Measurement in schools and kindergartens in different town and regions in Bulgaria

Transcription

1 National Center of Radiobiology and Radiation Protection Ministry of Health Measurement in schools and kindergartens in different town and regions in Bulgaria Kemena Ivanova Sofia Bularia

2 Bulgarian legislation Regulation on Basic Norm of Radiation Protection Article 45 (1) The equivalent dose rate of gamma radiation in buildings, public buildings, industrial and other buildings should not exceed the local dose rate outdoors by more than 0,2 µsv/h. (2) reference levels for limiting exposure to radon are: 1. annually averaged radon concentration in the air - 200Bq.m -3 for new residential and public buildings; 2. annually averaged radon concentration in the air Bq.m -3 for existing residential and public buildings; 3. average radon concentration in the air Bq.m -3 jobs. (3) In specific cases where the duration of occupancy in existing public buildings is small, the Minister of Health may determine for an annual average concentration of radon in the air a reference level more than 300 Bq.m -3, but not more 1000 Bq.m -3 2

3 3 Pilot Study in schools and kindergartens Method passive measurement (E-Perm system) Short-term and long term measurements Period - August 2011 to April 2012 (short term- 1 week, longterm 6 month) Investigated area - Kremikovtsi region of Sofia district (close to former uranium mining and milling industry)

4 Pilot Study method (strategy) 4 1 -st Stage - Short-term measurements of ground floor No >300 Bq m -3 Short-term measurements Yes Long-term measurements 2 -nd Stage Follow-up measurements > 300 Bq m Bq m -3 No No >300 Bq m -3 >300 Bq m -3 Yes Yes Reducing the level of radon Control measurements Reducing the level of radon

5 Pilot study - steps 1 -st stage - screening measurements o meeting with the school s manager o short-term measurement during the summer vacation under closed conditions o all classrooms occupied the ground floor and basement was measured. 2 -nd stage follow-up measurements o Long-term measurement depending on the result above than or approximately equal to referent level of 300 Bq.m th stage control measurements after reducing the Rnconcentration 5

6 Pilot study - Results 6 Short-term Long-term No. of premises School 9 4 Kindergarten 7 4 Minimum C Rn (Bq m -3 ) Median C Rn (Bq m -3 ) Maximum C Rn (Bq m -3 ) AM C Rn (Bq m -3 ) SDV C Rn (Bq m -3 ) GM C Rn (Bq m -3 ) GSDV

7 7 Pilot study - Results Relationship between short and long term measurements - linear regression between shortterm and long-term measurements 8 ln CRn(Bq/m 3 )-long y = x R 2 = R = ln CRn(Bq/m 3 )-short Observations P redictions Conf. on pred (95.00%) Conf. on mean (95.00%)

8 8 Pilot study Results of control measurement The post-mitigation measurements were performed in October 2012 in 24 premises of all 9 buildings with EICs passive integrating detectors for 1 month Results of C Rn measurements before and after mitigation

9 9 Pilot study Results of control measurement Assessment of effectiveness of these measures the criteria of efficiency are used. Reduction efficiency reduction factor RF R [%] S 2-S 3-S 4-S 1-K 2-K 3-K 4-K 5-K RF = C C befor after Public Buildings Reduction efficiency in 5 buildings is above 70%, in the other buildings is below this rate.

10 10 Pilot study Lesion learn The obtained results for schools and kindergartens were higher, mainly due to location close to uranium mining and milling sites. Higher radon concentrations were observed in kindergartens than in schools because of different building characteristics. The comparison between the measurements performed by short and long term detectors, confirms the reliability of the short term measurements. Radon sources, radon concentrations and radon transport mechanisms should influence on the choice of mitigation strategies.

11 11 Systematic measurement in kindergartens in Sofia- city Number of buildings - all public kindergartens according the national information system 296 buildings Number of premises 922 rooms, which situated: at the ground floor situated directly on the ground or above unoccupied (basements, crawlspaces, or utility tunnels) the constantly occupied underground rooms (kitchen, swimming pool etc.). Period - from February to April 2013 Method alpha tract detectors Radosys systems

12 Systematic measurement - distribution of detectors The first step - collecting the information about the number of rooms on ground floor, by telephone. 12 The second - preparing a package with the detectors, instruction forms, brochures and questionnaires. The third gathering kindergarten managers by Sofia-city mayoralty for receiving the packages and instruction. The fourth in 7 % of kindergartens were distributed duplicate and onsite inspection.

13 Systematic measurement in Sofia city - results C Rn [Bq m -3 ] 600 Number of rooms Minimum 9 Frequency Median 98 Maximum 1415 Arithmetic mean Standard deviation 118 Coefficient of variation (CV=SD/AM) CRn [Bq/m3] Geometric mean 101 Geometric standard deviation 2.08 The measured data can be well described by a log-normal function. Descriptive statistic of indoor radon concentrations in kindergartens Results of Pilot Radon Survey in dwellings for Sofia city is 78 Bq.m -3.

14 Systematic measurement in Sofia city - results 14 C Rn [Bq m -3 ] Factor Factor data subset N Min. Med. Max. GM GSD Region West East North Central Southern West violet East - red North green Central orange Southern - rose

15 Systematic measurement in Sofia city - results 15 Factor Building materials Factor data subset N Min. C Rn [Bq m -3 ] Med. Max. GM GSD Bricks Reinforced concrete Concrete panel Brick + concrete Buildings built of brick have the higher geometric mean of C Rn than the buildings made of concrete, or reinforced concrete, or both.

16 Systematic measurement - results 16 Factor Presence of foundation Presence of basement Factor data subset C Rn [Bq m -3 ] N Min. Med. Max. GM GSD Without foundation with foundation Without basement with basement Higher indoorc Rn is in buildings without basement and foundation.

17 17 Systematic measurement in towns and regions in Bulgaria X X X Numbers of towns Plovdiv, Burgas and Pernik region Number of buildings public kindergartens 91 buildings in Plovdiv; 49 in Burgas and 34 in Pernik region 174 total buildings Number of premises 473 rooms in Plovdiv; 193 in Burgas and 111 in Pernik region 777 total measurement rooms Period 3 month from January/February to April/May 2014 Method alpha tract detectors Radosys systems

18 Systematic measurement in towns and regions in Bulgaria - results 18 Descriptive CRntotal CRn- CRn- CRn- Statistics Plovdiv Burgas Pernik Number AM Median SDV Skewness Kurtosis GM Minimum Maximum Results have a lognormal distribution Results of Pilot Radon Survey dwellings for Plovdiv district is 137 Bq.m -3.

19 19 Systematic measurement in towns and regions in Bulgaria - results Influence of renovation of buildings on the concentration of radon Factor Renovation of buildings Factor data subset C Rn [Bq m -3 ] N Min. Med. Max. GM GSD Renovation Not renovation The higher radon concentrations is related to buildings which was renovated without taking into account radon concentration (KW, p<0.0001).

20 20 Systematic measurement in towns and regions in Bulgaria - results Influence of type of windows on the concentration of radon Factor Type of windows Factor data subset C Rn [Bq m -3 ] N Min. Med. Max. GM GSD new type (PVC, ect.) old type (wood etc.) The higher radon concentrations is related to buildings with new type of windows (KW, p<0.0001).

21 Systematic measurement conclusions 21 The distribution of detectors trough majority is easy and quick way. Information days of kindergarten's staffs were performed. The buildings of kindergartens have higher levels of radon concentration in comparison with the dwelling. The measured C Rn were generally higher in buildings made from bricks, with new type of windows, without basement and foundation. Renovations of the building and change the old windows with new one (PVC, ect.) without taking into account the concentration of radon, may increase the concentration of radon in the building. The measurement protocols is under consideration with the inclusion of direct measurements in buildings with a high concentration.

22 22 Pilot study During the weekend During the week from

23 Special thanks to my colleagues from Radon monitoring and prevention laboratory and from Reginal Health Inspectorates who helped me to carry out researches and analysis of results! 23