At SCI, we have had the Personal Dosimetry Service since 1993, when it was authorised by the Council for Nuclear Security (CSN). This is an authorisation which has been continually renewed following successful passing of inspections carried out by the CSN itself.
Furthermore, this personal dosimetry service has been part of the intercomparative campaigns organised by the CSN at a national level, always with satisfactory results.
Dosimetry of radiation is the technique used by scientists to study the relationship between quantitative measurements of radiation and its effects on a system, generally a biological one.
Dosimetry is essential to be able to quantify the incidence rate of biological changes with respect to the amount of radiation received, as well as to control radiation exposure to human beings and the environment.
This can be split into various Types of Dosimetry with respect to their location.
Dosimeters located at chest height are used to perform this measurement. The use of the dosimeter is personal and it must be used when there is a risk of exposure to ionising radiation.
The doses received in the entire group of workers who are exposed to ionising radiation can be estimated with these dosimeters. It is measured in terms of ‘shallow dose equivalent’ (Hs = Hp (0.07)) and of ‘deep dose equivalent’ (Hp = Hp (10)).
According to the relevant regulations, “RD 783/2001 (Article 27 ”, the doses received by exposed workers must be measured on a monthly basis at minimum, meaning that the usage term of the dosimeters, and therefore their reading, must also be monthly.
Each person (user) in the facility (entity) who is registered for the Personal Dosimetry Service shall be assigned two dosimeters which shall be used in an alternating fashion (the dosimeter being used must not be sent off until the replacement has been received).
If lead clothing (apron, vest, etc.) is being used, the dosimeters must always be placed underneath.
If you are using sinkers clothing (apron, vest…), the dosimeters always be below them.
dosimetry, the user in question must be registered for the body measurements.
This ring is used when the estimation of the radiation dose received by the extremities (the hands) could be significantly higher than the dose received by the body dosimeter.
The use of the ring is personal and it must be used when there is a risk of exposure to ionising radiation. In the event that gloves are being used, the ring must be placed underneath the glove.
The ring is placed on one finger of the hand, with the detector aimed towards the radiation beam and is used to estimate the dose received by the extremity (the hand) of the worker who is exposed to ionising radiation in terms of the extremity’s equivalent dose (Hext = Hp(0.07)).
When both hands are subject to a significant risk of ionising radiation, both hands are assigned this type of dosimetry. To do this, a ring is placed on one finger of each hand (for example, they are used by Nuclear Medicine Personnel, PET, etc.).
For each extremity of the facility’s user who is registered for the Dosimetry Service, two ring dosimeters shall be assigned, to be used in an alternating fashion each month, bearing in mind the dosimeter being used must not be sent off until the replacement has been received, which, given the frequency of both usage and reading, must be monthly.
The same dosimeters which are used to assess the body are used, but they are located at the height of the abdomen. It is a dosimetry aimed at workers who are exposed to ionising radiation during their pregnancy It is used to estimate the dose received by a foetus. The ‘abdomen equivalent dose’ is obtained from this dosimeter (Habdomen = Hp (10)).
Workers who are exposed when pregnant must wear both the personal dosimeter as well as the abdomen dosimeter. For monitoring purposes, it must be kept in mind that the dose limit for the foetus (1 mSv from the time of pregnancy) is equivalent to the abdomen dose limit (2 mSv from the time of the declared pregnancy).
The types of non-personal dosimetry are:
This type of dosimetry is performed using dosimeters the same as those used for the body. These are placed at representative points for the locations of the workers who are exposed when carrying out their duties.
The doses are measured in terms of ‘shallow dose equivalent’ (Hs = Hp (0.07)) and of ‘deep dose equivalent’ (Hp = Hp (10)). The Dosimetry Service shall provide these doses to the facility so that its UTPR or SPR can perform the dose estimation of the exposed workers, although this is only possible for those who are classified as category B.
This is carried out using dosimeters which are the same as those for the body which are placed at strategic points (those places which present a good possibility of collecting larger dose values) around the premises in such a way that they check the suitability of the shielding and therefore the security of the environment.
The Dosimetry Service shall provide the dose to the facility in terms of the shallow dose equivalent (H = Hp (0.07)) and deep dose equivalent (Hp = Hp (10)).
This is carried out using the same dosimeters as are used for the body, which are used by the people in charge of radiological protection in facilities for the assessment of different situations or to carry out investigatory work.
The Dosimetry Service shall provide the dose to the manager in charge of radiological protection at the facility in terms of the shallow dose equivalent (H = Hp (0.07)) and deep dose equivalent (Hp = Hp (10)).
There are two types of dosimeters:
There are thermoluminescent dosimeters. They are made up of four parts: Two of them of nLi2nB4O7:Cu and a further two of CaSO4:Tm, inserted into a dosimetry carrier made of plastic which has a windows of thin plastic.
They are used for the detection ofX-rays and gamma rays as well as for Beta particle radiation. When the readings from the four elements are gathered, an algorithm applied to evaluate the type of radiation (photons or Beta particles), its energy and the shallow (Hs=Hp(0,07)) and deep (Hp=Hp(10)) dose equivalents.
They are two thermoluminescent dosimeters, made up of a part of 7Li211B4O7:Cu, inserted in a ring. They are used to measure X-ray, Gamma, and Beta radiation.
After the element has been read, the equivalent dose is collected for the extremity wearing the ring (right hand or left hand) (Hext. = Hp (0.07)).
SCI’s Dosimetry Service has defined some regulations for the correct usage of the dosimeters. Among them is the procedure to be followed in the event of a loss of dosimetry information (PID) for personal dosimetry, in compliance with guidelines from the CSN.
The loss of dosimetry information could be due to:
As well as the material loss of the dosimeter, it shall be considered as lost if a period in excess of five months should pass without it being returned. This shall be treated as a loss of dosimetry information.
The loss of dosimetry information entails the assignation to the user of a dose which is equivalent to the proportional part of the annual dose limit corresponding to the dosimeters usage period.
The aforementioned dose, bearing in mind the relevant regulation (RD 783/01), shall be:
In the event of a loss of dosimetry information due to the dosimeter not being returned, the period of use calculated for the dosimeter shall be equivalent to the alternate months for the period during which the dosimeter was not returned, meaning three months. The following doses shall be assigned:
These assigned doses (administrative doses) due to loss of dosimetry information could be modified. For this occurrence to come about, three conditions must be met:
Three signatures must appear on the proposal and the original document must be sent to the Dosimetry Service.
The following forms must be used for the communication of new registrations of facilities (entities) and users, as well as for their termination and other incidents.
Dosimetry Reports can be divided into two types: personal and non-personal.
These reports can also be divided again into two types:
Any monthly dosimetry data for the users of the facility is contained in this report. It shows information both about the body dosimetry as well as information about ‘other doses’. Among these ‘other doses’ are: extremities, abdomen, etc.
For the body reading, the assigned monthly equivalent doses are stated for each user, both shallow and deep, as well as the doses accumulated throughout one official year, and in the case of the deep dose equivalent, that accumulated throughout five official years.
In the case of those classed as ‘other doses’, the monthly equivalent doses for each user assigned to each of the extremities (right ring dose and/or left ring dose) and/or the abdomen are stated alongside the doses accumulated throughout one official year for the extremities and throughout the pregnancy term for those of the abdomen.
This report contains dosimetry information for a time period of the user of the facility On it information is displayed both about the body dosimetry as well as information about ‘other doses’.
For the body reading, the assigned equivalent doses for each month of the term are stated for the user, both shallow and deep, as well as the doses accumulated throughout one official year, and in the case of the deep dose equivalent, that accumulated throughout five official years.
In the case of those classed as ‘other doses’, for each user, the equivalent doses which are assigned for each month of the period to the extremities (right ring dose and/or left ring dose), and/or the abdomen are stated alongside the doses accumulated throughout one official year for the extremities and throughout the pregnancy term for those of the abdomen.
These non-personal reports are divided into general and points of measurement.
It contains the monthly dosimetry information for the points of measurement around the facility. These are going to be used to show, for each measurement point, the shallow and deep equivalent dose assigned for each month.
It contains the dosimetry information for a period of time for a point of measurement in the facility. For each point the shallow and deep equivalent doses which are assigned for each month of the period are stated.
The regulations of our Dosimetry Service include clarification about dosimetry reports.
In accordance with current regulations (RD 783/2001) the Dose Limits for workers who are exposed to ionising radiation are:
Per official year:
For five official (consecutive) years.
Dose limit during pregnancy term (from the moment of the pregnancy’s declaration):
