Radioactive Sources service web site

_yellow metal box, source, isotope permit, warning panel

Brochure 'Use of Radioactive Sources'   [pdf]

Source request form   [restricted access to CERN users]

Website of the Radiation Protection Group

Website of the Radioactive Shipping service

GESO database   [restricted access to RP]

Sources RP-Tools page   [restricted access to RP]

Shipping RP-Tools page   [restricted access to RP]

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The Radiation Protection Group DGS/RP maintains a stock of radioactive sources for various uses. The RP Group is in charge of the purchase and loan of the radioactive sources, holders and shielding, as well as the registration and updating of the radioactive sources database. The RP group performs periodic inspections on sources installed in various parts of CERN.

The service is open every day from 8:00am to 5:00pm
Building 24/E-024
- Email: 
- TÚl: +41 22 76 73171
- Fax: +41 22 76 69200

Use of radioactive sources

Radioactive sources

a. Length of loan and periodic checking
  • Any request for sources should be made using the corresponding form, the Radiation Protection Group DGS/RP, which holds a stock of the most commonly used radionuclides (22Na, 54Mn, 55Fe, 57Co, 60Co, 65Zn, 90Sr + 90Y, 106Ru, 109Cd, 134Cs, 137Cs, 152Eu, 207Bi, 241Am), will contact you later. Every person who uses a radioactive source must be in possession of an personal dosimeter and cannot be registered as short-term visitor (VCT).

  • At the time of the loan, an expiry date for an inspection will be given. It is then the responsibility of the source-user to arrange with the Radioactive Source Service an inspection of the state of the source for the loan-renewal or the return of the source when it is no longer required.
  • For special sources (radionuclides not kept in stock, non-standard holder, etc...), the RP Group provides advice to users in order to find the most appropriate solutions.
  • Radioactive sources used and imported at CERN must be sealed according to ISO2919 standard.
b. Transport
  • An authorization from RP Group is required before the source is moved: internally at CERN (transfer from one room or site to another) or externally (import or export).
Source movement
c. Dosimetry
  • Personal dosimeters must be worn at all times when a radioactive source is being used. You will be provided with other dosimeters (operational or extremity dosimeters) as necessary.
d. Using and storing the source safely
  • Each user is responsible for borrowed sources and is provided with comprehensive safety instructions on their use. This information must be passed on to all those using the sources. If in doubt, do not hesitate to contact RP Group (73171) for additional information.
  • Sources must be returned to the RP Group if they are no longer in use or if the person responsible for it is leaving CERN. However, if they remain in the same users group, the name of the new person in charge will have to be forwarded to the RP Group.
"Isotope permit"
  • For dangerous and highly dangerous sources, the RP Group supplies storage safes which are resistant to fire. Care must therefore be taken to ensure that the sources are stored inside them and locked when not in use. Lower-radioactivity sources must be locked away in small clearly marked metal boxes.
Storage safe
  • Every source must be accompanied by a small yellow warning sign.
  • The presence of dangerous or highly dangerous sources and their location must be clearly indicated at the entrance to premises where they are used. During lengthy uses not requiring the physical presence of an operator, NO ENTRY or NO CLEANING signs must be posted in the area concerned.

  • Users must keep an up-to-date map (useful to the CERN Fire Brigade in case of problem) showing the location of all sources which are under their responsibility.

  • For obvious reason, abrasion or etching of the surface of the sources and any structural modifications to the latter are prohibited.

  • Do not use a source in a "hazardous" environment (corrosive, vacuum, high or low temperatures, ...), without agreement of the RP group.


  • Never place a source in the vicinity of, or in a beam.
  • For gamma radioactive sources of high intensity, please consult  the specific requirements available in EDMS 607580.

External irradiation and contamination risk

Gamma irradiation

a. Exposure to gamma radiation

The three parameters to be taken into account to minimize radiation doses are:
  1. the distance from the source,

  2. thickness of the shielding,

  3. the length of exposure.

The RP Group assists with the installation of high gamma activity sources and draws up special instructions.

b. Exposure to beta radiation or X rays

In the case of 90Sr and 106Ru sources, which are widely used at CERN, localized exposure of skin and eyes remains the major hazard. For a 37 MBq (1 mCi) source, the beta radiation dose rate is of the order of 10 Sv/h.

To avoid any accidental exposure, make sure prior to handling the source that the collimator is in the off position. Once the collimator is on, never point the unscreened part of the source towards the eyes, the hand or any other part of the body.

Although having equivalent activities, doses are lower in case of X-ray or low energy g emitting sources (55Fe, 109Cd, etc....), the same rules as for beta sources must be applied.

c. Contamination risk

There is a latent risk of contamination from open alpha sources and from sources where the alpha emitter (essentially 241Am) is deposited by electrolysis onto a metal disk. It is therefore strictly forbidden to touch the radioactive deposit of such sources with the fingers. The dose equivalent of 241Am when ingested or inhaled is very high (0.2 ÁSv/Bq by ingestion - 27 ÁSv/Bq by inhalation). If this figure is compared to the CERN annual dose limit (20 mSv), it will be realized that this value can very rapidly be exceeded by ingesting or inhaling alpha emitters.

In case of problems or questions please contact :
Phone: +41 22 76 73171

Last Update: 08/02/2021