Using antineutrinos to monitor nuclear reactors

Dr. Nils Haag developed an experimental setup that allowed him to determine the missing spectrum of uranium 238. 

Credit: Wenzel Schuermann / TU München 

When monitoring nuclear reactors, the International Atomic Energy Agency (IAEA) has to rely on input given by the operators. 

In the future, antineutrino detectors may provide an additional option for monitoring.

However, heretofore the cumulative antineutrino spectrum of uranium 238 fission products was missing.

Physicists at Technische Universität München have now closed this gap using fast neutrons from the Heinz Maier Leibnitz Neutron Research Facility.

In addition to neutrons, the fission reaction of nuclear fuels like plutonium or uranium releases antineutrinos.

These are also electrically neutral, but can pass matter very easily, which is why they can be discerned only in huge detectors.

Recently, however, detectors on the scale of only one cubic meter have been developed. They can measure antineutrinos from a reactor core, which has generated great interest at the IAEA.

Prototypes of these detectors already exist and collect data at distances of around 10 meters from a reactor core.

Changes in the composition of nuclear fuels in the reactor e.g., when weapons-grade U-239 is removed, can be determined by analyzing the energy and rate of antineutrinos.

This would free the IAEA from having to rely on representations of reactor operators.

Antineutrino spectrum of uranium 238 revealed
In the 1980s the antineutrino spectra of three main fuel isotopes, uranium 235, plutonium 239 and plutonium 241, were determined.

However, the antineutrino spectrum of the fourth main nuclear fuel, uranium 238, which accounts for approximately 10 percent of the total antineutrino flux, remained unclear.

It had only been estimated using inaccurate theoretical calculations and thus limited the accuracy of the antineutrino predictions.

Dr. Nils Haag

Dr. Nils Haag from the Chair of Experimental Astroparticle Physics at TU München recently developed an experimental setup at the FRM II that allowed him to determine the missing spectrum of uranium 238.

"I needed a high flux of fast neutrons to induce the fission of the U-238," says the physicist. This is why he located his experimental setup at the NECTAR radiography and tomography station of the FRM II, a source of fast neutrons.

Second detector allows background-free measurement
The neutrons induce nuclear fission in a film of U-238. The radioactive decay products then emit electrons and antineutrinos.

The electrons were investigated using a scintillator – a block of plastics that converts the kinetic energy of the electrons into light. A photomultiplier then translates this into electrical signals.

The nuclear decay also generates gamma radiation that produces unwanted events in the scintillator.

Therefore, Haag placed a second detector right in front of the scintillator: a so-called multi-wire proportional chamber.

Since only charged particles like electrons trigger a signal in the gas detector, the researcher was able to determine and subtract the proportion of gamma radiation.

Haag then inferred the antineutrino spectrum using this background-free measurement data.

Method allows better monitoring of reactor cores
The measurement of the antineutrino spectrum can be used to monitor the status, performance and even composition of reactor cores.

"Our results open the door to predict with significantly higher accuracy the expected antineutrino spectrum emitted by a reactor running on a fuel composition reported by the operator," explains Dr. Nils Haag.

"Deviations of antineutrino detector measurement data from expected reactor signals can thus be exposed."

The development of this methodology is embedded in basic research on the phenomenon of so-called "sterile" antineutrinos.

Comparing previously made measurements and predictions of reactor antineutrino spectra gave rise to the assumption that some of the antineutrinos turned "sterile" after being produced.

They were then no longer able to react with other matter. A better understanding of this effect would expand our knowledge of elementary physical processes.

More information: 
Experimental Determination of the Antineutrino Spectrum of the Fission Products of U238, N. Haag, A. Gütlein, M. Hofmann, L. Oberauer, W. Potzel, K. Schreckenbach, and F. M. Wagner, Phys. Rev. Lett. 112, 122501 (2014), DOI: 10.1103/PhysRevLett.112.122501

Pentagon considers NASA's nuclear-powered drones

NASA long duration Global Hawk. Furture UAVs could be powered by nuclear batteries staying airborne for months at a time.

NASA scientists are working on new-generation nuclear-powered unmanned aircraft capable of staying in the air for up to several months.

While being able to tackle a wider range of more complicated tasks compared to their existing analogues, the new drones will not require a costly air base network for refueling and technical maintenance.

What's more, on February 14 President Barack Obama signed the Federal Aviation Administration Reauthorization Act that allows the use drones in U.S. airspace by both state-owned and private companies.

The CIA has often resorted to drones in its war on global terrorism. In the past decade, U.S. drones flew various missions in Afghanistan, Pakistan and other "hot spots".

Unlike manned warplanes, they offer considerable advantages and help avoid a diplomatic scandal that normally erupts whenever pilots are taken prisoner.

In October 2009, the CIA reported that more than a half of 20 most dangerous Al Qaeda leaders were eliminated with the help of drones.

Despite being an effective anti-terror tool, drones have become a nightmare for local residents. Civilian deaths inflicted by drone strikes have repeatedly strained relations between America and Pakistan, one of its key allies in the crackdown on terrorism.

According to a report published by the Washington-based Brookings Institution in 2009, ten times as many civilians as suspected terrorists died in U.S. drone attacks.

Pakistan's patience expired in November 2011 after a drone strike erroneously targeted Pakistani troops, prompting Islamabad to shut NATO supply routes to Afghanistan.

The above Reauthorization Act approved by the Senate and signed into law by President Obama shows that no lessons have been learnt from that incident.

While providing virtually unlimited opportunities for the use of drones in search and rescue effort as well as in battling wildfires, the document gives the "green light" for drone-based domestic spying.

A tandem of the Sandia National Laboratories and Northrop Grumman company is said to be the closest ever to creating nuclear-powered highly-maneuverable missile-carrying drones that can fly for months on end without refueling.

Analysts are warning that the improved drone technology has some major drawbacks to consider.

Drones are not easy to control and the intended proliferation of drones in the skies over the US and other countries may affect the safety of passenger planes and other manned aircraft.

Human rights activists are also ringing alarm over civil liberties violations arising from drone spying.

Japanese Tsunami: TEPCO Fukushima reactor Helicopter videos

TEPCO has released video shot from SDF helicopter on March 16, 4pm, of Fukushima reactors

'Cold fusion' moves closer to mainstream acceptance

'Cold fusion' moves closer to mainstream acceptance ScienceBlog.com

"Years ago, many scientists were afraid to speak about 'cold fusion' to a mainstream audience," said Jan Marwan, Ph.D., the internationally known expert who has organised the 'New Energy Technology' symposium.

Marwan heads the research firm, Dr. Marwan Chemie in Berlin, Germany. The symposium will include nearly 50 presentations describing the latest discoveries on the topic, including cold fusion.

The presentations describe invention of an inexpensive new measuring device that could enable more labs to begin cold fusion research; indications that cold fusion may occur naturally in certain bacteria; progress toward a battery based on cold fusion; and a range of other topics.

Marwan noted that many of the presentations suggest that cold fusion is real, with the potential to positively contribute to alternative energy supplies in the 21st Century.

"Now most of the scientists are no longer afraid and most of the cold fusion researchers are attracted to the ACS meeting," Marwan said. "I've also noticed that the field is gaining new researchers from universities that had previously not pursued cold fusion research. More and more people are becoming interested in it.

Clearly, there's still some resistance to this field but we just have to keep on as we have done so far, exploring cold fusion step by step, and that will make it a successful alternative energy source. With time and patience, I'm really optimistic we can do this!"

The term "cold fusion" originated in 1989 when Martin Fleishmann and Stanley Pons claimed achieving nuclear fusion at room temperature with a simple, inexpensive tabletop device.

That claim created an international sensation, because nuclear fusion holds the potential for providing our world with a virtually limitless and arguably, clean, new source of energy.

Fuel for fusion comes from ordinary seawater, and estimates indicate that 1 gallon of seawater packs the energy equivalent of 16 gallons of gasoline at 100 percent efficiency for energy production.

The claim also ignited scepticism, because conventional wisdom said that achieving fusion required multi-billion-dollar fusion reactors that operate at tens of millions of degrees Fahrenheit.

When other scientists could not reproduce the Pons-Fleishmann results, research on cold fusion fell into disrepute.

To read the full article, click here.

Radiation Leak Incident at Three Mile Island leads to Evacuation

A radiation leak at Three Mile Island, the site of the worst nuclear accident in US history, has sent home about 150 workers, the Nuclear Regulatory Commission reported Sunday.

"They had an airborne radiological contamination alarm," NRC spokeswoman Diane Screnci told AFP. "They evaluated all the workers, a handful of workers -- I don't have a precise number -- had contamination. They since have been decontaminated," she said.

About 150 people work in the building where the leak occurred.

Screnci said what she called a "leak... happened at 4:00 pm Saturday (2100 GMT) and they resumed work in the contaminated building" near Middletown, Pennsylvania.

"There was no impact on public health safety and it does not appear to have an impact on the workers," she said adding that "this kind of incident occurs once in a while."

So far, "they don't know the origin of the contamination," Screnci said. "There were a lot of activities going on at the time and when the alarm sounded. The engineers are working to determine what the cause was."

"It's a minor incident," she said stressing it was "under control."

Three Mile Island suffered a major accident in 1979, with the core of a reactor partially melting down. Since then no new nuclear power plants have been built in the United States.

Nuclear energy supplies 20 percent of power in the United States with 104 reactors, while 50 percent comes from coal burning plants.

The rest is from natural gas, oil and renewable sources such as hydroelectric power as well as solar and wind power.

Chernobyl: The aftermath goes on!

Souz Chernobyl

The monument to Chernobyl in Sochi, a resort city on the Black Sea. On its base is part of a poem about the fate of the people who were drafted or volunteered to clean up the reactor: "We thought that our Motherland was with us. We were proud of the glitter of our golden epaulets. The steps of our rubber boots took measure. Of Chernobyl's deadly testing ground."

NY Times Article