Frequently Asked Questions

While passing from one supervised radiation area to another through a simple controlled area, no operational dosimeter (DMC) is required. This applies as well if you need to work in a simple controlled area. The operational dosimeter is only required in Limited Stay Controlled Radiation Areas, as indicated on the classification signs.

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 1st of January and then the 20th 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 2nd 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 passive dosimeter at CERN is the personal, legal or DIS dosimeter. Dosimeters such as TLD or OSL are called 'passive' as they do not provide direct readouts and can operate without any active means. The measured dose is usually taken as an estimate for the effective dose which is recorded and reported after evaluation. The CERN DIS dosimeter should be called semi-passive as it has a battery and can be read at anytime at a reader station for a direct reading of the dose stored inside. But it is called passive as well in order to differentiate it from the active or operational dosimeter.

The active dosimeter is also called electronic, operational, alarm or DMC dosimeter. It provides a direct display of the accumulated dose as well as having some additional functions such as alarm threshold settings for dose or dose rate values. In addition it provides an audible and visual indication of the dose rate level. The dosimeter requires a battery to operate. This dosimeter is used for complementary dosimetry in the case of high radiation levels or for work and dose optimisation purposes.

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.

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.

The passive dosimeter at CERN is the personal, legal or DIS dosimeter. Dosimeters such as TLD or OSL are called 'passive' as they do not provide direct readouts and can operate without any active means. The measured dose is usually taken as an estimate for the effective dose which is recorded and reported after evaluation. The CERN DIS dosimeter should be called semi-passive as it has a battery and can be read at anytime at a reader station for a direct reading of the dose stored inside. But it is called passive as well in order to differentiate it from the active or operational dosimeter.

The active dosimeter is also called electronic, operational, alarm or DMC dosimeter. It provides a direct display of the accumulated dose as well as having some additional functions such as alarm threshold settings for dose or dose rate values. In addition it provides an audible and visual indication of the dose rate level. The dosimeter requires a battery to operate. This dosimeter is used for complementary dosimetry in the case of high radiation levels or for work and dose optimisation purposes.

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 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.

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).

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.

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. 

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.

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)

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 1st of January and then the 20th 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 2nd 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 first answer would be: why do you need a dosimeter if you don't go into radiation areas? If you don't use your dosimeter for more than one month please return it to the Dosimetry Service.

The technical explanation is that the dose that you read on the reader is the background compensated by 2.33 µ​Sv/day since the attribution of your dosimeter. If you don't go into radiation areas you should read 0 mSv all the time, however your dosimeter is continuously registering a natural dose. This 2.33 µ​Sv is a fixed mean value estimated for all CERN locations. But in reality the natural background is not the same everywhere within CERN's larger boundaries and it fluctuates from one place to another. Should the natural background be a little higher at your 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 have been accumulated since the attribution of your dosimeter.

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

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.

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)

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.

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).

Use (12)

While passing from one supervised radiation area to another through a simple controlled area, no operational dosimeter (DMC) is required. This applies as well if you need to work in a simple controlled area. The operational dosimeter is only required in Limited Stay Controlled Radiation Areas, as indicated on the classification signs.

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.

All European countries have integrated the EURATOM directives concerning workers occupationally exposed to ionising radiation into their national regulations. One of these directives concerns the obligation for the employer to ensure the dosimetry and medical follow up of his exposed workers. This obligation exists in the Swiss ordonnance on radiation protection and in the French labour regulations (code du travail). It is therefore a legal obligation for the employer. In parallel, CERN controls that the dose limits of its own Radiation Protection Code are properly observed. For this purpose, the Organisation uses its own dosimeters that are directly readable at CERN. The doses that are registered by CERN cannot be transmitted to all CERN's member countries or beyond because our Dosimetry Service is not accredited in these countries.

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 1st of January and then the 20th 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 2nd 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 first answer would be: why do you need a dosimeter if you don't go into radiation areas? If you don't use your dosimeter for more than one month please return it to the Dosimetry Service.

The technical explanation is that the dose that you read on the reader is the background compensated by 2.33 µ​Sv/day since the attribution of your dosimeter. If you don't go into radiation areas you should read 0 mSv all the time, however your dosimeter is continuously registering a natural dose. This 2.33 µ​Sv is a fixed mean value estimated for all CERN locations. But in reality the natural background is not the same everywhere within CERN's larger boundaries and it fluctuates from one place to another. Should the natural background be a little higher at your 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 have been accumulated since the attribution of your dosimeter.

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

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.

The passive dosimeter at CERN is the personal, legal or DIS dosimeter. Dosimeters such as TLD or OSL are called 'passive' as they do not provide direct readouts and can operate without any active means. The measured dose is usually taken as an estimate for the effective dose which is recorded and reported after evaluation. The CERN DIS dosimeter should be called semi-passive as it has a battery and can be read at anytime at a reader station for a direct reading of the dose stored inside. But it is called passive as well in order to differentiate it from the active or operational dosimeter.

The active dosimeter is also called electronic, operational, alarm or DMC dosimeter. It provides a direct display of the accumulated dose as well as having some additional functions such as alarm threshold settings for dose or dose rate values. In addition it provides an audible and visual indication of the dose rate level. The dosimeter requires a battery to operate. This dosimeter is used for complementary dosimetry in the case of high radiation levels or for work and dose optimisation purposes.

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.

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.

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 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.

Readout (3)

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.

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.

Return (1)

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.

Exchange (2)

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.

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.

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