Introduction to radiation protection at TSL

This introduction is compulsory reading to be studied and digested by persons requesting access authorization to restricted areas at TSL. An application form must also be filled in to get a personal radiation protection code number. Some basic radiation protection training is also required to be allowed to enter into restricted areas.

Persons not following the described procedures may be subject to disciplinary measures, e.g. loss of access authorisation or legal action.

For further information contact the Radiation Protection Unit:


The RP Unit at TSL (since 2016):

  • Elke Passoth, radiation protection and neutron physics, phone 018 - 471 38 05, mobile phone 0701 – 67 91 95

Access codes can be obtained from Elke Passoth.
Radioactive sources can be borrowed through Elke Passoth.
 


Contents:
General
Priorities in radiation protection at TSL

Doses and dose rates, hazards and limits
Personal dosimetry
Responsibility
Restricted areas
Clearing procedure
Warnings and alarms
Radioactive sources
Radiochemistry


General

  • Do not expose yourself or anybody else to hazardous radiation.
  • Do not put yourself or others in any potentially hazardous situation.
  • Do not trust any single safety system. Be aware that technical systems may failand people may make mistakes. Use doubled safety whenever possible. As anexample, the personal dosimeter (RAD-52) can warn you of the primary beamif the interlock system fails.

Priorities in radiation protection at TSL

Priority I

The primary beam of high energy ions can rapidly deliver lethal doses because of very high dose rates. All areas around the beam lines, where this kind of hazard exists, are contained within thick concrete walls with labyrinth entrances and locked doors guarded by an interlock system. These areas must always be cleared of people and sealed before the beam can be let in (see Clearing procedure below).

Priority II

Work with radioactive material, like radionuclide production for medical purposes or maintenance of activated pieces of equipment, can give high doses. The dose rates are usually to low to give lethal doses within reasonable times of exposure but the absorbed dose can increase the risk of getting cancer. This source of radiation is the main contributor to dose to personnel at the laboratory. There is also an obvious risk of contamination and intake of radioactivity and this kind of work may only be performed by a´special group of the staff at TSL.

Priority III

Radiation leaking out from activated parts inside the beam line or through the walls into areas next to cleared areas usually present low dose rates and no risk of contamination. However, the time of exposure can sometimes be long and many people, like most TSL personnel and visiting researchers, are exposed to this irradiation that might increase the risk of cancer.


Doses and dose rates, hazards and limits

Always wear a personal dosimeter, RAD-52, when working in the restricted areas or
when working with radioactive material.

Radiation hazards

  • Lethal (50 % risk) whole body dose: 4,5-5 Sv
  • Increased risk of dying from cancer from an effective dose of 1 Sv (adults): 4 %-units

General information:

  • Average dose to the Swedish population: 4 mSv/year (0.46 µSv/h)

Legal limits of dose for category A workers (special group of the staff at TSL):

  • Maximum effective dose: 50 mSv/year
  • Maximum equivalent dose to the lens of the eye: 150 mSv/year
  • Maximum equivalent dose to skin, hands or feet: 500 mSv/year
  • Maximum accumulated effective dose over 5 years: 100 mSv

Legal limits of dose for category B workers (some personnel and visitors at TSL):

  • Insignificant risk of receiving an effective dose of 6 mSv/year
  • Insignificant risk of receiving an equivalent dose to the lens of the eye of 45 mSv/year
  • Insignificant risk of receiving an equivalent dose to skin, hands or feet of 150 mSv/year

Personal dosimetry

The nature of the activities at TSL raises a demand for personal dosimetry from the authorities. The local dosimetry system is based on electronic personal dosimeters, RAD-52, a reader unit and a data base of everyone with an access permission and their detected doses. The RP Unit has to have knowledge about the identity of everyone with access to the laboratory.

Everyone who wishes to have access to the experimental areas at TSL need a personal code number to

  • log into the dosimetry system to obtain an electronic personal dosimeter (RAD-52).
  • open doors into restricted areas.
     

To obtain a personal code number you must contact the RP Unit, in advance of the experiment, and fill in the form “Application for radiation protection code”.

The dosimeter (RAD-52) must always be worn by everyone who is entering restricted areas or is working with radioactive material because ...

  • in case of an accident it is of vital importance to know how much dose the exposed person received
  • the built in alarm function can warn the person if the dose rate or the accumulated dose reaches hazardous levels.
  • the doses to everyone working at TSL must be monitored according to regulations from the authorities.
  • it helps the RP Unit to identify jobs and work places with high exposure to radiation

There is a pool of instruments from which dose rate meters, contamination detectors and neutron detectors can be borrowed whenever required. Ask the RP Unit or the cyclotron operator for help.


Responsibility

Research groups must appoint one group member to take the responsibility for the group and the experiment concerning radiation protection. This person must inform him- or herself and the group members about the rules presented here and see to that they are obeyed.

Everyone must act in accordance with the local rules presented here.

It is everyone’s duty to inform collegues and others at TSL about potential hazards so that the risk of accidents is minimized.

Anyone who performs the clearing procedure in an area takes on the heavy responsibility
that nobody is left behind in that area.


Restricted areas

Before entering a restricted area:

  • Log into the dosimetry system and get a personal dosimeter (RAD-52).
  • Read the beam schedule and check with the cyclotron operator (phone 3880) if it is safe to work in the area.
  • Control the clearing status and the dose rates on the display beside the door leading  to the restricted area.
  • If the display at the entrance (see below) shows a yellow warning light (10-500 µSv/h) you must contact the operator and try to find out the source of the radiation and measure the dose rate with a dose rate meter while working in the area.
  • Read the local rules for radioactive sources and consult the RP unit before bringing any such material into the area.
  • NOTE! Eating, drinking, smoking or any other intake is prohibited in all restricted areas!


In the restricted area:

  • Identify emergency exits and emergency stop buttons (all clearing buttons also act as emergency stops).
  • Borrow a dose rate meter if you need to measure the radiation level at your work place.
  • Label construction details or areas with increased dose rates with suitable warning signs. Inform the RP Unit and others in the area.
  • If the radiation alarm sounds, leave the area immediately. Avoid the beam line.

If possible, avoid high radiation areas such as

  • the Cyclotron Hall with the radioactive accelerator. 
  • the Marble Hall where the beam frequently hits the beam pipes due to many bending magnets .
  • areas close to targets, scattering foils, collimators, beam dumps and similar equipment.

Doors to restricted areas should normally be closed, also during Free Access conditions, to prevent unauthorized persons from entering the area and to stop the spread of fire and smoke in case of fire. The doors are automatically locked by the control and interlock system but can be opened using the personal code number. The code is the same as for the personal dosimetry system but followed by an asterisk (*). 


Clearing procedure

An area must be cleared of people with a special clearing procedure before high-energy beams can be let into that particular area. There is a procedure defined for each area. The procedure states that a responsible and well informed person walks through the area to check that nobody is left behind and pushes a number of clearing buttons in the correct sequence. When the clearing procedure is initiated both an acoustic alarm and read lights are activated in the area. After the clearing procedure is completed, red lights on the lamp panel at the entrance indicate that access is forbidden and that the beam is allowed to enter the area.
NOTE! The responsibility lies heavy on the person who carries out the clearing procedure. The
person who takes the task of clearing the area also takes the responsibility that nobody is left working, hiding or lying unconscious anywhere in the cleared area. This is of highest priority of the radiation protection system. Anyone who fails this responsibility can be certain to meet legal action.


Warnings and alarms

The personal electronic dosimeter, RAD-52, has a built in alarm that sounds if the dose rate exceeds 100 µSv/h. This can happen during work with or near activated parts of the beam line or if the primary ion beam by accident enters the area. Sometimes interference with mobile telephones occurs and triggers the alarm. Keep mobile telephones away from the dosimeters!

In all areas with accelerators and/or beam lines there are acoustic alarms and rotating warning lamps installed. During and after the clearing of an area, the acoustic alarm sounds and the rotating lamps are lit to warn anyone that the area is being cleared and that the primary ion beam soon may be allowed to enter the area.

In case the dose rate in the area raises above 10 µSv/h the acoustic alarm sounds.

If the radiation warning alarm sounds (or the fire alarm), leave the area at once. Keep as long a distance as possible between you and the beam line to minimise the risk of being hit by the primary ion beam or irradiated by secondary radiation.

The restricted areas are, at the entrances, equipped with lamp panels showing the status of and the overall dose rate in the area. The displays show information according to the following table: 
 

Status Colur of lamp Acoustic alarm Action
No access red yes Access not allowed
Beam on red yes Access not allowed
Restricted access yellow yes Access only for authorized personnel and users
Free access green no Free access for authorized personnel and guided guests
Dose rates
 > 500 µSv/h  red  yes Access not allowed
 10-500 µSv/h  yellow  yes Access only for authorized personnel and users
 > 10 µSv/h  green  no Free access for authorized personnel and guided guests


Radioactive sources

It is forbidden to bring or remove any radioactive sources to or from TSL without permission from the Radiation Protection Unit.

Every individual user of radioactive sources in the buildings of TSL must have knowledge about the hazards of ionizing radiation in general and about the specific sources, including main dose contributing type of radiation, and dose limits for personal irradiation.

Sources may only be borrowed through the RP-unit. Lending sources man to man is not allowed. All sources must remain completely traceable both physically and through the bookkeeping system. For detailed information consult the RP Unit. Always put radioactive materials and sources into safe storage after use. 


Radiochemistry

TSL has closed Radiochemistry laboratory since 2016.

 

(page revised 2017-03-24 /MP)