Radiation safety training for protected areas

1. Applicable regulations

The regulations below are in Swedish and are listed for reference.

SSMFS 2008:27

Strålsäkerhetsmyndighetens föreskrifter om verksamhet med acceleratorer och slutna strålkällor

SSMFS 2008:51

Strålsäkerhetsmyndighetens föreskrifter om grundläggande bestämmelser för skydd av arbetstagare och allmänhet vid verksamhet med joniserande strålning

There is also a MAX IV specific permit issued by the Swedish Radiation Safety Authority (SSM) concerning operations at the facility.

Radiation safety related instructions, descriptions, routines and rules and the organizational plan of the radiation safety work are compiled in a MAX IV quality manual.

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 exposed to an average 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 lab 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 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 rings or to the Short Pulse Facility (SPF). There are four main sources of ionizing radiation at MAX IV:

  • Electrons lost from the accelerator and rings result in gamma and neutron radiation.
  • The radiation mentioned above induces radioactivity in the components of the accelerator/ring and nearby materials. This radiation remains after the accelerator/ring has been turned off and decays with time constants specific for the produced radionuclides.
  • Synchrotron radiation, which is used for research at the beamlines.
  • The klystrons in the klystron tunnel generate radiation during operation.

4. Area definitions

Ionizing radiation is produced when the accelerator or rings 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 area)
  • Protected areas (increased radiation levels may be present)
  • Normal areas
MAX-IV-p08-(v.2016-02-23)-2-cropped
The figure shows the controlled areas (red) in the basement (floor 8), namely the gun test room, linac tunnel, SPF and SPF beamline hutch. The remaining areas in the basement are protected (yellow).
MAX IV - R1-(v.2016-02-24)-cropped
The figure shows the controlled areas (red) on the ground floor (floor 10), namely the 1.5 GeV and 3 GeV ring tunnels, the beamline hutches, the two entrances to the linac tunnel and the cavity test room. The remaining areas are protected (yellow), except the office building, which is a normal area (green).

All entry points to protected (skyddat) and controlled (kontrollerat) areas are labelled as shown below.

skyddat_område

kontrollerat_område

 

 

 

 

 

 

 

5. Access

Access to protected and controlled areas is only granted to those who have read the relevant safety information and obtained a personal access card. Doors leading to the protected and controlled areas are locked and the access card is required to open them. It is forbidden to give the access card to others and it is also forbidden to let in others who do not have an access card of their own. However, if you have access you are allowed to bring visitors into protected and controlled areas provided they are escorted at all times and are registered as visitors at the reception desk. In this case, you are personally responsible for the visitors.

A personal dosimeter must be carried in the protected and controlled areas. This applies to the entire site (the office building is a normal area and is therefore exempt). The personal dosimeter is normally stored at one of the dosimeter boards when not in use. 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. You are asked to estimate the number of months per year you will spend at MAX IV on the safety certificate.

If you do not have 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.

TLD_small
A TL-dosimeter (TLD).
DIS_small
A DIS dosimeter.

During visits, it is sufficient if the person responsible for the group carries a TLD or DIS dosimeter.

6. Access to controlled areas

Controlled areas, i.e. accelerator areas and beamline hutches, are areas where radiation levels may be significant. All entry points, including concrete doors, leading into a controlled area are marked “Kontrollerat område” (controlled area) and are equipped with information lights above the door.

Access to the controlled areas is not allowed unless an additional separate training is completed.

acc_dörr_liten
Accelerator access door.
20160302_172506-rot
Beamline access door.
20160729_163515_resized_cropped
Open concrete door to an accelerator area.

7. Radiation outside the controlled areas

The design goal for MAX IV is that the maximum dose for personnel should not exceed 1 mSv over a 1-year period (2000 h). The dimensioning of the walls surrounding the accelerator and ring areas and the beamlines was calculated using this constraint. The radiation levels in the adjacent areas are monitored by the radiation safety team using hand-held and stationary detectors.

The klystrons situated in the klystron tunnel generate radiation while in operation. The klystron tunnel runs parallel to the linac tunnel and contains 19 klystrons. An electronic dosimeter must be carried when working less than 2 m from a klystron. The radiation safety team must be contacted should the active dosimeter trigger an alarm.

The klystron tunnel can be sealed off during operation should the radiation levels be deemed high. It must then be searched before the linac can be turned on.

8. Radiological work permits

It is forbidden to modify or remove equipment that may affect radiation safety without prior permission from the radiation safety team. This includes the following:

  • It is forbidden to move 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.

20160801_142103_resized20160801_142410_resized

 

 

 

 

 

 

 

Before work involving the equipment listed above is carried out, a radiological work permit 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.

9. Additional regulations

  • 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 women have the legal right to be reassigned to work that does not imply exposure to ionizing radiation during the remainder of the pregnancy. You are welcome to contact the radiation safety team with any questions in the matter.

 

20131009_135743-600
Temporarily cordoned-off area.

If you have questions or want more information, please contact the radiation safety team.

Radiation safety officer MAX IV 0703-973296 At MAX IV during operation
Magnus Hörling 0706-695960 Radiation safety engineer
Magnus Lundin 0709-997947 Radiation safety engineer
Anders Rosborg 0733-323307 Radiation safety engineer
Dadi Thorsteinsson 0722-492525 Manager safety group