Navigation Links
Physicists detect low-level radioactivity from Japan arriving in Seattle

University of Washington physicists are detecting radioactivity from Japanese nuclear reactors that have been in crisis since a mammoth March 11 earthquake, but the levels are far below what would pose a threat to human health.

On March 16, the scientists began testing air filters on the ventilation intake for the Physics-Astronomy Building on the UW campus, looking for evidence of dust particles containing radioactivity produced in nuclear fission.

The first positive results came from filters that were in place from noon on March 17 to 2 p.m. on March 18. Readings peaked three days later and then dropped, but have risen slightly since then.

"It's a faint signal. You have to filter a lot of air to see it," said Michael Miller, a UW research associate professor of physics. "We've definitely seen it fluctuate up and down, and we are correlating those peaks and drops with any changes in normal background radiation levels."

The measurements were begun because of concerns about effects of radioactivity on very sensitive physics experiments. They also document that radioactivity in airborne particles arriving in the United States is well within safety limits, said R.G. Hamish Robertson, a UW physics professor and director of the Center for Experimental Nuclear Physics and Astrophysics.

Using the air filters allowed sampling of 10 times more air than in methods used previously and proved to be a key in successfully detecting larger dust particles that had attracted radioactivity from the Japanese nuclear plants, Robertson said.

The readings allowed the physicists to make some detailed findings, including:

  • The presence of cesium isotopes in ratios that indicate the radioactivity was a result of fission in a nuclear reactor, not nuclear weapons.
  • The presence of relatively short-lived iodine 131 and tellurium isotopes, indicating the material came primarily from fuel rods, not spent fuel.
  • The absence of iodine 133, an isotope with an even shorter half-life than iodine 131, signaling that at least a week must have passed since the reactors were stopped.

"What that means is that they were successful in shutting down the reactors at the time of the earthquake," Robertson said. "The lack of iodine 133 indicates that the chain reaction was shut down."

The researchers speculate that, because they see only three of the many possible products of nuclear fission, the material that arrived in Seattle came from the evaporation of contaminated steam released from the reactors. Similar tests following the Chernobyl nuclear reactor meltdown in 1986 found a much broader spectrum of elements, indicating that material from actively burning fuel was being sent into the atmosphere.

While the radioactivity is arriving in the United States at levels far lower than are considered harmful to humans, it can raise havoc with sensitive physics experiments. That includes one called Majorana, in which the UW physicists are deeply involved, that is being planned for a lab nearly 1 mile down in the proposed Deep Underground Science and Engineering Laboratory in the old Homestake Mine in Lead, S.D.

The experiment is designed to determine the precise mass of subatomic particles called neutrinos, and any radioactive dust particles that make it into the lab could wreck the experiment, Miller said. Increased atmospheric radioactivity could cause problems for experiments in other laboratories as well, he said.

"This work helps us to understand filtering efficiency, how well the filters keep the radioactive materials out of the lab," he said.

The findings are contained in a paper the scientists posted on an open-access website called Besides Robertson and Miller, authors are graduate students Jonathan Diaz and Alexis Schubert and research associates Andreas Knecht and Jarek Kaspar, all with the UW experimental nuclear physics center.

The paper will be updated as new results warrant and eventually will be submitted for publication in a peer-review journal.


Contact: Vince Stricherz
University of Washington

Related biology news :

1. Stretching the truth: JILA biophysicists help unravel DNA stretching mystery
2. Rice physicists help unravel mystery of repetitive DNA segments
3. UCLA physicists control chemical reactions mechanically
4. Applied physicists create building blocks for a new class of optical circuits
5. CU physicists use ultra-fast lasers to open doors to new technologies unheard of just years ago
6. Digging deep into diamonds, applied physicists advance quantum science and technology
7. Rice physicists kill cancer with nanobubbles
8. Diamonds may be the ultimate MRI probe, say Quantum physicists
9. Louisiana Tech physicists highlight top 10 science stories of 2008
10. How do bacteria swim? Brown physicists explain
11. Penn biophysicists create new model for protein-cholesterol interactions in brain and muscle tissue
Post Your Comments:
(Date:10/29/2015)... Va. , Oct. 29, 2015 Daon, ... today that it has released a new version of ... customers in North America have ... IdentityX v4.0 also includes a FIDO UAF certified ... are already preparing to activate FIDO features. These customers ...
(Date:10/29/2015)... Oct. 29, 2015  Connected health pioneer, Joseph ... explosion of technology-enabled health and wellness, and the business ... The Internet of Healthy Things . ... smartphones even existed, Dr. Kvedar, vice president, Connected Health, ... care delivery, moving care from the hospital or doctor,s ...
(Date:10/29/2015)... 29, 2015 Today, LifeBEAM , ... with 2XU, a global leader in technical performance ... hat with advanced bio-sensing technology. The hat will ... monitor key biometrics to improve overall training performance. ... two companies will bring together the most advanced technology, ...
Breaking Biology News(10 mins):
(Date:11/24/2015)... NEW YORK , November 24, 2015 ... in a European healthcare ... in which the companies will work closely together in identifying ... of unmet medical need. The collaboration is underpinned by a ... LSP fund. This is the first investment by Bristol-Myers Squibb ...
(Date:11/23/2015)... with a certain type of lung nodule visible on lung ... cancer than men with similar nodules, according to a new ... the Radiological Society of North America ... Lung nodules are small masses of tissue in the lungs ... appearance on CT. Solid nodules are dense, and they obscure ...
(Date:11/23/2015)... Columbia, Md. (PRWEB) , ... November 23, 2015 ... ... R&D 100 award for the development of its Nexera UC Unified Chromatography system. ... the 100 most technically significant new products of the year in the analytical ...
(Date:11/23/2015)... PISCATAWAY, New Jersey , November 23, ... Centre (CCDC) announces the launch of the ... and the CSD-System, now complemented by three powerful ... support the discovery of new molecules, CSD-Materials for ... complete set of the CCDC,s applications incorporating CSD-Discovery ...
Breaking Biology Technology: