Radiation Flashcards
What is radioactivity
Radioactivity is the disintegration of the atoms of a substance. During this process energy is emitted in the form of particles or electromagnetic waves. This energy is known as ionising radiation. Radiation which has sufficient energy to cause ionisation of matter through which it passes. Ionisation radiation can be disruptive to the cells in the human body possibly causing mutations, cancer or death.
When may radioactive involvement be suspected?
- Prior knowledge or intelligence that radioactive materials are in a building
- A radioactivity warning placard on a building, a vehicle or package.
- The caller may state that radioactive materials are present
- An electronic personal dosimeter (EPD) alarm actuates.
- a survey meter shows a dose rate above background
- Terrorist or other malicious acts.
What is the standard measure of radiation? What measurement does our equipment measure radiation in?
The standard unit for measuring radiation is the sievert (Sv). However, this unit is too large for practical use when dealing with emergencies and our instruments measure the radiation in milli-sieverts (mSv) and micro-sieverts (uSv).
1 mSv= 1000 uSv
What is the “absorbed dose” and what is the “dose rate”?
The absorbed dose is the measurement of how much radiation has been absorbed. It is measured is uSv or mSv. The higher the absorbed dose an individual receives the greater risk to their health
The dose rate specifies how fast a dose is being absorbed and is measured as the amount of radiation that would be absorbed in an hour (uSv/hr or mSv/he)
What is the dose constraint for employees as per LFB policy in a 12 month period?
10 mSv in any 12 month period
The constraint can be exceeded to 100 mSv. In what circumstances can this be justified
Save life or rescue endangered people
Prevent people being exposed to radiation
Save valuable installations when appropriate (e.g. To maintain the stability of any containment).
What are the 4 types of radiation?
Alpha
Beta
Gamma
X-ray
What is alpha radiation
Alpha particles are, relatively speaking, large and cumbersome and do not travel very far. In fact a single sheet of paper will stop or reduce any radiation from alpha emitting source. An alpha particle cannot even penetrate the skin that covers the human body.
However should an alpha emitting radiation material be swallowed or ingested it can be very damaging to cells in living tissue.
What is beta radiation?
Beta particles are much smaller and travel further in air. Although a beta particle could still penetrate the outer dead layer of skin into living tissue a very thin sheet of aluminium (a light metal) will stop radiation from beta emitting source. Additionally, the beta particles is not as ionising as the alpha particle.
Both alpha and beta particles present a significant internal hazard to the human body.
What is gamma radiation?
Gamma radiation consists of electromagnetic rays and does not have any mass. Like light and other forms of energy it can travel immense distances in air. Although gamma rays only produce small amounts of ionisation they can travel through large amounts of matter. This means they have a higher chance of producing ionisation. It takes a significant thickness of lead or concrete to reduce gamma radiation.
Gamma radiation presents a significant external hazard to the human body.
What is X-ray radiation
X-ray are also electromagnetic rays. They behave in a similar way to gamma radiation although the source is not radioactive material. Commonly found in medical facilities, they are generated by high voltage electricity. They can be harmful and will register on detection equipment at close range.
Although doses are generally much lower, X-ray radiation represents an external threat to the human body. Any risk will be eliminated by isolating the electricity supply. If the supply cannot be isolated it should be treated in the same way as gamma radiation.
What are the 3 factors effecting the amount of radiation absorbed?
Time
Distance
Shielding
What sounds does the EPD make on the initial doses? When does this actuate?
Intermittent double fast tone, LED flash with tone, for 20 seconds. EPD will reset itself (tone and LED off) when the dose rate falls below 90 uSv/hr.
Goes off at 100 uSv/hr
What sounds does the EPD make on the dose constraint alarm? When does this actuate?
Continuous slow dual tone for 2 minutes followed by a beep every 30 seconds. LED constantly illuminated.
Goes off at 5 mSv
What sounds does the EPD make on the exceptional dose alarm? When does this actuate?
Continuous single tone for 10 seconds, followed by a beep every 30 seconds. LED constantly illuminated.
Goes off at 100 mSv
