Monitoring radioactive materials

Units to monitor ionising radiation

Becquerel

Bq

A measure of absorbed dose

Gray

Gy

What is 1 Gy?

1 joule of radiation energy per kilogram of matter

What's a Sievert?

A measure of effective dose that allows for the differing effects of the different types of radiation.

Number of Sieverts

Number of Sieverts = Number of Grays x radiation weighting factor for the type of radiation

What's a weighting factor for alpha radiation?

20

What's a weighting factor for beta radiation?

1

Geiger counter

A device that measure ionising radiation. It measures in micro-Sieverts per hour (µSv/hr)

Monitoring Workers

- Workers can have personal dosemeters which give a reading of current exposure

- Photographic film badges which measure the long term exposure

- Air monitors that can detect atmospheric particles (including alpha emitters)

- Contamination monitors, which monitor workers as they leave the remises and detect any contamination

Critical Pathway Analysis

- Normal discharges from nuclear establishments release very small amounts of radioactive materials

- However, it cannot be assumed that they will be dispersed and diluted, so that the risks drop to an insignificant level

- It is possible that natural processes may concentrate them in locations where they could be hazardous

- So CPA identifies the possible environmental routes that radioactive materials may take in the environment after release

Why is CPA good?

The analysis makes it possible to predict where discharges could cause problems by becoming more concentrated

What factors does CPA involve?

- The physical state of the effluent

- Density

- River flow and ocean currents

- Meteorological conditions that determine atmospheric dispersion (including wind speed and direction)

- Geology (porous/permeable vegetation cover)

- Effect of pH and oxygen availability on solubility

- Bioaccumulation and food chain concentration

- Food sources and consumption by local people

- Half lives of the isotopes involved

Critical Group Monitoring

If there are concerns about radioactive contamination, then it is important to determine the level of risk to people. So an effective way to do this is to review the risk to the Critical group.

What is the critical group?

The group is comprised of those who are most at risk due to where they live, where their water comes from, what they eat, etc

What can you conclude from CGM?

If the critical group is found to be safe, then all other members of the public should be safe too, so then we wouldn't have to monitor all members of the public.

Does the critical group include occupational workers?

No because they are monitored a different way

Factors when identifying the critical group:

- Where the person lives in relation to the source

- Time spent outside, like farmers, dog walkers, walkers

- Sources of food, like local food (milk, seafood, veg)

- Source of water, like local well

Environmental Monitoring

- If places in the environment where radioactive materials are likely to be most concentrated are identified and monitored, and it is established that levels are found to be acceptable, then it is assumed that everywhere else is safe

- However, it is important to recognise that this assumes the pathways have been predicted correctly

What else should be assessed in environmental monitoring?

Atmospheric dust, soil, grass, milk, meat, fish, and veg.

They should be assessed as they are materials that are most likely to be contaminated and indicate direct risk to humans.