The recent measurements of radon and project

relating to the implementation of corrective

actions at schools in Montenegro

RER 9136

Natasa Bjelica

Perko Vukotic

23 - 27 May 2016, Tallinn, Estonia

Every year, from 1999 up today, within the Program of monitoring of radioactivity in MNE, short-term measurements (up to 48 hours) are carried out at 10 to 20 randomly selected locations (individual and common residential buildings, schools and kindergartens).

Those type of measurements was the only possible ones. (only 1 institution has accreditation for short- term measurement, no one with accreditation for remediation)

During 2013 short-term measurements were conducted in 10 schools from municipality of capital Podgorica. We decided to measure in the schools where we already did some measurements earlier and where results were above the levels prescribed in national legislation (400 Bq/m3).

N0 Lokacija I Ciklus II Ciklus 2013.

Srednja vr.

[Bq/m3]

Prethodna mjerenja

Min. [Bq/m3]

Max.

[Bq/m3]

Srednja vr.

I ciklus [Bq/m3]

Min. [Bq/m3]

Max.

[Bq/m3]

Srednja vr.

II ciklus [Bq/m3]

Godina Srednja vr [Bq/m3]

1. OŠ “Savo Kažić” Barutana

603 2100 1450 ± 238 572 2500 1600 ± 434 1525 2012 1177

2. OŠ “18. Novembar” Bioče

42 832 412 ± 80 28 936 515 ± 91 463.5 2012 613

3. OŠ “ Mahmut Lekić” Milješ

20 1448 608 ± 99 132 1376 870 ± 129 739 2012 483

4. OŠ “Milan Vukotić” Srpska

8 330 157 ± 45 342 1020 673 ± 111 415 2009 494

5. Vrtić “Palčica” Gornja Gorica

0 584 275 ± 61 8 644 360 ± 73 317.5 2008 426

6. Muzicka škola “Andre Navara” Podgorica

240 677 482 ± 98 572 1360 1150 ± 138 816 2008 729

7. OŠ “Vlado Milić” D.Gorica

14 703 375 ± 174 552 1192 894 ± 132 634.5 2003 620

8. O. Š. “Oktoih”

Zabjelo

37 780 419 ± 80 199 1192 718 ± 115 568.5 2002 472

9. OŠ “Sutjeska”

Podgorica

3 258 97 ± 33 111 788 432 ± 83 264.5 2002 483

10. OŠ “Sergije Stanić” Podgorica

0 284 97 ± 76 91 618 416 ± 82 256.5 2002 591

We decided to recommend five (5) schools for remediation,based on criteria: If average value of repeated and previousmeasurement is above 400 Bq/m3 and if one of measurement isabove the 600Bq/m3, remediation have to be considered.

First team for radon mitigation, consisting of 16 members (5

civil engineers, 2 architects, 7 physicist, and 2 mechanical engineers)

is established last year at the Faculty of Civil Engineering.

In June 2015, 6 members of the mitigation team did detailed

visual inspection of 5 schools which were pointed as a schools with

increased radon indoor concentration. Proper information regarding

that was submitted to the Ministry of Education with

recommendation for further steps which should be taken in order to

reduce radon risk in them.

Schools are old from 32 up to 120 years. Two schools are

ground buildings and three has one floor more. In two schools (the

oldest ones) outer walls are from stone up to 80 cm thickness.

In some schools there is no concrete floors at all; in majority ofschools there is only in some classrooms or offices. Only in one schoolthere is a concrete floor in the whole building, but some damages on itare obvious. No one of those schools have good (without cracks or somedamages) concrete floor in all classrooms, halls and offices, even some ofthem have had one or more reconstructions. In two schools over the hardrammed soil there are boards over the beams, boards over the beams withlaminate or parquet floor. Some schools after reconstructions changed thewindows (PVC - in almost all schools, there is intention of replacing asmuch as possible of the windows, depending on finance), in some schoolsparquet is put over the bitumen in some classrooms, in one schoolcorridors are from xelolit (good Rn barrier). Lot of schools doreconstructions of roofs and bathrooms.

One school have a specific problem: it is built over the deep concretechannel, because car service was on that place earlier, so today thischannel is probably a good radon reservoir.

All schools have chimneys but only in one school they are in use; inall others they have central heating or air-conditioning.

Recommendation of mitigation team for all schools are not the same, but for all schools common recommendation are :

• repeat the measurements with electrets radon detectors (7-10 daysmeasurement),

• where is necessary do “sniffing” of thoron in order to find a radonentry points,

• depending on the results make a plan for further remediation, butthe assumption is that floor reconstruction will be the mostrecommendation measure (new concrete floor with the drainagelayer underneath it inside which perforated tube were placed –passive remediation method will be probably the mostrecommendation method).

Under the bilateral project between MNE and Czech Republic :

“Promotion of modern radon diagnosis methods in Montenegro” financed

by UNDP was conducted some important activities were conducted:

� One SV of four mitigation team member in SURO institution was

realized (mostly devoted to remediation issues)

� 5 days workshop of SURO’s expert was organized at the Faculty of

Civil Engineering (University of Montenegro). SURO expert demonstrate

the various measuring techniques and diagnostic methods.

� SURO’s expert conducted (during the workshop) additional

comprehensive radon measurements ( indoor radon and radon in soil) in

two elementary schools in Podgorica previously identified as a schools

with insufficient radon barriers.

So, the main goal of the project was the transfer of Czech expert

knowledge and experience in radon diagnosis and radon corrective

actions to Montenegrin experts:

Radon diagnosis of SURO’s expert was consist of the next steps:

� Building and building site description (building age, number of floors,

number of the classrooms on the ground floor, eventual earlier

reconstructions, heating, windows, overview of geological and

hidrogeological characteristics of the site). Visual inspection of the

buildings

� Continuous indoor radon measurement were carried out with

continuous radon monitors installed in areas that are in contact with

the subsoil (with continuous radon monitors RADIM3, RADIM3A,

TERA system within period of 3 days)

� Spot measurement methods - grab sampling of soil gas within

leakage areas, suspected as a potential radon sources with soil

radon monitor system RM2 with electrometer unit ERM-3 and

ionizing chamber IK-250, with puncture needle of 150 ml.

� Sniffing of thoron (with RAD7 continuous radon monitor, Durridge

Company)

� Radon potential quantification of the building site (radon

concentration in soil gas, permeability of soil) – determination of

Radon Index of the building site

� Gamma dose rate mapping in order to identify building materials with

elevated levels of natural radionuclide (with radiometer DC-3-E98 for

fast identification of building materials)

School No 1:

� Located in the central part of MNE which is recognized as a part with

huge carbonate rocks concentration with karts depressions.

� This school was built 1982, in 2013 reconstruction was made

(almost all windows are new PVC (doubled glazed), two classrooms,

halls and corridors has xelolot floors - other classrooms have old

wooden parquet over the composed soil, or over the so-called

“death” concrete plate, thermal isolation of external walls and the roof

is made, existing heat system is renovated, also in some parts new

central heating systemic is installed.

� Gamma dose rate was measured: Measured values were from 0,1-

0,12 µGy/h what means that there is no elevated levels of

radionuclide in building materials of school.

� Spot radon concentration measurements - grab sampling of soil gas

air within the leakage areas (14 sampling points: wall- floor joint

leakage in 7 classrooms and in 3 teachers lounge, in chimney

cleaning windows in 3 classrooms ) It was founded radonconcentration higher than 10kBq/m3 what indicate there was thesignificant radon entry roots into indoor.

� Continuous radon concentration measurements started on

Wednesday up to Saturday (partly covered the period of normal

occupancy). The mean radon concentration on the ground floorexceed 300 Bq/m3 (average value for the whole period ofmeasurements) in all classroom except the classroom no 15.

School No 1 Bq/m3 (mean)

Classroom 1 783

Classroom 3 453

Classroom 15 154

Classromm 1 682

Classroom 4 452

Classroom 13 307

Clasroom 5 on the 1st floor 58

Gym 54

Flat 473

Director office

Preschool classroom

123

333

Radon index determination (School No 1):

Radon index (RI) determination is based on the assessment of soil radon gas

concentration and the permeability of the soils and rocks:

Soil gas samples are taken from at least 15 samples near the building, from

0,8m depth where it was possible, and from 0,5m or 0,75m from the soil

where the fragments of rocks were present in upper layers.

Radon concentration in soil (Ca) was from 2,1 to 215 kBq/m3, andpermeability (k) was from 7,6 E-13 to 1,8 E-11 m2 (high permeabilityenvironment).

Arithmetic mean for Ca is 36,8 kBq/m3, and for k is 9,7 E-12 m2.

The large spatial variability of radon concentration in soil is a consequence

of geological characteristics, porosity, moisture, pressure differences,

permeability, as well as of the different depth of gas sampling.

RP (radon potential mode) can be used for determining RI is defined by

equation:

RP = (Ca -1) / ( -log k – 10)

Radon index for School No 1 Conclusion:

School No 1 falls into building with high radon index category

(Ca max =215kBq/m3 is a higher than 30 kBq/m3, and RP max is 268,9 what is higher than 35)

School No 2:This school was built 1984, located on Zeta valley – the largest karst area in MNE, also sand, gravel and rocks are present over the karst.

Windows are mostly PVC double –glazed, building has only ground floor, heating is by wood, floor is compressed soil (mixture of gravel, stone and earth, 30 cm above the terrain level), so –called “death “ concrete plate , isolation, floor cover is not the same in all classrooms: somewhere wooden parquet, somewhere is marmor tiles.

Radon diagnoses was the same as it was in School No 1, and

Conclusion is:

• Gamma dose rate indicate that there is no elevated levels of radionuclide in building materials of school ( from 0,11 to 0,13 µGy/h)

• Spot radon concentration measurement-grab sampling of soil gas within the leakage areas in contact building construction ( wall- floor joint leakage points in 10 classrooms , floor crack point s in 2 classrooms) indicate that there is the radon concentration exceed the level of 10 Bq/m3,

• Continuous radon measurements from 3 classrooms , teachers lounge and entrance hall indicate that in 1 classroom and in teacher lounge average value of radon concentration exceed the level of 300Bq/m3

• 15 soil gas samples taken , grid was 10x10m, depth of sampling 0,5m and 0,75 m ( was not possible to do on 0,8m),

• Ca from 8,5 to 169 kBq/m3 (arithmetic mean 56,3kBq/m3),

• k ( permeability) from 7,2 E-13 up to 1,6E-11m2 (high permeable environment)

• RP = 79,7 ( high radon index)

Conclusion is:

� The results of radon measurements conducted by Czech experts confirm the conclusions of the visual inspection of the schools which were previously conducted by the national mitigation team.

� Also, it is very important to emphasize that criteria what we usedto select the schools for a candidate for remediation measures,based on results of Programme of monitoring radioactivity inenvironment for 2013, was good (repeated and previousmeasurement conducted with short-term measurement have to bemore than 400Bq/m3 and one of measurement must be above the600Bq/m3) because mean value of indoor radon concentrationreceived by Czech experts are about 50% less than we get what isstill above (or near) 300 Bq/m3.

� Agreement regarding projection of remediation measures for two elementary schools between the Ministry of Science and the Faculty of Civil Engineering is signed.