NM#3 - Stories of Ionizing Radiation and Helicopters: From Chernobyl to the Super Bowl

Welcome to the third edition of NeutronMode!

In-depth Analysis

Helicopters, with their ability to quickly cover large areas and access difficult-to-reach zones, have long been a valuable resource for radiation monitoring, surveying and emergency response.

For instance, during the Chernobyl disaster in 1986, helicopters were essential to implement the planned containment efforts. In the immediate aftermath of the explosion, helicopters were used to drop up to 5000 tons of sand and boron onto the burning reactor.

The idea was conceptually sound: boron, commonly used in nuclear reactors as a neutron poison (absorber), would help mitigate further fission reactions by reducing neutron flux, thereby providing time to address the situation. Meanwhile, the sand would serve to smother the fire and act as a temporary shield, limiting the immediate release of radioactive particles.

However, the extreme conditions under which the pilots were operating prevented the complete success of this strategy, as the materials being dropped from the helicopters often missed the intended target. As a result, several pilots died, either from acute radiation syndrome or in accidents during these dangerous flights.

Many years later, a similar situation unfolded during the Fukushima disaster. Helicopters sprayed tons of water over the damaged reactors in a desperate attempt to prevent a meltdown. As with Chernobyl, extreme conditions—such as strong winds and high radiation levels—rendered these operations ineffective to some extent.

However, on special occasions, helicopters equipped with custom radiation detection instruments, such as gamma spectrometers and scintillators, are routinely used for national security. Let’s explore why.

Let's say someone is considering using a radiation source to contaminate an area that will eventually be crowded. In terms of health impact, there are two main ways to be affected: by inhaling radioactive aerosols (i.e., alpha-emitting radionuclides sticking to dust particles) or by being exposed to gamma rays. I introduce these concepts in my 'Emergency guide to understanding radioactivity'

We can characterize the radioactive material as a point source, with an isotropic radiation pattern. Thus, it's guaranteed that some of the gamma rays emitted (or scattered) by the decaying radioactive material will strike the scintillator(s) located in the helicopter.

For instance, in the following diagram, we can see a radioactive material hidden in a trash bin. Typically, the radius of the detector's field of view doubles with the helicopter's height, at the expense of precision, primarily due to the inverse square law. That's why these helicopters usually fly at low altitudes, following specific patterns to ensure complete coverage of the target area.

As opposed to Geiger-Müller tubes, where the energy of the impinging high-energy photon (gamma ray) is 'lost' (cannot be recovered) after the townsend avalanche, in the scintillators, such as Nal(l), or HPGe, the scintillation light coming from the photoelectrons is detected by a photodetector, usually a photomultiplier tube (PMT) or photodiode. This photodetector converts the light into an electrical signal, which is then processed by the spectrometer to determine the energy of the incoming gamma ray. In this process, the amplitude of the electrical signal is proportional to the energy of the gamma ray that caused the scintillation, enabling the study of the spectrum to identify specific radioisotopes. This is a crucial capability when carrying out national security operations, as detecting a medical-related radioisotope (e.g. Tc-99m) is not the same as detecting traces of fissile material such like Plutonium-239.

Let’s look at a specific example of this scenario, focusing on a major event in the US that will take place in just a few days: The Super Bowl. I honestly have no interest in this event, but I think it's a good example to illustrate some of the concepts we've covered

Probably to avoid mass hysteria, similar to the situation with drones, and to prevent helicopter skeptics from attacking them with lasers, stones, and sticks (those 'magic flying machines'), the Department of Energy recently issued a heads-up.

These brand-new Agusta-Westland 139 helicopters, which replace a previous Bell 412 model, belong to the Nuclear Emergency Support Team (NEST), a National Nuclear Security Administration group of first responders. As part of the NNSA's Aerial Measuring System, the requirements for this new aircraft are publicly available, allowing us to learn more about them

The requirements match the pictures, so we can see that the AW-139 is equipped with the RSX-3, a compact airborne system for security surveillance manufactured by Canada's -still a sovereign country at the time of this publication-, Radiation Solutions INC.

This system is comprised of custom hardware (RSX-3 Scintillators, multi-channel-analyzers,...) and spectroscopy software (RadAssist, RadView), enabling the NEST team to fully perform the required radiation monitoring.

For those interested in the internals of this system, you can find more details in the trove of documentation available on the NNSA's Frontline app: https://nsddkmw.energy.gov/frontline/app/.

By the way, I want to believe that all the documents on that web app are intended to be publicly available, but there are some that contain non-default passwords for things like Wi-Fi and laptops, which would make me a bit nervous. If you happen to know someone involved with it, it might be a good idea to remind them to double-check.

News

• The issue of the ZNPP will be among the diplomatic mission - Zelensky

https://interfax.com.ua/news/general/1045555.html

"Today, this nuclear power plant is not working, because there is no Ukrainian management there - fair and professional. It is not working, it is degrading and it is very dangerous. And in any case, the issue of the Zaporizhzhia plant will be discussed during the first meeting of the parties in a diplomatic format," Zelensky told reporters following a meeting with IAEA head Rafael Grossi on Tuesday.

ICYMI in the previous edition of NeutronMode, I discussed this issue from the cyber perspective.

Curiosities

Maybe you're familiar with this iconic photograph, taken from a helicopter by Igor Kostin, just a few hours after the Chernobyl catastrophe.

He used an analog Pentax 6x7 camera to take the shot. If you closely observe the texture, you'll notice a very characteristic film grain—a 'radiation fog'—which is the result of the interaction between gamma rays and the silver halide photographic emulsion.

In the digital era, a company leveraged this phenomenon to turn any CMOS/CCD-based camera into a gamma detector. The concept is simple yet clever: by covering the camera so that visible light cannot reach the sensor, gamma rays—high-energy photons—will still hit it, ionizing the silicon substrate and causing groups of bright pixels to appear.

So, the next time you’re facing a nuclear fallout, just remember: all you need is some duct tape and your mobile phone to find a safe place.