[piajensen]

Out-of-control Sydney bush fire spreads towards nuclear reactor and army ammunition warehouse as residents in surrounding suburbs are told 'it's too late to leave
http://www.dailymail.co.uk/news/article-...uated.html

Residents told to "Shelter in place"

[vital1]

Residents told to "Shelter in place"

Here is a screen shot  from the Australian Nuclear Science and Technology Organisation (ANSTO) own local radiation monitoring station at Endagine. Endagine is located East of the Lucas Heights reactor. Their radiation monitor shows a significant spike in radiation.

What caused this spike in local radiation?

Did the fire release local radioactive contamination?

Reactor venting?

Fault in equipment?

Their rainfall monitor shows it definitely was not raining at the time, so not was not a Radon wash out event.



ANSTO live monitoring site,


http://www.ansto.gov.au/Resources/Locale.../index.htm

Here are notes from the ANSTO monitoring site page.

Gamma radiation is a penetrating form of short wavelength electromagnetic radiation, similar to X-rays. 
The environmental radiation graph (above) shows measurements in nanoGrays (nGy) which are units of absorbed radiation dose commonly used in environmental monitoring. A nanoGray is one billionth (one thousand millionth) of a Gray.

A temporary rise in environmental gamma radiation is often detected when it rains. This occurs because rain affects the behaviour of naturally occurring radionuclides, such as the gas radon. These radionuclides can be absorbed by rain drops and temporarily concentrated near the ground. Also, radon naturally builds up in air spaces in the soil and can be released when rain soaks into the ground.

"Spikes" in the environmental radiation graph (above) may occur during the regular calibration checks (see below) of the instrument that are needed to ensure accurate data. Gaps appearing in either graph are usually associated with delayed radio transmission of data from Engadine.

[vital1]

More significant spikes showing on the live Engadine ANSTO monitor station chart.

[piajensen]

Here's the surface wind for 09:00 on the 19th
   

And at 70 hPa at 06:00 - could have been northern hemisphere winds mixing with southern... but, the fire would be most likely source.