By Neal Singer
Technicians at DoD’s White Sands Missile Range Gamma Irradiation Facility ordinarily use pneumatic air to propel the little cylinder from its insulated location to its exposed test position and back again, like drive-up banking facilities use pneumatic tubes to shuttle cylinders between customer and teller. The method had worked satisfactorily for decades.
But on Oct. 2, after the irradiator finished a test sequence, a switch along the cylinder’s path caught in one of its ribbings and would not release. The cylinder, emitting 20 rads/second at a distance of one foot, wouldn’t move, says White Sands health physicist Douglas McDonald.
Five hundred rads is considered a lethal dose; half the people receiving it die in 30 days.
Researchers significantly increased pneumatic pressure on the 3-by-1-inch cylinder, but it would not budge.
Warning horns blared. Warning lights flashed. They would do so for almost three weeks.
The facility’s primary mission is to irradiate electrical circuit boards to test their survivability under extreme circumstances. But because vehicles are sometimes irradiated as well, emissions intentionally extend beyond the building through a raised overhead door into an already cordoned-off area outside. These emissions were now unceasing.
“We’re required to alert staff [24 hours a day], using a visual and audible signal, to the existence of a radiation area,” Richard Williams told the Lab News. Williams is White Sands’ associate director for its Survivability, Vulnerability, and Assessment Directorate.
The facility also had to be staffed around the clock, he said, to warn security personnel and other potential visitors not to enter the area because radiation was present.
Because of these precautions and the lab’s layout, there was no danger to staff or the environment. But the approximately 3,000-square-foot test facility was now inoperative.
The White Sands team’s options, say McDonald and Williams, were expensive, labor-intensive, and time-consuming. No human was strong enough to carry a shield heavy enough to protect him or her. There were robots on the East Coast that might be located and flown in. The facility also had the capability to design, manufacture, transport, and maneuver in a very heavy lead shield on a front-end loader to block and then surround the errant source. Technicians drilling through the shield might send in a rod to free the switch.
But the quickest, simplest option was to work with NNSA’s local RAP (Radiological Assistance Program) team, DOE’s usual responder-of-choice in assessing and resolving emergency radiological situations.
On Oct. 3, White Sands personnel called Sandia RAP — exactly the right thing to do, says Richard Stump (12345), Sandia RAP leader. “Part of RAP’s mission is to help out in jobs like this,” he says.
Able to draw upon many Sandia resources, Richard called robotics manager Phil Bennett (6644) and explained the problem.
Phil said his group had a robot that might do the job. The 600-pound, five-foot-long robot, now unofficially known as M2, rolled on treads, could maneuver around obstacles, and had a long, multi-jointed gripper arm. It had the dexterity to reach into awkward places and apply force to drills and screwdrivers. It could remember positions, important in starting with tools at the right height and depth.
But radiation that can kill a human can kill a robot. Phil estimated M2 could withstand intense radiation for only 50 minutes. That might be long enough, perhaps, to free the cylinder.
The plan was to drill through the protective 3/16-inch steel plate covering the switch. By inserting a wire through the drilled hole, the switch — which rotated on a hinge pin, similar to a teeter-totter — could be nudged to change its alignment. A bomb-disposing robot might have been capable of this in simpler circumstances. But this plate was four feet off the floor, three feet away from any vertical position, and sat on a 45-degree angle. The height, depth of extension, and angle were beyond the capabilities of ordinary explosive ordnance disposal robots to drill.
Problems overcome, one after another
But when the call came, M2 was down with a faulty motor control board in its forearm. A call to DOE provided immediate funding to get it working; a replacement part was built and shipped from Agile Manufacturing in Waterloo, Ontario. Manufacturing, shipping, installation, testing, and querying White Sands took two weeks.
“Our people at first wondered what the holdup was,” says White Sands’ Williams, “and then we saw how well [the Sandia RAP team], with all their questions to us, had prepared.”
Because the robot lacked a trigger finger to depress and release a drill control, the Sandia team stalked the aisles of local hardware stores, buying cordless drills and other equipment they modified into remotely operated drills, hooks, and grippers. On tests performed at Sandia by Bob Anderson and Jim Buttz (both 6644) on a mock-up sent north from White Sands, M2 performed perfectly.
On Oct. 21, the team — including DOE team leader Gregory Sahd from WIPP, and RAP team members Richard, Phil, Bob, Jim, and Al Horvath (12345) — made the trip to White Sands, where reality — as it often does — proved more complex than the dry run had led the team to expect.
Aided by M2’s video camera, Bob steered the robot around two free-standing radiation shields and stopped it at the work site. The robot drilled through the steel plate on target, leaving room for a probe that pressed down the back side of the teeter-totter.
The switch did not budge.
The robot drilled a second hole and applied the probe, with the same negative result.
A third hole, drilled through the switch’s hinge pin, failed to dislodge it.
Using a hook, the robot attempted to pull the switch by yanking at two linked wires; the wires came apart. Grasping one of the wires in its pincer, the robot only succeeded in detaching it.
By this time an hour and a half had gone by, and the team was temporarily out of ideas. Phil had estimated that the robot could remain ambulatory in the radiation field for only 50 minutes, and in fact the robot’s lower portion was no longer responding to commands.
Wouldn’t touch it with a 10-foot pole
The RAP team, working with White Sands personnel, as a precaution against this specific circumstance, had tied a rope to M2 before sending it into the work area. The rope, attached to a RAP team winch 100 feet outside the structure, insured the robot could be hauled out if radiation damaged its drive unit. But radiation shields now blocked a direct haul. M2, powerless, was hemmed in.
The radiation field fanned out like a flashlight beam, strongest at its center and weakest at its edges. Using a ten-foot-long pole and standing at the edge of the field, the team hooked and then tugged at the rope hauling M2. The deflection of the rope’s pull slid the robot around a moveable radiation shield without knocking it over. The RAP team’s winch then pulled the robot directly out.
Rebooting the robot and performing other maintenance, Bob and Jim found they could reactivate it, and the team finished the day ready to return the next morning.
The new plan was to unscrew six bolts securing the 3/16-inch steel plate that blocked the team’s direct access to the switch.
When they returned the next morning, however, the robot again would not start. The problem was traced to a damaged fiber optic line, apparently chewed by one of the numerous rabbits in the area.
“The orange fiber optic cable probably looked like a carrot,” said Williams of the line transmitting control data to the robot. “Fortunately, White Sands has another facility that uses fiber optic lines, and it was able to repair the cable.”
But it was Sunday morning. It took half a day to replace the damaged line.
The time was not wasted. The group, making frequent trips to the local Home Depot and Lowe’s, modified its tools. Three screws required Allen wrenches to turn them; the other three screws were single-slotted. The drills needed to turn on in reverse when pushed, yet move slowly enough to engage the screw heads at the start of each effort. The robot could not control the speed via the trigger, since it had only a pincer grip, and accuracy was difficult when trying to insert a turning screwdriver into a single-slot screw head. The team purchased a small, clear acrylic bubble that acted as a see-through guide for Bob to aim the screwdriver head; unfortunately, heat from the radiation source melted the plastic.
So ended the second day.
The third day
A metal guide bought from the hardware store the next morning was opaque, but small enough in diameter to satisfactorily seat the tool on the screw.
By counting revolutions, the team could estimate whether the screw had been rotated enough times to free it from the plate. The team then tried air pressure and hook tools to remove the plate. When neither worked, they steered the robot out of the area and outfitted special tips to the end of its gripper. This time M2 succeeded. A blast of air then blew the entire switch out of the cylinder’s pathway, and the radiation source at long last was blown back to its storage position.
Inspection revealed the problem: Forceful early attempts to blow the cylinder back apparently had bent the straight switch into a right angle. Nothing other than plate removal could have freed it.
It was at White Sands that the robot came to be affectionately (and unofficially) dubbed “M2,” for the cartoon character Mighty Mouse (“Here I come to save the day”).
“It would have been impossible to return the source to storage without removal of that switch,” says Richard.
Cleanup extended for another day.
The four-day on-site effort ended the problem, to the exuberance of the RAP team and relief of White Sands personnel.
“The warning lights and horns that could be heard for miles away finally stopped after 21 straight days of annoying personnel at White Sands,” says Richard.
Says McDonald, “The facility is being evaluated. We’re looking at what happened and considering what we can do to prevent similar incidents in the future.”Says Williams, “The team effort [between White Sands and Sandia RAP] produced a marvelous job.”
-- Neal Singer
Today, as a contractor to the Sandia Tribal Energy Program, she provides technical advice about maintaining photovoltaic units to people on Indian reservations who live remotely like she did. For many, it’s the first time they’ve had electricity in their homes.
“I can identify with the people I’m helping,” Debby says. “Many live the way I grew up, and I fully appreciate their excitement in having electricity and light at night.”
Photovoltaics technology harvests the energy from the sun and converts it into electricity, which is stored in batteries for future use in the home.
As part of Debby’s job, she and program director Sandra Begay-Campbell (6218) offer technical advice to tribal governments, which receive DOE Tribal Energy grants. Her work also includes teaching Native Americans how to use and maintain photovoltaic units, supporting proj-ect management plans, and helping people network and learn from each other about their photovoltaic systems. In addition, she is enhancing DOE’s PV Reliability database with off-grid system information which includes Navajo PV systems’ maintenance data.
Debby and Sandra work closely with the Navajo Nation with which Sandia signed a memorandum of understanding in 2000 to encourage further collaboration between the two entities. The Navajo Utility Authority, through DOE funding, has installed photovoltaic units at more than 300 homes on the reservation since 1993.
“There is still a long way to go,” Debby says. “It’s estimated there are 18,000 families in the Navajo Nation without electricity.”
The reason there are so many, she adds, is that many Navajos live at remote sites, like she did as a youth, and it is prohibitively expensive to string electricity lines to those areas. The cost of expanding the gridline is about $27,000 per mile. Many Navajos make do with kerosene, wood, and coal.
Debby lived with her grandmother in the unelectrified house through the fifth grade. Then she moved to Tuba City, Ariz., to live with her parents — they had a telephone, electricity, and water.
After graduating top of her class from Sherman Indian High School in Riverside, Calif., she attended Northern Arizona University (NAU) where she spent two years but didn’t earn a degree then. She decided to take the nontraditional path and went to a trade school to become an electrician.
After earning her electrical theory and application certification, she worked briefly as an electrician for the Gila River Indian Reservation south of Phoenix. In 1987 she joined NativeSUN, a Hopi-managed nonprofit organization that installs photovoltaic units at homes in remote areas off the grid.
She spent 11 years there, first as an electrician and later as a program manager, bringing electric light to people who never had it before.
One of the people she helped with her first photovoltaic system was her aunt, who quickly adapted to the new technology.
“She’s had her system for 12 years now and just changed the battery for the first time,” Debby says. “She’s happy with the system.”
Debby talked to her customers in their Hopi language and helped them understand what was involved in having a photovoltaic unit.
After 11 years, she went back to school at NAU and earned her BS degree in Applied Indigenous Studies with a minor in Environmental Science. Sandra recruited her as a student intern three years ago to assist her with the tribal energy work.
Her current job has given her some interesting experiences, she says. For example, she’s been working with the Ramona Band of Cahuilla Indians in Southern California. They are developing an ecotourism business that brings geologists to learn about the local flora and fauna. They were not hooked up to the electric grid. Debby works with their electrical contractor to set up a hybrid system for their business that consists of a small wind unit, photovoltaic system, and a back-up diesel generator.
She also gives photovoltaic workshops to women, most recently in August at the American Solar Energy Society Conference in Florida. As part of the workshop, the 20 participants installed a photovoltaic unit at an elementary school in Orlando, Fla. Helping with instruction were Sandian Marlene Brown (5733) and Lori Stone of Solar Energy International.
Soon she will be back working with her native Hopi people. The tribe recently received a DOE grant to develop a wind turbine program.“I’ll be offering them technical assistance,” she says. “It’ll be good helping people at home again.”
After a six-month stint taking cloud and aerosol measurements at Point Reyes National Seashore on the California coast, the ARM Mobile Facility moved to Niamey, Niger, in October for a year’s deployment there.
Going along to help set up the climate monitoring equipment was Sandia engineer Mark Ivey, who spent a week in the West African country.
ARM — for Atmospheric Radiation Measurement — is the largest global change research program supported by DOE. It was created in 1989 as part of the Global Change Research Program to help resolve scientific uncertainties related to global change, focusing on the role of clouds. ARM has three permanent research sites around the globe, plus the mobile facility that recently was deployed to Niger.
“This is the mobile unit’s second deployment,” Mark says. “For the next year, the ARM Mobile Facility [AMF] will be measuring cloud properties, solar and thermal radiation, and meteorological conditions at the surface.”
He adds that a multinational experiment is investigating how mineral dust from the Sahara and biomass burning play a role in the West African monsoon and the climate in general. The belief is that these aerosols, as well as deep tropical convection in the sub-Saharan wet season, have a big impact on climate in that region, and possibly well beyond Africa.
“This experiment will help us better understand how solar and thermal radiation are transferred in the atmosphere when deep convection and aerosols are present,” Mark says.
While the mobile unit will be taking climate measurements on the ground, a European satellite positioned over the Sahara will be taking them from the sky. The combined measurements will provide the first well-sampled, direct estimates of changes of solar and thermal radiation across the atmosphere. The mobile unit will also be used to study the impact of clouds, aerosol, and water vapor on the surface.
Niger is one of the hottest countries in the world, with heat so intense that it often causes rain to evaporate before it hits the ground. Mark calls the Sahara “the biggest dust aerosol generator on the planet.”
Teams from the participating organizations will be spending time at the research site on a rotating basis. An Australian couple will be there for more than a year to take care of the equipment and work with local meteorological observers.
Mark, a member of the first rotation team, arrived in Niamey, Niger’s capital, on Oct. 11, three days after a chartered 747 jumbo jet carrying the equipment landed at the airport. The AMF equipment includes seven containers, each 8 feet tall, 8 feet wide, between 12-20 feet long, and weighing 5,000-10,000 pounds. One extra container with equipment will arrive in January. A separate container for batteries and other types of potentially hazardous materials was shipped from California to Niger, taking 12 weeks to get there by sea.
The mobile unit has its own power generation, communication system, and state-of-the-art climate measurement instrumentation.
Mark worked closely with colleagues at Los Alamos National Laboratory in planning the Niger deployment. His involvement in the ARM Program dates back to the late 1990s when he led a team at Sandia that designed, built, and integrated ARCS — Atmospheric Radiation and Cloud Stations. The ARCS systems are still used at the Tropical Western Pacific ARM sites, and two ARCS vans were included in the AMF deployment in Niger. -- -- Chris Burroughs