Introduction to
Radiation Protection at TSL
(Page revised 2011-05-17)
This introduction is compulsory reading to be studied and digested by persons requesting access authorisation 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:
- Torbjörn Hartman, head of the RP Unit,
phone 018 - 471 38 83, mobile phone 0701 - 67 92 11, pager 0740 - 17 52 43
Also in the RP group:
- Alexander Prokofiev, neutron physics, phone 018 - 471 38 50, mobile phone
0701 - 67 91 88
- Anders Hjalmarsson, neutron physics, phone 018 - 471 38 05, mobile phone
0701 - 67 91 95
Access codes can be obtained from Torbjörn
Hartman
Radioactive sources can be borrowed through Torbjörn
Hartman
Contents
Priorities in radiation protection at TSL
Doses and dose rates, hazards and limits
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 fail and people may make mistakes. Use
doubled safety whenever possible. As an example, the personal dosimeter
(RAD-52) can warn you of the primary beam if 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 mSv/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 colleagues 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 mSv/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 are 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 mSv/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 occur
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 mSv/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:
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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.