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White House new system guidelines for nuclear power in space includes weapons grade materials

White House Overhauls Launch Approval Process for Nuclear Spacecraft, AIP, 23 Aug 19, The White House has announced a new launch authorization process for spacecraft that use nuclear-powered systems, instituting a tiered framework that delegates decision-making for less risky missions and provides explicit guidance on acceptable risk levels……

The memo categorizes missions into three tiers based on the amount and type of nuclear material they contain as well as the estimated probability that a launch accident would result in a certain level of exposure to any member of the public. Unlike the prior policy, it also lays out criteria specific to fission reactor systems and non-federal missions.

The least risky missions fall in Tier 1, where the director of the sponsoring agency can approve the launch. In Tier 2, an interagency review process is triggered, though the sponsoring agency director maintains authority over the launch decision. The memo directs NASA to establish a standing Interagency Nuclear Safety Review Board to perform this function, which formerly was handled by an ad hoc committee empaneled on a mission-by-mission basis.

Spacecraft that use fission reactors automatically fall in at least Tier 2, and the memo requires NASA to identify additional safety guidelines for “safe non-terrestrial operation of nuclear fission reactors, including orbital and planetary surface activities.”

Tier 3 missions require presidential authorization, which for non-defense missions is delegated to the OSTP director, who may opt to forward the decision to the president. Due to nuclear nonproliferation considerations, missions that use highly enriched uranium automatically fall in Tier 3.

The memo also establishes a set of safety guidelines that apply to spacecraft across all tiers. It specifies that the probability a launch accident would result in any individual receiving a total effective dose between 0.025 rem and five rem should be no greater than 1 in 100. The probability for exposures between five rem and 25 rem should not exceed 1 in 10,000, and above 25 rem the probability should not exceed 1 in 100,000. For comparison, the average effective doseindividuals receive from natural background radiation in the U.S. is about 0.3 rem per year, and the Nuclear Regulatory Commission’s dose limit for radiation workers is five rem per year…….

According to a 2015 study, the U.S. has launched 47 nuclear power systems and hundreds of heater units on 31 missions since 1961. The most recent scientific missions to employ an RPS were New Horizons, a Pluto fly-by mission launched in 2006, and the Mars Curiosity Rover, launched in 2011. The follow-on Mars 2020 Rover and the recently selected Dragonfly rotorcraft mission to Saturn’s moon Titan are currently the only two approved NASA spacecraft in development that will use an RPS.

The relatively infrequent use of nuclear systems on spacecraft is in part attributed to the complexity and cost of the safety review process, which generally has limited them to flagship-class missions. Low availability of plutonium for civilian uses has also constrained the mission cadence…….

NASA has recently emphasized the potential value of fission reactors for human deep space exploration missions. At the National Space Council meeting this week, NASA Administrator Jim Bridenstine said nuclear thermal propulsion technologies could significantly reduce transit time to Mars. He also pointed to other potential applications, such as using fission to power a space-based laser that could deflect asteroids and deorbit space debris.

NASA is also exploring how nuclear reactors could meet the power demands of planetary bases. One such concept, called Kilopower, could provide up to 10 kilowatts per reactor using highly enriched uranium. Bridenstine visited members of the Kilopower team this week at NASA’s Glenn Research Center.

The concept is not without critics. Rep. Bill Foster (D-IL), a former Fermilab physicist who advocates using alternatives to highly enriched uranium, pressedBridenstine on the subject at a hearing this year.

A future where every space-faring nation has a big inventory of weapons-grade material to service the reactors that they are using all over the Moon and all over Mars is not a very safe space environment,” Foster said. “There will be some small performance compromises in going with low enriched non-weapons grade material, but I really urge you to look hard at keeping alive the prospect of having an international collaboration to develop workable non weapons grade-based materials that the whole world will use.” …….https://www.aip.org/fyi/2019/white-house-overhauls-launch-approval-process-nuclear-spacecraft

August 24, 2019 - Posted by | space travel, USA

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