Check Sources

6706 + 6706-1Check Source 6706 with Lead Container 6706-1, nuclide Cs-137, nominal activity 333 kBq, design according to DIN 44427 (although this standard has been withdrawn in the meantime). In EU Member States, practices involving this Check Source require reporting to the respective competent authority because the source's activity exceeds the exemption value of 10 kBq.

Together with the respective Source Holder this Check Source is suited for regular checks of many of our instruments.

Data sheet 6706

Why exactly 333 kBq as the activity? This comes from the history of German radiation protection regulations. Back in 1965, the »exemption value« for Cs-137 was 10 µCi (370 kBq). In order to remain below this limit, and because the source's activity tolerance is 10%, a long time ago the nominal activity was chosen at 90% of the then valid exemption value of 10 µCi, which amounts to 9 µCi or 333 kBq (mathematically correct would have been 370 kBq / 1.1 = 336 kBq, which provides an additional safety margin of 3 kBq).

On this occasion it is quite interesting to have a look at history showing how differently the Check Source was classified in the course of time:

German regulation of Exemption value for Cs-137 Activity of one 6706
1965 10 µCi (370 kBq) 0.9 exemption values
1976 1 µCi (37 kBq) 9 exemption values
1989 500 kBq 0.667 exemption values
2001 10 kBq 33.3 exemption values

This is how things can change, even if the things themselves do not change at all!


6707Check Source 6707 with Steel Container 811.1, nuclide Cs-137, nominal activity 333 kBq ±10%. In EU Member States, practices involving this Check Source require reporting to the respective competent authority because the source's activity exceeds the exemption value of 10 kBq.

This Check Source is intended and suited for the Scintomat 6134A(/H) only. It has the shape of a cylinder the circular faces of which have collars allowing to click either end of the cylinder onto the Scintomat's probe in place of the protective cap. One face is made of grey material, the other one is black like the body of the cylinder. The radioactive source is inside the cylinder directly behind the centre of the black face. Therefore the distance from the source to the scintillator depends on the orientation you put the check source on the Scintomat. This allows to expose the Scintomat to two well-defined dose rates which differ by approximately a factor of 10 (7 µSv/h and 0.07 mSv/h).

Nuclide and activity (Cs-137 and 333 kBq) are the same as for the type 6706, so for the 6707 the same rules for practices apply.


6708Check Source 6708, emits alpha- and beta radiation, 1 kBq Am-241 + 2 kBq Sr-90, activity tolerance ±30% for both nuclides. Particularly suited for checks of the Contamination Probes 6150AD-k and 6150AD-17. The total activity is below the European exemption value (10 kBq for both Am-241 and Sr-90) which considerably facilitates practices involving this Check Source.


Notes on Practices (particularly Transport) involving Check Sources

Practices involving radioactive substances are subject to national regulations, see our leaflet on this subject. For EU Members the Council Directive 96/29/EURATOM or, at latest on 6 February 2018, its successor 2013/59/EURATOM applies.

Shipping check sources may be a transport of dangerous goods. We strongly recommend to use a suitable forwarder for that purpose. Even then you will have some duties regarding packaging and shipping documents. We would now like to give you some information on this subject, however, although carefully compiled, without obligation and restricted to our Check Sources. We took this information from the following regulations: ADR is an European regulation referring to international road transport of dangerous goods, and RID is a regulation referring to international rail transport of dangerous goods. In case of air freight IATA (International Air Transport Association) rules apply. All these regulations specify exemption values for the total activity of one shipment. As long as these exemption values are not exceeded, the substances are not radioactive in the sense of the respective regulation and thus are no dangerous goods. The exemption values of the nuclides contained in our Check Sources are:

Nuclide Status of 2014: exemption values according to ADR and IATA, and also according to 96/29/EURATOM and its successor 2013/59/EURATOM
Cs-137 10 kBq
Sr-90 10 kBq
Am-241 10 kBq

It is surely not mere coincidence that all these regulations specify identical exemption values. Nevertheless, note that each regulation specifies exemption values of its own. If the exemption values are exceeded, however do not exceed certain multiples (»A1 / A2 values«) of the exemption values, the goods can be shipped as »Excepted Package«. An Excepted Package is a safe package containing dangerous goods in a condition that allows safe transportation. Transporting Excepted Packages is facilitated and does not require a particular transport authorisation, at least according to German regulations.

ADR and IATA requirements for Excepted Packages are almost identical. Those of our Check Sources which exceed the exemption value can be shipped as »UN2910 RADIOACTIVE MATERIAL, EXCEPTED PACKAGE - LIMITED QUANTITY OF MATERIAL, CLASS 7, ADR (or RID)« (exceeding the »A1 / A2 values« would require hundreds or even thousands of Check Sources). Apart from the limited quantity there are other requirements the excepted package has to meet:

  • The dose rate at any point on the external surface of the package must not exceed 5 µSv/h. For a physically small radioactive substance this goal may already be reached by placing it at the centre of a sufficiently large carton. In case of the Check Source 6706 we recommend to store it such that any point of the lead container is at least 5 cm away from the surface of the package. This will meet this requirement with sufficient safety margin.
  • The package must enclose its radioactive content safely under standard transport conditions. The inside of the package must bear the marking »RADIOACTIVE« thus indicating clearly the presence of radioactive substances when the package is opened.
  • The package must meet general design rules for good packaging. However there are no special rules for design, testing or approval of the packaging of Excepted Packages.
  • The removable surface contamination on the external surface of the package must be as low as possible and must not exceed these limits:
    4 Bq/cm² for beta or gamma emitters and low toxicity alpha emitters;
    0.4 Bq/cm² for all other alpha emitters. Since our Check Sources 6706 and 6707 are leak-proof, they cannot cause contamination, neither of the package nor in general, as long as they are not damaged.
  • The outside of the package must be marked, clearly legible and durable, with the identification of both the shipper and the consignee.
  • The outside of the package must be marked with the four digit UN identification number preceded by the letters »UN«, that is »UN2910« in our case. The official designation of that UN number, that is »RADIOACTIVE MATERIAL, LIMITED QUANTITY OF MATERIAL« in case of UN2910, is not required on the outside of Excepted Packages. Should the packages be within an outer packaging, that outer packaging must also bear this marking.
  • All (external) markings
    a) must be clearly visible and legible,
    b) must withstand weather without substantial reduction in effectiveness,
    c) IATA only: must clearly contrast with the background. For this purpose the edges of the label »UN2910« must bear a red diagonal hatch. Of course it is convenient to use such particularly well noticeable labels also for other than air freight shipments.

The shipping documents must include these declarations:

  • UN identification number and official designation, that is »UN2910 RADIOACTIVE MATERIAL, EXCEPTED PACKAGE - LIMITED QUANTITY OF MATERIAL«.
  • Number and description of the packages, and for each UN number the total quantity of the dangerous goods as gross or net weight (e.g. 1 carton, total gross weight 3 kg).
  • Name and address of the shipper and the consignee.
  • The following note: »TRANSPORT NOT EXCEEDING THE MAXIMUM QUANTITIES SPECIFIED IN SUB-SECTION 1.1.3.6 OF ADR«.
    However, you must not include this note if you have the dangerous goods transported by third parties and do not know which dangerous goods these third parties may else transport on their vehicles. Only the third party can know whether the quantities specified in sub-section 1.1.3.6 of ADR are exceeded, and has to act accordingly.

Not required for Excepted Packages, however not disturbing either, are these additional declarations in the shipping documents (not on the outside of the package):

  • Class (category) of the dangerous goods, i.e. 7
  • Name or symbol of each radionuclide (e.g. Cs-137).
  • Description of its physical or chemical form (e.g. Check Source 6706).
  • Maximum activity (e.g. 370 kBq).
  • Notes on actions the forwarder may have to take (e.g. »No special steps must be taken for loading, stowing, transportation, storage, handling, and unloading.«).

Here you can find a sample for a covering letter we use. It includes more than the required information.

If a shipment contains radioactive substances below the exemption values, this may nevertheless lead to unjustified excitement should the shipment be checked during transportation. In order to avoid this, ADR expressly allows to include an appropriate declaration in the shipping documents, e.g. »NO DANGEROUS GOODS OF CLASS 7«. This permits the shipper to state clearly that the goods are no dangerous goods in the sense of ADR. Here you can find a sample for a covering letter we use for that purpose.


Other Countries, other Manners...

As just discussed, there is considerable international agreement on exemption values. However, needless to say that there are also national differences. Let us take Switzerland as an example. Although Switzerland is not an EU Member, it has close economic relations to the EU. Nevertheless, Swiss exemption values are different:

Nuclide Exemption values according to 96/29/EURATOM and its successor 2013/59/EURATOM Permission limits (»Bewilligungs­grenzen«) according to the Swiss radiation protection regulation, status of 01 January 2012
Cs-137 10 kBq 700 kBq
Sr-90 10 kBq 60 kBq
Am-241 10 kBq 0.2 kBq

This results in the surprising fact that our Check Sources are classified inversely in Switzerland and the EU:

Check Source where 96/29/EURATOM or its successor 2013/59/EURATOM applies in Switzerland
6706, 6707 requires reporting/notification free
6708 free requires permission because of Am-241

Probably there are many more examples. However, we shall not try to compare all countries on this earth with respect to their exemption values. We would just like to recall that »global economics« do not release you from the duty to take care of your national regulations.


Check Sources with other Radionuclides?

Of course it would be desirable to use Check Sources the activity of which does not exceed the exemption values. This rules out Cs-137 as a candidate because 10 kBq are not enough to produce a sufficiently high indication at the instruments. Alternatives would be Ba-133 (half-life 10.5 years) and Eu-152 (half-life 13.5 years). The exemption value for both of these nuclides is 1 MBq (status of 2010). Eu-152 is better suited from the technical point of view because of its longer half-life and its higher average photon energy. A 1 MBq Eu-152 Check Source would be quite a strong source producing approximately 17 µSv/h at a 10 cm distance. Without an additional shielding, and in a small package, this Eu-152 Check Source would not meet the requirements for Excepted Packages although it is not even a dangerous good because it does not exceed the exemption value. This sounds contradictory. In 2006 we asked our competent authority to resolve this contradiction, however did not get an officially binding reply. Therefore we decided not to change to a different Check Source. Such a change would require considerable effort (amendments to type approvals and manuals) and might after all be in vain, for example because the exemption values may change again, or some authority may take the view that for other legal reasons handling such a Check Source needs supervising although its activity does not exceed the exemption value.


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