Detecting Anti-Neutrinos From Distant Fission Reactors Using Pure Water At SNO+

April 16, 2023 by Maya Posch 32 Comments

Although neutrinos are exceedingly common, their near-massless configuration means that their presence is rather ephemeral. Despite billions of them radiating every second towards Earth from sources like our Sun, most of them zip through our bodies and this very planet without ever interacting with either. This property is also what makes studying these particles that are so fundamental to our understanding so complicated. Fortunately recently published results by researchers behind the SNO+ neutrino detector project shows that we may see a significant bump in our neutrino detection sensitivity.

The Sudbury Neutrino Detector (Courtesy of SNO)

In their paper (preprint) in APS Physical Review Letters, the researchers describe how during the initial run of the new SNO+ neutrino detector they were able to detect anti-neutrinos originating from nuclear fission reactors over 240 kilometers away, including Canadian CANDU and US LWR types. This demonstrated the low detection threshold of the SNO+ detector even in its still incomplete state between 2017 and 2019. Filled with just heavy water and during the second run with the addition of nitrogen to keep out radioactive radon gas from the surrounding rock of the deep mine shaft, SNO+ as a Cherenkov detector accomplished a threshold of 1.4 MeV at its core, more than sufficient to detect the 2.2 MeV gamma radiation from the inverse beta decays (IBD) that the detector is set up for.

The SNO+ detector is the evolution of the original Sudbury Neutrino Observatory (SNO), located 2.1 km below the surface in the Creighton Mine. SNO ran from 1999 to 2006, and was part of the effort to solve the solar neutrino problem, which ultimately revealed the shifting nature of neutrinos via neutrino oscillation. Once fully filled with 780 tons of linear alkylbenzene as a scintillator, SNO+ will investigate a number of topics, including neutrinoless double beta decay (Majorana fermion), specifically the confounding question regarding whether neutrinos are its own antiparticle or not

The focus of SNO+ on nearby nuclear fission reactors is due to the constant beta decay that occurs in their nuclear fuel, which not only produces a lot of electron anti-neutrinos. This production happens in a very predictable manner due to the careful composition of nuclear fuel. As the researchers noted in their paper, SNO+ is accurate enough to detect when a specific reactor is due for refueling, on account of its change in anti-neutrino emissions. This is a property that does not however affect Canadian CANDU PHWRs, as these are constantly refueled, making their neutrino production highly constant.

Each experiment by SNO+ produces immense amounts of data (hundreds of terabytes per year) that takes a while to process, but if these early results are anything to judge by, then SNO+ may progress neutrino research as much as SNO and kin have previously.

Honey, We Shrunk The Nuclear Reactor

November 25, 2022 by Al Williams 99 Comments

[Power Engineering] took a trip to the Westinghouse facility that provides maintenance for nuclear reactors. The research division there has a new microreactor called eVinci and — according to the company — it is a disruptor. Technically, the device is a heat pipe-based passive cooling design that can generate 5 MW of electricity or 13 MW of heat from a 15 MW heater core. You can see a video about the device below.

The company says its initial targets are remote areas like mines that usually depend on diesel generators. Hundreds of passive heat pipes inside a graphite core which contains TRISO (tristructural isotropic) fuel pellets. The heat pipes allow efficient transfer of thermal energy with no pumps.

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Self-Driving Laboratories Do Research On Autopilot

September 29, 2022 by Lewin Day 16 Comments

Scientific research is a messy business. The road to learning new things and making discoveries is paved with hard labor, tough thinking, and plenty of dead ends. It’s a time-consuming, expensive endeavor, and for every success, there are thousands upon thousands of failures.

It’s a process so inefficient, you would think someone would have automated it already. The concept of the self-driving laboratory aims to do exactly that, and could revolutionize materials research in particular.

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Commonwealth Fusion’s 20 Tesla Magnet: A Bright SPARC Towards Fusion’s Future

September 27, 2021 by Maya Posch 62 Comments

After decades of nuclear fusion power being always ten years away, suddenly we are looking at a handful of endeavours striving to be the first to Q > 1, the moment when a nuclear fusion reactor will produce more power than is required to drive the fusion process in the first place. At this point the Joint European Torus (JET) reactor holds the world record with a Q of 0.67.

At the same time, a large international group is busily constructing the massive ITER tokamak test reactor in France, although it won’t begin fusion experiments until the mid-2030s. The idea is that ITER will provide the data required to construct the first DEMO reactors that might see viable commercial fusion as early as the 2040s, optimistically.

And then there’s Commonwealth Fusion Systems (CFS), a fusion energy startup. Where CFS differs is that they don’t seek to go big, but instead try to make a tokamak system that’s affordable, compact and robust. With their recent demonstration of a 20 Tesla (T) high-temperature superconducting (HTS) rare-earth barium copper oxide (ReBCO) magnet field coil, they made a big leap towards their demonstration reactor: SPARC.

A Story of Tokamaks

CFS didn’t appear out of nowhere. Their roots lie in the nuclear fusion research performed since the 1960s at MIT, when a scientist called Bruno Coppi was working on the Alcator A (Alto Campo Toro being Italian for High Field Torus) tokamak, which saw first plasma in 1972. After a brief period with a B-revision of Alcator, the Alcator C was constructed with a big power supply upgrade. Continue reading “Commonwealth Fusion’s 20 Tesla Magnet: A Bright SPARC Towards Fusion’s Future” →

TerraPower’s Natrium: Combining A Fast Neutron Reactor With Built-In Grid Level Storage

July 6, 2021 by Maya Posch 66 Comments

Most new nuclear fission reactors being built today are of the light water reactor (LWR) type, which use water for neutron moderation into thermal neutrons as well as neutron capture. While straightforward and in use since the 1950s in commercial settings, they are also essentially limited to uranium (U-235) fuel. This is where fast neutron reactors are highly attractive.

Fast neutron reactors can also fission other fissile elements, covering the full spectrum of neutron cross sections. TerraPower’s Natrium reactor is one such fast reactor, and it’s the world’s first fast reactor that not only targets commercial use, but also comes with its own grid-level storage in the form of a molten salt reservoir.

The upshot of this is that not only can these Natrium reactors use all of the spent LWR fuel in the US and elsewhere as their fuel, but they should also be highly efficient at load-following, traditionally a weak spot of thermal plants.

TerraPower and its partners are currently looking to build a demonstration plant in Wyoming, at the site of a retiring coal plant. This would be a 345 MWe (peak 500 MWe) reactor.

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The Soviet RBMK Reactor: 35 Years After The Chernobyl Disaster

May 5, 2021 by Maya Posch 66 Comments

Thirty-five years ago, radiation alarms went off at the Forsmark nuclear power plant in Sweden. After an investigation, it was determined that the radiation did not come from inside the plant, but from somewhere else. Based on the prevailing winds at that time, it was ultimately determined that the radiation came from inside Soviet territory. After some political wrangling, the Soviet government ultimately admitted that the Chernobyl nuclear plant was the source, due to an accident that had taken place there.

Following the disaster, the causes have been investigated in depth so that we now have a fairly good idea of what went wrong. Perhaps the most important lesson taught by the Chernobyl nuclear plant disaster is that it wasn’t about one nuclear reactor design, one control room crew, or one totalitarian regime, but rather the chain of events which enabled the disaster of this scale.

To illustrate this, the remaining RBMK-style reactors — including three at the Chernobyl plant — have operated without noticeable issues since 1986, with nine of these reactors still active today. During the international investigation of the Chernobyl plant disaster, the INSAG reports repeatedly referred to the lack of a ‘safety culture’.

Looking at the circumstances which led to the development and subsequent unsafe usage of the Chernobyl #4 reactor can teach us a lot about disaster prevention. It’s a story of the essential role that a safety culture plays in industries where the cost of accidents is measured in human life.

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Certifying Nuclear Reactors: How The NRC Approved Its First Small Modular Reactor Design

October 1, 2020 by Maya Posch 38 Comments

The US Nuclear Regulatory Commission (NRC) recently announced that it had approved certification of NuScale’s SMR (small modular reactor) design, completing its Phase 6 review of NuScale’s Design Certification Application (DCA). What this means is that SMRs using NuScale’s reactor design can legally be constructed within the US as soon as the rulemaking process completes. An NRC certification would also mean that certification of the design in other countries should pose no significant hurdles.

A question that remains unanswered at this point for most is how this certification process at the NRC actually works. Are there departments full of engineers at the NRC who have been twiddling their thumbs for the past decades while the US nuclear industry has been languishing? What was in the literally millions of documents that NuScale had to send to the NRC as part of the certification process, and what exactly are these six phases?

Stay tuned for a crash course in nuclear reactor certification, after a bit of SMR history.

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