BIBLIOGRAFIA

The development and deployment of highly automated remote technology was in its infancy at the time of the accidents at A1, Windscale Pile1, TMI-2 and Chernobyl NPP. At TMI-2, manual defueling was chosen over development of complex mechanized equipment because the development time needed and the uncertainty for achieving a highly reliable, remotely operated system presented too much project uncertainty.

Since those accidents, there has been much progress in remote technology evolution and today there are many applications within the nuclear power industry to support operations and maintenance. For post-accident cleanup and decommissioning, Fukushima Daiichi will set many precedents for the application of remote technology to

manage the condition. The sophisticated application of robotics will be a major aspect of decommissioning of FIG. 11. Project steps for each remote technology application.

Fukushima Daiichi for the long term. The strong need for R&D and innovations for decommissioning of nuclear facilities, including those after an accident, are addressed in Refs [28, 29].

5.2.1. Project management perspectives

Current decommissioning systems typically employ many of the advanced approaches used in other nuclear and non-nuclear industries. This includes advanced electronics, the design of robots, virtual reality simulation and software that makes robots intelligent and adaptable to a variety of tasks. The development of industrial robots and remotely operated equipment in non-nuclear sectors has provided technological advancement, especially in those sectors that deal with hazardous materials (the chemical industry) and special and difficult tasks (the defence or space industries).

The application of remotely operated equipment for any decommissioning work requires a complex combination of highly skilled resources and a programme to conceptualize, design, fabricate, test and place this equipment in operation. Compared with repair and replacement work at non-accident NPPs, this complexity can be more demanding for post-accident work because of extreme conditions involving radiation and physical damage.

Situations that make human access impossible include, but are not limited to, the following:

(a) High gamma radiation and alpha/beta contamination;

(b) Atmospheric conditions with noxious gases;

(c) High temperatures;

(d) Difficulty of access, such as in narrow spaces;

(e) Lack of visibility;

(f) Heavy loads.

There are non-accident situations that can be equally challenging, for example in fuel reprocessing facilities or nuclear legacy facilities. From the perspective of the project manager and project engineer, obtaining remote equipment for decommissioning tasks can be a comprehensive project on its own. Weeks or months may be required, the total duration depending on factors such as complexity of the task, whether or not adaptable components are available, or if considerable development will be needed. Once it is clear that the situation confirms the impossibility of human operations and the need for remotely operated equipment, evaluations are to be conducted for the technology to be applied. In order of preference, the first choice is to use the available commercial equipment, the second is to adapt existing equipment and systems for the conditions to be encountered.

A final resort is development from the ground up for the specific need. The complexity of such undertakings is illustrated by the steps in Fig. 11.

FIG. 11. Project steps for each remote technology application.

Some of the technical information needed to obtain remotely operated equipment includes the following:

— Specification of the operating method and scenarios that define the needed performance, functionality, safety and operating conditions;

— Identification of required supply (power, gas, hydraulic) that needs to be available;

— Radiation exposure, source term and associated dose rates to be taken into account;

— Space constraints, such as limited access, interferences, pathways to be traversed;

— Special needs, such as radio-controlled command, instruments (cameras, dosimeters) and types of end effector tools.

5.2.2. Considerations for choosing remote technology

From the preceding discussion of project management perspectives, it is not difficult to imagine the increased challenges for post-accident situations where extreme physical conditions and the many unknowns that may exist prior to deployment of equipment. In this regard, insights for what is needed are often best provided by those at the site who will use the equipment. Such individuals need to participate with engineers and suppliers at each step of design, procurement, development and deployment.

For each remote technology to be adapted or developed, in addition to photographic, video, radiation and other characterizations, the use of simulations, 3-D models, and physical mock-ups are key to development and demonstration of reliable performance prior to operation in the accident environment. These tools also provide a means to train operators in control of the remotely operated equipment, both generally and for specific tasks to be conducted in situ. Models and mock-ups should be retained as long as the situation for which they are built continues to exist.

The development of remotely controlled manipulators to be used in a highly contaminated facility includes the following:

— Recognition, characterization, quantification and sample analysis resulting in the creation of 3-D disposition and 3-D radiation models.

— Drafting of a preliminary decontamination plan including definition of the requirements for tools, supporting construction and use of remotely controlled manipulators.

— Decontamination and dismantling simulations for:

● Specification of tools and supporting construction;

● Specification of geometrical, mechanical and kinematics parameters for manipulators.

— Generalization of requirements, screening of existing tools, equipment and manipulators:

● Modification of existing tools, equipment and manipulators;

● Detailed specification, basic design and development;

● Purchasing of commercially available tools, equipment and definition of requirements for their modification.

— Modification, improvement or manufacture of tools, equipment and manipulators (in cooperation with vendors).

— Factory acceptance tests to ensure that specification parameters and functions are met and to confirm reliability of equipment.

— Mock-up tests and operator training to provide:

● Detailed descriptions of decontamination and dismantling operations;

● Advice for operations;

● Familiarity with tools, equipment, manipulators — design, operation, maintenance;

● Training of decontamination and dismantling tasks — obtaining operating skills.

— Performing decontamination and dismantling tasks — feedback, improvement and further development.

5.2.3. Post-accident applications of remote technology

Applications of remote technology in post-accident situations are focused heavily on, but not limited to:

(a) Characterization using direct observation, data collection and sampling;

(b) Decontamination of walls, floors, structures, and equipment;

(c) Size reduction and retrieval of damaged fuel and fuel debris.

A few examples of characterization and decontamination are presented in the following sections. Many other devices for these functions exist for use throughout the nuclear power industry. Removal of damaged fuel and fuel debris is more unique to a post-accident situation [7].