumulation of gas in low lying areas.
The gas will be delivered by specialist transports under supervision of the CERN cryogenics
group and all deliveries will be made through the CERN Prevessin site. All cryogenic and gas
equipment will be reception tested and have regular safety inspections and tests.
3.2 Use of cryogenic liquids
The liquid argon will be contained in double walled, thermally insulated basins which are in
turn inside liquid Nitrogen basins which provide the necessary cooling to the Argon system. The
basins are sealed in normal use: no liquid or gaseous Argon or Nitrogen should be lost to the
atmosphere. The detector basins will be embedded in trenches within the detector buildings, -11m
for the near detectors and -6.5m for the far detector facility. Furthermore, the detector areas will be
equipped with permanent exhaust extraction from the lowest points, the evacuated air will be
rejected via exhaust stacks above the roofs of the buildings where any Argon or Nitrogen gas will
safely disperse (ref EIGA IGC 154/09).
A safety system which monitors Oxygen levels in the building will also be installed to provide
evacuation alarms to the personnel in the case of a serious gas loss, this will also activate a major
ventilation exhaust stack, with heating to ensure that only warm gases which are easily dispersed
are evacuated offsite.
3.3 Accidental release of Argon in large quantities
The possibility of a major release of gaseous or liquid Argon or Nitrogen cannot be excluded
and these cases have been studied in depth and measures taken to minimise their probability and
consequences (ref. ICARUS T600 working group report). In total 14 causes of release were
analysed ranging from ruptured welds to serious earthquakes and including human errors such as
delivery manipulations and mishandling of the overhead crane. The resulting series of measures that
were implemented at Gran Sasso and will be copied at CERN include redundant safety valves for
cryostats and storage vessels, safety vents ducted to extraction manifold where gases are heated
before release, intercepting valves and a full sensor system for plant monitoring, and finally
correctly dimensioned seismic shock absorbers on the cryogenic tanks. In addition the CERN
cryogenics group will operate and maintain the equipment to the same levels as all their other
installations and will harmonise the equipment to their standards.(.?)
3.4 Cryogenic services
To maintain the temperature of the liquid argon, cryogenic services will be needed. The
biggest units such as compressors, liquefiers or storage tanks will be placed in the trenches inside
the buildings.
3.4.1 Cooling
The necessary cooling of over 1 MW per detector facility will be provided by external chilled
water circuits. There are no particular hazards associated with the cooling because there are no toxic
or radioactive substances in the detectors. The only hazard is a rupture of the piping causing a
partial inundation of the trench; this can be, however, easily detected and the cooling circuit closed.
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3.4.2 Noise
All compressors will be of low noise and hidden inside their trenches. The propagation of
noise will be prevented by additional sound isolation, if necessary, and by orienting outlets of the
detector facility buildings towards the inner part of the site.
3.4.3 Lubricants
All compressors will be equipped with retention basins of sufficient volume and the trenches
will provide additional retention capacity. Hence, no lubricant leaks to the environment will be
possible.
3.5 Ionizing radiation
The facility will send to its detectors only neutrinos and weak muon calibration beams.
3.5.1 Neutrinos
Neutrinos are particles that interact with matter with extremely low probability. Even if a
person would be exposed to the maximum annual integrated fluence of neutrinos produced at CENF
(<5×1011 cm-2), the incurred effective dose shall remain below 0.01 µSv as resulting from a very
conservatively screening calculation using a fluence to dose coefficient of 2×10-14 µSv cm2
[Moknov99].
3.5.2 Testing and calibration muon beams
To adjust the detectors, very low-intensity muon beams will be provided to the sensitive
volumes of the detectors. The main interaction way of muons with matter is ionization. These weak
testing beams will produce negligible stray radiation mostly absorbed in the structures of the
detectors. Another feature of muons is that they activate materials only weekly.
No part of the detectors will become activated during the operation of the experiment and the
experimental facilities will be accessible without individual dosimetric control.
3.5.3 Greenhouse gases
The detector gas will contain small admixtures of other gases that improve its detection
properties. Namely:
C2H2F4 (Global Warming Potential GWP = 1200)
SF6 (GWP = 23’900)
Z
….
C2H2F4, SF6, Z are classified as greenhouse gases. In compliance with EU regulations The
costs of some of them are so high that the gas admixtures will be completely recycled.
3.5.4 Gases depleting ozone layer
Admixtures X, Y, Z are classified as gases depleting the ozone layer. In compliance with EU
regulations The costs of some of them are so high that the gas admixtures will be completely
recycled. (references needed- which gasses will be used?)
4 Dismantling phase
Prior to dismantling, the argon gas will be removed for storage and re-use, the remaining
equipment and materials will not have been activated or contaminated due to operation and so
would be available for reuse or removal without special precautions. As no hazardous chemicals or
materials such as asbestos or lead are integrated in the building structure, the building materials may
be disposed of using normal techniques and services.
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5 Conclusion
The detector facilities will use standard technologies proven from the Safety point of view
and they will not contain or release radioactive or toxic substances. The only serious environmental
aspect is use of a large quantity of liquid argon that might pose a cryogenic hazard. It will be
mitigated by a series of measures based on industrial best practice and the considerable experience
of operating the very same detectors at Gran Sasso laboratory in Italy. The gas and cryogenics
systems will be installed and operated by the CERN Cryogenics group who have many years’
experience of building and running cryogenic systems at CERN and all the equipment will be
subject to regular safety checks and tests.
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6 References
[Mokhov99] Mokhov N.V., Van Ginneken A., Neutrino induced radiation at muon colliders,
Proceedings of the 1999 Particle Accelerator Conference New York, New York (1999),
3074–3076.
MSDS Argon
http://www.ca.airliquide.com/file/otherelement/pj/argon_air_liquide_canada_gl%202011engli
sh%20(us)81745.pdf
EIGA IGC 154/09 “Safe location of Oxygen and Inert Gas Vents”
http://www.eiga.org/fileadmin/docs_pubs/Doc_154_09_E.pdf
ICARUS T600 working group report
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