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HAL Id: ineris-00976221

https://hal-ineris.archives-ouvertes.fr/ineris-00976221

Submitted on 9 Apr 2014

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evolution of the French radioprotection legislation

Stéphane Lafortune, Jean-Claude Pinte

To cite this version:

Stéphane Lafortune, Jean-Claude Pinte. NORM in the petroleum and geothermal industries : evo- lution of the French radioprotection legislation. 3. European IRPA Congress, Jun 2010, Helsinki, Finland. �ineris-00976221�

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NORM in the petroleum and geothermal industries:

evolution of the French radioprotection legislation

LAFORTUNE, Stéphane; PINTE, Jean-Claude

Institut National de l'Environnement Industriel et des Risques / French National Institute for Industrial Environment and Risks (INERIS)

Parc Technologique ALATA - BP 2 60 550 Verneuil-en-Halatte

FRANCE

e-mail: stephane.lafortune@ineris.fr phone: +33 (0)3 44 55 67 91

Abstract

Fluids produced from oil or gasfields and aquifers are naturally radioactive due to the presence of potassium-40 and isotopes from decay chains of uranium-238 and thorium- 232 in these reservoirs. Thus, natural radionuclides can be carried away towards surface when petroleum or geothermal reservoirs are drilled and produced. These radionuclides can precipitate in deposits forming in process equipment, which can then be unusually radioactive, expose workers to hazardous materials and create waste disposal problems.

Workers can also be exposed to high concentrations of radon. Due to their natural origin, these accumulations of radionuclides in equipment are called Naturally Occurring Radioactive Materials (NORM). They are also known as TENORM, because they are "technologically enhanced".

In closed systems, exposition to gamma radiations penetrating equipment to the external surface can be reduced by restricting and controlling access to appropriate areas. But personnel may come into direct contact with NORM during maintenance and cleaning operations, when opening equipment and vessels.

In France, hygiene and safety rules concerning the protection of workers in the petroleum and geothermal industries are formulated in a specific regulation related to extraction and mining. Presently, both petroleum and geothermal industries are not included in the list of activities which have to follow radiation protection measures concerning exposition to NORM. French authorities are currently planning to update the list by including these two activities. There is a real need to realize a state-of-the art of the exposition level of workers and to standardize the dose limits with those given by the French Labour and Public Health Codes.

This paper will present the origin of NORM and radon contamination in the petroleum and geothermal industries and discuss the French legislation evolution for the radiation protection of personnel working in these two industries.

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containing radionuclides (or radioactive materials) from natural sources (Californian DHS 1996).

NORM can be found in underground oil and gas reservoirs or aquifers. They are present in rocks as uranium-238 ( U), thorium-232 ( Th), potassium-40 ( K) and their radioactive progeny.

Whereas potassium-40 has only two stable daughter isotopes: calcium-40 (40Ca) and argon-40 (40Ar), uranium-238 and thorium-232 have longer decay chains before reaching final stable isotopes: lead-206 (206Pb) and lead-208 (208Pb) respectively. The main decay chains of uranium-23 8 and thorium-232 are shown on the figure below (see fig. 1).

238|j

4.5 E+09 y

a 234T h

24.1 d

234Pa 1.2 mn

V

Found in oil and gas production

facilities

234J

2.4E+05y

y

a

230T h 7.5 E+04y

a

2 2 6Ra

1.6 E+03 y

a

2 2 2Rn

3.8 d

a 218P o

3.1 mn

a 214P b

26.8 mn

URANIUM

PROACTINIUM

THORIUM

RADIUM

RADON

2 1 4Bi

19.9 mn

y

214P o 1.6E-O4S

V

a

210P b 22.3 y

210Bi 5.0 d

y

THORIUM

ACTINIUM

RADIUM

210Po 138.4d

y

2 3 2T h

1.4E+10y

a

2 2 8Ra

5.8 y

POLONIUM

a BISMUTH

206P b STABLE

LEAD

2 2 8Ac

6.1 h

y

RADON

POLONIUM

BISMUTH

LEAD

THALLIUM

228T n 1.9 y

y

a

2 2 4Ra

3.7 d

a

2 2 0Rn

55.6 s

a 216Po

0.2 s

a 212R b

10.6 h

2 1 2Bi

60.1 mn

V

a

208T l 3.1 mn

212Ro 3.1 E-07s

y

a

208R b STABLE

y

Fig. 1. Decay chains of uranium-238 (left-hand) and thorium-232 (right-hand). Half-life times are given in years, days, hours, minutes or seconds. Mother isotopes are shown by a red background, daughter radioactive isotopes by a blue background and daughter stable isotopes by a white background. Red frames show the main radionuclides present in NORM and found in oil and gas production facilities.

If the less soluble isotopes, such as uranium and thorium, remain bound to the rock matrix, soluble and gaseous elements produced by radioactive decays can accumulate in fluid phases and migrate out of the reservoir (Paschoa 2009).

Thus, NORM can be found in different phases. As for radon (Rn), they can be in gaseous phase. They can also be dissolved in fluids (oil, water) and reprecipitate as carbonates and sulphates of calcium, barium and strontium... if there is any change in temperature or pressure conditions of the fluid phase.

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NORM in the petroleum and geothermal industries

A technologically enhanced occurrence

In oil and gas fields or in the geothermal industry, NORM may occur as radioactive materials that have been concentrated through production processes. Thus, some people also call them TENORM because they are "technologically enhanced". Concentration processes are different and depend on the nature of the radionuclide.

Depending its solubility and its ability to precipitate as a mineral phase, a radionuclide can (1) stay trapped in the rock matrix within the reservoir, (2) precipitate along the pipes of the industrial installations, (3) be present in residues or (4) in produced fluids (oil, gas, water) (Gray 1993; SNIFFER 2005).

During extraction processes, produced fluids are submitted to temperature and pressure changes: equilibrium with reservoir conditions is no more ensured and deposits can precipitate onto the internal surface of pipes or as particulates which will be accumulated in residues and sludges. These deposits can contain radionuclides and be considered as NORM (Betts and Wright 2004).

Considering the half-life times of the different radionuclides from uranium-238 and thorium-232 decay chains, radium (224Ra, 226Ra and 228Ra), radon (220Rn and 222Rn), lead-210 and polonium-210 are the main radionuclides that could be found in oilfield, gasfield and geothermal facilities.

Fig. 2 draws the list of possible NORM occurrences in these industrial facilities.

Gas: 222Rn

Condensate: 222Rn, particulate scale Oil: particulate scale, 222Rn

°- Produced water: 226Ra, 228Ra, 210Pb, 222Rn

Upper surrounding formations

Cap rock

Reservoir

rock

J

^ Plating out of 222Rn daughters: 210Pb and 210Po

^ + Co-precipitation of Ra isotopes with Ba2+, Sr2+ and Ca2+

B 222Rn migrates with gas and condensate

— 22SRa, 226Ra, 224Ra, 222Rn „„••"""' dissolved in produced water

Additional unsupported 210Pb2* ( \ from 222Rn decay transported in solution v_-/ — WELL

Rock: 238U and 232Th remain bound to the rock matrix

Fluid phases: 238U and 232Th daughters transported with the different fluid phases

Fig. 2. Schematic cross section of an oil/gas reservoir or an aquifer with migration pathways and phases of the main radionuclides which can induce occurrences of NORM accumulations in petroleum and geothermal industrial facilities.

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problem to operating and cleaning personnel. The radioactive decay of radionuclides from chains of uranium-238 and thorium-232 takes place by emission of either alpha or beta particles and by the emission of gamma rays. Exposition to these ionising radiations can cause damage to the body tissues.

Whereas alpha particles are stopped after a penetration of about 50 micrometers in a human tissue, and beta particles go no further than 1 centimeter, gamma rays are highly penetrating. One must be aware that even if they do not penetrate far the human body, alpha particles are particularly hazardous when they are inhaled or ingested, because the energy released by the radioactive decay is expended over a very short distance (Reed et al. 1991).

Personnel working near closed systems where NORM accumulations occur could then be exposed to gamma rays. For personnel working near open systems or opening closed systems for cleaning operations, the risk of direct contact with radioactive materials by inhalation of gaseous NORM and ingestion of solid NORM is real (Gray

1993; Reed et al. 1991; Takhautdinov et al. 1996).

NORM issues have been well studied in different states of the USA or in countries as Canada, Norway, United Kingdom and by other oil-producing countries.

Several studies have been performed and have permitted to detect equipments where NORM accumulations can preferentially occur (see fig. 3 and 4) (Gray 1993).

Valves and Production Manifolds

Gas Scrubber Knockout

System

Downhole Safety

Valve

Separators Flotation

Deshydrators

Seawater / Produced Water Dump

Seawater intake

Oil

Shipment

System

Export Lines

o

Water Injection

System

NORM

Production Well Rn or Po

Fig. 3. Simplified design of an offshore oil production unit. Equipments where NORM accumulations are mainly found are shown by red frames. Equipments where radon or polonium are mainly found are shown by a red background (Reed et al. 1991).

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Gas into terminal

Slug Catcher / Separator

O

Compressor

Gas Separator

Gas

Separator

0 0

Fractionated Gases and LPG Fuel Gas

Separator

O

Polonium Traitment

Unit

Condensate storage

i—\

L-|/ Condensateexport

Separator

c>

MethanoLRecovery MethanolStorage / For Re-injection Water discharge

NORM

Water discharge Rn or Po

Fig. 4. Simplified design of an onshore gas terminal. Equipments where NORM accumulations are mainly found are shown by red frames. Equipments where radon or polonium are mainly found are shown by a red background (Reed et al. 1991).

Taking into account experts' conclusions and experience feedbacks, stakeholders have to define hygiene and safety rules concerning the radiation protection of workers that are appropriate to risks incurred by the personnel of the petroleum and geothermal industries.

French regulation for radiation protection of workers

Dose limits and categories of workers

In France, hygiene and safety rules concerning the protection of workers are formulated in the Labour Code.

But, hygiene and safety rules specific to extractive and mining industries (including petroleum and geothermal industries) are an exception and are formulated in a dedicated regulation called Règlement Général des Industries Extractives (RGIE or

"French specific regulation related to extractive and mining industries").

Concerning radiation protection aspects, the two legislative texts divide workers in three categories referring the level of exposition that they can encounter: "A category" workers, "B category" workers and other workers who do not belong to one of the two previous categories.

Each category is defined by specific levels of exposition: the classification of a worker in one category depends on the "effective dose" and/or the "equivalent dose"

(see glossary for definitions) received by this worker.

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category" workers.

Each category also implies specific constraints for the employers concerning risks prevention in terms of information, formation, medical care of their employees...

Dose limits given by the two texts to define the categories of workers are different. The dose limits defining categories of workers in the French Labour Code are below the values given by RGIE. A standardization is currently under study. The limit values are given in the two tables below (see tables 1 and 2).

Table 1. Dose limits for each category of workers defining by the French Labour Code.

All workers A category workers B category

workers Population

Effective dose limit

< 20 mSv per 12-month

period

> 6 mSv/year

> 1 mSv/year

< 1 mSv/year

Equivalent dose limit for

the hands, the forearms,

the feet and the ankles

< 500 mSv per 12-month

period

> 150 mSv /year no value

no value

Equivalent dose limit for

the skin (for a 1 cm2

surface)

< 500 mSv per 12-month

period

> 150 mSv /year

> 50 mSv/year

< 50 mSv/year

Equivalent dose limit for the crystallnie

lens

< 150 mSvper 12-month

period

> 45 mSv/year

> 15 mSv/year

< 15 mSv/year

Articles in the French Labour Code

R4451-12 R4451-13 R4453-1 R4453-2 R4453-3 French Public

Health Code Table 2. Dose limits for each category of workers defining by the French specific regulation related to extractive and mining industries (RGIE).

All workers A category workers B category workers

Effective dose limit

< 50 mSv per 12-month period

< 30 mSv per 3-month period

> 15 mSv/year

> 5 mSv/year

Specific effective dose limit

< 12.5 mSv per 3-month period for pregnant women

< 10 mSv/year for pregnant women

Each legislative text defines the list of activities where radiation protection aspects have to be considered by the employers.

French law requires employers from extractive and mining industries to implement measures to prevent their workers from exposure to radiation while (1) mining radioactive substances, (2) when using a radioactive source, or (3) working underground. Petroleum and geothermal industries are possibly concerned by items (2) and (3).

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Exposition to NORM

Presently, the French legislation does not regulate the risks of exposition to NORM for workers from petroleum and geothermal industries.

But exposition to NORM is regulated for industries whose hygiene and safety rules are formulated in the French Labour Code. Indeed, the French authorities have drawn for these industries a list of professional activities or classes of professional activities, where exposition to NORM has to be taken into account for the radiation protection of workers (Cazala et al. 2009). The following diagram (see fig. 5) shows the provisions of the French Labour Code for the listed professional activities.

The employers must determine the doses absorded by their workers and send the results of the dosimetry studies

to the French authorities

Individual effective dose < 1 mSv/year The employers do not have to take

new specific measures to protect their workers from exposition to

NORM

Individual effective dose > 1 mSv/year The employers take measures to avoid

the exposition of their workers to NORM or to reduce the individual effective dose below the limit value

If the individual effective dose cannot be reduced under the limit value, the employers have to respects provisions

of the French Labor Code concerning radiation protection measures for"B category" and "A category" workers

Fig. 5. Measures for the radiation protection of personnel exposed to NORM and working in industries whose hygiene and safety rules are formulated in the French Labour Code.

The principles presented in the previous diagram could be used as a working basis for the updating of the French legislation, in the case where the exposition to NORM for workers from extractive and mining industries would be regulated.

Conclusions

The French law regulates the risks of exposition to NORM (Naturally Occurring Radioactive Materials) for people working in industries whose hygiene and safety rules are formulated in the French Labour Code.

But these risks are not presently taken into account in the French specific regulation related to extractive and mining industries, and more precisely for people working in the petroleum and geothermal industries.

Considering experience and feedback from other countries and from industrial companies, French authorities are currently discussing the updating of the specific

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industries.

Because a good knowledge of the real exposition to NORM of the French workers in the petroleum and geothermal industries is a fundamental basis for discussions, dosimetry studies will certainly be launched in a next future.

Glossary

Equivalent dose

The equivalent dose takes into account the fact that for the same quantity of energy deposited in an organ or a body by radiation, the biological effects will depend on the nature of the radiation received (alpha/beta particles or gamma rays). It is expressed in sievert (Sv) and is determined by multiplying the absorbed quantity of energy by a weighting factor depending on the nature of the radiation.

Effective dose

The effective dose takes into account the fact that at a same equivalent dose value, biological effects will depend on the irradiated organ. It is expressed in sievert (Sv) and is the product of the equivalent dose with a sensitivity factor depending on the organ which has been irradiated.

References

Betts S. H., Wright N. H. NORM management and disposal -Options, risks, issues and decision making. Proceedings of the SPE Health, safety and environment in oil and gas exploration and production conference. 2004 Mar 29-31; Calgary, Alberta, Canada.

Californian DHS (Department of Health Services). A study of NORM associated with oil and gas production operations in California. 1996.

Cazala C., Loriot G., Pires N., Doursot T., Matouk F., Rannou A., Cessac B., Despres A. NORM industrial plants with potential radiological impact on workers and local population: first lessons from the review of available risk assessment studies in France. Radioprotection 2009; 44 (5): 233-236.

Gray, P. R. NORM contamination in the petroleum industry. Journal of petroleum technology 1993; 45 (1): 12-16.

Paschoa A. S. NORM from the monazite cycle and from the oil and gas industry:

problems and tentative solutions. Radioprotection 2009; 44 (5): 957-962.

Reed G., Holland B., McArthur A. Evaluating the real risks of radioactive scale in oil and gas production. Proceedings of the SPE Health, safety and environment in oil and gas exploration and production conference. 1991 Nov 11-14; The Hague, Netherlands. p. 549-558.

SNIFFER. Identification and assessment of alternative disposal options for radioactive oilfield wastes. Summary guidance. Project UKRSR07. 2005.

Takhautdinov Sh. F., Sizov B. A., Diyashev R. N., Zaitsev, V. I., Antonov, G. P., Tatnipineft, A. Influence of radon and decay products on fiel equipment service personnel. Proceedings of the SPE Health, safety and environment in oil and gas

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exploration and production conference. 1996 Jun 9-12; New Orleans, Louisiana, USA. p. 845-854.

Weblinks

French Labour Code: http://www.legifrance.gouv.fr/

RGIE (French specific regulation related to extractive and mining industries):

http://www.industrie.gouv.fr/sdsi/dtss/regl/cdrgie/entree.htm

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