The Design, Construction and Operation of NORM Descaling Plants

1
The Design, Construction and Operation of NORM
Descaling Plants

• E Taylor and L Fellingham

2
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

3
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

4
NORM-contaminated Equipment
5
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.

6
RWE NUKEMs 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

7
The Facilities
8
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.

9
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

10
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.

11
Deployment of High Pressure Water Jetting
12
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

13
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
14
Typical Results of Radiological Safety Assessments
Fault Dose to Operator (mSv) Dose to Public (mSv)
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
15
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.

16
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

17
The NORM Descaling Plant at Dounreay
18
Tubular Monitoring in the NORM Descaling Plant at
Dounreay
19
Equipment Descaling in the NORM Descaling Plant
at Dounreay
20
A View of the Front of the Al-Furat Petroleum
Company (AFPC) facility in Syria
21
The Burning Bay/Stripdown Area
22
Tubular Descaling Unit in the NDF Plant
23
The Liquid Effluent Settling Tanks in the NDF
24
The Winfrith NORM Decontamination Facility
25
The Winfrith NORM Descaling PlantTubular Receipt
Area
26
The Winfrith NORM Descaling PlantTubular
Descaling Area
27
The Winfrith NORM Descaling PlantSkid Mounted
Pump and Extract System
28
The Management of the Residual Radioactive Waste

• Options
• Storage on-site
• Use of National Repository Facilities
• Dedicated long term safe storage
• Re-injection

29
View of the Interior of a Dedicated Waste Store
30
NORM Descaling Plants The Next Generation
31
Modular Descaling Facility using ModuCon Units
Fixed Unit (1)
32
Modular Descaling Facility using ModuCon Units
Fixed Unit (2)
33
Modular Descaling Facility using ModuCon Units
Field Transportable Unit (1)
34
Modular Descaling Facility using ModuCon Units
Field Transportable Unit (2)
35
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.