Characterisation Challenges · Game Changers A Sellafield Ltd initiative, delivered and managed by...

Game Changers A Sellafield Ltd initiative, delivered and managed by Innovus

Characterisation

Challenges

Part of the “Sellafield Ltd Game Changers” Series How to use this document This document is designed to introduce the challenges associated with the dismantling, size reduction and decommissioning of the legacy nuclear plants on the Sellafield site.

The document has been formatted to provide information on

The current baseline technologies which are available for use today

The limitations which those technologies present, that could potentially be addressed with innovation

Perceived gaps with the existing approaches and suggestions on areas where there is an opportunity for innovative solutions

Innovation may take the form of technologies or approaches which have been successfully deployed in other industrial sectors, or may take the form of completely novel ideas and concepts.


Contact: Robert Alford; E: [email protected]; T:+44 (0)19467 88959

Introduction to Decommissioning Decommissioning of ageing nuclear engineering facilities represents one of the major challenges of the

21st century. The international market in nuclear decommissioning and waste management

relating to power generation and reprocessing plants is estimated to be in the region of £250

billion, with the operations requiring in excess of 100 years to complete1. The UK component of this is estimated to be approximately £70 billion2, with completion on similar timescales.

The UK has been at the forefront of the development of nuclear technology since the early 1940’s progressing through the post war period in the design, build and operation of power reactors and their associated reprocessing and waste treatment facilities. This has resulted in significant technical waste management and decommissioning challenges and opportunities for the UK to develop and deploy technological solutions on UK sites, including Sellafield, and for the international nuclear market. Sellafield Site Overview Sellafield is the most complex industrial site requiring remediation in Western Europe, comprising approximately 700 acres in West Cumbria. Nuclear operations on the site commenced in the late 1940’s, with the site operations performed reflecting the full range of activities undertaken by the UK civil

nuclear industry. The site consists of more than 2200 buildings including 170 major nuclear facilities. As the site transitions from reprocessing operations, which will cease around 2020, the major focus will shift to Post Operational Clean Out, waste management and decommissioning activities. Due to the variety of operations performed at Sellafield, a wide range of challenges will need to be addressed including:

Characterisation of enclosed cells containing redundant chemical operations

Gloveboxes used for research, development and fuel fabrication operations

Facilities used for the storage of spent fuel

Waste storage and handling facilities

Spent nuclear fuel reprocessing facilities

Pipe and ductwork within a range of plants

Sewers, pipe bridges and trenches

Sellafield Ltd performs a lot of characterisation for decommissioning requiring significant input from the supply chain. This will ramp up significantly as the site prepares for an increased intensity in

decommissioning activity in the next 5 to 10 years. Provision of timely and fit for purpose data will be a key enabler to underpin and optimise decommissioning and waste management

which has the potential to significantly reduce the decommissioning liability.

The current projected cost of decommissioning relies on numerous assumptions, such as the extent of radioactive contamination and waste generated during decommissioning however, due to uncertainties with the data available, the expected cost of decommissioning covers a wide range. Consequently there

is a significant opportunity and need to reduce the decommissioning cost and duration through the deployment of innovative characterisation tools and techniques.

1 A Review of the UK’s Nuclear R&D Capability, Technology Strategy Board, 2008. 2 Nuclear provision – Explaining the cost of the cleaning up Britain’s nuclear legacy, Nuclear Decommissioning Authority, February 2015

mailto:[email protected]



Business Benefit Sellafield need to integrate a diverse range of information to plan and execute decommissioning and waste management activities. The aim is to provide information to enable better decision making at the design and planning phase; provide virtual environments to test options and tools; link to additive manufacture, support for safety assessment; train operators; provide human performance and other information to operators via for example augmented reality.

Sellafield need to reduce the cost of decommissioning and have identified ‘improved characterisation’ as a key area of focus.

The baseline cost of decommissioning is estimated to run at £150m per annum in 10 years’ time and £300m per annum in 15 years’ time.

Characterisation Challenge Overview Characterisation aims to deliver robust information on the radiological, chemical and physical status of a facility, materials and wastes from all areas of the Sellafield site in order to inform decisions. These decisions define the Post Operational Clean Out (POCO), decommissioning and waste management strategies. POCO is the first stage after plant operations designed to use existing plant reagents and operating regimes to remove as much of the radioactivity as possible prior to potentially moving the plant

to care and maintenance. Innovative characterisation tools and techniques will seek to complement the existing ‘baseline methodologies’ so that teams are better placed to perform

characterisation activities and collect qualitative and quantitative data.

Baseline Costs of Decommissioning at Sellafield




Below are a number of factors which challenge the effective characterisation of facilities, materials and wastes across the Sellafield site: Difficult deployment in areas of restricted access:

Access may only be possible via small holes (approx. 100mm diameter) Access is sometimes located at height and through several metres of concrete, and

potentially through lead or water High radiation, loose and fixed contamination Complex and highly congested environment due to numerous pipes, vessels, vents and

cables in close proximity that criss-cross large closed spaces A range of different pH environments (pH<0 to greater than 11) in different plants Heterogeneity of materials being measured Speed of deployment; Currently weeks, desire real time and cheaper data assessment and reporting Lack of ‘through the wall techniques’ to look inside shielded cells Lack of efficient and secure data transmission in large robust buildings across the Sellafield site Requirement to collaborate widely without sophisticated or costly IT packages, data that can be

exported to standard Microsoft office packages Requirement to be cheap enough to be disposable or robust and designed for maintenance and

decontamination. Desire for field deployment of laboratory based equipment (e.g. Laser ablation) Desire for operation by non-specialists without the need to recalibrate

Characterisation Vision Imagine if we could with minimum, or no, intervention into hazardous environments, provide accurate and timely characterisation of a facility and that this characterisation addressed all our information needs for decommissioning and waste management.

Moreover imagine that in changing environments we could use small, cheap, disposable networked sensors to monitor changes such as ageing, performance of vent systems and air-borne radioactivity levels. Our vision is therefore an integrated capability that combines isotopic radiometric, physical, chemical, spatial and other information to provide a complete understanding of the hazards and leaves a virtual and in-situ record or label. An integrated capability that can identify the chemical and physical nature of contamination and provide advice on decontamination; that can also intelligently optimise its own investigation based on real-time data and is operable by non-specialists. This may use machine intelligence to utilise existing information and knowledge to determine what further characterisation is needed to fill the gaps to identify infrastructure and other requirements that are needed to support decommissioning objectives. Using Virtual Reality to combine plant knowledge and characterisation information to support decision making, planning and training. On a day-to day basis via Augmented Reality making (historic and real-time) radiometric and other information available to that ensures work is done efficiently and safely.




Characterisation - Beta gamma dose measurement and waste

forecasting

The objective is to map multiple sources of radioactivity in facilities which may contain a complex network of vessels and pipework. The purpose is to inform the strategies and plans for Post Operational Clean Out (POCO), decommissioning and waste management. This will also enable Sellafield to determine the relative quantities of each radioactive waste category3 for all the items within the facility but does not include sentencing of the radioactive waste. Current Baseline Methodology Deployed

Historical information and flowsheets Health physics surveys – deployment of

conventional Geiger Muller tubes, using manual entry or deployment of a probe on a pole

Gamma Cameras (e.g. RadScan or N-visage)

Limitations

The non-destructive techniques are also largely manual which leads to: o Dose to operators o Secondary waste o Operational time and cost

Dose intensive nature of sampling and destructive analysis, limits the opportunities and may lead to more pessimistic waste assessments

These techniques are limited by access to the area

Perceived Technology Gap / Opportunity

More efficient mapping (cost and time) whilst reducing the risk to workers

Measurement of radioactive contamination on the internals of vessels; some with internal features such as cooling coils and pipework ranging from centimetres to a few metres in scale

Translate spot dose measurements to a dose map with sufficient resolution to determine discrete areas of activity, the ability to get 360o view and take measurements through water or shielding

Electronics and data transmission need to be robust to high radiation dose rates Dose mapping is primarily for determination of dose rate with a secondary interest in

determination of isotopic composition Waste forecasting requires determination of key specific radionuclides

3 http://llwrsite.com/wp-content/uploads/2013/04/WasteAcceptanceCriteriaOverviewWSC-WAC-OVR-Version3-0-Ap.pdf

Beta Gamma Dose Mapping


http://llwrsite.com/wp-content/uploads/2013/04/WasteAcceptanceCriteriaOverviewWSC-WAC-OVR-Version3-0-Ap.pdf

http://llwrsite.com/wp-content/uploads/2013/04/WasteAcceptanceCriteriaOverviewWSC-WAC-OVR-Version3-0-Ap.pdf



Characterisation – Alpha contamination

The objective is to determine the location and quantity of loose and fixed alpha contamination within items of plant (e.g. pipes, vents, vessels, sumps and gloveboxes). The purpose being to inform the strategies of Post Operational Clean Out (POCO), decommissioning and waste management. Current Baseline Methodology Deployed

The construction of a new enclosed (tented) environment prior to commencement of sampling operations

Wipes and swabs taken by health physics operators from the site surfaces for offline counting

Close proximity (<1cm) hand held electronic contamination probes

Sampling for offline assay Limitations

The nature of sampling and the need to prevent internal dose leads to bulky protective equipment including air fed suits and respirators

The use of air fed suits is slow and labour intensive and generates secondary waste Data is monitored and recorded manually

Perceived Technology Gaps / Opportunities

More efficient alpha contamination monitoring and reduced risk to workers

Measurement of alpha emissions with high radiation backgrounds

Measurement of alpha activity from greater distances

Measurement of alpha activity of wet items and wastes

Faster deployment and measurement – including opportunities for remote deployment

Data logging and recording of positions within shielded areas (which may be in GPS denied areas)

Cameras which detect alpha contamination and can operate in normal light conditions

Alpha Contamination is often located in

Gloveboxes




Characterisation – Fissile material assessment

The objective is to measure the fissile content within an environment (material, item, cell or facility). The purpose is to assist with Post Operational Clean Out (POCO), decommissioning and waste strategies and to avoid overly pessimistic safety cases. Current Baseline Methodology Deployed

Non-destructive testing (neutron / gamma assay) and modelling

Sampling and radiochemical analysis

Limitations

Neither technique, as currently deployed, allows in-situ measurement

Vessels and pipework requiring assessment have been designed to be criticality safe and therefore have a low neutron flux

Must be criticality safe Safeguarding regulations lead to additional constraints Long count times (days)


Tools to achieve lower limits of detection for fissile content and enable safety case requirements to be relaxed

Techniques need to be able to operate and provide data in high background radiation environments

Shorten count times during the collection of the data Map location of fissile material (which may be GPS denied areas)

Nuclear Fission




Characterisation – Physical and visual

The objective is the inspection of cells, drains, sumps, vents and gloveboxes, which are not easily accessible, to confirm the location, dimensions, thickness, weight, internal components, stored energy and structural integrity of plant items. The purpose being to determine the condition, appearance and location of items in order to confirm the inventory and inform decommissioning, POCO waste strategies and plans. Current Baseline Methodology Deployed

Camera inspection Laser Scanning Photogrammetry Drawings Scale models Endoscopes

Limitations

Lifetime of cameras is low due to irradiation Cameras require good lighting Inability to deploy in small pipework (<1 cm)

or through grills Historic drawings and models do not always

match current plant conditions and configurations

Capturing images and recording the position within areas which may be GPS denied


Improved deployment methods (ability to get a device to the point of inspection)

Higher quality images and videos (HD) Location recognition (which may be GPS denied) Radiation tolerance of the imaging system Integration of images and radiometric data to rebuild 3D models Waste mass, volume and centre of gravity calculations Remote chemical sensors (e.g. Raman) Determining / quantifying thickness of components and structures Ability to highlight structural defects (holes, weaknesses etc.) Measurement of components within items Stored energy assessment Use of remote vehicles (e.g. Drones)

Visual Inspection

Laser Scanning




Characterisation – Depth of penetration of radioactivity

The objective is to determine the radioactive penetration into porous substances (such as render, concrete and bricks). The purpose being to inform decontamination and decommissioning strategies in accordance with the principles of the waste management hierarchy. Current Baseline Methodology Deployed

Core sampling and non-destructive / destructive analysis in the laboratory

Micro drilling

Limitations

Destructive Time consuming Limited number of samples Concrete not homogenous Contamination generated during coring (dust) Deployment area limited due to access


Verified methodologies for determining the depth profile non destructively Large scale measurement of surfaces to understand heterogeneity Methodology for identifying key radio-nuclides other than 137Cs (e.g. 241Am for alpha) Interface and reporting to assess the depth profile in 3D Data integration with physical and visual assessments (mapping) Characterisation at boundaries between intermediate level waste (ILW), low level waste

(LLW), very low level waste (VLLW) and exempt wasteiii

Active Profiling




Characterisation – Airborne alpha

The objective is to monitor and quantify airborne alpha activity. The purpose being to determine the appropriate designation for the area and reduce pessimistic safety case requirements. Current Baseline Methodology Deployed

Assume default C5 requirements (>40Bq/cm2 alpha, >400 Bq/cm2 Beta) which leads to the use of air fed suits

Use of fixed position alpha air samplers Personal air samplers Swabs and wipes carried out by health physics

personnel Limitations

C5 dictates use of air fed suits Alpha air quality monitors provide data from fixed

positions Personal air samplers give retrospective results


Equipment which is suitably accurate and sensitive to confidently enable lower contamination classification of an area

Personal ‘real time’ alpha monitors Monitor the effectiveness of HEPA filters

Airborne Alpha Contamination Air Fed Suit

Operations




Characterisation – Hazardous and chemotoxic The objective is to determine the chemotoxic properties of residues and materials (e.g. asbestos, acidity, heavy metals, solvents, polycyclic aromatic hydrocarbons (PAHs)). The purpose being to inform the strategies of Post Operational Clean Out (POCO), decommissioning and waste management. Current Baseline Methodology Deployed

Sampling and analysis of residues and materials Written records Simple sampling and measurement tools (e.g. pH meter)

Limitations

Time and cost Change in composition from records Non-standard operation for existing site analytics


Ability to detect an extensive range of hazardous components Non-destructive sampling and analysis methods Faster, easier deployment and turnaround of results Technologies which can be deployed and measure at the workface Development and deployment of commercial off -the -shelf techniques Indicative in-situ measurements for preliminary surveys

Warning Labels for Hazardous and Chemotoxic Substances


https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjFmcSQ39vKAhWj8XIKHWZ2BKUQFggdMAA&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FPolycyclic_aromatic_hydrocarbon&usg=AFQjCNETZmDlyUIfDQ5NcKmfB5iHm8QsCA



Characterisation – Post operational clean out efficiency

The objective is to monitor the wash out and movement of solids during the Post Operational Clean Out (POCO) operations to determine wash out efficiency. The purpose is to inform operator decision-making when determining the extent of clean out required. In the next 20 years there are over 30 major facilities due to undergo POCO at Sellafield. These facilities include reprocessing plants, highly active and alpha contaminated facilities. Current Baseline Methodology Deployed

Health physics operator monitoring In cell radiometric equipment

Limitations

Installed radiometric equipment was designed to monitor throughput rather than efficiency of POCO operations. (i.e. monitoring accumulations and heels)

Access limitations for installation of new equipment and to take direct measurements


Continuous real-time data (only the data required) provided to the operators Measurements taken in-situ Measurements of solids and non-intrusive measurements of liquids

Typical Pipework at Sellafield


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