No Exit

On February 1, 2010, a luminous sign manufacturer in Peterborough, Ontario, Canada accidentally released tritium gas to the atmosphere. The radiation release was 147 x 10E+12 Becquerels (Bq)! (147,000,000,000,000 – the E+ symbol is a way of showing positive exponents without using superscript). That's 3,973 Curies, if I did my calculations right (1 Curie = 3.7 x 10E+10 Bq).

This event went unreported and unnoticed by the world, probably because not even critics of nuclear power could know what the implications for public health were. The number is large and shocking, but this illustrates once again how confusing these mega-numbers are to anyone who is trying to understand the risks of nuclear energy. The more the number of zeroes goes up, the more numbing and senseless the figures seem to become, and the numbers themselves don’t tell anything about how the particular radionuclide interacts with living things, or how fast it disperses, decays, or leaves the human body. Tritium (a hydrogen atom with two extra neutrons) is an extremely dangerous substance to handle in even small amounts of less than a milligram, and catastrophic accidents are possible, but it has been difficult to prove any harm from the way that it has been handled in the nuclear industry.

The accident in Canada illustrates a point often made by antinuclear activists: there is no place to run, and no way to know for sure what you might be running from or toward. The message is there for you in the tritium-illuminated signs found in most public buildings, reminding you that man-made radioactivity is now everywhere.

The Fukushima accident is said to have released 511 x 10+E18 Bq (six more zeroes than the release of tritium in Canada, but hey, after the first twelve zeroes, who’s counting?) of Iodine 131 to the air, most of which blew out to sea and decayed away within a month. Iodine 131 poses a larger health risk because of its absorption in the thyroid, but there is a lot of guesswork in figuring out how much of the amount released was absorbed by people. One could run from this danger only to be caught downwind from the next accident, whether it comes from a meltdown or a luminous sign factory.

Another interesting dimension of the Canadian accident is that it highlighted an absurdity in the way the Canadian Nuclear Safety Commission (CNSC) sets its safety limits. Gordon Edwards reported on this in a recent article for Canadian Coalition for Nuclear Responsibility. (“Nuclear Regulator Allows ‘Tritium Unlimited.’” Canadian Coalition for Nuclear Responsibility. September 15, 2012.)

Peterborough, Ontario, Canada, April 2012

He described how on Feb. 1, 2010,  Shield Source Incorporated (SSI), the maker of luminous signs in Peterborough, released 147 x 10E+12 Bq of radiation from tritium gas to the atmosphere, tritium which it buys from Ontario’s nuclear power stations. This was 29% of the company’s permitted annual limit of 500 x 10E+12 Bq. Yet the CNSC also had a derived release limit for the company: 34 x 10E+18 Bq!

Gordon Edwards cites another report done in 2009 by Dr. Ole Hendrickson, writing for Concerned Citizens of Renfrew County (where Peterborough is located):

“CNSC has currently set the derived release limit for HT at 3.4 X 10E+19 Bq/year. This is over 200 times higher than the total global natural tritium production rate, and more than the ten times the total world steady state natural inventory of tritium. Each year during the past five years, in theory, SSI could have emitted more than ten times the world’s current natural tritium inventory. Had they done so, tritium levels in rainfall, and in every water body in the world, would have risen several hundred-fold, reaching levels exceeding those measured at the peak of nuclear weapons testing in 1963. This would have triggered a global health crisis. There would have been a tremendous outcry from scientists, health professionals and civil society around the world. This scenario, of course, is impossible. All the reactors in Canada could not produce enough tritium for SSI to do this. The derived release limit is literally absurd.”

The CNSC says the derived limits “represent an estimate of a release that could result in a dose of 1 mSv to an exposed member of the public” and this forces them, in the case of tritium, to imagine an extremely large release.

Dr. Hendricksen goes on to say, “SSI’s derived release limit is absurd, and has no legal effect. So why have two so-called “limits” for radioactive emissions from a Canadian nuclear facility? The answer is simple… [this practice]… assures the public that radiation releases – whether “routine” or “accidental” – are of no concern. For years, Canada’s nuclear regulatory agency has used derived release limits in this fashion.”

Regardless of the continuation of the derived limits, Gordon Edwards concludes by noting that in May 2012 it was learned that SSI had been violating its license for at least two years, and since then it has not been allowed to engage in tritium handling operations.

About Tritium:

From the Canadian government:

Tritium produced from nuclear weapons tests in the 1950s and 1960s was dispersed into the global atmosphere and reached 120 Bq/L in precipitation in Ottawa in the mid-1960s. Concentrations since then have steadily declined and are now about 2 to 3 Bq/L across Canada.

Tritium exposure can pose a health risk if it is ingested through drinking water or food, or inhaled or absorbed through the skin in large quantities. The Canadian public is not at risk from tritium intakes at current levels. There is no evidence of adverse health effects, based on biological experiments, observations of humans following accidental intakes of tritium, or routine surveillance of radiation workers at these levels.

Tritium taken in as tritiated water has a biological half-life of 10 days, which means half of the tritium is excreted in this time. However, a small amount does become organically bound (bound to proteins, fat and carbohydrates) with an average 40-day half-life.

From Wikipedia on CANDU reactors:

Tritium is a radioactive form of hydrogen (H-3), with a half-life of 12.3 years. It is found in small amounts in nature (about 4 kg globally), created by cosmic ray interactions in the upper atmosphere. Tritium is considered a weak radionuclide because of its low-energy radioactive emissions (beta particle energy 0 -19 keV). The beta particles do not travel very far in air and do not penetrate skin, so the main hazard is intake into the body (inhalation, ingestion, or absorption).

Tritium is generated in the fuel of all reactors; however, CANDU reactors generate tritium also in their coolant and moderator, due to neutron capture in heavy hydrogen.

Allowable tritium level in Canadian drinking water: 7,000 Bq/liter. The figures for the EU, Finland and Australia are, in order, 100, 30,000, and 76,000.

1.     Tritium emits 10,000 curies/gram, or 3.7 x 10E+14 decays/second

2.     US reactors emit 1/10 of a gram/year, sometimes one gram.

3.     CANDU reactors release 20 times more than US reactors.

4.     One gram of tritium in the body would bring a rapid death.

5.     Amounts released by reactors must be tremendously diluted.

6.     The American EPA standard for tritium is 740 decays/second per liter of drinking water (about 1/10^th of the Canadian limit). (1 decay/second equals one Bq).

7.     If a human body holds 40L water, this would equal 30,000 decays/second, assuming a person drank water at the limit to the point that all water in his body was replaced by contaminated water. [Regulatory limits seem to be based on the assumption that this prolonged exposure will never happen. It is assumed that emergencies will be of short duration and people will get alternative sources of water.]

8.     Natural radiation in the body (from radioactive potassium, K-40) = 4,400 decays/second.

source:  Ace Hoffman. The Code Killers. 2008. p. 10. www.acehoffman.org  

Greenpeace report on Tritium at Canadian Nuclear Facilities

Nuclear Industry Review of Greenpeace report on tritium

From Shield Source Incorporated:

“The World’s Leading Manufacturer of Self-Luminous Safety Signs…  no wiring, electricity, maintenance, lamps to replace [with] gaseous tritium light sources (GTLS)… These days it’s all about GREEN environmentally friendly products and there’s nothing GREENER than our self-luminous signs.  Our innovative technology transforms a waste product [tritium] into a commercially viable life safety device whose components, at the end of its’ effective life, can be recycled.”

Further reading:

“Tritium leaks at Peterborough airport: Four NGOs call for shutdown, protest re-licensing.” Straight Goods.ca. April 12, 2012.

Gordon Kennedy, “Activists unfurl Welcome to the Tritium Zone banner on Hwy. 7/115.” The Peterborough Examiner. April 20, 2012.

Zach Ruiter, “Nuclear Radiation in Ontario: Tritium Toxic Emissions have Increased Dramatically in Peterborough.” Center for Research on Globalization. April 26, 2012.

Jessica Murphy. "Green groups raise Peterborough radiation fears." The Toronto Sun. April 11, 2012.