Using site investigation data to drive the decision making ...€¦ · Using site investigation...

Using site investigation data to drive the decision making process

Peter M BoothSenior Technical Director

25/04/2012

Introduction

• Urenco UK Ltd (UUK) is based in Capenhurst in the Northwest of England, UK.

• The UUK site is a Nuclear Licensed Site.

• The UK Nuclear Decommissioning Authority (NDA) also leases an adjacent Nuclear Licensed Site to Sellafield Limited.

• Primary business of UUK is to enrich uranium using centrifuge technology.

• The adjacent NDA site is in a decommissioning and storage phase.

• UUK has a strong and open relationship with UK Regulators.

• UUK is an informed client with clear objectives for their business.

UUK Site Layout

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How operations have evolved

• The Capenhurst site has been industrialised since the 1940s, having started as a Royal Ordnance Factory.

• 1950s a new gaseous diffusion plant was constructed and operated to enrich uranium.

• 1960s the plant reached full output before a new centrifuge technology was developed.

• 1970s centrifuge enrichment plants were constructed and British Nuclear Fuels was formed as a new company to operate the new centrifuge plants.

• More centrifuge plants were constructed and operated through the 1980s and the old diffusion plant commenced decommissioning.

• In 1993 Urenco (Capenhurst) Limited was created as a limited company from BNFL to operate enrichment plants at Capenhurst.

• Today UUK (current name) continue to develop centrifuge enrichment activities and the former BNFL operations are being decommissioned.

UK regulatory regime

Office for Nuclear Regulation (ONR) Licensing and day-to-day regulation. Licence conditions cover all the arrangements for managing safety, including

responding to accidents, leaks and spillages of radioactive materials, emergency planning arrangements, and all aspects of transporting radioactive material on the sites.

The ONR are accountable to the Secretary of State for Energy and Climate Change for their nuclear safety work.

Environment Agency (EA) (England and Wales) To minimise the environmental impact of day-to-day operations, regulate the

routine discharges and disposal of nuclear waste and other radioactive material.

UUK Drivers for undertaking Site Investigation

Regulatory – early pressure for UUK to demonstrate that the potential impacts on human health and the environment from their operations were understood and well managed.

• Requirement of both the EA and ONR.• External stakeholders. • Driver to gain acceptance for the building of new facilities where previous

facilities may have stood.

Business – internal need to define and manage contaminated land liabilities and to use accumulated data to support commercial business development decisions and strategy.

• Challenge to reduce waste management costs.• Driver to recycle and re-use more material and apply the waste hierarchy. • Driver to assist decision making processes on environmental remediation.

Application of the Waste Hierarchy

Objectives of the SI’s

• Each SI required specific outputs.

• Primarily a baseline of site conditions was required by the Regulators and UUK to satisfy their Site Licence conditions (and Environmental Permits) and inform their management strategy and define liability.

• Latterly project specific data on ground conditions and development constraints were required to underpin business development strategy.

• Several common objectives:

• Maximise the data gathered to minimise re-visiting locations.• Communication with stakeholders to deliver all data requirements.• Complete the work without incident.• Produce high quality data which is defensible and can be used into the

future.

Type of data collected

A wide range of data has been gathered to support decision making around new developments and remediation decisions:

• Geotechnical soil and rock properties (e.g. CPT, SPT, PSD, UCS etc.).• Radiological analysis (soil and water – use of screening e.g. GAB and Gamma scan

with limited speciation of uranics and tritium).• Chemical analysis (soil and water – wide spectrum suites).• Hazardous ground gas and vapour sampling and in-situ monitoring.• In-situ health physics monitoring.• Groundwater levels and fluctuation data.• Geological lithology data.• Analysis of drain sediments (radiological and non-radiological).• Analysis of concrete cores (radiological).• Geophysical data.

SI Process adopted

• A phased approach to SI was adopted to allow costs to be managed and to give time to develop management strategy after each stage completed.

• A few historical site investigations had been completed prior to 2000 to support building projects.

• A site-wide baseline investigation was completed first in 2005/2006 in order to identify key areas which were impacted and should be accounted for in financial and development terms.

• A delineation phase was then adopted to constrain the nature and extent of potentially problematic areas and issues.

• Once understood and discussed with Regulators the approach then turned to more focussed ground feasibility studies to support specific business development projects.

• Investigations informed issues related to waste management, human health impact assessment, geotechnical ground engineering and remedial strategy.

Phases of Ground Investigation


Site Investigation techniques utilised

A variety of techniques were applied:• Cone Penetration Technology• Geophysics• Cable Percussion• Rotary Open Hole• Rotary Core• Windowless sampling• Slit trenches• Inspection pits• Concrete coring• Plate loading• Vapour monitoring and Health Physics control

Data Management and Data Visualisation

• One of the most valuable assets UUK holds in relation to site characterisation is the site investigation database.

• Relational database containing all information gathered about geology, hydrogeology, geotechnical parameters and chemical and radiological analysis.

• This allows cumulative understanding and development of the conceptual site model.

• Data is visualised using a Geographical Information System (GIS) which generates high quality images far easier to understand than a complex written description.

• All data from site investigations is added to the database in a universal format (e.g. AGS III) so all staff and contractors can make use of this high value asset.

Geology

2003

2010

Shows contours of the surface of sandstone in mAOD, the darker the colour, the deeper rockhead. A development of understanding of the deep linear ‘channel’ feature was gained between 2003 and 2010.


Groundwater in Sandstone

2004 2007

Shows contours of groundwater in sandstone in 2004 and 2007 developed through gathering time-series water level data in mAOD. The darker the colour, the shallower the groundwater on both images. Despite using more data points, the groundwater regime in the sandstone remained consistent.


Evolution of Distribution of TCE

Proportional circles show the largest circles where the highest concentrations of TCE were found resulting from legacy operations prior to the formation of UCL in 1993.

Understanding developed through gathering time-series data from the site-wide borehole monitoring network. The understanding of the issue from being a local occurrence to a site-wide groundwater impact issue was developed over time.

Discussions with the Regulators reached agreement that although levels of TCE exceeded drinking water standards, levels were still reasonably low and no potable water abstractions were affected. Therefore a monitoring programme was established but no other remediation is required at this time..


Distribution of Gross Alpha in Soil (Bq/Kg)

The levels of Gross Alpha in soil shown here are related to legacy operations at the site prior to the formation of UCL in 1993. The activities at the site are not considered problematic in the UK and have been demonstrated in the majority of cases to represent background levels. Generally soils have been demonstrated by UUK to be exempt (free release) across the site.


Summary

• Site characterisation undertaken in a prioritised way has enabled UUK to satisfy the Regulators that they are in full knowledge and control of environmental issues.

• Understanding the environmental liability has reinforced the management decisions made with regard to developing the business.

• Soil analysis data has enabled UUK to follow a protocol to dispose of spoil off-site for re-use rather than classifying it as a waste saving significant costs. Making full use of historical site knowledge has enabled a focussed sampling strategy to underpin this process.

• Understanding the level of contamination on the site e.g. low, has enabled UUK to make the decision to clean up any legacy issues prior to re-developing land = a clean start and reduction in Regulatory process.

• Site characterisation has enabled de-designation of some site areas and hence release from government control.

• Clarification of regulations has helped UUK to be clear about their legal obligations and design suitable processes.

Summary

• Understanding why you need to undertake site investigation is essential to designing a needs driven programme.

• The reasons behind the programme can determine how it is phased, funded and maximised to everyone's benefit.

• Internal communication between all departments requiring information is crucial to determining a fit for purpose and economical programme.

• Understanding Regulatory concerns allows data to be collected in a targeted way and gives ability to know when to stop collecting data.

• Cumulative use of all historical and current data gives the most complete picture of the site conceptual model – don’t discount data because it is ‘old’

• Visualisation tools (such as GIS) are very important when trying to communicate complex scenarios – easy to understand.

Acknowledgements

We would like to thank Urenco UK Limited for permission to use the content of this presentation and for input into the company approach adopted in managing

regulatory and business drivers.

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