Science at WIPP

Science at WIPP EXO-Detector


The deep geologic repository at the Waste Isolation Pilot Plant (WIPP) is more than a place to dispose of transuranic (TRU) waste – it is also a science laboratory. Following the designation of the DOE’s Carlsbad office as a field office in 2000, numerous universities and research institutions across the nation have taken advantage of WIPP’s open door policy and unique underground geology.

WIPP’s underground has proven to be an excellent environment for a variety of scientific disciples to conduct experiments in laboratory conditions unlike any in the nation. WIPP’s visiting scientists have become regular members of the facility’s working community.

Scientific experiments were suspended following events in February 2014 that also suspended waste emplacement operations. However, the underground, once again, has become an exciting and natural laboratory for scientific discovery.

1993: WIPP begins accommodating the calibration of prototypes of the neutral-current detectors for the Sudbury Neutrino Observatory.

1999: WIPP is used for research with prototype WIMP (Weakly Interacting Massive Particles) detectors by measuring gamma and muon background radiation in the underground.

2000: The DOE Carlsbad office and Institute for Nuclear Particle Astronomy and Cosmology sponsor a workshop to encourage the research community to discuss the use of the WIPP site as a next generation underground laboratory.

2000: Scientists manage to cultivate bacteria from 250-million-year-old spores found in WIPP salt crystals.

2004: The MAJORANA Project’s Segmented Enriched Germanium Assembly (SEGA) and Multiple Element Germanium Array (MEGA) experiments begin in the WIPP underground.

2006: An Argonne counting chamber is refurbished and placed in the WIPP underground.

2007: The first two clean room modules for the Enriched Xenon Observatory (EXO) project are successfully placed in the WIPP site.

2008: In examining fluid inclusions in the salt and solid halite crystals of the WIPP underground, scientists find abundant cellulose microfibers, estimated to be 250 million years old.

2009: Researchers begin an experiment in the WIPP underground designed to examine the effects of low background radiation on bacteria.

2010: The detector for the EXO project, called the Time Projection Chamber (TPC), is installed in January. The experiment itself begins in the fall of 2010.

2010: The Dark Matter Time Projection Chamber (DMTPC) is installed in the WIPP underground.

2011: The U.S. Environmental Agency (EPA) concurs with the DOE Carlsbad Field Office (CBFO) on plans to mine a new underground research laboratory.

2011: Mining begins on the new underground research laboratory in the north end of WIPP.

2012: CBFO notifies the EPA and the New Mexico Environment Department of the intent to conduct salt disposal investigations in the north end of WIPP.

2013: Salt thermal testing begins.

2014: Operations in WIPP’s underground are suspended.

2016: The EXO experiment resumes data collection, seeking to further understand double beta decay.

2016: Low background radiation experiments resume.

The deep geologic repository at WIPP provides an ideal environment for experiments in many scientific disciplines, including particle astrophysics, waste repository science, mining technology, low radiation dose physics, fissile materials accountability and transparency, and deep geophysics.

The designation of the Carlsbad DOE office as a field office has allowed WIPP to offer its mine operations infrastructure and space in the underground to researchers requiring a deep underground setting with dry conditions and very low levels of naturally-occurring radioactive materials.

One of the most elusive and exotic subatomic particles being investigated around the world today is the neutrino or “small neutral one.” Understanding the family of neutrino particles and how they interact with other matter (and among themselves) has become one of the most intensive physics research efforts ever attempted by mankind.

With a virtually undetectable mass and without electric charge, these weakly interacting particles have been devilishly difficult to measure. They can travel through a light year of solid lead without interacting, and they have been recently shown to “oscillate” from one neutrino flavor to another. Most of the neutrino searches involve enormous detectors in deep underground cavities.

A group of researchers has fielded a unique device at WIPP that attempts to make the neutrino mass measurement. Led by Stanford University, they have designed a detector called the Enriched Xenon Observatory (EXO), which uses a special pressurized chamber of the rare gas Xenon.

The Enriched Xenon Observatory 200, or EXO-200, is designed to look for an ultra-rare phenomenon that could reveal key secrets about the nature of the neutrino.

Double beta decay is the radioactive decay of the nucleus of an atom — such as xenon. Typically, two electrons or positrons (beta particles) and two antineutrinos — are emitted from the nucleus when two neutrons become protons. This was first observed in 1986. Neutrinoless double beta decay has not yet been seen but is thought to exist. In neutrinoless double beta decay, no neutrinos would be emitted from the nucleus. In order for this to occur, the neutrino must be its own antiparticle. Most particles have an antimatter partner with the opposite electric charge. Because neutrinos and antineutrinos are both neutral, they could be identical.

The experiment essentially involves cycling enriched xenon through an ultra-sensitive detector that could pick out a single atom produced by neutrinoless double beta decay.

Scientists involved with the project say they believe in starting small when it comes to understanding the nature of the universe. But understanding the nature of the neutrino, they say, will ultimately help them understand more about the nature of stars and galaxies.

What’s especially interesting about the project is that it is an experiment which demands that it not be exposed to any avoidable amount of radiation – and it is taking place in an underground repository for nuclear waste. The EXO-200 takes advantage of the shielding against cosmic rays by the WIPP overburden for conducting its search.

The final component of the EXO observatory, called the Time Projection Chamber, arrived at WIPP in November 2009. Scientists began collecting data in the fall of 2010.

The EXO-200 device was recovered following the events of February 2014 and began again collecting data. EXO experiments resumed in the summer of 2016.

The WIPP underground has been a unique laboratory for scientists attempting to solve the universe’s major missing mass problem.

Their quest has been to search for the presence of particles that may have mass, but hardly interact with other matter. Based on observations of the relationships between mass and gravity and the speed of the stars and other cosmological systems, scientists believe that more than 90 percent of the universe’s mass is “missing.” A portion of this “missing mass” may be what is called dark matter.

Without dark matter of some type, scientists are unsure whether such basic theories as the Big Bang withstand modern scrutiny. Theoretical particle physics also attempts to help us understand ourselves and our place in the universe.
Prior to the events of February 2014, MIT’s Dr. Peter Fisher lead experiments in the WIPP underground seeking to find weakly interacting massive particles, or WIMPs, which pass through most other matter. WIMPs are postulated candidates for dark matter.

The experiment’s laboratory connex was assembled in the WIPP underground in 2010. It is located next to the EXO project. Students installed a small detector in the WIPP underground and then began putting together a larger device.

“We’re looking for a particle that comes from the galaxy that can go through anything, but just happens to bump into one of the atoms in our detector,” Fisher said. “What we’re using is basically a refrigerant. It’s the most common thing in the world, but we’re just looking for a very rare interaction.”

Dr. Fisher’s dark matter experiments in the underground have been on hiatus but are expected to resume following commencement of waste emplacement.

WIPP’s underground isn’t just suited for physics experiments aiming to unlock the mysteries of the universe. It is also a perfect “dig site” for biologists who want to chronicle the history of life.

Some 250 million years ago, the area around WIPP was all part of the Permian Sea. Today, the salt beds that make up the WIPP underground provide a time capsule, of sorts, from this ancient era. Researchers have uncovered ancient bacteria, cellulose and evidence of DNA from intrusions in the salt crystals of the WIPP underground.

Life on Earth has been bathed in background radiation since the dawn of time. This ionizing radiation comes from cosmic rays, terrestrial radioactivity, and internally-deposited, naturally-occurring radioactive material in organisms themselves. While other experiments in the WIPP underground have taken advantage of the location’s low levels of background radiation, one biology experiment actually conducts tests related to this phenomenon.
Ancient Salt Beds

The key to the search for life on other planets may go through WIPP’s ancient salt beds.
In 2008, a team of scientists led by Jack Griffith, from the University of North Carolina, Chapel Hill, retrieved salt samples from the WIPP underground and studied them with a transmission electron microscopy lab at the Lineberger Comprehensive Cancer Center of the University of North Carolina School of Medicine. In examining fluid inclusions in the salt and solid halite crystals, scientists found abundant cellulose microfibers, estimated to be 250 million years old. Evidence of ancient DNA was also observed, but in much smaller amounts than cellulose.

Cellulose is the tough, resilient substance known as the major structural component of plant matter. The source of the cellulose is undetermined. In addition to plant sources of cellulose, cyanobacteria (which have been present for the last 2.8 billion years of earth history) also produce cellulose. The age of the cellulose microfibers is estimated to be 253 million years old, making them the oldest native macromolecules to have been directly isolated, visualized and examined biochemically.

An examination of the salt samples revealed that the cellulose was very much like modern-day cellulose. Researchers noticed microfibers as small as 5 nanometers in diameter, as well as composite ropes and mats. Because cellulose appears to be extremely stable and highly resistant to ionizing radiation, scientists believe that the search for life on other planets may begin with looking for cellulose in salt deposits.


Ancient Bacteria

Scientists also have managed to cultivate bacteria from 250-million-year-old spores found in WIPP salt crystals – it’s all similar to the plot of the movie “Jurassic Park”!

In 2000, researchers cultivated a colony of a previously unknown species of halophilic bacillus from spores inside salt deposited at the end of the late Permian period (some 220-250 million years ago). This discovery has pushed the envelope for resurrecting living things back in time by a factor of about 10 and allows the previously unknown bacteria (Bacillus species, designated 2-9-3) to lay claim to the title of “oldest known organism.”

Some micro-organisms form resistant structures called spores when exposed to adverse conditions. These spores have been found to survive for hundreds, and even thousands, of years under the proper conditions.

How did scientists “uncover” this bacteria? Intact salt crystals were carefully collected from the walls of WIPP’s air intake shaft at a depth of 569 meters (1867 feet) below the surface. The nearly pure salt crystals contained fluid inclusions. After thoroughly sterilizing the surface of the crystals, researchers drilled into and removed fluid from a tiny inclusion. The fluid was then inoculated into a growth medium under carefully controlled conditions. The new bacteria then grew from these spores.

Drs. Russell Vreeland and William Rosenzweig of West Chester University, Pennsylvania, and Dr. Dennis Powers, a Consulting Geologist in Anthony, TX, continue to conduct research by studying the new organism and comparing it with its present-day relatives.
Low Background Radiation Experiment

We’re all bathing in it. It’s in the food we eat, the water we drink, the soil we tread and even the air we breathe. It’s background radiation. It’s everywhere, and we can’t get away from it.

But what would happen if you somehow “pulled the plug” on natural background radiation? Would organisms suffer or thrive if they grew up without constant exposure to background radiation? That’s what a consortium of scientists conducting an experiment at WIPP sought to find out.

Dr. Raymond Guilmette, director of the Center for Countermeasures Against Radiation with the Lovelace Respiratory Research Institute, was one of the scientists who first conceived the idea of a biology experiment at WIPP.

The experiment at WIPP involved using two different types of bacteria, one of which is very sensitive to radiation and the other which is very resistant.

The bacteria strains were grown in both simple and complex growth media, and future experiments will involve growing the bacteria with and without manganese, which is connected with the second strain’s ability to resist radiation.

One-third of the experiment took place in the WIPP underground, next to the EXO project in the northern end of the repository. The idea was to let the two strains of bacteria grow side-by-side in an environment where they would receive virtually no background radiation. In fact, the bacteria incubator was placed in a pre-World War II steel chamber to eliminate even the slightest amount of background radiation. The bacteria underground received close to zero radiation doses for hundreds of generations.

The rest of the experiment took place inside of a room near the waste handling bay at WIPP’s above-ground facility. There, for comparison, the two strains of bacteria grew at natural background radiation levels, and another part of the experiment exposed both types of bacteria to significantly higher levels of radiation above normal background. Potassium chloride, a naturally occurring radioactive material normally used as a dietary salt substitute, was used to provide these higher levels. Researchers compared how well the bacteria did at zero, natural and above-natural levels of background radiation.

Biological effects measured included growth rate, growth yield and protein production. Incubators were used to control temperature, light, humidity and air quality.

The experiment at WIPP sought to better understand the effects of low-dose radiation by providing more insight into the role of background radiation in maintaining the fitness of living organisms.

Following the February 2014 events, the Low Background Radiation Experiment needed approximately two years to recover. The experiment resumed in the summer of 2016, with different organisms and media planned for the future.

Authorized for the permanent isolation of TRU waste, WIPP also provides an ideal platform for field-scale tests of salt repository performance for other waste forms. Planning and design for intermediate to large-scale heater tests in a newly-mined underground research area of WIPP is progressing, and proposals for other in-situ tests are being formulated.

An area of ongoing research at WIPP is a planned test of bedded salt as a host for heat-generating radioactive materials. There is a continued need for research into the potential performance of a repository for heat-generating waste in bedded salt and a need to better understand the integrated response of the salt at the field scale. In particular, it will be important to investigate the evolution of the small, but non-negligible, quantities of water within the salt, as the heat from radioactive decay diffuses into the surrounding geologic medium.

Testing concepts include small-scale diameter borehole tests in the salt formation to larger tests, including heated drifts with multiple heater canisters. These configurations will enable the study of small-to-large scale behavior under both sub-boiling conditions and above-boiling conditions. The emphasis will be on confirmation of expected behavior and validation of numerical models under both conduction-dominated and perhaps coupled thermal-hydrologic-chemical conditions. Standard measurements will be planned aimed at determining the fate and transport of mobilized water from inclusions, intergranular space and hydrous minerals.

Planning and preparations for small to field-scale heater tests is continuing, with plans to begin the smaller tests first and then increase in size and complexity in subsequent years.

Over 2,000 meters of mining for the test locations in the underground has been substantially completed in the north end of WIPP. In addition, a full-scale prototype heater canister was designed and fabricated in Fiscal Year 2014 that is being tested in a surface facility in Carlsbad, with plans to move the heater to the WIPP underground for continued operational testing.

In addition to the planned thermal tests, large salt samples (core and slabs) are periodically collected to provide specimens for laboratory analysis, including thermal-mechanical investigations, hydrological studies and bacterial investigations. Occasionally, these sampling activities are complex and labor-intensive, using core rigs or mechanical miners to obtain large-diameter cores and blocks for analysis. A substantial quantity of 12-inch diameter cores were collected in 2013 and sent to Germany for collaboration on basic salt research.