Category Archives: Nuclear

Ancient Roman glass may yield clues to containing nuclear waste

A shipwreck 1,800 years ago in the Adriatic Sea might give scientists at Pacific Northwest National Laboratory better information about how well modern glass might work to contain radioactive waste.

The Department of Energy is building a $12.2 billion vitrification plant at the Hanford nuclear reservation to glassify radioactive waste before it is buried deep in the ground.

The glass, formed from the waste and glass-forming materials, is planned to keep the radioactive waste secure for thousands of years. But until recently, the longest test on a piece of man-made glass holding simulated radioactive waste has been about 25 years.

Thanks to the shipwreck “we can use data points Romans thoughtfully started for us hundreds of years ago,” said Joseph Ryan, a senior scientist at the Department of Energy national laboratory in Richland.

He and scientist Denis Strachan, a laboratory fellow, are taking an atom-by-atom look at ancient glass to see how the glass has held up to corrosion.

Thursday, the two held up a chunk of green glass, marbled with iridescent streaks, that once was the handle of a jar.

It was among the glass that archaeologists believe was carried on the merchant ship Iulia Felix 1,800 years ago. The ship, which measured about 50 feet long, sank six miles off the coast of Grado, scattering glass at the bottom of the Adriatic Sea.

The Iulia Felix is believed to have carried containers of oils and spices, but also a barrel of glass pieces that may have been bound for the port of Aquileia, a center of Roman glass making. The glass pieces would have been recycled there.

Strachan and Ryan also have obtained glass from an archaeological dig at the ancient ruins of Aquileia. The glass is not as well dated, but also could be about 1,800 years old.

The most likely way for modern glass incorporating radioactive waste to corrode and dissolve after it is buried, contaminating the environment, is by exposure to water.

In the Iulia Felix sample, the scientists have pieces of glass that have been sitting in water for 1,800 years. The glass also has some chemical similarities to the glass that will be produced using Hanford’s radioactive waste. Both should contain about 20 percent to 25 percent sodium.

Strachan traveled to Italy to get the glass from the Aquileia archaeological excavation. He didn’t want just another piece of ancient glass, but glass still buried in the soil so researchers could look at how the glass dissolved and material from the glass moved into and through the soil.

The PNNL researchers have used a focused ion beam to machine minute cones out of the iridescent streaks in the glass from the Iulia Felix to look at samples measuring about 20 nanometers, or a ten-thousandth the diameter of a human hair. The iridescent streaks are caused by the reflection of light off the areas where the glass has corroded at the points the handle was attached to the jar.

The samples are being studied with an atom probe at the Environmental Molecular Sciences Laboratory on the PNNL campus, which can show an atom-by-atom picture of the structure of the iridescent glass. Images show individual atoms arranged in layers of magnesium and oxygen.

The ancient glass wasn’t designed to be durable over 1,800 years, but it has held up well, Strachan said. And the glass planned to incorporate nuclear waste can be designed to be even more durable, he said.

But the study will put data to that assertion. It will provide a mathematical look at how glass dissolves that can be used to confirm and refine computer models now used to predict the performance of glass.

“We want to show if we put (waste) glass underground and let it sit for millions of years, the public will be safe,” Strachan said.

The study, which is part of international research on glass corrosion, is being paid for by the Department of Energy.

In addition to information about glassified waste from national defense projects, such as plutonium production at Hanford, DOE also is interested in information that could be useful if the nation decides to reprocess commercial nuclear fuel and then glassify the waste from reprocessing.

The project also could help archaeologists. By learning more about the rate of glass corrosion, archaeologists may be better able to date ancient glass.

SOURCE: http://www.thenewstribune.com/2011/08/12/1779898/ancient-roman-glass-may-yield.html#ixzz1UoYBBnji

75 percent of US nuclear sites have corrosion issues — leaking tritium

BRACEVILLE, Ill. (AP) – Radioactive tritium has leaked from three-quarters of U.S. commercial nuclear power sites, often into groundwater from corroded, buried piping, an Associated Press investigation shows.

The number and severity of the leaks has been escalating, even as federal regulators extend the licenses of more and more reactors across the nation.

Tritium, which is a radioactive form of hydrogen, has leaked from at least 48 of 65 sites, according to U.S. Nuclear Regulatory Commission records reviewed as part of the AP’s yearlong examination of safety issues at aging nuclear power plants. Leaks from at least 37 of those facilities contained concentrations exceeding the federal drinking water standard – sometimes at hundreds of times the limit.

While most leaks have been found within plant boundaries, some have migrated offsite. But none is known to have reached public water supplies.

At three sites – two in Illinois and one in Minnesota – leaks have contaminated drinking wells of nearby homes, the records show, but not at levels violating the drinking water standard. At a fourth site, in New Jersey, tritium has leaked into an aquifer and a discharge canal feeding picturesque Barnegat Bay off the Atlantic Ocean.

Any exposure to radioactivity, no matter how slight, boosts cancer risk, according to the National Academy of Sciences. Federal regulators set a limit for how much tritium is allowed in drinking water, where this contaminant poses its main health risk. The U.S. Environmental Protection Agency says tritium should measure no more than 20,000 picocuries per liter in drinking water. The agency estimates seven of 200,000 people who drink such water for decades would develop cancer.

The tritium leaks also have spurred doubts among independent engineers about the reliability of emergency safety systems at the 104 nuclear reactors situated on the 65 sites. That’s partly because some of the leaky underground pipes carry water meant to cool a reactor in an emergency shutdown and to prevent a meltdown. Fast moving, tritium can indicate the presence of more powerful radioactive isotopes, like cesium-137 and strontium-90.

So far, federal and industry officials say, the tritium leaks pose no health or safety threat. Tony Pietrangelo, chief nuclear officer of the industry’s Nuclear Energy Institute, said impacts are “next to zero.”

EAST COAST ISSUES

One of the highest known tritium readings was discovered in 2002 at the Salem nuclear plant in Lower Alloways Creek Township, N.J. Tritium leaks from the spent fuel pool contaminated groundwater under the facility – located on an island in Delaware Bay – at a concentration of 15 million picocuries per liter. That’s 750 times the EPA drinking water limit. According to NRC records, the tritium readings last year still exceeded EPA drinking water standards.

And tritium found separately in an onsite storm drain system measured 1 million picocuries per liter in April 2010.

Also last year, the operator, PSEG Nuclear, discovered 680 feet of corroded, buried pipe that is supposed to carry cooling water to Salem Unit 1 in an accident, according to an NRC report. Some had worn down to a quarter of its minimum required thickness, though no leaks were found. The piping was dug up and replaced.

The operator had not visually inspected the piping – the surest way to find corrosion- since the reactor went on line in 1977, according to the NRC. PSEG Nuclear was found to be in violation of NRC rules because it hadn’t even tested the piping since 1988.

Last year, the Vermont Senate was so troubled by tritium leaks as high as 2.5 million picocuries per liter at the Vermont Yankee reactor in southern Vermont (125 times the EPA drinking-water standard) that it voted to block relicensing – a power that the Legislature holds in that state.

In March, the NRC granted the plant a 20-year license extension, despite the state opposition. Weeks ago, operator Entergy sued Vermont in federal court, challenging its authority to force the plant to close.

At 41-year-old Oyster Creek in southern New Jersey, the country’s oldest operating reactor, the latest tritium troubles started in April 2009, a week after it was relicensed for 20 more years. That’s when plant workers discovered tritium by chance in about 3,000 gallons of water that had leaked into a concrete vault housing electrical lines.

Since then, workers have found leaking tritium three more times at concentrations up to 10.8 million picocuries per liter – 540 times the EPA’s drinking water limit – according to the New Jersey Department of Environmental Protection. None has been directly measured in drinking water, but it has been found in an aquifer and in a canal discharging into nearby Barnegat Bay, a popular spot for swimming, boating and fishing.

SOURCE: http://gazettenet.com/2011/06/17/75-percent-of-nuke-sites-have-leaked-tritium