Decommissioning and Dismantling of the Moata Reactor Documents... · A History of Moata • Graphite moderator / reflector • Cooled by light water • Shielding - high density and

Decommissioning and Dismantling of the

Moata Reactor

Alec Kimber

Australian Nuclear Science &

Technology Organisation

A History of Moata

• Graphite

moderator /

reflector

• Cooled by light

water

• Shielding - high

density and low

density concrete

• Constructed at ANSTO in 1961

• ARGONAUT type reactor

• Built as a 10 kW reactor, but modified

in 1972 to 100 kW

The Moata Reactor

From 1961 to 1995:

– Neutron

radiography

– Training

– Soil analysis

– Cancer

treatment

research

– Quality Control

for HIFAR

Shutdown & Decommissioning

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.

1995 1997 1998 2008 2009 2010

Sh

utd

ow

n a

fter 4

,51

9 s

tart-u

ps

Fu

el u

nlo

ad

ed

Prim

ary

co

ola

nt (lig

ht w

ate

r) dra

ine

d

Re

acto

r Co

ntro

l Syste

m re

mo

ve

d

Pre

limin

ary

Dis

mantlin

g J

uly

2009

Co

nta

inm

en

t ten

t insta

lled

Bio

logic

al S

hie

ld D

ism

antlin

g b

egan

Bio

logic

al S

hie

ld D

ism

antlin

g C

om

ple

te

Pla

nnin

g fo

r Moata

Dis

mantlin

g

2000 –

De

co

mm

issio

nin

g L

ice

nce

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

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]

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

Biological Shield - Dismantling

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”

Challenge 2 – Regulatory

Challenge

• ARPANSA had never dealt

with a reactor

decommission / dismantle

• Regulatory caution

Mitigation

• Communication

– Start early (Identification of

requirements)

– Continuous


– Development of knowledge

– Developing organisational

confidence

“They can do this”

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




confidence

“ANSTO can do this”

• Stakeholder management

– Early communication

– Continual information

Challenge 4 – External interest

Challenge

• Pressures from external

interest groups and

stakeholders

– Politicians / government

– ANSTO Board

– IAEA

– Public

– Media

Mitigation

• Communication

– Continuous

– Factual

– Managed




confidence

“ Lets see if ANSTO can do

this”

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

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

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




confidence

“ANSTO can do this”

Challenge 8 – Drawing inaccuracies

Challenge

• 1950’s drawings

– Imperial

measurements

• Uncertainty of as-

built drawings

– Unknown details

• Known inaccuracies

Mitigation

• Expert draughtsman

• 3D CAD drawings produced

• Physical 3D model

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


– Tooling

– PPE

– Shielding

• Contingency planning

– What if?

• Identification & removal of

hottest items

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

Challenge 11 – Contractor

engagement Challenge

• Interfacing

– ANSTO safety procedures

– ANSTO ‘systems’

• Fear of radiation

• Understanding the

decommissioning process

• An Australian first

• Keeping the cost realistic

Mitigation

• Initial contractor evaluation

• Presentation to eligible

contractors

• Detailed Specification

– Responsibilities table detailing

contractor interfaces with

ANSTO

• Final contractor evaluation

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

Challenge 13 – Waste removal and

clearance Challenge

• Waste handling processes

– Waste types

– Quantities

– Handling and transport

– Packaging

• Availability of staff

– Project vs operational needs

• Clearance processes

– Methods & Instrumentation

– location

Mitigation

• 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

Challenge 14 – Records

Challenge

• Preparation (1995 - 2000)

– 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

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

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

Radiation Protection –

Dose results

– Estimated doses vs. actual doses:

Dose ANSTO

Estimated

ARPANSA

Constraint

ANSTO

Constraint Actual

Collective 10,400 person-

μSv

13,000 person-

μSv

10,400 person-

μSv

1,679 person-

μSv

Max.

Individual 1444 μSv 1750 μSv 1500 μSv 252 μSv

Daily - - 50μSv 46μSv (max)

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!

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)

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

Project Achievements

• Extremely powerful visualisation tool

• Aid to contractor understanding

• Enabled good understanding of the tasks ahead

3D Modelling including Physical Model

Project Achievements

• Physical Model

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