Scientists dismiss radiation scare

Radiation laboratory scientists are doubting stories about high radiation levels detected in Dunedin during the weekend.

The claim that a handheld Geiger counter detected radiation at eight times higher than normal background levels is posted on the website of  the Sunshine Coast Computer Club Inc.

It includes a photograph of the detector reading 0.81 micro sieverts per hour, with the author sating it was briefly reading 1.89 outside in the wind.

Normal background levels in Dunedin are about 0.10-0.12 micro sieverts per hour.

ESR radiation laboratory scientist Chris Adwin says the Dunedin readings are spurious. They are made on a suspect hand held device and they do not correlate with levels recorded at any of the south pacific monitoring station readings.

“We can’t comment on the validity of those measurements,” says Chris.

“It’s all down to looking at the instrument that’s been used.

“It’s not a professional environmental radiation counter.

“It is a Geiger counter, but there are Geiger counters that cost $400 and there are Geiger counters that cost $4000 and there’s a big difference in what you get for that, and what their intended purpose is.

“Some Geiger counters are really indication only, and others are fully calibrated instruments for the full range of radiation measurements including natural background radiation – you need to take the instrument into account.”

Whether there’s any relationship between the Dunedin reading and the Fukushima meltdown in Japan, there is no indication of any such readings in this part of the world, says Chris.

And information posted on a website is not verifiable data that he can comment on.

Senior scientist Klaus Hermanspahn says the international network of fallout monitoring stations shows the vast majority of the Fukushima radioactive fallout is remaining in the northern hemisphere.

“There is some detection in southern hemisphere at very, very, low levels,” says Klaus.  “At the levels that we have now in the northern hemisphere, even if something did blow down here, he wouldn’t be able to pick it up with that instrument.”

Those measurement stations suck air through a filter for 24 hours, says Klaus.

The air flow is about 600cubic metres per hour or about 20,000cubic metres per sample. The filter papers are laced over a measuring instrument for 24 hours where any airborne radioactive particles are counted.

“Just waving a hand held instrument around doesn’t work, you wouldn’t be able to pick up anything that comes from Fukushima,” says Klaus.

“We know what type of instrument he used and those are not totally reliable, you can get interference from natural background events.”

Solar activity, such as the recent large solar flares are known to increase natural background radiation.

“But whether it is that, I do not know. It may be possible to pick that up with hand held instruments.”

If shortly after a solar flare someone did measure two microseiverts for a short period of time there is no reason to be concerned about that.
A recent similar alarm about a radiation spike in Colundra, Queensland is similarly unverified scientifically, says Klaus.

“That person had more data on his instrument, but apart from that we don’t know what he actually measured. It could be southern flares, it could be radon, it could be a variety of naturally radioactive sources that could contribute to an instrument fault or problem.

“When I had a look at some of those websites involved there is a lot of panic and misinformation out there, which is a worry,” says Klaus.

“All we can do is put out how we seen the issue, and hope people understand.”

A claimed spike of about eight times higher than normal radiation background, sounds like a lot, says Klaus, but only a very small part of humans’ total exposure to radiation is from external radiation.

“So even if the external radiation was to increase somewhat, it wouldn’t have a large effect,’ says Klaus.

“Of course that doesn’t mean we can just be careless about the use of radiation.”