Across the world, large inventories of nuclear waste from both civilian and military activities are awaiting transfer to an eventual geological disposal site. Sellafield has the responsibility for the safe custody of the UK’s nuclear waste and continuously invests in improving current storage facilities. A key aspect of this is the move from large-scale pond and silo storage to modular containers suitable for transport by road or rail. The evolution of small quantities of hydrogen is a normal and expected feature of many of these containers. Hydrogen is a flammable gas however and nuclear waste stores represent an environment with many challenges for the operation of gas monitoring sensors.

In a very different context, oxygen therapy is routinely prescribed for a range of respiratory conditions including chronic obstructive pulmonary disease (COPD). As far back as the 1950s, cylinders of oxygen were delivered to patients’ homes. In-home oxygen concentrators became popular in the mid-1980s and this in turn paved the way for ever-smaller portable oxygen concentrators, giving patients new-found freedom and independence. However, limited battery life still prevented patients from enjoying many activities others take for granted. Philips Respironics, the first company to achieve Federal Aviation Administration (FAA) certification for its portable concentrators, needed to put every component of their devices under the microscope to meet growing expectations for portability and battery life.

A common sensor platform

Sellafield and Philips approached TTP to work in close partnership with their respective engineering teams to solve their different business challenges. Both benefited from TTP’s prior investment in SonicSense, a gas sensor platform that incorporates knowledge gained on projects as diverse as 3D printing and wound care. In the end, both partnerships delivered robust low-power gas sensors operating on an acoustic principle.

Working with TTP was a pleasure and a very good fit for Philips Respironics. They were able to provide us with novel sensing technology that created a significant cost improvement over existing options. While we traditionally did not develop new sensors like this, TTP was able to lead us through the process very effectively and within budget.”

Peter Bliss
‍Principal Engineer, Philips Respironics

TTP has developed many different sensors using almost as many different physical principles, but for both Sellafield and Philips Respironics a sensing solution was found through speed-of-sound as a measure of gas composition.

Speed-of-sound devices are highly resistant to chemical attack, can measure the full range of composition from 0 to 100% and can be very sensitive. Historically, it has been difficult to miniaturise and reduce the cost of these devices and long term measurement drift has been a particular challenge.

Aware of these limitations, TTP has redesigned the mechanical architecture to deliver a step change in the cost–size–sensitivity trade-off for these devices. The resulting sensors offer unusually good measurement stability and a radical reduction in per-sample energy consumption. TTP worked with Sellafield and Philips to customise the SonicSense platform for their different applications.

Oxygen on the go

Philips Respironics has been at the forefront of portable oxygen concentrators from the beginning with a passion for giving COPD sufferers greater freedom. Having searched for a more efficient sensor to measure the purity of the oxygen delivered to the patient, Philips came across SonicSense on a visit to TTP’s science park near Cambridge.

For Philips’ application, SonicSense technology offers several advantages compared to current sensors. Firstly, it has a long operating life, this is important as concentrators can run continuously for tens’ of thousands of hours. Secondly, it requires no periodic field calibration, which would be impractical in a device used in patients’ homes. This long term and stable operation is due to TTP’s novel integration of physics, mechanical, and thermal design in a small, lightweight, low-cost sensor package ideally suited for this application. And as Philips’ battery-powered portable oxygen concentrators have become increasing popular with patients for use outside of the home or even on flights, the low power-consumption of the SonicSense sensor also helps provide longer battery life which patients value greatly.”

TTP took Philips’ new sensor from the proof-of-concept stage through cycles of development and verification tests to deliver a manufacturable design suitable for close integration with Philip’s products. The engineering teams worked together to merge electronics and algorithms with Philips PCB designs. TTP also supported Philips’ Global Sourcing team in assessing new and existing suppliers.

Better custody of legacy nuclear waste

Sellafield’s modular waste containers similarly represent an unusual sensing environment. Beyond the typical safety requirement for the sensor not to be an ignition source, high radiation levels present unique challenges. The sensor itself must be hardened to radiation, but it also needs to function without local intervention for 10 years – access to change the battery is not trivial.

Sellafield recognised that SonicSense had the potential to achieve the stability and power consumption needed to meet these requirements. Based on Sellafield’s brief, TTP used analytical and computational tools to model the feasibility of a smaller, lower power-consumption variant of the core technology, optimised for hydrogen detection. TTP followed up by fabricating a prototype sensor in TTP’s labs, know internally as SonicH2, which Sellafield successfully tested in its laboratories.

You can read more on the Sellafield website.

We look forward to working with Sellafield to take this technology into service in the coming years.

Platforms and technology development

The sensor technology described here provides an example of a broader trend that TTP is playing a leading part in. Traditionally, technology development companies like TTP develop bespoke solutions for clients needing particular technology, processes or products to enable their commercial ambitions, or to respond to regulatory or societal drivers.

Increasingly TTP serves the same clients by building the technical foundations to address anticipated market needs, for example through technology platforms like SonicSense, that can be customised for different applications and licensed to partners on a market-by-market basis. It can also be a collection of platforms, processes and expertise with a well-defined value proposition to an important market, for example TTP’s desktop biology initiative.

This approach reduces time to market and offers more flexibility in sharing risks and reward, whilst still allowing our clients to integrate the technology we develop into their businesses and to control the way the resulting products are brought to market and exploited.