At the first step of the assessment of dust dispersion data during cutting fuel debris of Fukushima Daiichi Nuclear Power Station, dust dispersion data during cutting cold simulants with four cutting methods under dry condition were obtained against wide range of operating parameters. This presentation summarizes the dry cutting tests with chisel and core boring.

The tests were conducted by measuring the generated floating aerosols with particle size analyzers (Welas2000 and/or ELPI+). Since amount of aerosol generation is not sufficient for measuring in large casings, dry cutting tests with core boring and chisel were carried out within small area such as an acryl box of roughly 30cm cubic. The inlets of the particle size analyzers were inserted close to the cutting position so that the aerosols were sucked without dilution by the air flow. With a correction to same flow condition according to computational analysis, the measured data for dry cutting with four different cutting methods were compared each other. The detail and result of each cutting test are summarized as following.

The chisel tests were conducted using both Φ30mm flat and point chisels of Makita with an electric hammer of Makita HM1511 after modification to allow changing the beating frequency at 500-950 bpm. The applied static load ranged 600-800 N including the weight of the hammer. As for test results, the peak diameter of the dispersed particles was around 10μm, similarly to disk cutter. The maximum Airborne Release Fraction (ARF) for various kinds of simulants reached tens of percent for zircon and several percent for porous alumina and mortar due to small mass defect of chisel cutting.

The core boring tests were conducted using Φ76mm impregnated core bits of Asahi Diamond with the rotation speed of 60-600 rpm. The applied load ranged 1-6 kN. The mass defect was estimated by the weight loss of the simulant or the volume of the generated ditch. As for test results, the peak diameter of dispersed particles was in the range of 10-30μm. The ARF for mortar and porous alumina were less than 1%, and that for other simulants ranged less than 10%.

We propose using Laser-Induced Breakdown Spectroscopy (LIBS) for preliminary, simple analysis to efficiently analyze the fuel debris generated by the accident at TEPCO’s Fukushima Daiichi Nuclear Power Plant (FDNPP). LIBS is an elemental analysis method that uses laser-generated plasma. The plasma emission is measured by a spectrometer to identify is used to create the calibration curve, but this ratio may be affected by the plasma temperature. Therefore, it is preferable for the plasma temperature to remain constant in LIBS. However, the plasma temperature can change depending on the measurement conditions, which may also affect the spectrum. This study conducted experiments under various conditions to verify whether the plasma temperature changes.

Radiation tolerant optically reconfigurable gate arrays (ORGAs) have been developed [1]-[5]. These radiation-tolerant optically reconfigurable gate arrays have two characteristics: high total ionizing dose and soft error tolerance and fast reconfiguration. To improve the performance of radiation-tolerant optically reconfigurable gate arrays, we proposed the Mono Instruction Set Computer (MISC). MISC is a processor architecture that reduces the number of instructions to one by relying on reconfiguration of the circuit with programmable devices to change functions. As a result, MISC can be implemented in a small gate array area and can provide a higher clock frequency than RISC (Reduced Instruction Set Computer), which is currently widely used as a processor architecture. In addition, since the implementation area is small, performance can be improved by implementing multiple MISC processors in parallel in the same area as a RISC processor. In this study, we implemented the arithmetic part (ALU) of a 4-bit MISC processor with six functions (logical AND, logical OR, addition, subtraction, multiplication, and division), and compared and evaluated it with an implemented RISC processor. The results confirm that MISC processors have higher performance than RISC processors. In addition, a 32-bit MISCALU was implemented and its performance was verified with maximum operating frequency and footprint

The configuration procedure of field programmable gate arrays (FPGAs) is executed serially. Therefore, if only one transistor of the configuration circuit is permanently damaged by radiation, the device cannot be reconfigured. Therefore, the configuration circuit of FPGAs is weak point for radiation.

Therefore, we have been developing optically reconfigurable gate arrays (ORGAs) to realize a parallel configuration by using light. In this architecture, even if a part of programmable gate array and/or a part of the configuration circuit are broken by radiation, the rest region of the programmable gate array can be reconfigured correctly so that the total-ionizing-dose tolerance can be increased. On the other hand, integrated circuit, to decrease the frequency of soft errors happen on its configuration memory, a scrubbing technique was used. In a conventional scrubbing operation, correct configuration data is frequently written onto the configuration memory. Always, higher the scrubbing speed can increase the soft-error tolerance. In FPGAs, scrubbing speed was very slow or 100 ms. In ORGA, the parallel optical configuration architecture can realize 50 ns configuration. So, high-speed scrubbing operation could be executed.

However, in this study, we aim to achieve faster scrubbing operation than the optical scrubbing.

We have implemented a new triple-modular-redundant optical configuration circuit. The proposed method enabled a 200 ps scrubbing period. The ORGA-VLSI was fabricated.

This paper reports on the development of a Pipe Cutting Tool for the Blanket Remote Handling System, an essential tool for remote maintenance of the Blanket Module (BM) attached to the Vacuum Vessel (VV) of the international fusion experimental device, ITER. The BM, comprising a First Wall (FW) and a Shield Block (SB), necessitates cutting and welding water cooling pipes before removing or after installing the BM. Ensuring quality welding without leaking and with strength is crucial to maintain the vacuum environment inside the VV. Therefore, before blanket replacements, a deformation of the pipe is required to be as small as possible after cutting.

In this study, we have designed the Pipe Cutting Tool with a pad-type centering mechanism and fabricated prototype pipe cutting test equipment to evaluate the effectiveness of the developed mechanisms. This design enables the Pipe Cutting Tool to mitigate its own weight during cutting in any orientations and maintain load stability. We conducted the cutting tests under multiple cutting conditions. Specifically, we identified the influence of cutter feed rate to the pipe deformation. Consequently, we have confirmed the cutting condition to minimize the deformation of the pipe in the event that the feed rate is below 0.004 mm/s using the equipment. In the past, the pipes processed with machining were used for the welding tests, simulating the pipe weld after FW replacements. However, in the future, the welding tests will be performed using pipes cut with the swage cutter to better simulate the actual conditions.

In 2020, the "TEPCO Collaborative Research Cluster for Decontamination and Decommissioning Frontier Technology Creation" was established to promote the decommissioning of the Fukushima Daiichi NPP. By matching the on-site needs of TEPCO with the technological seeds of Tokyo Tech, the new decommissioning technologies according to the on-site needs is developed systematically. Eight basic research subjects are currently conducted at this research cluster, including the research on debris retrieval, the research on waste treatment and disposal, the research on analysis and harsh environmental sensing, and the research on environmental remediation. Among them, the technologies with high field applicability are selected, and proceeded in the METI’s national project, “Project of Decommissioning, Contaminated Water and Treated Water Management” and practical application research with TEPCO.

Some granular adsorbents used at the Fukushima Daiichi Nuclear Power Plant (1F) are expensive, contributing to the high cost of radioactive wastewater treatment. This study examined the optimization of the structure of the adsorbents to reduce their costs. The cesium and strontium adsorbent currently used at 1F (the current adsorbent) was assumed to adsorb contaminants primarily on its surface layer. Therefore, the core–shell-type adsorbent (the low-cost adsorbent), in which inexpensive materials are placed inside the grains and expensive adsorbent components are placed only on the surface layer, was considered, and its adsorption performance and degree of embrittlement were evaluated. The adsorption performance and degree of embrittlement of the low-cost adsorbent are equivalent to those of the current adsorbent. This study concludes that a core–shell structure with an adsorbent component only on the grain surface layer effectively treats radioactive wastewater at 1F.

This study introduces a Visual Simultaneous Localization and Mapping (vSLAM) system employing a "Monocular-Stereo Camera," designed to achieve omnidirectional stereo imaging with a single camera for the semi-autonomous control of decommissioning robots. Using a feature-point-based vSLAM method to estimate the camera pose (position and orientation), we integrate point clouds derived from the camera's depth information into the vSLAM map. This method enhances pose estimation accuracy, resolving the sparse map issue in vSLAM by producing a dense 3D environmental map. We evaluated our proposed system in an environment simulating the structured pattern lighting used in decommissioning sites to obtain distance information in dark conditions. The results confirmed that the average recognition error rate, calculated by dividing the mean absolute error by the travel distance, was 1.5%.

At the Fukushima Daiichi Nuclear Power Plant Unit-1 (1F1), three attempts were made to open the small Suppression Chamber (S/C) vent valve (AO valve) at 10:17, 10:23, and 10:24 on March 12th. The monitor near the main gate recorded a series of high dose rates from 10:20, seemingly in response to the vent operation. However, no clear decrease in the Drywell (D/W) pressure was observed, suggesting a potential failure of this venting. At present, it remains unclear whether the small S/C vent valve was indeed opened, and in case it was, whether it was the main cause that triggered the rise in the dose rate near the main gate at 10:20 on March 12th, 2011. These two issues were attempted to be clarified in this study by the following two steps.

As the first step, the possibility of the opening of the small vent valve was assessed by reproducing the behavior of the D/W pressure using GOTHIC v8.4 code. The boundary conditions (gas inflow, heat source, the opening of the small vent valve, etc.) were estimated based on the 1F1 accident scenario events (Primary Containment Vessel (D/W) leak, Molten Core-Concrete Interaction (MCCI), etc.), which was estimated based on the plant measurement data and the on-site observations. These estimated conditions were adjusted until the simulation results aligned with the D/W pressure measurement data. As a result, the potential opening status of the small S/C vent valve was evaluated based on the criterion of D/W pressure reproducibility.

Based on the result from the first step, the second step aims to discuss the relationship between the opening of the small S/C valve and the rise in the dose rate near the main gate at 10:20 on March 12th. Although the wind direction and speed were recorded by the monitor in the plant field, the information was insufficient to draw a conclusive inference. Therefore, this study planned to clarify this issue from another approach by comparing the amount of radioactive material released through S/C vent lines and the Reactor Building (R/B) to identify the major radiation source that led to the rise in the dose rate. The results of the D/W pressure reproduction simulation at the first step make it possible to estimate the leakage conditions through the reactor building and ventilation lines. The discussion on the primary cause responsible for the increase in the dose rate near the main gate will be discussed based on the results of this simulation and previous relevant studies.

It should be noted that only the results of the first step are included in this paper, as the second step is still ongoing.

In general, electronic devices are affected by radiation in high radiation environments such as nuclear power plants and outer space. Therefore, it is necessary to develop devices with high radiation tolerance. Therefore, we have been studying repairable FPGAs, which are programmable devices with high total dose tolerance. In this paper, we report the circuit implementation of a repairable FPGA.

In the accident of Fukushima Daiichi Nuclear Power Station, various reactor structures melted and formed fuel debris, which accumulated in the primary containment vessel region. This fuel debris is considered to have a heterogeneous distribution of components at different locations. Understanding the distribution of Gd₂O₃, which may behave as potential neutron absorber materials in the fuel UO₂, is especially important from the viewpoint of criticality safety for fuel retrieval. We conducted solidification tests of reactor materials to investigate component segregation and solidification behavior in fuel debris using a Cold Crucible Induction Heating technique at the Research Centre Řež (CVR) in Czech Republic. In particular, melted samples weighing more than 1 kg were melted using the furnace to reproduce macroscopic component segregation in fuel debris. After melting the sample at about 2500°C, the melt was gradually solidified by pulling the crucible out of the heating section to control the solidification direction. As for the simulated fuel debris, a mixture of core materials (UO₂, ZrO₂, Gd₂O₃), structural material (FeO), simulated fission products (MoO₃, Nd₂O₃, SrO, RuO₂), and concrete materials (SiO₂, Al₂O₃, CaO), were used under four conditions. After the test, the distribution of each component was evaluated using an SEM-EDS analysis of the sample cross-section.

The sample solidified gradually from the bottom to the top with cooling rate of approx. 13 ℃ / min in two samples and 3-4 ℃ / min in other two. and a shrinkage porosity was observed in the upper part of the predicted final solidification zone. Initial solidified areas show fine microstructure. Gd₂O₃ was concentrated in the periphery of the sample, suggesting that it may segregate in the early solidification region. On the other hand, Fe was concentrated in the central region, i.e., in the late solidification region. Fe is considered to be concentrated in the late solidification position because, thermodynamically, it is distributed to the liquid phase during the solidification process. No significant segregation was observed in the simulated fission products. EDS analysis might not have detected he simulated fission products due to the small amount added and evaporation during heating. In the sample containing concrete, the concrete component formed a glass phase and separated from the fuel oxide phase, although there were differences in microstructure depending on the location of the sample

A Based on the advanced FCVS technology, such as a gas-liquid mixing nozzle and a multi-layer metal fiber filter, and a silver zeolite filter for the purpose of removing organic iodine. we have developed a demonstration machine for a large-capacity air purification system that purifies a large amount of contaminated air. With this acceleration and centrifugal force field of water, almost all of the fine particles in the bubbles can be transferred to the liquid phase water and dissolved. We have developed a demonstration machine of an air purification system that can remove fine particles and viruses in the air of 100 m3/h with a single nozzle and we also developed a large-capacity air purification system that can purify 2400 m3 of air per hour with 24 nozzles, and results of the paper.

FCVS has succeeded in improving the decontamination factor (DF) of radioactive materials using scrubbing technology. By applying these technologies and making the system robust and compact, and by making it mobile. We expect to be used in a wide range of applications. To realize mobile use, we developed a prototype was manufactured in 2020, and performance tests such as DF tests were conducted in 2021. High DF was confirmed in tests using

In our laboratory, we have been developing a radiation- hardened optically reconfigurable gate arrays (RHORGAs) with 1 Grad total-ionizing-dose tolerance [1]-[5]. The RHORGAs is about 1000 times higher total-ionizing-dose tolerance than current available radiation-hardened VLSIs. For example, in order to implement an AI system for autonomous decommissioning robots, a large-size RHORGA-VLSI is required. However, in this case, the yield ratio of RHORGA-VLSIs is main concern. Since the huge-scale RHORGA-VLSIs fabricated by using a latest process technology might have many defects points. However, the RHORGA-VLSIs can accept production failures in addition to permanent failures caused by total-ionizing-dose effect. A RHORGA consists of a programmable gate array VLSI, a holographic memory, and a laser array. In current field programmable gate arrays (FPGAs), the gate array is configured electrically in a serial connection. On the other hand, the RHORGAs can be reconfigured optically in parallel using a holographic memory and a laser array. Parallel configuration is robust for any defect mode while serial configuration is weak for defects. Therefore, the RHORGAs is more robust than current available radiation-hardened VLSIs. In this paper, we have designed a new RHORGA-VLSI with four clock distributions and have implemented four 16-bit adder circuits onto the RHORGA-VLSI with defect areas. The 16-bit adder circuits could work correctly on the RHORGA-VLSI. In the RHORGA, even if three clock distribution are down, the rest clock signal can correctly keep any operation. Therefore, the RHORGA is strong for both of total-ionizing-dose effect and production failure.

Under a strong radiation environment such as decommissioning situation of nuclear power plants, radiation-hardened processors are required for robots and other systems. Currently, space-grade processors are available. However, currently available space-grade processors are always weak for radiation and the life-time of the space-grade processors is limited to an extremely short period. So, we have introduced triple modular redundancy (TMR) for RISC-V processor to increase the total-ionizing-dose tolerance. This paper presents a triple modular redundancy RISC-V processor design. In the RISC-V processor, majority voting operations are executed automatically at every clock cycle. The RISC-V processor was implemented onto a Cyclone-V Field Programable Gate Array (FPGA) on a DE1-SOC FPGA board. It has been confirmed that the RISC-V processor can work correctly. Additionally, the maximum operating clock frequency was measured as 64.82MHz. The FPGA’s resource usage was 45%.

In Fukushima Daiichi Nuclear Power Plant, it is necessary to use a radiation-hardened remote communication system to control remotely working robots. Currently, we are developing a radiation-hardened remote communication system using a DE1-SoC field programmable gate array (FPGA) board. When a communication must be done under a radiation-environment, soft error and total-ionizing-dose tolerances must be considered. To block the phenomena, a triple modular redundant design was introduced. We have developed a triple modular redundant serial communication circuit for a 200 m metal-wired communication between a computer and the remotely located system. The serial communication circuit mainly consists of triple modular redundant delay type flip flops, majority voting circuits, and state transition logic circuits. For long-distance communication, the hardware macros of differential input ports and differential output ports were used on a Cyclone FPGA. Here, we are using a serial communication data format constructed by 8 bits data, a start bit, a stop bit, and a parity bit.

Using the serial communication circuit, we conducted a bidirectional communication test using 200-meter wires. In this test, no errors were observed when the communication frequency is lower than 8.0 MHz.

Very large-scale Integrations (VLSIs) used in high radiation environments such as space environment and nuclear power plants are constantly damaged by radiation. VLSIs are vulnerable to radiation. Therefore, we have been developing radiation-hardened optically reconfigurable gate arrays. Conventional optical reconfigurable gate array VLSIs have a weakness in clock distribution. This problem can be solved by a new clock distribution using reconfigurable switching matrices. However, in this case, a clock skew problem is caused. Therefore, to solve this problem, this paper presents a proposal of a new clock distribution method using a two-phase clock signal and switching matrices on an optically reconfigurable gate array VLSI. This paper also presents a new optically reconfigurable gate array VLSI to support the new clock distribution method and simulation result of a 4-bit counter circuit on it.

At Units 1 to 3 of the Fukushima Daiichi Nuclear Power Plant, it is believed that nuclear fuel melts together with the structures inside the reactor and exists as fuel debris in the Primary Containment Vessel (PCV), including the Reactor Pressure Vessel (RPV). Therefore, it is necessary to perform fuel debris retrieval work and environment maintenance work for retrieval under a high-dose environment, and remote technology is essential. Since these operations require an enormous number of repetitive operations, autonomous mobility of remote-controlled robots is considered effective in reducing the burden on workers. Generally, laser rangefinders are used for autonomous movement, but they do not have high radiation resistance. In this paper, we construct a pseudo-stereo camera by combining a radiation-resistant camera and a mirror, and propose an environmental recognition technology using the acquired images and ranging information. In the proposed technology, we developed a camera system that uses SiC semiconductors with high radiation resistance as the control board and installed it on a remote-controlled robot. In addition, we have developed a system that prevents video deterioration and acquires useful images for image processing by using digital signals while transmitting video signals over long distances of about 50 m. Next, we developed the "Monocular Stereo Camera System," a sensor equipped with two omnidirectional hyperbolic mirrors capable of shooting 360° horizontally and capable of obtaining distance information of a 360° horizontal structure from the parallax of two panoramic images. In addition, we developed map generation by Visual-Simultaneous Localization and Mapping (Visual-SLAM) using images of Monocular Stereo Camera and map generation technology that superimposes the above distance information. Using the above developed technology, we propose an environment recognition technology for robots to move autonomously in a high-dose environment.

The EUROCHEMIC reprocessing plant, established by an international consortium of 13 OECD countries, operated from 1966 to 1974 to process fuel from power reactors and research reactors.

The main building was a large concrete structure, covering an area of 55,000 m2, with a concrete volume of 12,500 m3, containing 1,500 T of metal components.

The building was divided into 106 individual cells, requiring dismantling. The dismantling of these cells involved removing and decontaminating of equipment from each cell, decontaminating of the cell walls, ceilings, and floors, and dismantling of the ventilation system.

Belgoprocess commenced the industrial decommissioning of two storage buildings (6A and 6B) in 1987, followed by the decommissioning of the main process building of the former EUROCHEMIC reprocessing plant in 1989, This initial phase served as a pilot project to familiarize operators with dismantling techniques.

The decommissioning project includes various steps as:

* removal of systems and components;

* first decontamination of the structure;

* removal of pipeline penetrations;

* final decontamination of the structure;

* free release measurements;

* demolition of the structure (building);

* brownfield.

The building was divided into three parts. The eastern part was demolished in 2008, followed by the removal of the central part in 2010. The demolition of the remaining part occurred in 2014, ultimately restoring the area to brownfield conditions.

Over the course of the 25-year decommissioning process, significant effort was invested in enhancing efficiency.

Belgoprocess's decommissioning policy prioritizes maximizing efforts for decontaminating metals, concrete, and other materials, aiming for unconditional release and minimizing nuclear waste.

Consequently, several installations were developed to reduce processing costs, increase decontamination output, and accelerate release measurements. These include:

▪The abrasive blasting installation*, utilized for removing a thin layer from metal components and concrete objects.

▪The concrete sampling installation*, employed as the final measurement before the unconditional release of concrete debris.

▪The concrete spec installation*, utilized to segregate contaminated parts from non-contaminated parts of concrete debris.

* These installations continue to be used for other decommissioning projects at Belgoprocess

We developed a signal processing system for radiation- hardened cameras that can receive and convert digital differential signals transmitted over long distances into video signal even when the drive frequency of a CMOS image sensor (CIS) fluctuates due to gamma radiation. The camera consists of a camera head component and a signal processing component, which are connected by a long-distance cable. The output signal of the CIS in the camera head component is a digital differential signal (LVDS signal). In the LVDS signal, the clock and pixel data are output in parallel. The pixel data includes a code indicating the start of a frame. The signal processing component receives the code and converts the pixel data into the video signal. In the gamma radiation test of the camera, the image was not output after 150 kGy. To investigate the cause, the clock and pixel data were evaluated. The clock frequency increased by two times after 150 kGy, while the clock slew rate (SR) did not degrade due to gamma radiation. In the code of pixel data after 150 kGy, some bits did not exceed the center voltage of the LVDS signal and were not judged as 1 (error bit). Therefore, we devised a signal processing system that can recognize the code even when gamma radiation causes the driving frequency of CIS to fluctuate. For the developed signal processing system, a part of the code ([0xFFFFFF]) was extracted that can predict the location of error bits and the increase in error bits as frequency increases. The extracted signal increases from the negative shift of the lower limit voltage at the same SR regardless of TID, so the number of error bits can be predicted to increase starting from the higher bits as the frequency increases. Therefore, in addition to the [0xFFFFFF], [0x7FFFFF] were programmed as recognition signals instead of the code for the signal processing system, and the system was designed to switch between these recognition signals depending on the increase in frequency. We determined that the proposed signal recognition system can receive the LVDS signal containing the error bit and output image. However, there was distortion in the output video received using [0x7FFFFF], which will need to be addressed in future work.

Decommissioning challenges at the Fukushima Daiichi Nuclear Power Plant are closely analogous to those encountered in other parts of the world. The proposal is to transfer and adapt existing high TRL technologies currently being deployed in an active cell at Sellafield, UK, and deployed in nuclear decommissioning environments in the USA.

The Barrnon Integrated Decommissioning System (BIDS) is an inherently radiation-tolerant hydraulically-powered mobile robotic system capable of performing a range of decommissioning tasks. Modular in concept and design, the system can be reconfigured for size and task-capability, for example the collection of fuel debris, the retrieval of sludges, granulates, zeolite and similar materials.

Subsets of the challenge are addressed and experimental results obtained indicate the achievability of deployment of a radiation-tolerant ROV and snake-arm robot capable of delivering tools and sensors into hard-to-access zones, semi-autonomous situational awareness, navigation, task characterization and prioritization in complex, unstructured environments; retrieval of liquid waste, sludges and granulates; VR-controlled size-reduction; object recognition in poorly lit and highly unstructured environments; radiation mapping; waste disposal decisions based on industry standard waste stream classification; and dynamic object handling. The integration of these capabilities in a scalable, modular and adaptable format is demonstrated and variant form-factor and task-capability versions of the system are mentioned.

EnergySolutions (ES), founded in 2005, was established by acquiring companies both from the United States (US) and from the international market with good capability or technology to enable providing a full value chain of nuclear backend service mainly in the areas of radioactive waste management and nuclear facility D&D. With over 50 years of combined experience, the company offers a full suite of integrated, often unique solutions to customers worldwide.

In the US, ES has been involved in the majority of D&D projects, including La Crosse, SEFOR, and Zion sites, which were fully managed and completed by the company as commercial D&D projects. One of the next major challenges is to complete D&D work at TMI-2 which still has fuel debris remaining in the plant.

Disc cutter is a representative cutting tool for debris retrieval. For the cutting experiment using a disc cutter, size of the disc blades, rotational speed of the disc, and pressing force is changed as a test parameter. Experimental data showed that dust generation by disc cutting is affected by the physical properties of the object. Therefore, in order to organize the dust dispersion characteristics in terms of the mechanical properties of the object, experiments were conducted using cold simulants with various physical properties (Al₂O₃, Zircon, Mortal, SS₄₀₀, and SUS₃₀₄). Furthermore, simulant debris containing UO₂ was manufactured and cutting experiments were also conducted using this simulant. Both Al₂O₃ and simulant debris containing UO₂, it was found that the porosity affects air bone dust characteristics such as ARF and particle size distribution.

High TRL and proven technologies successfully exploited in industries adjacent to nuclear, also in nuclear decommissioning in other parts of the world, can be advantageously applied at the Fukushima Daiichi Nuclear Power Plant. The challenges are closely analogous. The proposal is to adapt the REVO system to perform a range of specific decommissioning tasks in difficult-to-access operating environments.

The REVO Long Ops decommissioning system is specifically designed for operation in difficult-to-access places with the ability to deploy a range of tools and sensors. The system can be hydraulically actuated and hydraulically controlled for radiation-tolerance. REVO has an advantageous power-to-mass ratio due to its innovative geometries, using single actuators to create 3D translations: the snake-arm robot is capable of lifting and manipulating objects with a relatively large mass for the size of the robot and of applying significant force to perform decommissioning tasks. The unique geometries enable the robot arm to operate in all parts of the workspace without the need to avoid no-go zones that conventionally are created by singularities.

Equipped with specialized sensors for condition assessment, radiation levels can be mapped over a 3D model of the environment. A range of tools can be mounted on the robot arm including a laser-cutter for size-reduction and the Ross Innovation 3D Adaptive gripper for reliable object manipulation. The system is modular and can be reconfigured for reach and task-capability and is scalable to pass through access ports in the range 80mm to 500mm.

Subsets of the challenge are addressed and experimental results are obtained to indicate the achievability of deployment of the REVO system at Fukushima.

Commercial nuclear power generation has played a pivotal role in the provision of global clean energy over the last 70 years. As with all industrial processes and facilities commercial nuclear power plants also reach a point where an end-of-life determination is made, and the facility is shutdown.

The LongOps programme (2019-2024) unites three end users with similar multi-decadal challenges: TEPCO has the challenge of decommissioning the Fukushima Daiichi reactors and especially reaching into the reactor pressure containment vessels to retrieve fuel debris; the UK Nuclear Decommissioning Authority has a complex multi-building decommissioning liability estimated to be £178B over more than 100 years; and, the UK Atomic Energy Authority started in 2024 to conduct first of a kind decommissioning of the JET fusion reactor at Culham aiming to complete by 2040 using long reach booms to access the reactor pressure vessel.