CC BY
19
Научни трудове на Съюза на учените в България - Пловдив Серия В. Техника и технологии, том XIII., Съюз на учените, сесия 5 - 6 ноември 2015 Scientific Works of the Union of Scientists in Bulgaria-Plovdiv, series C. Technics and Technologies, Vol. XIII., Union of Scientists, ISSN 1311-9419, Session 5 - 6 November 2015.
THE RADIOACTIVE WASTE MANAGEMENT IN KOSOVO
Besire Cena
University of Pristina, Pristina, Kosovo
ABSTRACT
Describe the present situation in Kosovo concerning the radioactive waste management and namely the waste inventory, classification, interim storage and final disposal considering IAEA documents on this topics.
More than 100 sealed radioactive sources are out of use, radioactive waste generated in nuclear medicine departments of hospitals. As result of the necessary information lack for most radioactive sources, were used different methods to identify the type of radionuclide and its activity.
Using the IAEA waste classification scheme is carried out the determination of the appropriate methods for safe management of the different group of waste, including its interim storage and final disposal.
Key-words: radioactive waste, waste classification, , interim storage.
1. INTRODUCTION
The radioactive waste situation in Kosovo is not known with accuracy as results of its last three decades hard history. In our knowledge in Kosovo has not existed a detailed state inventory for both radioactive sources in use (e.g. radioactive gauges) or out of use. The lack of this information has become more difficult identification of the radioactive waste considering its location, type of radionuclide and its activity. As result of investigations and measurements in sity it was possible to give a real situation of the radioactive waste in Kosovo as well to propose recommendations for its safe management.
2. MATERIALS AND METHODS
2.1. Inventory of radioactive waste
The first step toward the classification and safe management of the radioactive waste in Kosovo was the establishment of the radioactive sources inventory, their location and source numbers and characteristics. For this purposes as primary source served the information provided by Radiation Protection Service of the Institute of Occupational Medicine, Pristina. From the other part a lot of information was collected from main institutions in Kosovo, which had used radioactive sources like Kosovo Electroenergy Corporation, Industrial Complexes in Mitrovica, Drenas etc. Some investigations were performed in different institutions, which possessed radioactive gauges and radioactive lightning. A permanent local generator of radioactive waste in Kosovo is nuclear medicine. A special care was paid investigation of the orphan sources, founded in some metallic scrap yards in Pristina and its neighborhoods regions. After a carefully investigation, were determined the list of institutions where radioactive waste still exist, their location and the number of radioactive sources for each institutions.
Based in the inventory of radioactive sources there are 25 institutions with a total number of 109 radioactive sources out of use, where the storage conditions are improvised mainly in warehouse without necessary precaution measures concerning its safety and security.
The second phase in the frame of inventory of radioactive waste was the determination of radionuclides and their activities. This investigation was perfomed entirely in the ground and was undertaken because of source certification lacks or other indication for type of radionuclide and activity. The determination of radioactivity for different sources was performed based in the relationship between the equivalent dose rate H', created in a fixed distance r and activity of the sources a. This relationship between the mentioned quantities is as follow:
H' = r a / r2 (1)
where H' is equivalent dose rate (mSv/h), r is specific gamma constant of the source (mSv. m2/MBq.h) , a activity of radioactive source (MBq) and r the distance of instrument from the source (m). Based in the mentioned relationship it is possible to get the activity of the source a as function of equivalent dose rate H' and the distance r.
a = H'. r2/.r (2)
For this purpose for each radioactice source the equivalent dose rate was measured in a fixed distance which usually has taken 1 m. Concerning the values of the specific gamma constant (/), they were taken by reference (Shleien 1992), where other than specific gamma constant, was given half life of radionuclide as well the value of the attenuation coefficient of gamma radiation in lead ^ (cm-1). As measuring istrument were used "Exploranium GR-130" and "Inspector 100", which gave the values of the equivalent dose rate and perform identification of the radionuclide. Concerning the radioactive waste generated by nuclear medicine, in collaboration with medical staff of the clinics were treated the waste from the use of molybdenum-technetium generators of "Gentec 2-120" type with initial activity of 6 GBq. In this generator is used radionuclide of Mo-99, which through decay gave radionuclide of Tc-99m with
roofs in which were installed radioactive lightning in Pristina and other cities of Kosovo. Now this lightning is out of use, becoming therefore a radioactive waste. The radionuclides used for this purposes were Co-60, Eu-152 and Eu-154. Considering the mentioned data half life 6 hours (T = 6 hours). Another radionuclide which is used by the clinics for therapeutic purposes is I-131 (T = 8,1 days). Both mentioned radionuclides are with very short half lives, and therefore the generated radioactive waste needs to store for relatively short interval of time (Ravichandram et al. 2011). Nevertheless it is an urgent need to inform the medical staff on the principal rules for safe management of the mentioned type of waste.
A particular sort of waste in Kosovo is radioactive lightning, which was very spread in exYugoslavia. There are many buildings and the fact that installation of the lightning occurred in 1980 with activity 2,5 GBq, after 30 years their activity now is nearly 25 MBq for Co-60 and 250 MBq for Eu-152 and Eu-154.
2.2. Classification and safe management of radioactive waste
Considering the exempted levels as well the situation of radioactive waste in Kosovo in relation with its activity and radionuclide it is possible to define the following groups of radioactive waste:
(i) Exempted waste - EW
(ii) Very short half lives waste - VSLW
(iii) Very low level waste - VLLW
(iv) Low level waste - LLW
(v) NORM waste -NW
Based in the five mentioned groups the classification scheme of radioactive waste in Kosovo is presented in Fig.2 in accordance to the classification scheme of IEAE (IAEA 2009). In this figure are represent seven groups of radioactive waste. The groups vi (Intermediary Level Waste - ILW)) and vii (High Level Waste - HLW)) are not exist in Kosovo and for this reason their representation in the figure is done by dashed line.
The description of waste which belongs to the groups (i) to (v) is done as follow
Activity contort
Fig. 2. Classification of radioactive waste in Kosovo
(i) There are some radioactive sources like Co-57 or Co-60 with low initial activity, which as result of their radioactive decay have the activity below 1 MBq or 0,1 MBq (exempted activity for Co-57 and Co-60 respectively). These sources belong to EW.
(ii) The radioactive waste generated in nuclear medicine clinics (Tc-99m and I-131) with very short half lives consist VSLW.
(iii) The majority of radioactive waste in Kosovo are with very low activity and belongs to the third group of radioactive waste - VLLW
(iv) There are some radioactive sources like Am-241, Pu-238, Th-228, radioactive lightning (Eu-152, Eu-154) which are with long half lives or alpha emitters. The mentioned sources needed to treat with caution considering their confinement and isolation, which as general rule ought to resist for some hundred years. These sources belong to LLW.
(v) There are big quantities of industrial waste near to chemical or mineral complexes in Kosovo, which content natural occurring radioactive material (NORM) of different activities concentration. This waste as general rule contents low concentration of natural radionuclides, but its their long half lives require special studies for considering its handling in different branches of economy or its management in accordance with its concentration. This group of radioactive waste belongs to NORM waste.
3. RESULTS AND DISCUSSION
Safe management of radioactive waste needed to be implemented in accordance with its pertaining in the mentioned different groups of the classification scheme. From safety point of view it is necessary to distinct the waste with radionuclide half life shorter than 100 days, the waste with half lives less than 40 years and the waste with half lives more than hundred years. This is related with radioactive danger represented by different group of radioactive waste, which is proportional with its half lives. A high degree of safety can be provided through implementation of the institutional control measures, considering the safety and security of storage installation (e.g. landfills). The limitations of waste activity, which might be stored in a specific installation is related also with radiological, chemical and biological waste properties.
Considering the radioactive waste group classification and its safe management in accordance with IAEA recommendation it is reasonably to propose as follows:
- Exempted waste (EW) which contents very low activities, did not need special conditions for radiation protection. This category of waste can be deposited in ordinary landfill or can discharged (for liquid waste) through urban sewer.
- Very short lived waste (VSLW) contents radionuclide, which ought to store just as its activity to decrease below the exempted one. Example of VSLW is waste of Tc-99m or I-131, which as rule are stored for ten half lives in a special place inside of medical clinics.
- Very low level waste (VLLW) is the majority of radioactive sources used in different gauges after their life. The safe management of this group requires to provide special radiation protection measures for time intervals of some decades. The storage of this waste needs simple surface installation.
- Low level waste (LLW) is the waste of Am-241, Cs-137, Th-228, which consist radionuclide with high half lives or emit alpha radiation. For such waste needed special confinement and isolation, which resist for some hundred years. The storage and final disposal for this group is related with more special installations (IAEA 2005).
- NORM waste after its control for the level of radioactivity can be used in different activity e.g. road construction layers, filler in cement industry etc.
For Kosovo did not exist yet a special installation for waste storage or disposal. Based in radiation protection act (Radprotact 2011), the Kosovo government is committed to invest for an interim storage centralized facility of radioactive waste in a short time. A scheme idea for such facility is prepared by authors based in the IAEA recommendations.
4. CONCLUSIONS
The study of radioactive waste has showed that more than 100 radioactive sources needs to collect and to manage in accordance with IAEA recommendations. Meantime exists a lack of information related with location and radionuclide identification as well. The present study is a first effort to put in evidence the issue related with safe management, its classification and the methods of its interim storage and disposal as well. For this purpose it is proposed to provide a full study of radioactive waste in the country and to invest for a centralized facility, which will provide the treatment and interim storage of radioactive waste in accordance with its classification group.
5. REFERENCES
1. International Atomic Energy Agency (IAEA), 2006, Fundamental Safety Principles, Safety Standards Series No. SF-1, IAEA, Vienna, Austria.
2. International Atomic Energy Agency (IAEA), 2009, Classification of Radioactive Waste, Safety Standards Series GSG-1, IAEA, Vienna, Austria.
3. Shleien B, 1992, The Health Physics and Radiological Health Handbook, Scinta Inc., MD, USA.
Food and Agriculturale Organizatio, International Atomic Energy Agency, International Labour
Organization, OECD Nuclear Energy Agency, Pan American Health Organization, Word Health Organization, (FAO), 1996, International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources, Safety Series No. 115, Vienna, Austria.
4. Ravichandram R, Binukumar, Sreeram JP and Arukumar LS., 2011, An overview of radioactive disposal procedures of a nuclear medical department, J. of Med Phys., 32(6), 95-99.
5. International Atomic Energy Agency, 2005, Management of Radioactive Waste from the Use of Radioactive Materials in Medicine, Industry and Research, IAEA, Vienna, Austria.
6. Radiation Protection Act, No. , (Radprotact), 2011, Kosovo National Assembly, Official Journal No. , Pristina, Kosovo.
