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

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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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Setting the SceneGeothermal Energy

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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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Energy Consumption & Generationthe Netherlands (2010 data)

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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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Geothermal Heating of Horticulture Greenhouses - Principle

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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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Geothermal Greenhouse Heating & NORM – Schematics

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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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Processing of Geothermal Waters – Gas Separation

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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

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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

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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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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Typical NOR concentrations found in Geothermal Facilities

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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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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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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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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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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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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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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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Acknowledgements

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Lonneke van Bochove

Radboud Vorage

Wart van Zonneveld

mailto:lonneke@stralingsupport.nl

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Q&A

Thank You

G.Jonkers5@UPCmail.nlTel +31 6 45576045

mailto:G.Jonkers5@UPCmail.nl