Navigation Links
Physicists detect low-level radioactivity from Japan arriving in Seattle
Date:3/30/2011

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 arXiv.org. 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
vinces@uw.edu
206-543-2580
University of Washington
Source:Eurekalert

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:
*Name:
*Comment:
*Email:
(Date:5/20/2016)...  VoiceIt is excited to announce its new ... By working together, VoiceIt and VoicePass will offer ... take slightly different approaches to voice biometrics, collaboration ... usability. Both ... "This marketing and technology partnership allows ...
(Date:5/12/2016)... 12, 2016 WearablesResearch.com , a brand ... overview results from the Q1 wave of its quarterly ... was consumers, receptivity to a program where they would ... health insurance company. "We were surprised to ... Michael LaColla , CEO of Troubadour Research, "primarily ...
(Date:5/3/2016)... , May 3, 2016  Neurotechnology, a provider ... MegaMatcher Automated Biometric Identification System (ABIS) , ... multi-biometric projects. MegaMatcher ABIS can process multiple complex ... any combination of fingerprint, face or iris biometrics. ... SDK and MegaMatcher Accelerator , which ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... 27, 2016 /PRNewswire/ - BIOREM Inc. (TSX-V: BRM) ("Biorem" or ... its major shareholders, Clean Technology Fund I, LP and ... based venture capital funds which together hold ... a fully diluted, as converted basis), that they have ... entire equity holdings in Biorem to TUS Holdings Co. ...
(Date:6/27/2016)... ... June 27, 2016 , ... Cancer experts from Austria, Hungary, ... be a new and helpful biomarker for malignant pleural mesothelioma. Surviving Mesothelioma has ... it now. , Biomarkers are components in the blood, tissue or body ...
(Date:6/27/2016)... ... June 27, 2016 , ... Newly created 4Sight ... solutions to the healthcare market. The company's primary focus is on new product ... marketing strategies that are necessary to help companies efficiently bring their products to ...
(Date:6/27/2016)... June 27, 2016  Liquid Biotech ... funding of a Sponsored Research Agreement with The ... cells (CTCs) from cancer patients.  The funding will ... levels correlate with clinical outcomes in cancer patients ... will then be employed to support the design ...
Breaking Biology Technology: