Archive for September, 2010

Nuclear Co-operation between Jordan and Japan

September 14th, 2010

A nuclear cooperation agreement has been recently signed between Japan and Jordan, to build Jordan’s first 1,000 MW reactor. Both Jordan and Japan are aiming at having the agreement ratified by early October, so that talks can progress between JAEC and Areva-Mitsubishi on the Atmea-1 reactor.
Two others companies short-listed for the project are Atomic Energy of Canada, with its Enhanced Candu-6, and Russia’s Atomstroyexport, with its VVER-1000

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New half-life determination of selenium-79

September 9th, 2010

Due to its long half-life, Se-79 is one of only a few nuclides that determine the long-term radiological impact of a repository on the environment. Over the years, a number of half-life determinations have been made. Results lie in the range 124 thousand years to 1.13 million years. This new measurement (1) of 327 thousand years is a major improvement in the measurement uncertainty.
Scientisits from Physikalisch-Technische Bundesanstalt, the Institute for Radiochemistry of the TU Munich, the Institute for Transuranium Elements in Karlsruhe and the Paul Scherrer Institute in Villingen (Switzerland) were involved in the collaboration.

(1) Gerhard Jörg, Rolf Bühnemann, Simon Hollas, Niko Kivel, Karsten Kossert, Stefaan Van Winckel, Christoph Lierse v. Gostomski. Preparation of radiochemically pure 79Se and highly precise determination of its half-life. Applied Radiation and Isotopes, 2010; DOI: http://dx.doi.org/10.1016/j.apradiso.2010.05.006

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Conan the bacterium is back again!

September 9th, 2010

In a recent paper (1), an explanation is postulated on how “Conan the Bacterium” can survive massive amounts of radiation which normally kills cells. The survival mechanism is based on protecting its proteins from oxidation – this saves the DNA repair enzymes from radiation damage.

Background (2): The bacterium Deinococcus radiodurans or D. radiodurans, which means “strange berry that withstands radiation”, was first identified in 1956. It was isolated from a can of beef which had been radiation sterilised. Normally bacteria do not withstand the radiation processing. This was not the case, however, with D. radiodurans now affectionately known among scientists as Conan the Bacterium.
Not only does the bacterium show resistance to toxic chemicals, but D. radiodurans is extremely resistant to massive doses of ionising radiation. Following a radiation dose in excess of 10,000 Sv (thousands of times higher than the lethal radiation dose in humans), the radiation damaged the bacterium’s genetic material by breaking each of the chromosomes into more than one hundred pieces. Due to a a unique repair system which efficiently repairs the damage to its DNA the bacterium returns to normal within a few hours.
The bacterium is believed to be as old as the Earth and could have been one of
the earliest forms of life on the planet. Due to its radiation repair abilities it could even have come from space.

An interesting application is to use a genetic manipulation of the bacteria to break down toxic organic chemicals at radioactive waste sites. In particular, the task is to engineer radiation-resistant microbes that degrade or transform this waste into less hazardous forms. Using bacteria for such purposes is known as bioremediation. In the US, some 3000 sites have been contaminated due to nuclear related activities. In many of the sites, the waste contains a mixture of organic pollutants with radioisotopes of uranium and plutonium. Traditional physicochemical cleaning methods would take decades and prove very costly. Bioremediation techniques should be considerably less expensive than the conventional methods.

(1) Daly MJ, Gaidamakova EK, Matrosova VY, Kiang JG, Fukumoto R, et al. 2010 Small-Molecule Antioxidant Proteome-Shields in Deinococcus radiodurans. PLoS ONE 5(9): e12570. http://dx.doi.org/10.1371/journal.pone.0012570

(2) J. Magill, J. Galy, Radioactivity Radionuclides and Radiation, p. 152, Springer Verlag, 2005. http://www.nucleonica.com/nuclTxtbook.aspx

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