Nuclear rocket puts Mars within reach

31 May 2013 Space travel to Mars and beyond may only be possible through the use of nuclear rocket technology, NASA suggests. Such spacecraft would be much faster than conventional craft, cutting the length of the mission and thereby reducing radiation exposure to astronauts. NASA considers a 3% increased risk of fatal cancer as an acceptable career limit for its astronauts currently operating in low-Earth orbit. This translates to a cumulative dose of between 800 and 1200 milliSieverts (mSv). Data from the radiation assessment detector of the Curiosity rover mission to Mars indicates that the rover was exposed to an average of 1.8 mSv of radiation per day on its 36-week journey to Mars. This suggests that astronauts travelling in conventional spacecraft would receive a dose of about 660 mSv during a round-trip to the planet, too close to NASA’s current limit, making missions appear impracticable. Cary Zeitlin, a principal scientist at the Southwest Research Institute, said, “In terms of accumulate dose, it’s like getting a whole-body CT scan once every five or six days.” He added, “Understanding the radiation environment inside a spacecraft carrying humans to Mars or other deep space destinations is critical for planning future crewed missions.” Nuclear option One way to reduce the exposure of astronauts to radiation and other effects of space travel is to use faster spacecraft to cut the duration of their missions. A craft powered by a nuclear rocket engine could be the answer. One approach uses a nuclear reactor to heat hydrogen to very high temperatures, which expands through a nozzle to generate thrust. NASA says that spacecraft powered by such engines generate higher thrust and are more than twice as efficient as conventional chemical rocket engines. NASA said that the nuclear rocket engine would be designed to be safe throughout the mission and would not be started up until the craft had reached a safe orbit and was ready to begin its journey into deep space. Prior to startup, the nuclear system would be cold, with no fission products generated from nuclear operations, and with radiation below significant levels. NASA has already reported the successful testing of power conversion and radiator systems for a nuclear power system it hopes to deploy on the Moon by 2020. Russia is also working on a nuclear rocket that would generate electricity for a plasma thruster. The specific thrust of such a system could be...
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Fear and stress outweigh Fukushima radiation risk

31 May 2013 The most extensive international report to date has concluded that the only observable health effects from the Fukushima accident stem from the stresses of evacuation and unwarranted fear of radiation. Some 80 international experts contributed to a report by the UN Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). It concluded “Radiation exposure following the nuclear accident at Fukushima Daiichi did not cause any immediate health effects. It is unlikely to be able to attribute any health effects in the future among the general public and the vast majority of workers.” The only exception are the emergency nuclear workers that received radiation doses of over 100 mSv during the crisis triggered by the 15 metre tsunami that struck the plant on 11 March 2011. Records show that 146 workers fall into this category. They will be monitored closely for “potential late radiation-related health effects at an individual level.” By contrast, the public was exposed to 10-50 times less radiation. Most Japanese people were exposed to additional radiation amounting to less than the typical natural background level of 2.1 mSv per year that comes mainly from the ground and from space. People living in Fukushima prefecture are expected to be exposed to around 10 mSv over their entire lifetimes, while for those living further away the dose would be 0.2 mSv per year. “On the whole, the exposure of the Japanese population was low, or very low, leading to correspondingly low risks of health effects in later life,” said Wolfgang Weiss of UNSCEAR. The conclusion reinforces the findings of several international reports to date, including one from the World Health Organisation (WHO) that considered the health risk to the most exposed people possible: a postulated girl under one year of age living in Iitate or Namie that did not evacuate and continued life as normal for four months after the accident. Such a child’s theoretical risk of developing breast cancer by age 89 would be increased from 29.04% to 30.20%, according to WHO’s analysis. Social and societal effects The emergency situation at Fukushima Daiichi began on 11 March 2011 but it was not until 15 March that the accident sequence culminated in its most significant emission of radioactivity. Japanese authorities used the intervening days to evacuate residents from a 20 kilometre radius and advise those in a further 10 kilometre zone to remain indoors when possible....
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Rostov reactor vessel delivered

30 May 2013 The reactor pressure vessel (RPV) for unit 3 of Russia’s Rostov nuclear power plant has been transported to the construction site ready for installation. The major component – weighing more than 300 tonnes – was produced by OMZ Izhora at its factory in Izhorskiye Zavody. The RPV was transported by boat up the River Neva before being loaded onto a low-loader truck for the final part of its journey to the construction site. Four 1000 MWe VVER pressurized water reactors have been planned at the Rostov site (formerly known as Volgodonsk) since the early 1980s. Construction of units 1 and 2 began quickly, but progress was slow. Units 1 and 2 eventually entered commercial operation in March 2001 and October 2010, respectively. In June 2009, NN-AEP, a subsidiary of AtomEnergoProm (AEP), won the tender as principal contractor for the construction of units 3 and 4, now slightly larger at 1100 MWe. Construction of unit 3 began again in late 2009, with its reactor building dome installed in October 2012. Units 3 and 4 are set to be completed by 2014 and 2016, respectively. Fuente:...
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Rokkasho steps forward

30 May 2013 The long-delayed reprocessing plant at Rokkasho-mura in Japan has passed a significant commissioning milestone, proving its vitrification lines and moving it towards operation. A test completed this week successfully trapped highly radioactive materials from 70 litres of liquid waste within 25 glass ‘logs’. This test of the ‘A’ vitrification line follows a similar successful trial at the ‘B’ line in January and completes an active test run of the entire reprocessing plant that began in January 2008. Vitrification is the end of the reprocessing operation, which starts with the input of used reactor fuel. This is chopped up and dissolved in acid before the resulting liquor is chemically processed to recover reusable uranium and plutonium. This mix is kept for recycling into new reactor fuel, while the waste liquor goes to vitrification. In the resulting glass form, the wastes are ready for long-term storage and permanent disposal at much smaller volume than the original reactor fuel. The Rokkasho plant took 13 years to build and its commissioning since 2006 has been extremely slow. Serious delays followed an incident when ceiling bricks in the glass furnace fell down, causing molten glass containing waste to stick on some surfaces. The plant is owned and operated by Japan Nuclear Fuels Ltd (JNFL), which designed the vitrification unit to go with the reprocessing section supplied by Areva. JNFL needs to secure a licence from the Nuclear Regulation Authority before putting Rokkasho to work on reprocessing Japan’s national stockpiles of used reactor fuel, currently slated to begin in October. Despite the uncertainty over nuclear power’s future in Japan, the country’s waste management policy remains centred on reprocessing before underground disposal. Fuente:...
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Indian-Japanese cooperation deal moves closer

30 May 2013 Talks on a cooperation agreement between India and Japan will be accelerated, the countries’ prime ministers have said following a meeting in Tokyo. Japanese prime minister Shinzo Abe and his Indian counterpart Manmohan Singh signed a joint statement on strengthening the partnership between the two countries. In the statement, they “reaffirmed the importance of civil nuclear cooperation between the two countries, while recognizing that nuclear safety is a priority for both governments.” Abe and Singh accordingly directed their officials to “accelerate the negotiations of an agreement for cooperation in the peaceful uses of nuclear energy towards an early conclusion.” Those negotiations were suspended after the March 2011 accident at Japan’s Fukushima Daiichi plant. The signing of such an accord would enable India to import Japanese nuclear technology and services. During his visit, Singh commented, “India’s growth will provide expanding opportunities for foreign investment. We welcome foreign investment in the development of our economy and especially so in the critical infrastructure sector.” He noted that over the past few years India and Japan have been in discussions “to address some of our shared challenges in the area of energy security.” India was largely excluded from international trade in nuclear plant or materials for over three decades because of its position outside comprehensive safeguards regime of the Nuclear Non-proliferation Treaty. Special agreements ended the isolation in 2009 and the country may now engage in nuclear trade with those countries with which it has since signed cooperation agreements: Canada, France, Kazakhstan, Russia, the UK and USA. Foreign technology and fuel are expected to boost India’s nuclear power plans considerably. Fuente:...
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