Proposed ANDES laboratory design - preliminary version - 2014

1. General Information

The ANDES laboratory is a proposed underground laboratory to be built at the interior of and as an integral part of the Agua Negra tunnel. It will be the first and only underground laboratory of this kind in the southern hemisphere. At present, about a dozen laboratories with similar capability are in operation in the northern hemisphere: in North America, Europe and Asia.

ANDES will be located in the deepest part of the Agua Negra tunnel, around 1750 m below the Andes, which will shield its facilities from cosmic radiation, particles of high energy emanating from all regions of space. By being protected from that radiation, will have the sensitivity needed to conduct unique experiments in a variety of scientific fields. These include:

  • searches for dark matter, which represents 85% of the matter in the universe, in a form completely unknown today;
  • research into the physics of neutrinos, elementary particles able to traverse the Earth without interacting;
  • studies of geophysics, investigating Earth tectonics from a laboratory at the inside of a mountain;
  • environmental impact studies; purity of materials; impact of cosmic radiation on integrated circuits; biology; and more.

The lab will be led by a Latin-American consortium, CLES (Latin-American Consortium of underground studies) {from the Spanish version: Consorcio Latinoamericano de Estudios Subterráneos}, with participation of at least Argentina, Brazil, Chile and Mexico.

ANDES will host numerous experiments, both Latin-American and International, installed in various caverns of the Andes underground facility. The selection of experiments will be based on their interest, scientific merit, and relevance for members of the CLES consortium. Experiments will be adjudicated by an evaluation Committee, which must ensure in particular that aspects of safety and environmental impact have been adequately addressed. The underground laboratory will be accompanied by two research or laboratory support centres located outside, but in the vicinity of, the tunnel. Given the elevated height of the tunnel, and given the necessary infrastructure required for the support labs, it is likely that one of supporting laboratories will be located in La Serena (Chile) and the other in Rodeo (Argentina).

The purpose of this document is the description of the underground facilities and infrastructure necessary for the realization of the activities proposed in the ANDES underground laboratory.

2. Location and Site

The ANDES laboratory will be located around 4.5 km from the Chilean end of the Chile-Argentina tunnel. At that point, the vertical rock coverage above the lab is 1750 m, and there is at least 1670 m of shielding rock in all directions. However, the exact location will depend critically on the type and nature of the rock that is found at those depths. The design shall take into account:

  • the geo-mechanical properties of the rock at the proposed construction site, and aspects regarding the stability of the caverns to be constructed;
  • the depth of the site, which is essential to protect the laboratory from cosmic radiation;
  • the natural radioactivity of the rock at the location, given that it has a non-negligible contribution to the background radiation expected in the laboratory.

In any case, the chosen location must not be too distant from the point of maximum depth, which is at the 4.5 km mark of the tunnel, passing through the tunnel in the sense Chile - Argentina.

3. Access to the Laboratory

From the main road tunnel, you will enter the laboratory by pulling off to the right hand side. The entrance will be sign-posted in advance, with appropriate road signs that emphasis the fact that the laboratory is a scientific facility with access only to authorized personnel. The widening of the vehicle tunnel at the entrance must be designed and dimensioned so that vehicles of any size can enter the laboratory. The design of the access should allow sufficient space so that a vehicle of any size that has mistakenly tried to enter the scientific complex can accelerate and return to the vehicular tunnel. There should also be a safety connection at the location of the laboratory area which would provide access to the Argentina - Chile tunnel in case of a fire in the Chile - Argentina tunnel near the location of the laboratory.

A gate (Access Gate 1) will control access to the gated complex. A barrier will be installed just after the gate, and this will be closed during the day when the gate is open. At the barrier there will be a guard post and automatic and manual access control systems enabling access to the laboratory. Once access has been granted, the vehicle can enter the parking area (of appropriate size) adjacent to the access point. Past the parking area, the access tunnel runs 45° towards the North and is parallel to the main tunnel. On the right there will be access to two secondary facilities (see sections 7 and 8). A left hand exit allows cars to return to the main vehicular tunnel, in this way avoiding the movement of vehicles in the most sensitive areas of the laboratory. The access tunnel then continues northward, where an interior gate (Access Gate 2) restricts the main access to the caverns and services (see sections 4 and 5). The only vehicles normally allowed to enter this area will be large vehicles carrying heavy equipment. The area must be dimensioned such that a low platform truck carrying a tall shipping container up to 24 feet long can enter and maneuver. In each cavern a crane will be responsible for the loading and unloading of equipment from trucks, and moving the equipment to the inside of the work area. At each exit to the complex, (the normal vehicle exit and the rear truck exit) there will be exit gates (Exit Gates 1 and 2 respectively) that prevent access to the complex and an acceleration zone so that outgoing vehicles can join the vehicular flow of the main tunnel.

4. Main Cavern

The main cavern will measure 21 m wide by 23 m high and 50 m long, with an egg shape to ensure structural stability. The cavern is located in the central part of the complex, and its left end can be accessed by following the main access tunnel after passing through Access Gate 2.

Also an access tunnel to the secondary cavern must be installed (see section 5) from the right end of the main cavern. In the upper part of the cavern there will be a 40 tonne capacity bridge crane which travels on rails in the longitudinal direction. The installation of columns to support some girders must be provided to allow the crane to reach into the main tunnel access, thus facilitating the loading and unloading of trucks. The most complete use of the installation space is achieved by making the girders of the bridge crane follow the curvature of the ceiling of the cavern. In this way, the displacement of the carriage in the transverse direction must be through a controlled stepping mechanism. An electronic system will prevent the payload from moving vertically as the carriage moves in the transverse direction.

The available surface area for experimental equipment will be rectangular, 35m long and 19m wide, slightly below the nominal grade. The finished floor in the equipment area is about 3m below the nominal reference grade of the cavern, (the access tunnel floor level). The maximum height of the cavern (23m) is calculated from the level of the finished floor in the equipment area. In this way, there will be a walkway at the outer edge of the cavern with a height of 3 m above the experimental area floor. The installation of removable safety rails along the entire perimeter walkway in envisaged. Also a removable ramp system must be provided so that a fork-lift or similar piece of machinery can enter and leave the equipment area, without having to occupy useful space. The experimental area must have a drainage system that channels any spillage of liquids to longitudinal side gutters, and a permanent pumping system in a sump to evacuate the drainage system. The liquids must be pumped to the service cavern for treatment. (see section 5).

Conveniently distributed electrical panels will allow the connection of experimental equipment to the mains supply in the laboratory. The installation of low-voltage power, communication networks, compressed air, water, and services should also be envisaged.

5. Service Cavern

The services cavern measures 40m long, 16m wide and 14m high, and is egg shaped to ensure structural stability. The existence of a centrally depressed pit is not required. Like the main cavern, this cavern has a bridge crane with the same specifications as the previous one, but with a capacity of 20 tonnes or less. While some experimental equipment is anticipated for this area, the main function of this cavern is to host the laboratory infrastructure services and to provide office space. In particular, in the services cavern, the following items will be installed:

  • main ventilation equipment. This should be sized to renew the total volume of the lab at least once per hour. This system will include the filtering of radon in the air of the laboratory.
  • air conditioning equipment to maintain the entire laboratory at an average temperature average of about 21 degrees Celsius. This must have sufficient capacity such that it can maintain the temperature when the laboratory is consuming all power available (at its full power consumption peak of 2MW). The ambient relative humidity shall be determined in a way so that the operation of the equipment in not affected, but not such that it is outside the standard limits for human thermal comfort;
  • power supply equipment, transformers and electric generators to provide electrical energy to the experiments; A bank of batteries (UPS power) will be installed on specific low voltage circuits to protect critical equipment against possible power outages;
  • storage tanks, and water and effluent treatment plants;
  • computer disk storage and cores for the processing of data;
  • communications centre (telephones, computer network, etc)
  • supply of basic services to the experiments: compressed air, water, data, communications, etc.
  • medical first aid kit equipped with supplies in case of accidents in workplace such as in the case of altitude sickness;
  • a variety of systems for fire-control.

The total maximum power required for the laboratory will be 2MW. In cases of emergency only a small fraction of the total power will be required to maintain critical systems, given that the majority of the primary systems will be powered off. Half of the power will be required for ventilation and air conditioning system. The other half will be available for experiments.

The ventilation system must maintain the laboratory with low levels of radon. It must recirculate the total volume of the lab through a filtration system at least once every hour. In addition to distributing fresh (low radon content) air from outside the tunnel systems to the caverns, the ventilation system will have a system of monitoring the quality of the air. Similar to other clean room facilities, a slight overpressure inside the complex creates an outward flow of clean air to improve the cleanliness of the laboratory. This can be obtained naturally with the flow of air circulating through the laboratory. The incoming air to the laboratory will come from outside the Agua Negra tunnel, and will be transported using a sealed pipe of stainless steel or similar material to avoid contamination by radon that accumulates within the vehicular tunnel. Therefore, the installation of the fresh air supply line for ANDES must be included in the design of the tunnel.

The water flow rate necessary for the consumption of staff and the experiments will be some liters per second. A 50 m3 water storage tank will be installed inside the services cavern. A wastewater treatment plant will also be installed to process and then discharge effluent waste produced in the laboratory in compliance with environmental rules.

The Computing Centre shall have optical fibre connections to both Argentina and to Chile. Redundant single-mode fibers will be used for internet access, and an additional fibre will be dedicated to providing a high precision timing signal calibrated by GPS. Two fixed copper lines will be added for emergency communications in case of the loss of connections by fibre. The systems required for security and laboratory monitoring will be installed in the services cavern and will be fully integrated with the system of the Agua Negra tunnel.

The medical kit should be equipped to provide basic first aid plus have oxygen for the treatment of altitude sickness. It must be located in such a way to be able to be used in case of an emergency or in the event of a serious accident within the vehicular tunnel, without affecting the sensitive areas of the laboratory.

6. Main Pit

A large sized pit, 30m in diameter and 42m in total depth must be excavated. Access to the upper part of it will be via a tangential or central (to be determined) secondary tunnel located at the right end of the services cavern, at a height of 30m from the bottom of the pit. The pit will accommodate a large sized high sensitivity experiment. In order to minimize the effects of ambient radioactive contamination, after having installed the experimental apparatus, the pit can be filled with water to a height of 30m from the bottom of the pit. The infrastructure will include a pumping system for filling and emptying the pit. This pumping system could also connect with the laboratory fire suppression systems so that the pit also acts as a fire water reservoir tank. Access to the bottom must be present, both to facilitate construction of the pit, but also for the installation of equipment. This access to the bottom will be closed and sealed prior filling the pit with water and the seal must withstand the pressure produced by 30m of water.

At the top of the pit, hanging from the back, is a 20 tonne bridge crane that will be installed to allow the entry of equipment into the pit. The pit installation must be arranged such that it can receive and install experimental equipment, keep the pit filled with water and provide a system of platforms and ladders to access the equipment during deployment. A system of removable railing sections will be installed at the top of the pit for safety. Finally, a waterproof umbilical cord will be required to transfer power, data, instrumentation signals, video and possibly air lines between the facility and any apparatus submerged within the pit.

7. Secondary Pit

A secondary pit, 9m in diameter and 15m in total depth, will be dedicated to low background assay measurements. Like the main pit, it will be accessed by a central corridor at the top of the pit, at a height of 10m from the bottom of the pit. The pit will be lined with low background material and be designed to be watertight, since eventually the pit could be flooded with water to provide extra shielding, depending on the nature of the experiments undertaken there. A system of watertight pipes will take power, data, instrumentation and control signals, video, and eventually vent lines from the laboratory to the equipment located inside. The water filled area will reach 10m from the bottom of the pit, and removable rails must be installed to prevent personnel from inadvertently accessing this area.

8. Secondary Caverns

Facilities at the complex are completed with the excavation of three secondary caverns of dimensions 10m x 10m x 10m. These will provide space for experiments of smaller size, offices, laboratories, and auxiliary facilities and services for the laboratory operations staff and any visitors.

9. Finishings

The surfaces of the caverns will be low radioactivity sprayed-on concrete (shotcrete). A laboratory protocol will be established requiring radioactivity screening of samples of 100% of all materials to be used, even in the auxiliary facilities. In addition to the electric power panels, the lighting, ventilation and communication systems will have regular and emergency backup components throughout the facility. All systems (or to the degree possible where there are no technically feasible alternatives) will use fire-retardant materials, flame retardants or materials for which combustion does not generate toxic fumes.