International Conference
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Bled / Slovenia / September 14-17
Radioisotopes Used in Analytical Chemical Instruments Helena Janžekovič, Milko Križman
Slovenian Nuclear Safety Administration
P.O. Box 5759, Železna cesta 16, SI-1001, Ljubljana, Slovenia helena.janzekovic@gov.si, milko.krizman@gov.si
ABSTRACT
Immediately after the discovery of radioactivity, radioactive materials become widely used in different types of research and application, and very often without any details of inventory of sources used. Inventory of sources in a country as well as the inventory of radioactive waste is a milestone of programmes related to the achievement of safety and security of sources. The Slovenian Nuclear Safety Administration (SNSA), as the competent regulatory body in Slovenia, performed in the last years inspection programme related to ionising sources and radioactive waste which were not under a control in the past. Among other facilities laboratories were inspected. While most applications of ionising sources in such laboratories are well known, some applications are very rare and as a consequence also less known. As for example, calibration of gamma spectrometers which is preformed with calibration sources e.g. Am-241, Cs-137 and Co-60, is a typical well known use of radioactive sources. In the chemical laboratories analytical instruments using radioactive sources are electron capture detectors (ECD) used for gas chromatography with Ni-63. In addition, in liquid scintillation techniques applied in chemical laboratories the radioisotopes H-3, C-14, P- 32, S-35 and Cr-51 are used commonly. But it is less known that in most of the liquid scintillation counters radioisotopes are installed for quenching control, as for example: Ba- 133, Cs-137, Eu -152 and Ra-226. Some chemical detectors use Ni-63 or Am-241. It is also less known that radioisotopes in ion mobility spectrometry techniques are usually built in the instrument using these techniques. This chemical method is widely used nowadays.
According to the knowledge of the authors this is the first published article giving overview over the instruments containing radioactive sources which are mentioned.
Although instruments mentioned above are made user friendly, a proper warning sign for radiation is labelled rarely. This can easily result in overlooking the presence of radiation source. Radiation safety requirements should be discussed before any use of such instruments taken into account also maintenance procedure. As appropriate, the transport and shipment regulations should be considered, as well as the storage before a purchase and after a use of an instrument, taken into account the contemporary security procedures.
1 INTRODUCTION
The inventory of ionising sources in a country is one of the main steps towards an effective control of the exposures to the population in general, workers or to the patients. In addition, such inventory can be also used as a tool in specific programmes related to protection of environment which became very important issue regarding The 2007 Recommendations of the International Commission on Radiological Protection of the
valuable data when assessments of the overall security of installations, sites or country as a whole is prepared, taking into account additional possible threats which could exist.
In the last years a comprehensive inspection programme is taking place in Slovenia in order to set up a complete inventory of ionising sources in the country. The programme was described several times e.g. in [1, 2, 3, 4, 5]. The initialisation of the programme is related to a fact that a basic legislation, namely a law related to radiations and nuclear safety was updated in the year 2002. After that year a comprehensive updating of all radiation and nuclear safety legislation has been taking place. The legislation related to ionising sources in mainly based on the EURATOM directives of the European Union, e.g. [6, 7, 8, 9, 10]. The inventory of ionising sources is very often related to an inventory of radioactive waste, so that the same item listed in an inventory of radioactive sources could be under specific circumstances treated as radioactive waste. A strong collaboration between SNSA inspection programme and activities of the Agency for Radioactive Waste Management, which is in Slovenia a responsible agency for management and storage of radioactive waste, was necessary.
The inspection programme of the Slovenian Nuclear Safety Administration - the responsible regulatory authority for all sources not used in medicine and veterinary medicine - was mainly focused on sources related to the highest risks e.g. sources used in industrial radiography or to the inspection of nuclear facilities and sources which were not at all under the control in the past. The inspectors focused on the research institute which was established after Second Word War performing activities related to nuclear fuel cycle. Later the inspectors focused on other research institutes as well as educational institutions (i.e.
universities) where radiation sources were either used in the past or were still used at the time of inspections. In both cases usually no data existed regarding inventory of ionising radiation sources. Some less known applications of radioactive sources were identified mainly in research laboratories, e.g. uranium compounds in a chemical laboratory which took part in renovation processes of artistic objects. In 2008 and 2009 the inspections of military facilities followed in accordance with the competence of the SNSA inspectors.
As a result, the inventory of sources used in Slovenia has been regularly updated. The statistical analysis of sources regarding their types and numbers has been regularly published in the Annual Reports on the Radiation and Nuclear Safety in the Republic of Slovenia, being available on the http://www.ursjv.gov.si/en/info/reports/.
2 CHEMICAL LABORATORIES
After the Becquerel’s discovery, radioactive materials become widely used in different types of research and application. Nowadays in research laboratories radioactive materials are used in laboratories performing radiobiological or radiochemical research, research of materials as well as in calibration laboratories. Some typical physical methods, related to radioactivity of material under a study, also use radioactive materials. As for example, calibration of gamma spectrometers is preformed by using typical calibration sources of smaller activity e.g. Am-241, Cs-137, Co-60. A use of radioisotopes in a typical chemical laboratory is less known, resulting in a lack of awareness required in order to apply all protection measures. A use of ionising sources in chemical laboratories could be:
a. electric apparatus which is due to a high voltage applied a source of ionising radiation e.g. electron microscope, X-ray fluorescence analyser
b. chemicals (U and Th compounds) or an object of a study in a chemical process e.g.
Tc-99
c. radioactive source built in a chemical equipment e.g. Ni-63 in the ECD.
Each of above mentioned group has its known characteristics regarding radiation safety:
a. Today radiation protection measures which are applied during design and construction of modern electric apparatus causing ionising radiation guarantee that during a normal use of such apparatus no unintentional exposure occurs. Additional caution is required only when performing servicing of such apparatus.
b. Far more caution is required when radioactive compounds in a form of chemicals are used, because laboratories and persons can be contaminated very easily. Also today researchers in chemical research laboratories use uranium or thorium compounds in a form of unsealed sources [4]. Their uses are less frequent as in the past when uranium acetate was for example widely used for the preparation samples to be investigated with an electron microscope. Moreover, sometimes also other radioactive compounds as unsealed sources could be identified in chemical laboratories as for example Tc-99 as given in [4].
c. Chemical instruments containing radioactive materials built in them require a comprehensive study of all lifetime phases in order to assess a risk associated to a specific phase. Namely, due to high standards of producers an appropriate use of such instrument does not pose a substantial risk to a user while dismantling a used instrument could require strict procedures related to radioactive waste management. In addition, in order to assess a radiation risk not only characteristics of radioisotopes should be studied but also handling the instruments during normal operation and during any servicing procedure. Risks associated to storage of such instrument should be studied either before purchasing or after its lifetime when a source could become a radioactive waste. In some cases also transport and shipment regulations should be studied in order achieve safety and security of radioactive sources from a cradle to a grave. A list of chemical instruments containing radioactive materials identified during inspections of the SNSA mentioned, contains:
- ion mobility spectrometers (IMS) - liquid scintillation counters
- electron capture detectors for gas chromatography.
According to the knowledge of the authors this is the first published list of chemical instruments containing radioactive materials used nowadays. The equipment containing radioactive materials is very often used not only within chemical laboratories but it is used in various areas by personnel not experienced in chemical methods. For example, it can be a standard equipment of military or civil security service on one hand while it can also be used by agronomical researchers conducting soil measurement. Regarding the literature also other chemical instruments containing radioactive sources called chemical detectors have been constructed [11, 12], e.g. for monitoring leakage of gases, refrigerants and products of combustion. Some authors include IMS in a group of so called chemical detectors [13].
3 CHEMICAL INSTRUMENT USING RADIOACTIVE SOURCES 3.1 Ion mobility spectrometer - IMS
In ion mobility spectrometry techniques the radioisotopes are built in the instruments.
Usually Ni-63 and Am-241 are used as a radioactive source. The source ionises a sampling gas which is than analysed using electric field. The details of the method which was extensively developed after 11 September 2001 attack on America are given in [11]. This chemical analysis which provides detection of toxic or harmful gases is widely used nowadays especially in relation to security issues. The IMSs are very often dedicated to detect
TNT) or drugs (e.g. cocaine, heroin) under very specific conditions e.g. high operating temperature. The detectors are known under commercial names e.g. M90, MGD1, ChemPro100, Vapour Tracer, Vapour Detector. Figure 1 shows photos of two types of such instruments, namely M90 and ChemPro 100, while table 1 gives details regarding radioisotopes used in such instruments.
Figure 1: IMSs used for detection of toxic or harmful gases, M90 on the left picture and ChemPro 100 on the right picture, both with Am-241 source installed in (Photos taken by the
inspection of the SNSA.)
Table 1: Characteristics of typical radioisotopes used in IMSs as well as exemption levels given by the European Union legislation [9]
Radioisotope Radiotoxicity [14]
Half life [years]
Typical activity [MBq]
Exemption levels [Bq]
Ni-63 5 100 100 * 1E+08
Am-241 1 432.7 5.9 1E+04
* Taken from [11]
Such instruments are widely available nowadays. High quality standards are usually followed by their producers so that instruments have better detection characteristics. They are also user friendly. As shown in the table 1 the activity of Am-241 is 590 times above the exemption level. This is not the case when Ni-63 is installed as a source. A user should very carefully study physical characteristics of the IMSs. Their normal use does not pose any particular attention but the service of such instruments requires special procedures taking into account also radiation protection measures. The personnel conducting a service should be trained, usually provided only by the producer. The user should be also aware about the radioactive waste management issue when purchasing such equipment especially taken into account half lifetimes of Ni-63 and Am-241. Any storage of such instrument should be appropriate taken into account that not only one source is usually stored as well as taken into account the fact that security measures should be appropriate.
Very often producer originates from countries with different standards than standards required within European Union. As a consequence no radiation sign is labelled on such instruments. Such neglecting of this basic requirement of radiation safety can easily lead to unsafe handling or disposal of the instrument taking into account that a user is not aware that the source is actually built inside the instrument.
3.2 Liquid scintillation counter
With liquid scintillation techniques applied in chemical laboratories, the radioisotopes H-3, C-14, P-32, S-35 and Cr-51 are measured commonly. It is less known that in most of the liquid scintillation counters, the radioisotopes are installed for quenching control, as for example: Ba-133, Cs-137, Eu -152, Ra-226. The details of the quenching method are given elsewhere [15]. Figure 1 shows typical liquid scintillation counters also sometimes called liquid scintillation detectors with external standards. Table 1 gives details regarding radioisotopes used in such instruments which were identified during inspections of the SNSA.
Figure 2: Liquid scintillation counters using Ra-226 radioactive sources for quenching control, Wallac LKB 1214 Rackbeta in a use on the left picture and already stored as a waste
on the right picture (Photo taken by the SNSA inspection.)
Table 2: Characteristics of radioisotopes used in liquid scintillation counters for quenching control identified during inspection of the SNSA as well as exemption levels given
by the European Union legislation [9]
Radioisotope Radiotoxicity [14]
Half life [years]
Typical activity [Bq]
Exemption levels [Bq]
Cs-137 1 30.2 1.1E+06 1E+04
Eu-152 3 13.5 7.40E+05 1E+06
Ra-226 1 1600 3.70E+05 1E+04
It is shown that, except in the case of Eu-152, the installed sources are well above the appropriate exemption levels. Regarding radiation protection measures no unintentional exposure is expected. In all cases identified during inspection of the SNSA, the source was installed at the most distant position from the position of a person handling the instruments in a normal operation mode. In all other circumstances e.g. maintenance a qualified personnel is required. In addition, a problem related to radioactive waste management should be envisaged when purchasing such equipment.
Producers usually label on the outer sites of liquid scintillation counters a warning sign.
But in all cases found at the SNSA inspections, the signs were given only at the closes site to sources, i.e. on the back of the instrument. As a consequence the user is usually not aware about radioisotopes within the equipment and can easily treat the instrument after its use as non-dangerous waste. Such a case was actually identified during the SNSA inspection of the research institution.
In should be also noted, that such application of sources is very rarely described in the literature giving an overview of uses of radiation sources.
3.3 Electron capture detector - ECD
Well known radioactive isotopes present in chemical laboratories are H-3 or Ni-63 used in gas chromatography. The instruments are known as ECDs and are widely used in the detection of pollutants. The radioisotopes are used as a source of low energy beta radiation in order to form negative ions together with the molecules studied. The details regarding the ECDs are described elsewhere [11]. Figure 3 shows the typical gas spectrometer using Ni-63 and table 4 presents characteristics of the radioisotopes used.
Figure 3: ECD on the left picture and a permanent warning on a metal plate inside the ECD which warns a user that Ni-63 source is inside the instrument on the right picture (Photos taken by the SNSA inspection.)
Table 3: Characteristics of the radioisotopes used in ECDs as well as exemption levels given by the European Union legislation [9]
Radioisotope Radiotoxicity [14]
Half life [years]
Typical activity [GBq] *
Exemption levels [GBq]
H-3 5 12.3 11 1
Ni-63 5 100 1 0.1
* Taken from [11]
Regarding activity of sources installed in ECDs, they do not pose any substantial risk when users strictly follow procedures given by producers. Usually, a special attention should be given to the gas exhaust because of a possible contamination of a laboratory by the contaminated gas. In addition, replacement of a sources as well as servicing procedures requires the qualified personnel provided usually by a producer. The user should be also aware about the radioactive waste management issues when purchasing such equipment especially when radioisotope Ni-63 is installed in the instrument.
Producers usually do not label on the outer sites of ECDs any sign to warn a user that a source is inside. As a rule they also do not label the instrument with the sign that a special caution should be taken regarding the gas exhaust. Usually they label a permanent warning on a metal plate which is firmly attached to the instrument. Such warning is not visible during the use of the instrument but only when a cover of the instrument is open.
4 CONCLUSIONS
Radioactive sources built in the instrumentation using chemical analytical methods have been used for decades. Today besides ECDs and liquid scintillation counters with built in radioisotopes, also IMSs are widely used. The radioisotopes built in them can have the activity around exemption levels while in some cases the activity could be few orders of magnitude above exemption levels. The radiotoxicity of sources spans from 1 to 5, and half lives from about ten years to 1600 years. Regarding all these facts a risk assessment should be very carefully done prior any use of such instruments. Although a normal use does not contribute any significant dose to a user, maintenance could require strict precautions. In some cases also storage and transport of such instruments should be assessed regarding radiation safety. Also handling of built in sources as radioactive waste could be necessary at the end of a use of the instruments. As a rule the inspection of the SNSA identified neglected precaution measures due to the fact that a producer did not pay enough attention to inform a buyer about a source inside the instrument.
Since the September 11, 2001 a new development of the IMS techniques has occurred in order to take into account required high standard of detection capabilities. In addition, producers take into account a fact that instruments can be used in a very demanding environment. They also consider a fact that such instrument will not be used only by experts.
Nowadays the handling of such instrument is not complicated and appearance of such an instrument is close to a look of a big cell phone by purpose [16]. As a result, the presence of a source built in such instrument can be very easily neglected leading to a non compliance with the basic safety standards and to potential radiation risk. Also a requirement to properly secure a storage of such instruments can be easily neglected.
Such non-compliances taking into account radiotoxicity of radioisotopes as well as the magnitude of activities - which is in some cases higher than orders of magnitude above exemption levels - could pose significant risk to the workers as well a general public. Handing of such sources without taking into account precautions required for such sources could lead in a short time to doses well above annual dose limits. Taking into account that unshielded sources pose a specific threat, a special attention should be paid to disposal of such sources or to a their safe return after their use to the producers.
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