German lab peers behind nuclear curtains | Science| In-depth reporting on science and technology | DW | 15.03.2012
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Science

German lab peers behind nuclear curtains

Global leaders doubt statements from Iran and North Korea about the state of their nuclear programs. At the Institute for Transuranium Elements dust particles are analyzed to find out who is building what and why.

Countries that allow in weapons inspectors from the International Atomic Energy Agency (IAEA) would find it virtually impossible to keep nuclear programs a secret these days.

"The inspectors can verify the amount of nuclear material, their enrichment and their nuclear activity," said Klaus Mayer, a chemical analyst at the Institute for Transuranium Elements (ITU) in the south-western German town of Karlsruhe.

The ITU, which is part of the European Commission, analyzes anonymous samples it receives from the IAEA and the agency's European counterpart, EURATOM.

If a country has an undeclared nuclear weapons program, the ITU would most likely find traces of it. "If you look at what the material is made of and how processes have been declared, you can see how it fits together, does it make sense?" Mayer said.

Satellites and gamma ray spectrometers

Klaus Mayer

Scientists pull together a number of strings to determine a facility's purpose

There are many ways for inspectors to ascertain whether a nuclear program serves military or civilian goals: They look for scientific publications in the country, they also examine satellite images to see where possible secret installations may be located, and they analyze trade and export data to find out what technologies are being imported.

"All that information helps us get a clearer picture," Mayer said.

There are two ways to produce weapons-grade nuclear material: uranium can be enriched in special centrifuges, or weapons-grade plutonium can be isolated from spent nuclear fuel in a reprocessing facility. Both methods leave traces that inspectors can find by analyzing particle samples from nuclear facilities.

Inspectors can use portable devices to identify the degree of radiation in specific substances. They can also take samples and analyze them in the laboratory, which is usually more accurate. Uranium enrichment, for example, can be measured by using a gamma ray spectrometer. At the ITU, researchers have a margin of error of 0.1 percent.

Magnus Hedberg

The spectrometer can make minute particles visible

Dust particle analysis

Analyzing dust particles is a particularly good way to determine if a country uses uranium enrichment for peaceful or military purposes. "Even particles that are just a thousandth of a millimeter can show clear traces of enrichment," Mayer explained. "We just need one or two particles in an ocean of ordinary dust."

This is where a secondary ion mass spectrometry (SIMS) comes in. Magnus Hedberg, an ITU engineer, said the SIMS can determine if you are dealing with natural uranium, which is a low-grade uranium used in nuclear reactors, or if the sample contains weapons-grade uranium.

Different types of isotopes

Two different plutonomium isotopes

Scientists need to know which plutonium isotope they're looking at

Pictures taken with the SIMS can show minute particles of uranium or plutonium down to the nanometer sphere, and differentiate among the elements' isotopes.

"We can analyze millions of particles in just a few hours - just to find the few uranium particles we are really interested in," Hedberg explained.

The method is accurate enough to determine the entire history of a nuclear facility, according to Mayer, "The material has a fingerprint made up of its mixture of isotopes, the type of contamination and its morphology, meaning its size and shape." All these factors determine what a substance can be used for.

Using atmospheric gases

The researchers can also obtain information on how radioactive substances were produced, what temperature was needed and which chemicals were used in their creation. In the case of plutonium, they can determine which type of reactor it was produced in without having to analyze samples taken from a lab.

While uranium enrichment can only be determined in the immediate vicinity of the nuclear facility in question, a reprocessing plant's activity can be measured outside the country it is based in, as it releases krypton and xenon into the atmosphere. However, researchers would not know if weapons-grade plutonium was being isolated in the process.

That is why it is so important for the inspectors to follow more than one lead. "As an inspector, I always have to be vigilant and the absence of certain indicators doesn't mean certain activities don't exist," Mayer emphasized.

Verification has to be a "continuous and always critical" process, he said. "But critical means it also has to be in cooperation with the country that's been subjected to this process."

Author: Fabian Schmidt / ng
Editor: Sean Sinico

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