Radon (Rn) Awareness Programme

Dr.Boopathi Gupta.M

Radon was discovered by Friedrich Ernst Dorn, a German chemist, in 1900 while studying radium’s decay chain. 

Originally named niton after the Latin word for shining (nitens) radon has been known as radon since 1923.

Today, radon is still primarily obtained through the decay of radium.

Discovery of Radon (Rn)

Symbol: Rn Atomic number: 86 Atomic Weight: 222 Atomic mass: 222 u Melting point: 202 K (-71°C or -96°F) Boiling Point: 211.45 K (-61.7°C or -79.1°F) Density: 0.00973 grams per cubic centimetre Phase at Room Temperature: Gas Chemical series: Noble gas Element Classification: Non-metal Period Number: 6    Group Number: 18     Radioactive

Properties of Radon (Rn)

Radon (Rn)

Radon is formed as one intermediate step in the normal radioactive decay chains through which uranium (u), thorium (Th) and slowly decay into lead (Pb) . 

 radon itself decays, it produces new radioactive elements called radon daughters or decay products.

Unlike the gaseous radon itself, radon daughters are solids and stick to surfaces, such as dust particles in the air.

Radon formation

Uranium decay

Half-life (t1⁄2) is the amount of time required for the amount of something to fall to half its initial value. The term is very commonly used in nuclear Physics to describe how quickly unstable atoms undergo radioactive decay.

Half life

If such contaminated dust is inhaled, these particles can stick to the airways of the lung and increase the risk of developing lung cancer.

The most common forms of radon decay through alpha decay.

Alpha decay usually isn't considered to be a great radiological hazard since the alpha particles produced by the decay are easily stopped.

However, since radon is a gas, it is easily inhaled and living tissue is directly exposed to the radiation.

Although it has a relatively short half life, radon decays into longer lived, solid, radioactive elements which can collect on dust particles and be inhaled as well.

For these reasons, there is some concern as to the amount of radon present within homes.

Radon seeps into houses as a result of the decay of radium, thorium or uranium ores underground and varies greatly from location to location.

On average, the earth's atmosphere is 0.0000000000000000001% radon.

If the gas is trapped in dwelling enclosure, radon and its daughter nuclides can attach to dust particles and then be inhaled in to lungs.

Radon (Rn) Invasion

Where the decay radioactively and increase lung cancer risk.

The radioactive decay of radon is by far the single greatest source of human radioactive exposure.

Radon mostly enters a home directly from

the soil through the lowest level in the home that is in contact with the ground.

Radon concentrations in the same location may differ by a factor of two over a period of 1 hour. Also, the concentration in one room of a building may be significantly different from the concentration in an adjoining room.

Typical entry points of radon into homes are,

Cracks in solid foundations. Construction joints. Cracks in walls. Gaps in suspended floors. Gaps around service pipes. Cavities inside walls and Water supply.

Source of cell damage in lungs. Short lived products most significant. Have static charges. Chemically reactive. Solid particles. Heavy metals.

Radon decay product characteristics

WHO presented in 2009 a recommended reference level (the national reference level), 100 Bq/m3, for radon in dwellings.

The actionable concentration of radon varies depending on the organization for example, the United States Environmental Protection Agency encourages that action be taken at concentrations as low as 74 Bq/m3 (2 pCi/L).

The becquerel (symbol Bq) is the IS derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. 

Action and Referral level

The European Union recommends action be taken when concentrations reach 400 Bq/m3 (11 pCi/L) for old houses and 200 Bq/m3(5 pCi/L) for new ones.

On 8 July 2010 the UK's Health Protection Agency issued new advice setting a "Target Level" of 100 Bq/m3whilst retaining an "Action Level" of 200 Bq/m3.

 The same levels (as UK) apply to Norway from 2010; in all new housings preventative measures should be taken against radon accumulation.

Radon is an known Carcinogen• Alpha particles

from the Radon decay products can damage lung tissue.

• Lung cancer is the main health effect.

DNA damage• Alpha energy

delivered directly to cells.

• Alpha particles strike Lung cells causing Physical and Chemical damage to DNA

* One picocurie/Liter is 2.22 disintegrations within that Liter.This comes from the fact that one curie is 37 billion disintegration per second (dps).

One picocurie is one trillionth of a curie (0.037 dps).There are 60 seconds in a minute (60 x 0.037 = 2.22)

Safe level: < 2.0pCi/L

Because the half-life of radon is only 3.8 days, removing or isolating the source will greatly reduce the hazard within a few weeks.

Another method of reducing radon levels is to modify the building's ventilation.

Generally, the indoor radon concentrations increase as ventilation rates decrease.

In a well ventilated place, the radon concentration tends to align with outdoor values (typically 10 Bq/m3, ranging from 1 to 100 Bq/m3).

Radon (Rn) mitigation

Control measure

For quires contact

Dr. BOOPATHI GUPTA.MProject Manager – CRES HSE,

Mail ID: boopathi.gupta@in.bureauveritas.comMobile: +91 9819373355.

Questions?

Thank you all