[Report] IBS 'YemiLab'... The 'Underground Observatory' Mining Nobel Prizes 1,000m Below Ground

Descent to 600m underground in 3 minutes, 1000m cart ride toward Yemi Lab
Initiating research on fundamental cosmic materials like dark matter and neutrinos
NASA also contacts for research collaboration

High-Precision Underground Research Facility 'Yemi Lab' LSC Hall at the Institute for Basic Science

[Asia Economy Reporter Kim Bong-su] What can humans do deep underground, 1000 meters below the surface, surrounded by mountains? Is it too deep and hot to breathe easily? With a slight sense of apprehension, I visited the ultra-large underground laboratory "Yemi Lab" in Jeongseon, Gangwon Province, on the 29th of last month. Above all, the advanced air conditioning system and the wide, open tunnels completely dispelled my anxiety about panic disorder. In short, this place was not a coal, iron, or nuclear test site, but a place to uncover the secrets of the universe. It was a unique experience that even inspired awe.

Entrance of the high-depth underground research facility 'YemiLab' at the Institute for Basic Science

'A Frightening' Journey 1000m Underground

At the foot of Yemi Mountain in Jeongseon, Gangwon Province, my heart was pounding despite the clear and comfortable early autumn weather. Entering a 1000m underground tunnel for the first time in my life was a bit intimidating. Here, the Institute for Basic Science (IBS) had established the cutting-edge, ultra-precise underground experimental facility "Yemi Lab" next to the mine shaft of the private mining company Handuk Iron & Steel. The vertical 600m shaft at the entrance was equipped with a German-made mining elevator costing 8 billion KRW, which carried people up and down. The guide said, "This is not an elevator but called a 'cage.' Please inform us immediately if you feel unwell." That made me even more nervous, so I deliberately started talking a lot. The 'cage' descended 600m underground at a speed of 4 meters per second, four times faster than a regular elevator. It took less than three minutes. This speed matches that of the high-speed elevator in Lotte World Tower, the tallest building in Korea at 555m. Finally arriving underground, fortunately, I did not suffer from panic disorder or claustrophobia. The tunnel from the elevator entrance to Yemi Lab was not suffocating but felt cool and clean. The spacious tunnel, over 10m wide and 15m high, left no room to feel cramped. It was wide enough for two vehicles to pass each other, so there was no feeling of confinement. Moreover, advanced air supply and temperature control systems maintain a constant 26 degrees Celsius and oxygen saturation at 24.1%, the same as at ground level.

Interior corridor of the high-depth underground research facility 'Yemi Lab' at the Institute for Basic Science.

Riding an electric cart provided by IBS, I descended about 100m further to Yemi Lab. The downhill slope was steep, about 12%. Finally, I reached a depth of 1000m underground. Since Yemi Mountain's elevation is 998m, this means I was deeper than sea level. The structure consists of a 1000m-long straight tunnel with about ten various laboratories, rest areas, and shelters arranged on both sides, covering an area of 3000㎡. The walls of all research facilities were coated with special concrete (shotcrete) capable of shielding radiation. I wondered what to do if an urgent 'bathroom break' was needed in such a place. At that moment, I noticed a mining toilet made by an Australian company in the middle of the tunnel. It looked like a small container but was a clean facility that could be managed without odor or pollutant discharge.

A restroom located in the corridor of the high-depth underground research facility 'Yemi Lab' at the Institute for Basic Science.

The full-scale 1000m underground 'cave exploration' began. Why here? Park Kang-soon, the lead engineer at IBS who guided me, explained that the site was chosen because the geology was stable, construction was relatively easy, and costs could be saved. Due to the geological characteristics, natural radioactivity detected below 1000m underground is significantly low, providing optimal conditions for various experiments. Also, groundwater is scarce, making construction easier and cheaper. Usually, 200 tons per hour of water is a problem, but here only 3 to 4 tons are discharged. The surface terrain also minimized the construction section, enabling a depth of over 1000m. Most importantly, sharing the 600m vertical shaft entrance with Handuk Iron & Steel greatly reduced costs. Park explained, "We reviewed several locations including Samcheok, but faced much opposition. Initially, the iron mine side opposed this site too, but later changed their stance, making it possible. We set a 35-year surface rights agreement and pay a fixed rent to share the entrance."

Unlike the world's largest underground laboratory, Italy's Gran Sasso underground lab, which was excessively excavated in height and width, wasting costs, Yemi Lab saved much excavation cost (7 million KRW per cubic meter) through appropriate height and efficient design. When placing experimental spaces on both sides of the tunnel, it was designed so that in case of fire or explosion, people could evacuate avoiding flames and debris. They also thoroughly prepared for possible collapse accidents. A safe shelter was built to support 40 people for three days without electricity, drinking water, oxygen, or other supplies. This shelter, designed by an Australian mining specialist company, automatically adjusts oxygen supply according to the number of people, maximizing safety. Park said, "Three days is the margin for rescue expectation in general mine collapse accidents. Normally, it can be used as a rest area, but in emergencies, it greatly increases survival chances."

A safety shelter established in the high-depth underground research facility 'Yemi Lab' of the Institute for Basic Science.

Uncovering the Secrets of the Universe

IBS conducts research here on dark matter and neutrinos, fundamental substances known to make up the universe but never detected by anyone. The thick ground above the 1000m underground tunnel acts as a kind of radiation shield. The goal is to block cosmic rays and natural radiation from space and the surface, then detect the signals (light) of dark matter and neutrinos. Kim Young-duk, head of the IBS underground experiment research team, explained, "At 1000m underground, radiation is reduced to one-millionth (10 to the minus 6) compared to the surface, blocking cosmic rays and eliminating most background signals (noise) in experiments. The deeper underground, the better to minimize cosmic ray effects. Also, the radiation level from the tunnel itself is significantly lower than other labs, about 100 times lower than Japan's Kamiokande."

Amore Hall of the high-depth underground research facility 'Yemi Lab' at the Institute for Basic Science

To this end, IBS established two large experimental halls here: the Amore Hall and the LSC Hall. Unlike other single-story buildings, these two halls are large enough to be two to three stories high and have a double structure. The Amore Hall already houses the AMoRE-2 detector, upgraded from the AMoRE-1 detector previously operated at the Yangyang underground lab, and is about to start full operation. The core component is a round molybdenum-100 crystal plate, equipped with five layers of shielding including a pure water tank and signal detection electronics. The shielding filters out cosmic rays and natural radiation to capture only the desired dark matter or neutrino signals. The official name of this experiment is "Neutrinoless Double Beta Decay Research (AMoRE - Advanced Mo-based Rare process Experiment)." Neutrinos are one of the 12 fundamental particles known to make up the universe. So far, only three types have been discovered: electron neutrinos, tau neutrinos, and muon neutrinos. Kim said, "Very rarely, double beta decay occurs where protons convert to neutrons and neutrons to protons twice without emitting neutrinos. Measuring the half-life of this double beta decay aims to determine the absolute mass of neutrinos and verify if they are the predicted 'Majorana fermions.'" He added, "Neutrinos are the key to explaining how matter asymmetrically remained after the Big Bang, forming the current universe from matter and antimatter. The core research task is to determine neutrino mass, the existence of a fourth neutrino, and antineutrinos."

Worldwide, major underground research facilities such as Canada's Sudbury Neutrino Observatory (SNOLAB), Japan's University of Tokyo Cosmic Ray Research Institute's Super-Kamiokande, and Italy's Gran Sasso National Laboratory's Borexino have all engaged in similar research but have yet to observe such phenomena after decades. In 2018, the IBS underground experiment team attracted global physics attention by publishing research showing that the dark matter candidate particle WIMP (Weakly Interacting Massive Particle), discovered by an Italian team, is over 97% unlikely to be dark matter. Park explained, "To expedite research, during excavation at other sites, we had to drill a hole in the ceiling to install equipment to prevent vibration. All detector components were made by us using materials with the lowest natural radiation emission, so we expect to produce results faster than elsewhere."

High-Precision Underground Research Facility 'Yemi Lab' LSC Hall at the Institute for Basic Science

The next place visited was the LSC Hall, the core facility of Yemi Lab, where the next-generation large liquid scintillator detector (LSC) will be installed. It is the largest laboratory here, with a double-structured large cavity over 20m wide and more than 28m high, giving a grand impression. The LSC will be equipped with 2,500 tons of liquid scintillator, a proton accelerator, and a linear accelerator to conduct the COSINE experiment, which aims to find dark matter, a long-standing goal in particle physics. Dark matter accounts for about 26% of the universe but has never been observed. Candidates include WIMPs, axions, and sterile neutrinos. These small particles are thought to cluster to form the first stars, enabling the birth of the universe and the existence of life, but their identity remains unknown. Kim said, "We plan to detect dark matter by analyzing photon signals generated when dark matter flying to Earth collides with crystals (sodium iodide, NaI) inside the detector. Installing a proton accelerator will allow studying the properties of freshly created neutrinos at close range, and using the linear accelerator, we can produce dark photons and conduct research to explore dark matter based on interactions with dark matter."

Unexpected Popularity

When IBS first announced plans to build Yemi Lab, people asked, "What use is such a place?" But now, it is so popular that domestic and international research institutions are eager to move in. All ten or so laboratories have already been fully booked. The Korea Meteorological Administration has rented one lab to install earthquake monitoring equipment, and the Korea Institute of Geoscience and Mineral Resources, Korea Atomic Energy Research Institute, Korea Research Institute of Standards and Science, and Kyungpook National University also plan to move in. The US neutrino research group (IsoDAR) has proposed joint research, and NASA has requested cooperation to study life responses during free fall in the 600m vertical entrance tunnel, showing international popularity. Park, who was responsible for the overall construction of Yemi Lab, said, "Other places have been observing for decades, but their equipment is old and radiation shielding is poor, so no results have been achieved yet. We hope to produce detection results within three years and win a Nobel Prize within ten years," expressing pride.

Worldwide, many research facilities with large-scale underground experimental setups at great depths operate. Italy's Gran Sasso Laboratory is famous for having the world's largest underground lab at 1400m depth. It consists of three experimental spaces measuring 100m wide, 20m long, and 18m high, with a total area including bypass tunnels of 180,000㎡ (about 55,000 pyeong). The Sanford Underground Research Facility in the US is located 1478m underground and has won the Nobel Prize in Physics twice for its detection results. Canada's Sudbury Observatory is 2300m underground (Nobel Prize in Physics twice), Japan's Kamiokande is 1000m underground (Nobel Prize in Physics twice), and China's Jinping Underground Laboratory has experimental buildings at a depth of 2400m underground.