natural radionuclide activity concentrations in spas of argentina

8/11/2019 Natural Radionuclide Activity Concentrations in Spas of Argentina

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Natural Radionuclide Activity

Concentrations in Spas of Argentina

Gnoni, G.A.; Czerniczyniec, M.; Canoba, A.C. and Palacios, M.A.

Presentado en: International Symposium on the Natural Radiation Environment NRE-VIIIBuzios, Brasil, 7-12 octubre 2007


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NATURAL RADIONUCLIDE ACTIVITY CONCENTRATIONSIN SPAS OF ARGENTINA

Gnoni, G.A.; Czerniczyniec, M.; Canoba, A.C. and Palacios, M.A.

Nuclear Regulatory AuthorityArgentina

ABSTRACT

Geothermal waters have been used on a large scale for bathing, drinking and medicalpurposes. These waters can contain natural radionuclides that may increase the exposure topeople. In this work the most important natural radionuclide activity concentrations indifferent thermal spas of Argentina were measured to characterize waters and to evaluatethe exposure of workers and members of the public.

Keywords: radon, geothermal water, natural radionuclides, thermal spa.

INTRODUCTION

People have used geothermal water with medical purposes for many thousand of years.Geothermal waters often have a very high mineral content because solute solubility increaseswith increasing temperature. Ground waters are in close contact with soil and rocks containingradium. Once formed by its decay from radium, radon gas may diffuse through rocks pores andgeological discontinuities and dissolve in these waters. Radon and natural radionuclides aretransported to the surface and radon can easily diffuse into the atmosphere and may produceelevated radon levels at places like geothermal spas.[1]

There are three types of geothermal water:

1. Water issuing from a hot spring heated by geothermal heat. Water percolates deeply into thecrust and is heated as it comes into contact with hot rocks.

2. Water arising from rain percolates and mixes with pre-existing geothermal water.

3. Water in volcanic zones heated by contact with magma. If water erupts in a jet it is calledgeyser, if it reaches the surface as steam it is called a fumarole.

In Argentina there are, at least, 35 thermal spas. In this work the most important naturalradionuclide activity concentrations in different geothermal spas of Argentina were measured tocharacterize the waters and to evaluate the exposure of workers and members of the public.One of the assessed spa has been chosen because of the volcanic origin of its geothermalwater (Thermal Spa 1). The rest of the spas monitored use water coming from aquifer systems,this is groundwater reservoirs (Thermal Spa 2 to 11).

MEASUREMENTS

Three passive methods were used to measure radon in air. One of them is an screening methodwith a maximun exposure time of seven days, based on the radon adsorption on activatedcharcoal and its subsequent measurement in a liquid scintillation counter. The other twomethods are time integrated ones, CR-39 or Makrofol tracks detectors, which can be exposedbetween two and three months.[4]. To characterize waters various natural radionuclides have

been also measured. Uranium concentration was measured by fluorimetry. Ra-226 and Pb-210


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measurements were performed by radiochemical methods and measurements by liquidscintillation.[5]. Dose rate measurements were carried out as well.

Measurements at Thermal Spa 1

In tables 1 to 3 radon concentration measurements, both in air and waters of the Thermal Spa 1

and surroundings, are shown.

It is important to point out that people who work in the spa, live in its neighbourghood. Due tothis situation it is also important to measure radon at dwellings.

Table 1.[Rn-222] (Bq/m3) at Thermal Spa 1.

Apri l 2005 December 2006

DescriptionActivatedcharcoal

Activatedcharcoal CR-39 Makrofol

Health office 140 15 86 10 120 25 -

Bath A 260 30 1543 170 - -

Office bath A 490 50 279 30 373 70 -

Corridor bath B 300 30 155 20 - 68 15

Bath C - 205 20 414 80 -

Corridor bath C 280 30 305 30 254 50 -

Bath D 770 80 117 15 - -

Bath D, sulphurous water 250 30 861 90 877 160 -

Corridor bath D 710 70 177 20 - 113 20

Bath E - 854 90 1755 340 -

Corridor bath E 600 60 535 60 459 90 -

Table 2. [Rn-222] (Bq/m3) in dwellings nearby Thermal Spa 1.

Apri l 2005 December 2006

DescriptionActivatedcharcoal

Activatedcharcoal CR-39 Makrofol

House 1 - Children bedroom 814 80 - 425 85 -

House 1 - Main bedroom 1080 110 95 10 - -

House 1 - Dining room 1258 130 93 9 - 125 25

House 2 - 28 3 198 40 -

House 4 - 38 4 125 25 -

House 5 - 24 3 - 12 3


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Table 3. [Rn-222] (Bq/m3) in geothermal waters used

for medical purposes at Thermal Spa 1.

Description RadonApri l 2005

RadonApri l 2006

RadonDecember 2006

Drinking water 1 1200 700 - < DL

Drinking water 2 1700 800 - < DL

Water at spring 1 4500 1400 8700 2000 -

Water at spring 2 3300 1100 7000 1700 -

Water at spring 3 1700 700 5400 1400 < DL

North spring 5752 1500 9000 2000 -

South spring 11083 2400 4200 1200 -

Outdoor bath 1 - 28900 6100 5163 1084

Outdoor bath 2 - 29800 6300 3591 762

Ferrous water at spring 1900 700 1100 800 < DL

Ferrous water in bath - - 2636 571

Sulphurous water at spring 2300 800 6100 1500 862 238

Sulphurous water outdoor bath - - 3327 708

Sulphurous water indoor bath - - 2518 574

Volcano water - 10900 2400 -

DL: detection limit. DL= 98 Bq/m3.

Radon concentration was also measured in other workplaces. In a nearby workplace it wasfound a value of 958 100 Bq/m3 with activated charcoal and 642 120 Bq/m3 with CR-39. Theradon concentration at the remaining eight places was below 29 3 Bq/m

3.

Uranium concentration was also measured in different waters. From 17 samples evaluated only

4 were above the detection limit (5g/l) the highest value being 21 2 g/l. Ra-226concentration was measured in 12 samples and only one sample was slightly above the

detection limit (25,5 12,6 mBq/l). Pb-210 was also measured and all values obtained werebelow the detection limit (0.059 Bq/l).

Dose rate measurements have been carried out in every sample point. Backgroundmeasurements were performed in the surroundings of the spa. All dose rate measurements

were within natural radiation levels (0.1 0.2 Sv/h).


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Measurements at Thermal Spas 2 to 11

Geothermal waters used at the different Thermal Spa were characterized as follows:

Table 4. Radionuclides concentrations in geothermal waters

for medical purposes at different Thermal Spas

Location Water Depth(m)

[Rn-222](Bq/m

3)

[Ra-226](mBq/l)

[U]

(g/l)

[Pb-210](mBq/l)

Termal Spa 2 NK


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REFERENCES

1. V. Radolic, B. Vukovic, G. Smit, D. Stanic, J. Planinic, Jour of Environmental Radioactivity 83,191-198 (2005).

2. F. Lpez y A. Canoba, Jour of Radioanalytical and Nuclear Chemistry, 240, 237-241 (1999).

3. Bomben A. M., Canoba A. C., A simple method for the determination of natural uranium and226

Ra in waters and soils. Jour of Radioanalytical and Nuclear Chemistry, Letters, 212, 3,209-219 (1996).

4. WHO Drinking Water Guidelines, 2nd

edition, (2004).

5. Radionuclides in Drinking Water: a Small Entity Compliance Guide (EPA 2002).

6. Decreto Reglamentario 831 de la Ley 24.051, Argentina.

7. IAEA, Coleccin Seguridad N 115: Normas bsicas internacionales de seguridad para laproteccin contra las radiacin ionizante y para la seguridad de las fuentes de radiacin,

IAEA, Viena, Austria (1996).

8. Norma Bsica de Seguridad Radiolgica, AR 10.1.1, Rev. 3 Autoridad Regulatoria Nuclear.

9. Protection Against Radon-222 at Home and at Work, ICRP 65, Vol. 23, N2 (1993).

natural radionuclide activity concentrations in spas of argentina

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