Radiation safety for supervised areas
1. Statutory and regulatory requirements
The acts, ordinances and regulations of primary relevance to MAX IV regarding ionizing radiation are listed below for reference (in Swedish).
Radiation protection act:
Strålskyddslag (SFS 2018:396)
Radiation protection ordinance:
Strålskyddsförordning (SFS 2018:506)
Main regulation for activities with ionizing radiation that require a licence:
Strålsäkerhetsmyndighetens föreskrifter om grundläggande bestämmelser för tillståndspliktig verksamhet med joniserande strålning (SSMFS 2018:1)
There is also a MAX IV specific licence issued by the Swedish Radiation Safety Authority (SSM) concerning operations at the facility.
Radiation safety related procedures, plans, instructions etc. are part of the MAX IV management system.
2. Risks in a radiation environment
Doses from ionizing radiation are measured in sievert (Sv). One sievert is a very large dose. Millisievert (mSv) or microsievert (µSv) are often used instead.
People in Sweden are on average exposed to a dose of about 4 mSv per year. Almost 50%, about 2 mSv, is due to indoor exposure to radon. The rest is due to cosmic radiation, radionuclides in food, water, soil and building materials, potassium-40 in the body and medical examinations. The background subtracted radiation dose received by MAX IV personnel is on average about 0.3 mSv/year. The doses at the facility are measured by personal dosimeters normally carried for a total of 2000 h per year.
The biological impact of ionizing radiation can be classified as either acute or delayed. Acute damage occurs at high doses (above 1000 mSv) received over a short period (weeks) and the result is damaged or dead cells. This could lead to the reduced functionality or failure of an organ. This damage always occurs above a certain dose threshold which depends on the organ and tissue type. The severity of the damage will increase with the dose above the threshold. Acute radiation damage primarily affects the bone marrow, stomach and intestinal system and the central nervous system. The symptoms may include nausea, vomiting, diarrhea, skin rashes, reduced immune functionality, cataracts and sterility. In severe cases, acute radiation injuries can lead to death.
The risk of delayed damage, i.e. cancer and hereditary effects, depends on the received dose. The risk of radiation-induced terminal cancer is 5% per 1000 mSv. This implies that all exposures result in an increased risk of cancer. The risk also depends on age – fetuses and infants have a higher risk compared with adults. Radiation-induced genetic damage in humans has never been conclusively established. However, animal research has shown that genetic damage may occur.
3. Sources of radiation at MAX IV
The linear accelerator (linac) at MAX IV is capable of accelerating electrons to high energies (3 GeV). The electrons are diverted to either one of the two storage rings (1.5 GeV ring and 3 GeV ring) or to the Short Pulse Facility (SPF). There are four main sources of ionizing radiation at MAX IV:
- Electrons lost from the accelerators result in gamma and neutron radiation.
- The radiation mentioned above can induce radioactivity in the components of the accelerators and nearby materials, a process referred to as (radio) activation. This radiation remains when the accelerators are turned off and decays with time constants specific to the produced radionuclides.
- Insertion devices in the storage rings and the SPF produce synchrotron radiation which is used for research at the beamlines.
- Klystrons generate radiation during operation.
4. Area designations
Ionizing radiation is produced when the accelerators at MAX IV are in operation. The resulting radiation levels differ between the areas. At MAX IV the areas belong to one of three categories:
- Controlled areas (high radiation level areas)
- Supervised areas (increased radiation levels may be present)
- Non-designated areas
All entry points to supervised areas (in Swedish skyddat område) and controlled areas (in Swedish kontrollerat område) are labelled as shown below.
5. Access to supervised areas
Unaccompanied access to supervised areas is only granted to those who have read the relevant safety information and obtained a personal access card. Additional requirements apply for access to controlled areas, see section 7 below. Doors leading to supervised or controlled areas are locked and the access card is required to open them.
6. Personal dosimetry in supervised and controlled areas
A personal dosimeter must be carried in supervised and controlled areas. This applies to the entire site, except for the office building (E building) which is a non-designated area. When not in use, the personal dosimeter shall be stored at one of the dosimeter boards located nearby the entrances to the A, B, C and D buildings. There are two types of personal dosimeters.
If you are MAX IV staff, you should carry a personal TL-dosimeter (TLD).
If you are not MAX IV staff, but spend more than two months per year at MAX IV, you should carry a TLD. On the safety certificate you are asked if you estimate that you will spend more than 2 months at MAX IV during the coming 12 months.
If you are not assigned a TLD, you should carry a DIS dosimeter instead. These can be obtained on the ground floor of the office building, where instructions for use/return are posted.
During visits, it is sufficient that the person responsible for the group carries his or her personal dosimeter.
7. Access to controlled areas
Controlled areas, i.e. accelerator areas and beamline hutches, are areas where radiation levels may be significant. No one, including visitors, under the age of 18 is allowed to enter a controlled area. Furthermore, only those who are assigned tasks that require access to controlled areas are allowed unaccompanied access to such areas. The training Radiation safety for controlled areas is required to get unaccompanied access to controlled areas.
All entry points, including concrete doors, leading to a controlled area are marked “Kontrollerat område” (controlled area) and are equipped with information lights above the door.
8. Radiation outside controlled areas
The dose constraint implemented at MAX IV is that the dose for workers should not exceed 1 mSv over a 1-year period. The walls surrounding the accelerators areas and the beamlines were designed using this constraint. The radiation levels in adjacent areas are mainly monitored by the online and personnel safety system-integrated radiation monitoring system.
The klystron gallery runs parallel to the linac tunnel and contains 21 klystrons. An electronic dosimeter must be carried when working less than 2 m from a klystron. Radiation safety on-call must be contacted should the electronic dosimeter trigger an alarm.
9. Radiological work permits
It is forbidden to modify or remove equipment that may affect radiation safety without prior approval from the radiation safety team. This includes the following:
- It is forbidden to move, remove or modify shielding material such as concrete, iron and lead.
- Beamline hutches are shielded with lead and painted orange. It is forbidden to drill or otherwise modify the hutches, as radiation could then pass through. This includes the pipe that transports synchrotron radiation from the optics hutch to the experimental hutch.
- It is forbidden to remove the orange covers (the chicanes) used for cable/media feedthroughs, which are fastened on the hutches.
- It is forbidden to alter or move devices and equipment related to the personnel safety system, such as door switches and radiation monitors.
- It is forbidden to work on the contactors for the klystron modulators and RF-transmitters.
In some cases the equipment is labelled, or labelled and locked. However, this is not always the case.
Before work involving the equipment listed above is carried out, a radiological work permit (RWP) must be issued together with the radiation safety team. The permit has to be signed by both the person carrying out the work as well as a member of the radiation safety team.
10. Additional rules
- Temporarily cordoned-off areas may be employed to protect personnel from exposure to increased radiation levels. If this is the case, the cordoning will be marked with radiation hazard signs and access to the area is prohibited.
- It is forbidden to power the klystron modulators and RF transmitters using alternative cabling.
- It is forbidden to bring, order or buy radioactive material, sources or any equipment that may emit ionizing radiation (e.g. x-ray tubes and UV lamps) to MAX IV without the prior approval of the radiation safety team.
- Pregnant workers have the legal right to be reassigned to work that does not imply exposure to ionizing radiation beyond the publicly allowed level of exposure. Furthermore, MAX IV is by law required to inform workers of the importance of early reporting of pregnancy to the employer. You are welcome to contact the radiation safety team, in confidence, with any questions in the matter.
11. Contact details
If you have questions or want more information, feel free to contact the radiation safety team.
|Radiation safety on-call
||+46 (0)703 97 32 96||At MAX IV during operation|
|Anders Rosborg – Team leader||+46 (0)733 32 33 07|
|Stuart Ansell||+46 (0)725 36 77 79|
|Konstantin Batkov||+46 (0)730 97 37 75|
|Magnus Hörling||+46 (0)706 69 59 60|
|Johnny Kvistholm||+46 (0)703 52 37 30|
|Magnus Lundin||+46 (0)709 99 79 47|
|Jimmy Malmqvist||+46 (0)725 53 62 54|
|Johanna Paulsson||+46 (0)722 25 45 25|
|Josefin Reftlér||+46 (0)724 51 29 91|