Please send a message to the Dosimetry Service giving details of the flights you have taken and their respective dates. Readout your dosimeter as soon as possible at one of CERN's reader stations so we can check the measured dose value.

You may take your CERN dosimeter outside CERN under certain circumstances if you are an employed member of the personnel. Please get in contact with the Dosimetry Service as soon as possible. We will require some information on the installation your will visit, the means of transport, the duration, the kind of intervention or work performed and contact names and addresses. You will in most cases require a radiation passport which will be established by the Dosimetry Service.

When you readout your dosimeter at the reader stations, the dose value displayed in mSv has been corrected for the natural background contribution. It is therefore normal that the value shown is 0 or close to 0 if you have not been exposed to ionising radiation or only to very low levels of radiation since the assignment of your dosimeter. The background subtraction is the same for all CERN locations, however the background is not the same within the larger CERN boundaries. If the background at you location is lower than 2.3 µSv/day your dosimeter is slightly over-corrected and this is why it might always be at 0.

If you have been accessing Radiation Areas and expected that you took a dose well above 0 ( > 100 µSv), please get in contact with the Dosimetry Service.

The first answer would be: why do you need a dosimeter if you don't go in radiation areas ? If you don't use your dosimeter for more than one month, please return it to the service.

The technical explanation is that the dose that you read on the reader is background compensated by 2.33 µ​Sv/day since the attribution of your dosimeter. If you don't go in radiation areas you should then read 0 mSv all the time, however your dosimeter is continuously registering a natural dose. This 2.33 µ​Sv is a fix mean value estimated for all CERN locations. But in reality the natural background is not the same everywhere within CERN large boundaries and it fluctuates from on place to another. Should the natural background be a little higher at you location, the value read is the part of the background that has not been compensated by the automatic subtraction of 2.33 µ​Sv/day. The value increases because the read doses are accumulating since the attribution of your dosimeter.

Should you read a value that unexpectedly increased of more than 0.2 mSv in one month, please contact the Dosimetry Service.

You should store your dosimeter, if you do not need to wear it, in an office at CERN or at a dosimeter shelf, which are still present in some buildings. Avoid taking your dosimeter off-site, if not required.

If you don't have an appropriate place at CERN to store your dosimeter, you may exceptionally take it with you off-site. The dosimeter shall not be kept in a car to avoid exposures to high and low temperatures.

In general, keep the dosimeter away from radiation sources, heat sources, cold temperatures, high humidity levels or strong light (sunlight).

Damaged dosimeters will be charged to the user at a value of 350 CHF.

The explanation is due to the fact that they are not calculated in the same way and not evaluated for the same periods.

The personal dose is background subtracted, all monthly doses below 75 µSv are rounded to 0 in official reports, following the recommendation (original pdf document only available in German​) of the Swiss Federal Commission on Radiation Protection, and the 'month'  is calculated on a period that depends on your reading frequency. If you read your personal dosimeter on the 1^st of January and then the 20^th of February, your month of January will be closed by your first February reading and will count 51 days. If you then read your dosimeter on the 2^nd of March, the month of February will only count 10 days.

The operational dose does not have background subtracted, no operations are performed on the dose and the monthly dose is simply the sum of all your doses based on calendar months.

Therefore the doses will never be comparable as they are not calculated in the same way and not accounted during the same time periods.

E.g.: If you accumulate 50 µSv each month, at the end of the year your official dose report will show a dose of 0 µSv ( 50 µSv is below 75 µSv so rounded to 0 µSv) whereas your annual operational dose will be 600 µSv.

Additionally, the two dosimeters do not have the same energy response and are not placed in the same place on your body and therefore do not necessarily 'see'  the same radiation levels.

The Dosimetry Service applies the legal recommendations for dose calculation in Switzerland. The 2004 recommendation (original pdf document only available in German​) by the Swiss Federal Commission on Radiation Protection states that all monthly doses below 75 µ​Sv (=0.075 mSv) should be rounded to 0 when transmitted to the Authorities. Why is this so? At CERN we use a very accurate dosimeter: the DIS-1. It has a detection limit as low as 1 µ​Sv, whereas most of the other dosimetry services in Switzerland use other detection techniques that have a detection limit of 50 µ​Sv. Below this threshold they cannot tell if there is a dose or not. It is therefore understandable that CERN does not report doses that the other dosimeters cannot 'see'.

The second reason is that there is high fluctuation in background in Switzerland, depending on your location. If someone is in a region with a high background he will record a higher monthly dose than in low background regions. But this dose is the result of natural radiation and it should not be taken into account as a real dose for workers. This is why the experts have fixed the limit at 75 µ​Sv. In practice, if you read a dose below 0.08 mSv on the reader your official monthly dose will be 0 mSv.

The Dosimetry Service provides you with a gamma and neutron dosimeter. The blue part on the top of your dosimeter is an RF identifier which allows identification for access control to certain areas. This part of the device is managed by the Access Service: acces.registration@cern.ch.

Access refusal is not necessarily linked to your dosimeter. It is possible that your access authorizations have been withdrawn or your safety courses are no longer valid. You can check all your access authorizations and safety course validity status on ADaMS. If the message "Person with RFID card and no active card in FOUNDATION" is shown on your ADaMS profile, your biometry is not active. You need to come to the Biometry Service in Building 55 to update your biometry status. However, if you dosimeter status is shown as invalid, please contact the Dosimetry Service.

Firstly, try to readout your dosimeter at another reader station. If the error message persists, please go to the Dosimetry Service in B.55. The problem could be with your dosimeter or the reader stations which do malfunction from time to time.

Please get in contact with the Dosimetry Service and pass by B.55. We need to check your records and that your dosimeter is functioning correctly.
 

Please ask a colleague or your secretary who have access to your dosimeter to change it for you. If you have taken your dosimeter abroad with you, do not return it via mail but contact the Dosimetry Service first.

Yes - if you are not entitled to a short-term dosimeter.

You will need to follow a radiation protection training course in accordance with the area classification where you will be working (Supervised or Controlled Radiation Area).

Persons under the age of 16, must not be classified as occupationally exposed radiation worker according to Safety Code F, 3.4.4. Hence they are not authorised to obtain a personal dosimeter and must not work in radiation areas.

Persons between 16 and 18, may be classified as occupationally exposed radiation worker if this activity is an essential part of their education. Their annual dose limited to 6 mSv, they must not be classified as Category A worker. (Safety Code F, 3.4.5)

No, once you have successfully completed the training you are not required to redo the training. Refresher course are currently under development and they will become mandatory every three years. The concerned personnel will be informed in due time.

A Radiation Passport is an official document edited by your employer, national dosimetry service or national authority in matter of radiation safety.

This document contains the details of the radiation doses integrated during previous years and current year. It might also detail your trainings, classification type as professionally exposed worker and abilities.

CERN can provide you with such a document to summarize doses integrated at CERN if needed by a third party or if you are visiting an external institute that would require it.