Alec Kimber Australian Nuclear Science & Technology Organisation

Transcription

1 Decommissioning and Dismantling of the Moata Reactor Alec Kimber Australian Nuclear Science & Technology Organisation

2 A History of Moata Constructed at ANSTO in 1961 ARGONAUT type reactor Built as a 10 kw reactor, but modified in 1972 to 100 kw Graphite moderator / reflector Cooled by light water Shielding - high density and low density concrete

3 The Moata Reactor From 1961 to 1995: Neutron radiography Training Soil analysis Cancer treatment research Quality Control for HIFAR

4 Shutdown & Decommissioning Shutdown after 4,519 start-ups Fuel unloaded Primary coolant (light water) drained Reactor Control System removed 2000 Decommissioning Licence Planning for Moata Dismantling Two phases of dismantling: Preliminary Dismantling the removal of the internal components of the reactor, including the steel core structures, graphite moderator and beam line facilities Structural (Biological Shield) Dismantling the cutting and removal of the concrete shielding and the floor area below the shielding. Containment tent installed Preliminary Dismantling July 2009 Biological Shield Dismantling began Biological Shield Dismantling Complete

5 Characterisation Survey Core samples extracted Radiological surveys carried out Determine dose rates Allow for waste reduction Data used to prepare a dose estimate for dismantling Internal reactor components Biological shield Radiological surveys allowed estimation of maximum individual and collective doses

6 Reactor Internals - Dismantling Control rod & drive assemblies Graphite moderator core & N, S, E & W cavities [approx 12 tonne] Aluminium core tanks Pipe work Steel framework graphite support Gamma curtain lead sheet [approx 750kg]

7 Structural (Biological Shield) Dismantling MOATA housed in a building used for AMS for C-14 dating A containment tent with HEPA filtered extraction system built around the reactor

8 Biological Shield - Dismantling

9 Challenge 1 An Australian first Challenge Nothing similar had ever been attempted previously Challenging to project team Slow start Mitigation Identifying and developing on-site expertise Explored use of external companies estimates: Turn key ($12M) Implementation ($8M) Partnership ($6M) Detailed planning we can do this

10 Challenge 2 Regulatory Challenge ARPANSA had never dealt with a reactor decommission / dismantle Regulatory caution Mitigation Communication Start early (Identification of requirements) Continuous Detailed planning Development of knowledge Developing organisational confidence They can do this

11 Challenge 3 Internal management Challenge Does ANSTO have the skills? Never undertaken a reactor decommission Easy to be less constructive Mitigation Project champion Staff training and expertise Detailed planning Development of knowledge Developing organisational confidence ANSTO can do this Stakeholder management Early communication Continual information

12 Challenge 4 External interest Challenge Pressures from external interest groups and stakeholders Politicians / government ANSTO Board IAEA Public Media Mitigation Communication Continuous Factual Managed Detailed planning Development of knowledge Developing organisational confidence Lets see if ANSTO can do this

13 Challenge 5 Project financial Challenge Decommissioning estimate developed from UK and US reactor dismantling Inherited a budget (AUS$3.8M) Minimal contingency Decommission within budget Mitigation Earned value analysis employed Job number allocation and control Early communication of cost overrun

14 Challenge 6 Tandem Accelerator Challenge Adjacent Tandem accelerator Sensitivity to carbon14 (1x10-14 ) [12 Tonne of graphite in MOATA] Risk to future of carbon dating program and research at LH Mitigation Localised tent and extract Fully enclosed and tented work area Double skinned Air inflow through tent skin Extract filtration Primary dust Secondary HEPA extract filtration

15 Challenge 7 Technology Challenge What methods were applicable? What technology was available and suitable? Lack of knowledge by project team Mitigation Research into methods Consultant advice sought Detailed planning Development of knowledge Developing organisational confidence ANSTO can do this

16 Challenge 8 Drawing inaccuracies Challenge 1950 s drawings Imperial measurements Mitigation Expert draughtsman 3D CAD drawings produced Physical 3D model Uncertainty of asbuilt drawings Unknown details Known inaccuracies

17 Challenge 9 Radiation protection Challenge Doses likely to be encountered Shielding methods Self shielding Distance No dose-sharing ALARA Mitigation Characterisation Dose modelling Physical measurements Detailed planning Tooling PPE Shielding Contingency planning What if? Identification & removal of hottest items

18 Challenge 10 Safety Challenge Industrial safety Working at heights Wire cutting Manual handling Dust Mechanical plant Mobile crane Excavator Mitigation In-house safety expert OHS + Radiation PPE 3-day contractor safety training Daily safety checks walkabout Daily safety talks Contractor ANSTO personnel

19 Interfacing Challenge 11 Contractor Challenge ANSTO safety procedures ANSTO systems Fear of radiation Understanding the decommissioning process An Australian first Keeping the cost realistic engagement Mitigation Initial contractor evaluation Presentation to eligible contractors Detailed Specification Responsibilities table detailing contractor interfaces with ANSTO Final contractor evaluation

20 Challenge 12 Work systems methodology Challenge Day to day safe working Contamination minimisation Waste clearance methods Communication Mitigation Site function plan Safe Work Method Statements Commitment to safety Full time, on-site supervisor Daily safety checks ANSTO supplied PPE Health physics on call Daily safety meetings Weekly project meetings

21 Challenge 13 Waste removal and Challenge clearance Mitigation Waste handling processes Waste types Quantities Handling and transport Packaging Availability of staff Project vs operational needs Clearance processes Methods & Instrumentation location Knowledge of reactor Materials, characterisation, size and location Understand demolition processes Consultant advice Contractor advice Consult Waste Management Team Utilise suitable methods Model and calibrate instruments and processes

22 Challenge 14 Records Challenge Preparation ( ) Operational records, drawings Preliminary planning incl DP Dismantling Project Project planning records Daily project records (log books, waste assessment and clearance, Health Physics) A story to be shared Mitigation Identified and collected all available historical records Team included former operators Engaged technical writer who also collated records Waste management group - Radioactive Waste Tracking System Contractor provides records of all wastes cleared from site. Project DVD

23 Final Survey Dose surveys carried out in grid pattern as per original survey Acceptance criteria of 0.5uSv/hr was met Samples taken and analysed for activity < clearance criteria Guides to determine the exemption and clearance criteria for the site IAEA No. RS-G.1.7 ARPANSA Reg 1999, Schedule 2, Part 2

24 Radiation Protection - outcomes Dismantling was completed safely and without incident Dose estimates higher than those recorded Overly conservative estimations Very detailed planning [ what if scenarios ] Concrete dismantling self shielding and greater distance Time taken to dismantle less than anticipated No surface or airborne contamination detected throughout the project No personal contamination events

25 Radiation Protection Dose results Estimated doses vs. actual doses: Dose ANSTO Estimated ARPANSA Constraint ANSTO Constraint Actual Collective 10,400 personμsv 13,000 personμsv 10,400 personμsv 1,679 personμsv Max. Individual 1444 μsv 1750 μsv 1500 μsv 252 μsv Daily μSv 46μSv (max)

26 Project - lessons learned Bridging the gap Telling the safety story in a way that the contractor can easily understand Documents The level playing field use of a single set of documents suitable for all purposes (regulator, contractor etc) Stakeholder A project champion Required to ensure early commitment from departments Operational v Project needs project requires rapid responses to maintain workflow. Thorough planning leads to success and constant review!

27 Project Achievements Setting Trends Ownership / Extending ANSTO department capabilities Procurement Adjusting their mandate to be more responsive to project requirements Survived it being a very high profile project Developed high quality stakeholder communication Regulatory approval and commendation Internal & External QA Audit incl Environmental Awards including National Best Small Project 2010 (Australian Institute of Project Management)

28 Project Achievements Site Function Plan Engagement of expert advice Comprehensive understanding of the project scope High quality specification of works Enhanced ability to deal with demolition contractor Significant savings on demolition contract Highly informed project team Development of in-house expertise Development of confidence for future needs Final cost within approximately 10% of budget

29 Project Achievements 3D Modelling including Physical Model Extremely powerful visualisation tool Aid to contractor understanding Enabled good understanding of the tasks ahead

30 Physical Model Project Achievements

31 Moving forward to HIFAR Experienced and highly informed project team in-house expertise now developed Engagement of expert advice Have a comprehensive understanding of the project scope Enhanced ability to deal with demolition contractor Organisation + project confidence in capabilities Proceed with detailed planning whilst local knowledge is available

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