Update (08 11 2004): Findings in RISQ article put to test in University Exam - 'Area definitely needs to be fenced off'

Responding in detail to questions posed by RISQ, Mr Toyoda says the marks he found on the guns render it more than likely that the radiation is due to the impact of depleted uranium ammunition. According to local residents, the area was a military target twice in 1991 and 2003, when it came under heavy fire from US aircraft.

Immediately after "the war of the invasion", as residents called it, US military cleared the area, picking up unexploded ordnance and other debris. However, they refused to remove the artillery pieces without any explanation. Later, when residents asked Dutch troops, stationed in the area since August last year, to remove the artillery, they too refused to do so.

To date, the site has not been fenced off or marked by warning signs. In fact, as Mr Toyoda conveyed to RISQ, "I was horrified to find that many children were playing near and around the abandoned guns".

Mr Toyoda's finding comes shortly after Dutch troops found a depleted uranium shell in the area of the kind commonly used by the US Airforce against armoured targets. Both findings confirm an earlier RISQ Report that there are, indeed, more areas contaminated with depleted uranium in As Samawah. However, since the US government has so far been unwilling to disclose any information on DU-firing locations, the question remains as to where exactly such sites are located.

Of course, the lack of reliable information bears, before all, on concerns about the health and safety of the local population but it also implicates Dutch troops and the newly arriving Japanese units. The main problem is that the troops only know of areas contaminated more than ten years ago, during the Gulf War in 1991. About areas that have been contaminated recently, they have received no information.

From  "‘Didactic version’ Answers, Exam Chemical Risk Management 8 th June 2004", Question 4:

Depleted uranium is 238 U (obtained as a waste product from the production of fissionable 235 U), with a half-life of 4.5x10 9 years. In natural uranium, the abundance of 238 U is 99.6 %. The risk value for nuclear radiation is 0.05 / Sv effective dose (5 killed of 100 people ex-posed). An A10 bullet contains roughly 100 g DU. The fire rate of the 30 mm Gatling gun of the A10 tank buster is 3900 rounds per minute (65 per second!); a salvo takes a few seconds (much longer causes the Gatling gun to melt). The aircraft operate in pairs and will have launched several salvos per pass; each attack will consist of a number of passes.

Answer the following questions:

A. Assume the surface area of the anti-aircraft artillery site that was fired at, to be 1000 m 2 . The natural concentration of uranium in the soil is 10 mg/kg. Assume further that only the top layer of 10 cm of soil contributes to the radiation levels measured with a Geiger counter. Estimate the mass of depleted uranium that would have to have been deposited by the American aircraft to increase radiation levels with a fac-tor 300. Is the result a realistic number in the scenario described?

B. A Geiger counter does not measure dose rate, but radiation intensity. But if you as-sume that the factor of 300 also applies to dose rate, and know that the typical natu ral dose rate is 0.17 mSv per year, what would the annual dose be that a child might receive by playing at the site for an hour per day? What is the associated risk in terms of probability of dying per year? Does the area need to be fenced off ac-cording to the acceptable individual risk criterion in Dutch law?

Answers:

a) 1000 m2 x 0.1 m = 100 m3. At a density of 2000 kg/m3, the total mass of natural ura-nium would be 100 m3 x 2000 kg/m3 x 10x10 -6 kg/kg = 2 kg of natural uranium present. And 300 times that would be 600 kg or about 6000 bullets equivalent to 2 minutes continu-ous firing or 2 times 30 salvos of 5 sec. And yes, that is realistic.

b) 300 x 0.17 mSv/yr x 1/24 = 2.1 mSv/yr. 2.1 mSv/yr x 0.05 /Sv = 1.1x10 -4 /yr and thus much higher than 10 -6 /yr, the Dutch ac-ceptability criterion. Yes, the area definitely needs to be fenced off.