Conference Paper

Radiation Tolerance of Commercial-Off-The-Shelf Components Deployed in an Underground Nuclear Decommissioning Embedded System

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Abstract

Robotics and embedded systems are increasingly used and deployed in harsh environments such as nuclear decommissioning and radioactive waste handling. Development of new, low-cost, robotic solutions, requires commercial-off-the-shelf (COTS) components to survive radioactive exposure. Understanding the response of these components to γ-radiation is important for safe and reliable deployment. Power supply regulation and microcontrollers have been highlighted as sensitive to radiation and this study determines experimentally the characteristics of degradation for COTS voltage references, voltage regulators and a microcontroller. The findings lead to development of a discrete voltage regulator constructed with individual BJTs that exhibits increased radiation tolerance.

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... Ducros et al. performed radiation tolerance testing, and found that power supply components were by far the most susceptible and had on average a tolerance of up to 210 Gray (Gy) total ionizing dose (TID) at a dose rate of 1.9 Gyh −1 . Other electronic components were found to be much more tolerant, surviving TIDs of 2200 Gy. Nancekievill et al. (2016) found similar results in their radiation tolerance testing of CoTS electronic components. ...
... For deployments into high dose areas an additional factor that needed to be considered was the effect of radiation on Vega. In particular, the electronic systems used in Vega will be damaged by gamma radiation (Nancekievill et al., 2016). ...
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This paper presents the Vega robot, which is a small, low cost, potentially disposable ground robot designed for nuclear decommissioning. Vega has been developed specifically to support characterization and inspection operations, such as 2D and 3D mapping, radiation scans and sample retrieval. The design and construction methodology that was followed to develop the robot is described and its capabilities detailed. Vega was designed to provide flexibility, both in software and hardware, is controlled via tele-operation, although it can be extended to semi and full autonomy, and can be used in either tethered or untethered configurations. A version of the tethered robot was designed for extreme radiation tolerance, utilizing relay electronics and removing active electronic systems. Vega can be outfitted with a multitude of sensors and actuators, including gamma spectrometers, alpha/beta radiation sensors, LiDARs and robotic arms. To demonstrate its flexibility, a 5 degree-of-freedom manipulator has been successfully integrated onto Vega, facilitating deployments where handling is required. To assess the tolerance of Vega to the levels of ionizing radiation that may be found in decommissioning environments, its individual components were irradiated, allowing estimates to be made of the length of time Vega would be able to continue to operate in nuclear environments. Vega has been successfully deployed in an active environment at the Dounreay nuclear site in the UK, deployed in nonactive environments at the Atomic Weapons Establishment, and demonstrated to many other organizations in the UK nuclear industry including Sellafield Ltd, with the goal of moving to active deployments in the future.
... A common but mistaken assumption is that only radiation-hardened robotics should be used within the nuclear industry, hence hydraulically actuated robots [17][18][19][20][21][22] and platforms that feature radiation-hardened components [23] have traditionally been in favour. Although this may be true for operations within high-radiation environments such as hot cells, other typical nuclear environments exhibit radiological levels which may be too high for daily human exposure but are not sufficient to damage conventional hardware. ...
... For a worker to receive a dose of 1 mSv over the course of a day would be seen as very high and almost certainly not As Low As Reasonably Practicable (ALARP). However, this dose is virtually irrelevant to COTS electronic components, where radiation hardness testing tends to begin at around five or six orders of magnitude higher than this [23]. Thus, although commercially available robotic platforms may not be useable within the primary containment vessel of a nuclear reactor, for example, they may be useable within activities such as the categorisation of general waste. ...
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A novel, semi-autonomous radiological scanning system for inspecting irregularly shaped and radiologically uncharacterised objects in various orientations is presented. The system utilises relatively low cost, commercial-off-the-shelf (COTS) electronic components, and is intended for use within relatively low to medium radioactive dose environments. To illustrate the generic concepts, the combination of a low-cost COTS vision system, a six DoF manipulator and a gamma radiation spectrometer are investigated. Three modes of vision have been developed, allowing a remote operator to choose the most appropriate algorithm for the task. The robot arm subsequently scans autonomously across the selected object, determines the scan positions and enables the generation of radiological spectra using the gamma spectrometer. These data inform the operator of any likely radioisotopes present, where in the object they are located and thus whether the object should be treated as LLW, ILW or HLW.
... Naturally, there is a significant interest in radiation hardened robotics within the industry, hence hydraulically actuated robots [6][7][8][9][10][11] and platforms that feature radiation hardened components [12] have traditionally been in favour. However, although operations within environments such as hot cells involve very high levels of radiation, other typical nuclear environments may exhibit radiological levels which, despite being too high for daily human exposure, are still far too low to damage conventional hardware. ...
... In terms of damage to commercially available off-the-shelf (COTS) electronic components, this is a low dose rate. Discussions of radiation hardness tend to begin at around eight orders of magnitude higher [12]. Thus, although commercially available robotic platforms may not be useable in very high radiation environments (e.g. ...
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A novel, semi-autonomous radiological scanning system for inspecting uncharacterised objects is presented. The research utilises commercially available off-the-shelf (COTS) electronic components, intended for use in relatively low radioactive dose environments. To illustrate the concept, a Microsoft Kinect, a Universal Robots UR3 (6 degree of freedom) manipulator and a Kromek RadAngel gamma radiation spectrometer are utilised. The new control software allows the remote operator to select the required object, before the robot arm autonomously scans it, enabling the generation of various radiological spectra shapes. These data inform the operator of any likely radioisotopes present and where they are located in the object.
... Testing complete circuits may provide more data than testing individual components, due to potentially unexpected interactions between the components. While some studies have investigated the radiation effects on electronic components in the context of the nuclear industry [13,14], microprocessor testing in literature is predominantly focused on single event detection and heavy particle irradiation. This research is mostly focused on space applications, and the results cannot be directly correlated with performance in a gamma radiation environment more prevalent in nuclear decommissioning [15][16][17][18][19]. ...
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The impact of gamma radiation on a commercial off the shelf microcontroller board has been investigated. Three different tests have been performed to ascertain the radiation tolerance of the device from a nuclear decommissioning deployment perspective. The first test analyses the effect of radiation on the output voltage of the on-board voltage regulator during irradiation. The second test evaluated the effect of gamma radiation on the voltage characteristics of analogue and digital inputs and outputs. The final test analyses the functionality of the microcontroller when using an external, shielded voltage regulator instead of the on-board voltage regulator. The results suggest that a series of latch-ups occurs in the microcontroller during irradiation, causing increased current drain which can damage the voltage regulator if it does not have short-circuit protection. The analogue to digital conversion functionality appears to be more sensitive to gamma radiation than digital and analogue output functionality. Using an external, shielded voltage regulator can prove beneficial when used for certain applications. The collected data suggests that detaching the voltage regulator can extend the lifespan of the platform up to approximately 350 Gy.
... Studies presented in Ref. [27] have shown that electronic components in nuclear decommissioning environments are exposed to different dose rates and total dose rates compared to other industrial applications. These findings need to be taken into account during the selection of dose rate and total dose to evaluate the effects of TID on components deployed in nuclear decommissioning environments. ...
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The effects of Total Ionizing Dose (TID) on electrical components is a key parameter to evaluate the life span of wireless sensor nodes for possible deployment in nuclear decommissioning environments. The aim of this study was to experimentally evaluate the effects of TID on capacitance, internal resistance and the self-discharge characteristic of 100 F supercapacitors. An automated test circuit was designed and assembled to charge and discharge the supercapacitors. The supercapacitors were irradiated using a Co-60 γ ray radiation source and the voltage across the supercapacitor terminals, charging current and discharging current were monitored and logged to calculate the capacitance during the irradiation process. Measurements of internal resistance and self-discharge characteristic were performed before and after the irradiation to examine the effects of exposure to γ radiation on these electrical properties. The experimental results show negligible effects on the capacitance of supercapacitors exposed to a maximum dose of 40 kGy. The internal resistance and self-discharge characteristics were not affected by TID up to 89 kGy. These results demonstrate that supercapacitors are a suitable technology to design an Energy Storage System to be deployed in the majority of nuclear decommissioning environments.
... Examples include undertaking irradiation tests on optical fibres (Coenen and Decreton, 1993), position sensing using laser systems (Decreton, 1995) Decreton, 1996;Sinclair and Chertov, 2015;Van Duy et al., 2015;Zhang et al., 2013). Similarly, high end computing is also regarded as greatly important (Bagatin et al., 2017;Lin et al., 2016;Nancekievill et al., 2016;Ostler et al., 2009;Schmidt et al., 2012;Sterpone et al., 2005;Wu et al., 2011). Furthermore, global advances have already proved to be beneficial for the robotic community. ...
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