RWE NUKEM

The Design, Construction and Operation of NORM Descaling Plants

E Taylor and L Fellingham

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Structure of the Presentation

Background to the Problem of NORM Contamination

Potential Solutions

De-scaling Techniques

Design of Plants

Examples of Operational Plant

Safety Assessment

Waste Management

Concepts for Next Generation Plant

Conclusions

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Nature of the Problem

Around the world there are significant arisings of NORM-contaminated plant being generated by the oil & gas industry

Much of this is stored in open yards

There is a potential contamination threat to workers and a long-term environmental liability

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NORM-contaminated Equipment

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Required Solution

Manage NORM wastes in accordance with best international practice

Reduce the volume of NORM-contaminated waste arisings

Concentrate the radioactivity into the minimum practical volume

Store the concentrated activity safely

Reuse or recycle as much of the contaminated equipment, etc, as possible.

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RWE NUKEM’s Experience of providing Solutions

Design, construction and initial operation of the Al-Furat Petroleum Company (AFPC) facility in Syria

Design, construction and operation of the NORM facility at the Dounreay site serving the North Sea oilfields (now closed)

Design, construction and operation of a modular facility at the Winfrith site to meet the requirements of the Wytch Farm oilfield operated by BP

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The Facilities

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Techniques evaluated for removing Scale and Sludge from contaminated Equipment Proprietary and developmental stage, chemical descaling

methods

Various forms of particle blasting using sand, ballotini, metal shot, solid CO2, etc;

Abrasion techniques using wire and other forms of brushes; and

High pressure jetting techniques, using water and other process fluids.

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High Pressure Water Jetting – The Optimum Choice for Descaling It is very efficient at scale removal, irrespective of the chemical and mineral

form of the scale;

The water is capable of penetrating into narrow crevices, cracks, corrosion pits, etc, and removing scale and other adhering deposits. Hence residual contamination levels are very low and high decontamination factors are achieved;

The speed of processing is higher than with any alternatives, so reducing the necessary size of any plant;

It does minimal damage to the metal surface of the components, etc, being descaled;

The process makes use of the very low solubility of the scale and particularly the radium salts. The scale and radioactive contaminants are not solubilised. Hence the process water treatment is very simple involving only filtration and no chemical treatment;

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High Pressure Water Jetting – The Optimum Choice for Descaling (2)

The process water is recycled after filtration, so enabling the minimum volume of water to be used and generating no or a minimal volume of liquid effluent;

The scale can be encapsulated or re-injected with the minimum of treatment.

It is compatible with hydraulic cements, making it ideal for encapsulation directly or after maceration.

It can be disposed of after maceration and slurrying by reinjection into appropriate geological formations, including those exhausted of oil and gas.

Left in the chemical form in which it was originally deposited, the very low solubility of the scale in aqueous environments makes it an ideal waste form for long-term storage and disposal in both near surface and geological formations.

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Deployment of High Pressure Water Jetting

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Safety Assessment of NORM Descaling Facilities

Calculation of radiological doses due to routine decontamination operations for operators of the plant and an assessment for the general public.

Determination of the radiological risk to both operators and the public from potential accidents arising from fault conditions.

A bounding credible accident scenario, which would demonstrate that “worst case” scenarios result in negligible dose uptake by members of the workforce and general public in the surrounding areas.

A review of industrial hazards

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Main Hazards assessed in Safety Assessment

Radiological Hazards Non-Radiological Hazards

(i) Loss of sludge settling tank containment.

(i)

Fire.

(ii) The dropping of a bundle of received "dirty" tubulars within NDF and Waste Store

(ii)

Handling of heavy components.

(iii) Failures of the ventilation system. (iii)

Noise.

(iv) Loss of containment (iv) Burns

(v) High Pressure Jets

(vi) Legionella

(vii) Slips, trips and falls

(viii) Fume emission from oxy-propane cutting

(ix) Loss of breathing air

(x) External events

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Typical Results of Radiological Safety Assessments

Fault Dose to Operator

(Sv)

Dose to Public (Sv)

Minor Tank Failure 13.5 Negligible

Major Tank Failure Negligible Negligible

Dropping of a Bundle of Tubulars

Negligible Negligible

Ventilation System Fan Failure

7.5 Negligible

Ventilation System HEPA Filter Failure

- Negligible

Dropped Drum 0.34 Negligible

Aircraft Crash - 1.36

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Design Concept for Plants

A high proportion of the equipment to be descaled is in the form of tubulars with a much smaller proportion in the form of valves, Christmas trees, heaters, treaters, separators, pumps, meters, dehydrators, salt water tanks, etc.

The tubulars are uniform geometry items, differing only in length and diameter.

The other equipment comes in a very diverse range of shapes and sizes, making process automation much more difficult without complex equipment.

Treat these as two distinct streams. In order to achieve high throughputs and to process the much higher quantities, use a semi-automated approach for tubular de-scaling where possible.

Use manual descaling with dismantlement and potentially cutting to expose internal surfaces for other equipment.

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Examples of Plant Design

NORM facility at Dounreay

Al-Furat Petroleum Company (AFPC) NORM facility in Syria

The modular NORM Decontamination Facility at Winfrith operated for BP

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The NORM Descaling Plant at Dounreay

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Tubular Monitoring in the NORM Descaling Plant at Dounreay

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Equipment Descaling in the NORM Descaling Plant at Dounreay

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A View of the Front of the Al-Furat Petroleum Company (AFPC) facility in Syria

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The Burning Bay/Stripdown Area

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Tubular Descaling Unit in the NDF Plant

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The Liquid Effluent Settling Tanks in the NDF

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The Winfrith NORM Decontamination Facility

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The Winfrith NORM Descaling PlantTubular Receipt Area

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The Winfrith NORM Descaling PlantTubular Descaling Area

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The Winfrith NORM Descaling PlantSkid Mounted Pump and Extract System

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The Management of the Residual Radioactive Waste

Options

– Storage on-site

– Use of National Repository Facilities

– Dedicated long term safe storage

– Re-injection

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View of the Interior of a Dedicated Waste Store

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NORM Descaling Plants – The Next Generation

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Modular Descaling Facility using ModuCon Units – Fixed Unit (1)

Gridded Area for Descaling Operations within ModuCon(double skin with flat roof on lined bund & sump). Active area under Depression

UHPWJ Re-circulation& waste handling Unitwith lined bund anddivided into active/cleanareas

‘Clean’ Receipt/Despatch Area, via insulated double doors, leadingto active dismantling area, serviced with lifting equipment

ModuCon Entry/BarrierUnit with decon,wash/shower pluschange/monitor facilities

Flow OUT via HEPAExtract Plant withSafe Change filters

Flow IN via AirConditioning units

Clean Service Unit(air/electric generators).

4 ISOs lined/barrieredwith ModuCon forinsulation and eas ofdecontamination

All ISO doors Open Normally

(Closed in Storm)

ModuCon Barrier/Tunnel

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Modular Descaling Facility using ModuCon Units – Fixed Unit (2)

ModuCon Entry/BarrierUnit with wash & shower+ change/monitor facilities

UHPWJ Re-circulation & wastehandling Unit(s)housed in linedISO(s)

Assembly installed on lined hardstand (bund & sump)

ModuCon Receipt/Despatch Area via insulated double doors serviced with lifting ‘I’ Beam on ‘A’frame. Double skin for insulation and flat transparent roof for natural lighting

Gridded Area behind for Descaling Operations - Active area under Depression

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Modular Descaling Facility using ModuCon Units – Field Transportable Unit (1)

Active Vessel under Depression

UHPWJ Re-circulation& waste handling Unitwith lined bund anddivided into active/cleanareas

ModuCon Entry/BarrierUnit with decon,wash/shower pluschange/monitor facilities

Flow IN via AirConditioning units

Clean Service Unit(air/electric generators).

4 ISOs lined/barrieredwith ModuCon forinsulation and eas ofdecontamination

All ISO doors Open Normally

(Closed in Storm)

Chiller SkidModuCon Barrier/Tunnel

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Modular Descaling Facility using ModuCon Units – Field Transportable Unit (2)

ModuCon Entry/BarrierUnit with wash & shower+ change/monitor facilities

UHPWJ Re-circulation & wastehandling Unit(s)housed in linedISO(s)

Active vessel under Depression

ModuCon Barrier/Tunnel

Ventilation Extractto VentilationModule

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Conclusions

There is now considerable design and operational experience of NORM de-scaling plants

Techniques for de-scaling have also been extensively developed

Waste management is an ongoing issue

New designs of plant using modular approaches could be more cost effective.