NORM in Geothermal Projects for Greenhouse Horticulture (NL) · 2019. 10. 17. · filter bag# 0.24...
Transcript of NORM in Geothermal Projects for Greenhouse Horticulture (NL) · 2019. 10. 17. · filter bag# 0.24...
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NORM in Geothermal Projects for Greenhouse Horticulture (NL)
Gert Jonkers Lonneke van BochoveIndependent Consultant Stralingsupport BV
NORM formation and options for reduction
Gert Jonkers (presenter)&
Lonneke van Bochove
September 2019 1GeJo (TE)NORM
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September 2019 2GeJo (TE)NORM
OUTLINE – Geothermal NORM
1. Setting the Scene – Geothermal Energy
2. Geothermal Greenhouse Heating & NORM – Schematics
3. Implementation of EC Directive 2013/59 Euratom
4. Reducing NORM Production
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September 2019 3GeJo (TE)NORM
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Setting the SceneGeothermal Energy
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September 2019 4
Geothermal Family
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Ground Source Heat Pumps (GSHP)Vertical (or Horizontal) (< 100 m); Limited Power < 100 kWth; 1000’s installed, individual houses
Heat/Cold Storage Aquifer Thermal Energy Storage“Shallow” Aquifers; up to 250 m (T = 5 – 30 °C); Power 0.1 – 10 MWth; ~1000 installed (mainly heating/cooling offices); 1 – 3 M€
‘Deep’ Geothermal Energy (direct use)Doublets (close loop, heat transfer via heat exchangers), Depths from 1000 m (T from 40 °C); ~10 installed 5 – 20 M€
‘Ultra-Deep’ Geothermal Energy Systems (Enhanced Geothermal Systems)/Hot Dry RocksDepths from ~ 3500 m; Temperatures from 100 °C; > 100 M€
Crust
Core
Mantle
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September 2019 5
Energy Consumption & Generationthe Netherlands (2010 data)
GeJo (TE)NORM
the Netherlands consumes 3,500 PJ/year• 38% heating with T > 100 oC, • 30% heating & cooling with T < 100 oC, • 20% transport, and • 12% electricity.
Dutch energy demand generated by combusting fossil fuels. • 9.1% Coal• 37.2% Oil• 47.1% Natural Gasremainder nuclear power and renewables (3.8%)
90% of the total heat demand provided by Natural Gas
costs of products from greenhouse horticulture: 20 to 30% due to energy
(natural gas) consumption
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September 2019 6
Geothermal Heating of Horticulture Greenhouses - Principle
GeJo (TE)NORM
greenhouse heating by fresh water circuit separated from
source water
geothermal heat (80 – 100 °C)transferred from hot
formation water pumped from 2 to 3 km depth
greenhouses
exchanger: transfers heat from formation water to fresh water
no transfer of Naturally Occurring Radionuclide’s (NOR’s)
from source water to fresh water circuit
NOR’s dissolved in source water:
226Ra, 222Rn, 210Pb, 228Ra & 224Ra
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September 2019 7GeJo (TE)NORM
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Geothermal Greenhouse Heating & NORM – Schematics
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September 2019 8
Geothermal Doublet - Wells
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Geochemistry – hot water pumped up (heat insulated well head = producer):➢ hot (T = 80 - 100 oC) brines (Total Dissolved Solids > 35 g/L) in chemical
equilibrium with rock forming minerals, so many elements (as cations notably [Pb2+], anions) are present, incl. NOR’s.Also low Z elements present as complex anions (e.g. HCO3-), but virtually no SO42-.
➢ Starting a new well as soon as possible after drilling co-produced reservoirmaterial shows 11 Bq[210Pb]/g[‘sand’]
Processing (next slides)
Geochemistry – cooled water going down (non-insulated well head = injector):➢ cool (T = 20 - 30 oC) brines with some
diminished elemental concentrations (due to processing)
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September 2019 9
Processing of Geothermal Waters – Gas Separation
GeJo (TE)NORM
Process chemistry - gas removal, change in pressure, temperature• dry CO2 is not corrosive, but CO2 in combination with water creates an acidic
environment > corrosion of iron pipe work > pH decreases to ~ 5.5• at the iron/liquid interface, an anodic reaction may oxidise Fe according
Fe(s) + CO2 + H20 -> Fe2+ + 2HCO3
- + H2• P and/or T changes will change solubility product of scale forming minerals –
suspended/deposited particles (baryte BaSO4, galena PbS, laurionite Pb(OH)Cl)
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Geothermal Installation – NORM (1)Scale Formation by (super)saturation
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• Group II cations (Mg2+, Ca2+, Sr2+, Ba2+ and Ra2+) present in source water, but in low concentrations
• Complex anions (CO32-, SO4
2-) present in source water, but in (very) low concentrations
so,➢ NO (super)saturation by exceeding solubility product of group II
carbonate or sulphate salts (“scale”)➢ NO inclusion of Ra2+ ions in the ionic lattice of group II
carbonate or sulphate salts (“radioactive scale”)
baryte scaling
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Geothermal Installation – NORM (2)Formation of Suspended Particles by Electro-Chemical Reaction
GeJo (TE)NORM
Pb2+-ions - present in source water (ppm) - are able to oxidize metallic Fe via a so-called electro-chemical supersession reaction; more noble metal (Pb) is deposited and lesser noble metal (Fe) is dissolved according to Fe(s) + Pb2+ → Pb(s) + Fe2+
➢ small Pb particles (incl. 210Pb) entrained/suspended in aqueous flow
bore
plan viewcross section
flo
wdi
rect
ion
pitting corrosion
O ringscales
bore
Iron (cast)Welding seamSteel pipe (drawn)
O ringdeposits
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hot brines (T = 80 - 100 oC) may contain suspended reservoir particles if brine comes into contact with iron (Fe) lead (Pb) micro-particles may be formed, that become entrained in the aqueous brine flow (previous slide)coarse filtering – bag filter unit fine filtering – candle filter unit
loadingcleanbags
dirtyfilter unit folded
paperremoved filterdirty removedbags
Pbstab contaminated by 210Pb no contamination by NOR’sSeptember 2019 12
Processing of Geothermal Waters – Suspended Solids
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September 2019 13
Geothermal Water - Heat Exchangers
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photographstop: heat exchangers in operationbottom left: dismantled plates source water sidebottom right: dismantled plates fresh water side
• corrugated plates diverting flow directions with separated hot source water (brine) flow and fresh water (heat transfer to greenhouses) flow compartment
• brownish colour of hot water side due to the applied corrosion inhibitor
• dark brown spots (salt crystals) due to drying of plates after dismantling
• blackish colour of the fresh water flow side due to applied (other) corrosion inhibitor
• no enhanced contamination c.q. radiation levels detected on the dismantled plates
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September 2019 14
Typical NOR concentrations found in Geothermal Facilities
GeJo (TE)NORM
Materiaal 226RaeqBq/g
210PbeqBq/g
228RaeqBq/g
228TheqBq/g
tubing deposits 4* 1600 1.9* 1.6*
filter bag# 0.24* 2350 0.08* 0.04
Filter deposits 0.8* 50 0.06* 0.06*
* MDA = Minimal Detectable Activity# including filter material
Red Highest value found in the NetherlandsGreen Average value (range 15 to 1000 Bq/gr)
N.B. subscript eq denotes: relevant subseries is in secular (226Raeq, 210Pbeq, 228Raeq, 228Theq) or transient (228Theq) equilibrium with their short-lived (t½ < 1 week) daughters
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September 2019 15GeJo (TE)NORM
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Implementation of EC Directive 2013/59 Euratom
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1. Exorbitant Rise in Filter Bag Disposal Costs
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< February 6, 2018 (Directive 96/29 Euratom)Disposed of by 3 distinct companies:Activity Concentration 300 – 900 Bq[210Pb]/g Amount 9 000 kgDisposal costs € 1 500 per tonneTotal costs € 13 500
> February 6, 2018 (Directive 2013/59 Euratom)Disposed of by 12 distinct companies: Activity Concentration 1 – 10 Bq[210Pb]/g Amount 6 700 kgDisposal costs € 1 500 per tonne Activity Concentration > 10 Bq[210Pb]/g Amount 28 500 kgDisposal costs € 2 000 per 60 kgTotal costs € 960 000
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2. Radiological Risks Pbstab/210Pbeq Deposits (1)
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The Dutch Association of Geothermal Operators (DAGO) had a study carried out into the radiological risks of lead(Pbstab/
210Pb) deposits for workers, public and environment in a “from cradle to grave” (cf. EC Radiation Protection 122 part 2)
Scenario’s included:- all work in the drilling/mining phase• maintenance (filter exchange, any work on flow lines & heat exchangers)• well intervention
- waste handling within different waste companies • vacuum distillation • bulk / pyrolysis• incineration • decontamination• landfill
Pbstab/210Pbeq denotes a deposit of stable Pb-isotopes contaminated by 210Pb radionuclides in secular equilibrium with 210Bi and 210Po
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September 2019 18
2. Radiological Risks Pbstab/210Pbeq Deposits (2)
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Results➢ specific exemption for 210Pbeq up to 100 Bq/g is an option
• all handlings with 210Pbeq contaminated material are justified• handlings intrinsically safe even in case one is unaware of the
presence of 210Pbeq• radiological risks are very low:
- occupational dose to all workers less than 50 µSv/annum- public dose less than 10 µSv/annum
• optimisation due to DAGO / NOGEPA standard operational procedures and waste regulation
• ADR (implementation of the IAEA Regulations for the Safe Transport of Radioactive Material) is not applicable
NOGEPA = Dutch Oil & Gas Exploration and Production Association
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September 2019 19
Effects of Implementing More Stringent Exemption Levels
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pre-2018 100 Bq[210Pbeq]/g[material] (Directive 96/29 Euratom EC RP 122b)2018 1 Bq[210Pbeq]/g[material] (Directive 2013/59 Euratom)
1. Increasing Costsa) Every operator needs to apply for a licenceb) Supervision needed always (additional workers to be trained as RPS)c) Almost all waste “radioactive”d) Disposal routes very limited and expensive
2. Low dose/risk for 210Pb below 100 Bq[210Pbeq]/g[lead] remains
3. EL cannot efficiently be measured on-site with a contamination monitorDetermining the risk of exceeding limit not possible in a direct wayDispersion into the environment not detectableAll waste must be analysed prior to disposalWorkers get confused about actual risk
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Reducing NORM Production
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Limiting Options for Electro-Chemical Reactions (1)
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Injection of corrosion inhibitor
inhibitor molecules adsorb (with their reactive side) on reactive sites of tubulars, flow lines and/or installation parts, by which the reactive sites become blocked.➢ electrochemical exchange Fe > Pb prevented➢ protection against oxidation of the inner
walls of the installation
before 2000 Bq[210Pbeq]/g[deposit] 2000 kg/aafter 1000 Bq[210Pbeq]/g[deposit] 250 kg/a
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September 2019 22
Limiting Options for Electro-Chemical Reactions (2a)
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Carbon steel pipework and installation parts as far as possible replaced by materials not eligible for electro-chemical supersession of Fe and Pb: - GRE (Glass Fibre Reinforced Epoxy)- Stainless steel (AISI 316)- Polypropylene
Tubulars (vertical pipes) may be coated with ‘polymer’
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September 2019 23
Limiting Options for Electro-Chemical Reactions (2b)
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View inside GRE tube after one year of service NO inner surface contamination detected
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September 2019 24
Conclusions
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• Geothermal operations in the Netherlands (2018) generate about 30 tonnes of NORM waste, mainly in the form of 210Pbeq contaminated filter bags
• The implementation of the generic exemption level for 210Pb leads to exorbitant costs for sustainable, but marginal geothermal operations
• Though a graded approach is advertised by the competent authority, despite the very low radiological risk of 210Pb in practice specific exemption seems yet to be unmanageable
• Geothermal operators work on options to reduce NORM generation
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September 2019 25
Acknowledgements
GeJo (TE)NORM
Lonneke van Bochove
Radboud Vorage
Wart van Zonneveld
mailto:[email protected]
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September 2019 GeJo (TE)NORM 26
Q&A
Thank You
[email protected] +31 6 45576045
mailto:[email protected]