HIFAR Dismantling Methodologies

Algis Lencus

R2D2P Conference - Australia

Contents

• Experience and planning by other organisations

• Possible methodology for HIFAR

• Issues that will drive a preferred methodology

Methodology

• Reactor details (drawings, knowledge)

– Composition (materials and makeup)

– Characterisation

• Available (& best practice) technology for the

various tasks

• Build a methodology or better… give yourself

options

Experience and Planning By Others

• Other “DIDO” Reactors

– Scotland: Dounreay – shutdown 1969

– England: DIDO & Pluto – shutdown 1990

– Denmark: DR-3 – shutdown 2000

– Germany: FRJ-2 – shutdown 2006

– Australia: HIFAR – shutdown 2007

DIDO-class Reactors

• Similar composition

across all reactors

• Key source of

radioactivity is cobalt

60 in the top shield

plug

DIDO & PLUTO: Methodology

• Immediate transition to “Care and

Maintenance”:

1. De-fuel core and drain circuits

2. Removal of external facilities & buildings

3. Removal of peripheral systems

4. Care & Maintenance mode until

decommissioning (funding & ILW repository)

DIDO & PLUTO: Care & Maintenance

• Before:

DIDO & PLUTO: Care & Maintenance

• Before & After:

DIDO & PLUTO: Objectives

• Minimise

– Minimise hazards

• Minimise contamination & fire risk

– Minimise maintenance & cost

• Remove redundant plant

• Refurbish remaining required plant

DIDO & PLUTO: Methods (non radiological)

• External uncontaminated and unactivated

systems removed using standard demolition

techniques after clearance.

• Attention paid to asbestos and other non-

radiological hazardous materials

DIDO & PLUTO – Secondary Cooling

DIDO & PLUTO - Peripheral Dismantling

• Pipework generally cut or unbolted

• Uncontaminated/unactivated steel

cut up with oxy-acetylene cutting

gear

• Experimental rigs: pipework

housed contaminants. Shearing &

crimping tool used to size reduce

and hold contaminants within &

store in 200L drums

DIDO & PLUTO: Methods

• Plasma cutting equipment used to

cut thicker steel material

– Operators in air hoods & heat

resistant clothing

– Local extract system (filter

changes)

– Others in the building to wear dust

masks

• Airhoods used (tritium)

DIDO & PLUTO: Systems

• Electrical cable strip out driven by:

– Clear areas with contamination

– Reduce fire load

– Use staff knowledge while available

– Only circuit continuously energised within the

building is the fire detection circuit

• Compressed air system kept in a modified

state to assist with decommissioning

DIDO & PLUTO: Methods

• Beam instruments removed

DIDO & PLUTO – Peripheral Buildings

• Marking and scabbling of contaminants

DIDO & PLUTO – Peripheral Buildings

• Final contamination checks & demolish!

DIDO & PLUTO: Methods

• Most of the decommissioning work carried out

using standard engineering techniques

• Use of the simplest available techniques

– Unbolting; sawing/cutting

– Plasma and Oxy-acetylene cutting

– Chipper and pipe shearing

– Basic decontamination methods

DIDO & PLUTO: Decontamination

• Decontamination effort was balanced against

dose received whilst decontaminating

• Little decontamination was performed

DIDO & PLUTO – Waste Management

• Part of the reactor facility included a shielded

room with extract which was utilised as an

active cutting room

DIDO & PLUTO – Waste Management

• Half-height ISO containers used where items

are too large to fit in 200L drums (where not

practical)

DIDO & PLUTO: Waste Management

• 200L drums had a 200kg weight limit (10kg

limit on individual items within)

• Half-height ISO had 25t weight limit (42t after

grouting) – weight limit was quickly reached

due to density of individual items

• Clearance Log sign off on contents in near the

Active Handling Bay

DIDO & PLUTO: Lessons Learnt

• Active waste accumulated

relatively fast, resulting in

congestion and high dose rate

• Resourcing in this area was

revised to ensure appropriate

throughput and reduced dose

rate

FRJ-2 and DR-3

• Similar route to

DIDO & PLUTO

FRJ-2 and DR-3

• Removal of peripheral systems and

refurbishment of required systems

• Picking of “low hanging fruit”

FRJ-2 & DR-3

• Unload core

• Drain circuits (dry circuits where possible)

• Removal of experimental facilities

• Removal of external process circuits and plant

DR-3

• Removal of peripheral systems

FRJ-2

• Cleared out the D2O Plantroom

• Removal of beam tubes

FRJ-2

• Removal of beam instruments

FRJ-2 & DR-3: Block dismantling

• Key problem is how to remove

the top shield plug?

FRJ-2 & DR-3: Block dismantling

• Scaffold and elevator

arrangement and work

platform installed

• Plug is lifted with the

assistance of hydraulic

jacks

FRJ-2 & DR-3: Block dismantling

• Cut RAT

• Removal of top shield rings

• Remove graphite

• Cut steel tank

FRJ-2 & DR-3: Block dismantling

• Break up bioshield

FRJ-2 & DR-3: Planning, Planning

• Mockups to be used to plan and

prepare

• Characterisation to plan and prepare

– Determine waste quantities

• Determine packaging and storage

requirements

– Determine dose rate

• Determine methodology, equipment

and monitoring requirements

FRJ-2 & DR-3: Methods

• Heavy movement by crane and

hydraulic jacks

• Remote cutting tools fixed to top

to cut tank

• Long reach manipulator fixed to

top to remove graphite blocks

• Possibly fill core with water to aid

with shielding

Dismantling Tools

• Concrete dismantling:

– Drilling; core drilling; sawing; jack hammering,

shearing; grinding; water jet cutting; abrasive jet

cutting

• Metal structure/component dismantling:

– Thermal: flame; plasma; arc; laser

– Remove bolted connections

Decontamination Methods

• Wiping, brushing

• Ultrasound

• High pressure water or steam cleaning

• Blasting with an abrasive (sand, steel etc)

• Chiselling, grinding

• Peeling/scraping

• Chemical

FRJ-2: Methods

• Reversible dismantling of the D2O

Plantroom

HIFAR Methodology

• Decommissioning driven by safety, cost, and

use of local knowledge

• First step is planning, characterisation and

awareness of decommissioning techniques

– Dose projection – determine dose limits and

methodology

– Waste estimates – determine packaging and

storage requirements

HIFAR Methodology

• Obtain a staged decommissioning licence and

EIS

• Stage 1: remove peripheral equipment

– Create space for future decommissioning

– Relatively low risk work (dose and waste)

– Serves as proving of techniques

• Stage 2: block dismantling

HIFAR Methodology

• General methodology is to remove most

hazardous accessible items first to create a

safer working environment for the remaining

work

HIFAR Methodology

• Remove top shield plug

– Diamond wire sawing

• Cut reactor aluminium tank

– Remote cutting tool

• Remove top shield rings

– Diamond wire sawing

HIFAR Methodology

• Remove graphite blocks

• Cut up and remove steel tank

HIFAR Methodology

• Cut up bioshield

– Diamond wire sawing (these can now be

bought from China for less than $20,000!)

Know your tools

• Remote/long reach manipulators

• Suppliers include:

– Kraft

– SA Technology

– OC Robotics

Know your tools

• Remote/long reach manipulators

Know your tools

• Tools suited to nuclear

decommissioning don’t need to

be complex (the simpler the

better!)

• Industries that have “off-the

shelf” equipment:

– Demolition

– Off-shore oil & gas

– Bomb defusers

– Quarrying & mining

– Factory automation

– General consumer

Know your tools

• Use proven commercial off-the-shelf equipment

that are cheaper and more reliable than

bespoke designs

• Don’t reinvent the wheel

• Several standard

cameras are cheaper

than a radiation-

hardened one

Know your tools

• Techniques reviewed for each task type and

materials

• For example:

– Chemical decontamination is more effective than

mechanical methods for internal pipework

– Plasma cutting more effective than

jackhammering for steelwork

– Diamond wire saw better than plasma cutting for

concrete

Know your tools

• Know the disadvantages for each method:

– Some may create liquid or airborne

contamination

– Is it reliable?

– Is it expensive?

– Are there safety risks?

It is all in the delivery…

• Finally – remember that a well executed poor

plan can be better than a poorly executed

good plan

Learn from Lessons Learnt

• You are decommissioning not de-constructing

• Don’t unbolt when cutting will do

• Plan for waste storage and processing

• Allow time for regulatory approval or structure

submissions so that work can proceed in parallel

Thank you

• Wait for the videos…

• Any questions?