Tag: radiation

Scientists: On Mars surface elevation doesn’t matter that much in terms of radiation protection

9:41 am

In a paper published in February, scientists determined from models and data that the thickness of Martian cave ceilings required to protect you from radiation is not that much different whether you are on top of Olympus Mons (the Mount Everest of Mars), or at the bottom of Hellas Basin (Mars’ Death Valley).

From the paper’s conclusion:

Overall, the atmospheric thickness is not a dominant parameter for the required shielding. However, at a low-altitude crater where the surface pressure is above 1,000 Pa, the required subsurface shielding is about 10–20 cm [4 to 8 inches] less than at the top of high mountains where the pressure is below 100 Pa. Moreover, solar activities which determine the GCR flux arriving at Mars play an role. To reduce the annual effective dose to be below 100 mSv, the required shielding is 1.5–1.6 m [about 5 feet] during solar minimum and 0.9–1.1 m [a little more than 3 feet] during solar maximum. For a threshold of 50 mSv, the required shielding is 2.1–2.2 m [about 7 feet] during solar minimum and 1.7–1.9 m [about 6 feet] during solar maximum.

Essentially, what this research suggests is that to properly shield any underground facility, you need to cover it with at least seven feet of material, or be in a cave where the ceiling is that thick. It really doesn’t matter how much atmosphere is above you. Even at its thickest at the lowest elevation, Mars’ atmosphere doesn’t provide much protection.

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Study proposes new radiation standards in space

9:14 am

Health limits of radiation for space missions

A new report issued today from the National Academies of Science is recommending that NASA adopt a new health standard for limiting the exposure of astronauts to radiation during long space missions. The new standard, based on a maximum accumulative dosage of 600, is indicated by the figure to the right, taken from the report [pdf] and annotated to show both the new recommendation as well as the standards used by other space-faring nations.

The key result of this change is expressed in the report in this one sentence:
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German instrument on Chang’e-4 documents dangerous radiation levels

2:07 pm

This result is not a surprise: A German instrument on China’s Chang’e-4 lander, located now on the Moon’s far side, has measured the radiation levels there, and found them to be much worse than found on Earth.

DLR radiation physicist Thomas Berger from the DLR Institute of Aerospace Medicine, who participated in the publication explains: “The radiation exposure we measured is a good indication of the radiation inside a spacesuit. The measurements give us an equivalent dose rate – the biologically weighted radiation dose per unit of time – of around 60 microsieverts per hour. For comparison, during a long-haul flight from Frankfurt to New York, the dose rate is five to 10 times lower than this. On Earth’s surface, it is some 200 times lower. In other words, a long-term stay on the Moon will expose astronauts’ bodies to high doses of radiation.”

“Human bodies are simply not made to be exposed to space radiation,” adds Robert Wimmer-Schweingruber of the Christian-Albrecht University (CAU) in Kiel, whose team developed and built the LND instrument . “On longer missions to the Moon, astronauts will have to protect themselves from it – by covering their habitat with a thick layer of lunar rock, for example. This could reduce the risk of cancer and other illnesses caused by long periods of time spent on the Moon.”

Previous instruments had only measured the cumulative radiation for the entire mission. This instrument took multiple readings lasting one, ten, or sixty minutes, which gives a more realistic measure of what an astronaut would actually experience, once there.

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Space radiation may increase risk of cancer

8:59 am

Using mice and models, scientists have concluded that humans who spend long periods in space, exposed to its radiation, will have a 3% higher risk for cancer.

A team led by researchers at Colorado State University and Frederick National Laboratory for Cancer Research, which is part of the National Institutes for Health, used a novel approach to test assumptions in a model used by NASA to predict these health risks. Based on the NASA model, the team found that astronauts will have more than a three percent risk of dying of cancer from the radiation exposures they will receive on a Mars mission. That level of risk exceeds what is considered acceptable. [emphasis mine]

And how did they come to this conclusion?

…For the study, Weil and first author Dr. Elijah Edmondson, a veterinary pathologist and researcher based at the Frederick National Laboratory for Cancer Research in Maryland, used a unique stock of genetically diverse mice, mimicking a human population. Mice were divided into three groups with the first group receiving no radiation exposure and the other two receiving varying levels of exposure.

Edmondson, who conducted the research while completing a veterinary residency in pathology at CSU, said that for this type of research project, genetic variability is crucial. “Humans are very genetically diverse,” he explained. “You want to model that when it’s appropriate and feasible to do so.”

Weil said although the research team saw different tumor types, similar to humans, but the heavy ions did not cause any unique types of cancer. They also saw differences by sex. In humans, women are more susceptible to radiation-induced cancers than men; one of the main reasons is that women live longer, allowing sufficient time for cancer to develop. In assessing the cancer risk between male and female mice in the study, scientists said the findings parallel human data.

Edmondson said the study validates the NASA model to measure cancer risks for humans from space radiation.

In a sense, this study is junk. First, it discovers the obvious (radiation increases your chances of getting cancer). Second, it is too model-dependent, so assigning any precise percentage to that increase in humans is absurd, especially when based on a sample comprised of mice.

Third, and most important, it completely forgets the reality that life is risk, exploration is dangerous, and to do great things you need to take greater chances. That NASA concludes these questionable numbers are unacceptable means that NASA will never send humans anywhere beyond Earth orbit. Ever.

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Cosmic rays a threat to Mars travel

8:45 am

The uncertainty of science: New research using rats has found that cosmic rays might damage human brains during a long mission to and from Mars.

Radiation oncologist Charles Limoli and his colleagues at the University of California Irvine bombarded mice and rats with low-doses of ionized oxygen or titanium. These charged particles have similar energies to those of cosmic rays that can pass right through the shielding on spacecraft. The dosage levels that the researchers used were similar to what astronauts would be exposed to during a three-year round-trip mission to Mars, Limoli says.

The researchers looked at the prefrontal cortex, the brain region linked to decision-making, executive function, and long-term memory. They saw significant damage and inflammation in the brains of exposed animals as long as six months after the exposure. The radiation damaged the tiny branches on neurons that help transmit electric signals to the nerve cell body. This led to a loss in learning and memory. The exposed animals performed poorly on behavioral tests that measure intelligence, and they showed higher, constant anxiety levels.

Though the uncertainties here are enormous, the research here has essentially discovered the obvious. The radiation experienced during a long interplanetary voyage is unhealthy, and any interplanetary vessel for carrying humans on such a voyage must be designed with sufficient shielding to protect its passengers. That this research has proven that cosmic rays are a threat also means that providing a ship with a safe room where passengers can take refuge during solar storms is not sufficient. Cosmic rays are random and come at all times in an unpredictable manner. The research suggests that the shielding will have to protect the ship’s entire living quarters.

The payload weight requirements for any rocket that will launch the first interplanetary ships just went up significantly. This means that space stations we have been building (Mir, ISS, and Tiangong) are not even close to sufficient for interplanetary travel, and need significant redesign to make them work. This also means that human interplanetary travel will require cost-efficient heavy lift rockets such as the Falcon Heavy.

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More Junk Science and Journalism

11:46 am

I can’t stand it. I just can’t stand it. It keeps happening and I just can’t stand it.

Yesterday there was this absurd short news piece posted on the website of the so-called journal Science, “Apollo astronauts much more likely to die from heart disease”. describing a research paper published by one of Nature’s side journals, Scientific Reports. Before I even looked at the story I said to myself, “How can they possibly come to that conclusion considering the tiny number of humans who have ever traveled beyond Earth orbit? The sample will simply be too small to allow for any such finding.”

Then I looked at the article and found my instincts confirmed. As Steve Milloy noted on his very aptly named website, Junk Science,

Yes, the result is based on a total of three (3) cases of heart disease deaths of out seven (7) Apollo astronauts. Past the vanishingly small sample size and even smaller number of cases, heart disease is a natural disease of aging and the Apollo lunar astronauts were 10 years older than the other comparison groups.

To put it more bluntly, this was a garbage piece of very bad science. While it was somewhat embarrassing for a Nature journal to publish it, it was far more disgraceful for the journal Science to highlight it. I, however, don’t have to join these two peer-review journals and participate in their stupidity, and thus I made no mention of the story on Behind the Black, because it is my policy to not waste much time on bad science, unless I think that bad science is going to have bad repercussions.

Well the bad repercussions have arrived. Since yesterday, the following so-called news organizations have run with this story, without the slightest indication that they have faintest understanding of science, statistics, or plain common sense:
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ISS data lowers radiation risk for humans in space

7:28 pm

Good news: Data collected on ISS for the past decade now suggests that the human body does a better job of shielding its internal organs from space radiation than previously believed.

For an astronaut working inside the space station, the overestimate was about 15 percent — a fairly close correlation given that the station’s exterior shell provides much of the protection needed.

But for astronauts working outside the station, the radiation absorption measured was substantially less than what had been registered by the personal dosimeters worn by astronauts. “Measurements of a personal dosimeter dramatically overstate the exposure of an astronaut, in the worst case by a factor of three,” according to a summary of the results by a Euro-Russian team. “[I]n an outside exposure the self-shielding of the human body is very effective. … [T]he effective dose equivalent is less than 30 percent higher than in an inside exposure.”

In other words, humans could fly 30 percent longer in space with the present shielding and suffer far less exposure than expected. Though this data is for operations in low Earth orbit, it still provides a strong counter to the bad news recently released about the high amounts of dangerous radiation expected in interplanetary space due to the Sun’s recent low sunspot activity. Even if radiation levels are higher, the human body is more resilient than expected. Interplanetary space travel is still possible.

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Solar minimum to limit interplanetary manned flights?

9:45 am

A new study suggests that the increased cosmic radiation reaching the inner solar system because of the Sun’s weak sunspot activity will increase the exposure to dangerous radiation levels for interplanetary astronauts, thus limiting mission lengths to about one year.

The new research finds that, during periods of low solar activity, a 30-year-old astronaut can spend roughly one year in space—just enough time to get to Mars and back—before the constant bombardment by cosmic rays pushes the risk of radiation-induced cancer above current exposure limits.

If the sun’s activity continues to weaken as many scientists predict, the number of days humans could spend in deep space before reaching their exposure limit could decrease by about 20 percent, making future crewed space flight more dangerous, according to the new study accepted for publication in Space Weather, a journal of the American Geophysical Union.

The numbers were worse for women, whose exposure would become dangerous in only 300 days, according to the study.

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Data from an experiment on Lunar Reconnaissance Orbiter has confirmed that light plastics can provide sufficient protection for humans against radiation.

11:45 am

Data from an experiment on Lunar Reconnaissance Orbiter has confirmed that light plastics can provide sufficient protection for humans against radiation.

This is very good news indeed. Combined with the data from Curiosity, which indicated that the radiation levels in interplanetary space were less intense that expected, it appears that radiation will not be a serious obstacle to interplanetary travel.

Now we just have to get the bone loss and vision problems solved.

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Data collected by a radiation sensor inside Curiosity during its journey to Mars suggest that it will be possible to build ships with sufficient shielding to protect humans on such a voyage.

9:04 pm

Data collected by a radiation sensor inside Curiosity during its journey to Mars suggest that it will be possible to build ships with sufficient shielding to protect humans on such a voyage.

Zeitlin and his colleagues analysed the radiation recorded by a small detector on board the craft that was active during most of the 253-day cruise to Mars. Although the craft was not uniformly protected from exposure to Galactic cosmic rays and charged particles from the Sun, the MSL’s shielding on average approximated that of human space-flight missions. ….

At NASA Langley, Thibeault and her colleagues are testing new types of shielding that consist of hydrogenated materials. Hydrogen offers protection because it breaks apart heavy charged particles without creating secondary particles that add to the radiation dose, she notes. One of the materials under investigation, hydrogen-filled boron nitride nanotubes, looks particularly promising because it is robust and lightweight enough to double as both the skin of a spacecraft and its shield. Using separate materials to build and shield a craft would add too much weight to a Mars-bound mission, Thibeault notes.

Thibeault says that she is heartened by the new study because she had feared that the radiation dose might be considerably higher. The results suggest “that this is a problem we can solve”, she adds.

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The radiation from the Fukushima nuclear power plant failure in Japan has turned out to be less of a problem than predicted.

3:36 pm

The radiation from the Fukushima nuclear power plant failure in Japan has turned out to be less of a problem than predicted.

[O]utside the immediate area of Fukushima, this is hardly a problem at all. Although the crippled nuclear reactors themselves still pose a danger, no one, including personnel who worked in the buildings, died from radiation exposure. Most experts agree that future health risks from the released radiation, notably radioactive iodine-131 and cesiums-134 and – 137, are extremely small and likely to be undetectable. Even considering the upper boundary of estimated effects, there is unlikely to be any detectable increase in cancers in Japan, Asia or the world except close to the facility, according to a World Health Organization report. There will almost certainly be no increase in birth defects or genetic abnormalities from radiation.

Even in the most contaminated areas, any increase in cancer risk will be small. For example, a male exposed at age 1 has his lifetime cancer risk increase from 43 percent to 44 percent. Those exposed at 10 or 20 face even smaller increases in risk — similar to what comes from having a whole-body computer tomography scan or living for 12 to 25 years in Denver amid background radiation in the Rocky Mountains.

The entire article is worth reading, as it outlines in detail the less than deadly consequences of both Fukushima and Chernobyl. This is the kind of information we should use to rationally decide whether we want to build more nuclear power planets.

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New research suggests that the high radiation experienced by astronauts on interplanetary journeys could accelerate the onset of Alzheimer’s.

9:32 am

New research suggests that the high radiation experienced by astronauts on interplanetary journeys could accelerate the onset of Alzheimer’s.

Some caveats: This research was done on Earth with mice. It also assumes that it will be impossible to protect astronauts from all types of radiation while on their journey.

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The radiation released from the Fukushima nuclear power meltdown in Japan last year will cause almost no cases of cancer according to two separate reports.

11:42 am

The radiation released from the Fukushima nuclear power meltdown in Japan last year will cause almost no cases of cancer according to two separate reports.

This story is almost a week old. I missed it initially because Nature buried the results, headlining the story in the most boring way possible: “Fukushima’s doses tallied”.

These results however illustrate again the success of the engineering at the nuclear power plant. Certainly they did things wrong, and certainly there were engineering failures there. Nonetheless, the safety features allowed them to contain the power plant even after it experienced the most powerful earthquake in recorded history followed by the most powerful tsunami in a thousand years.

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Scientists last week published a paper claiming that the Fukushima nuclear reactor meltdown caused 14,000 U.S. deaths.

9:53 pm

Junk science: Scientists last week published a paper claiming that the Fukushima nuclear reactor meltdown caused 14,000 U.S. deaths. You can download the paper here [pdf].

I expect the mainstream television press to push this story in the coming days. The story however is crap. I’ve read the paper, and all it shows is a small statistical increase in deaths in the fourteen weeks after the earthquake/meltdown, compared to the previous year. The scientists provided no context with other years, nor did they factor in changes in total population or a host of innumerable other variables that would influence these numbers. Worse, they presented no direct evidence linking the fallout from the meltdown with the deaths.

In other words, this is agenda-driven science, designed mainly to attack nuclear energy. We should not give it much credence.

One more point: the lead author of the paper is the executive director of Radiation and Public Health Project, an organization whose only purpose appears to be to prove that low level radiation has a negative effect on human health. From a science perspective, this is not a good way to do science. The only way the scientists in this organization can justify their fund-raising and research is to find evidence to prove their theory.

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New York Metropolitan Opera stars, fearing radiation, skip Japan tour

9:43 am

Cowards: Two New York Metropolitan Opera stars, fearing radiation, have backed out of a Japanese tour in the cities of Tokyo and Nagoya. This, despite the documented lack of radiation:

Tokyo briefly registered nominally higher radiation levels in its air and water, but they have subsided to pre-tsunami levels. There was never any scientific concern of a radiation impact on Nagoya, which is much farther away.

Meanwhile, the efforts to stabilize the reactors in Fukushima are proceeding.

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TSA to retest airport body scanners for radiation

10:25 pm

Does this make you feel safer? The TSA is going to retest the radiation levels of all its airport body scanners after maintenance records on some showed levels 10 times higher than expected. Also this:

The TSA is responsible for the safety of its own X-ray devices. The U.S. Food and Drug Administration has said it does not routinely inspect airport X-ray machines because they are not considered medical devices. The TSA’s airport scanners are exempt from state radiation inspections because they belong to a federal agency.

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