Category Archives: Nuclear War

The Science Behind the First Nuclear Chain Reaction, Which Ushered in the Atomic Age 75 Years Ago – Artemis Spyrou and Wolfgang Mittig. 

That fateful discovery helped give us nuclear power reactors and the atomic bomb. 

Over Christmas vacation in 1938, physicists Lise Meitner and Otto Frisch received puzzling scientific news in a private letter from nuclear chemist Otto Hahn. When bombarding uranium with neutrons, Hahn had made some surprising observations that went against everything known at the time about the dense cores of atoms – their nuclei.

Meitner and Frisch were able to provide an explanation for what he saw that would revolutionize the field of nuclear physics: A uranium nucleus could split in half – or fission, as they called it – producing two new nuclei, called fission fragments. More importantly, this fission process releases huge amounts of energy. This finding at the dawn of World War II was the start of a scientific and military race to understand and use this new atomic source of power.

The release of these findings to the academic community immediately inspired many nuclear scientists to investigate the nuclear fission process further. Physicist Leo Szilard made an important realization: if fission emits neutrons, and neutrons can induce fission, then neutrons from the fission of one nucleus could cause the fission of another nucleus. It could all cascade in a self-sustained “chain” process.

Thus began the quest to experimentally prove that a nuclear chain reaction was possible – and 75 years ago, researchers at the University of Chicago succeeded, opening the door to what would become the nuclear era.

Harnessing fission

As part of the Manhattan Project effort to build an atomic bomb during World War II, Szilard worked together with physicist Enrico Fermi and other colleagues at the University of Chicago to create the world’s first experimental nuclear reactor.

For a sustained, controlled chain reaction, each fission must induce just one additional fission. Any more, and there’d be an explosion. Any fewer and the reaction would peter out.

In earlier studies, Fermi had found that uranium nuclei would absorb neutrons more easily if the neutrons were moving relatively slowly. But neutrons emitted from the fission of uranium are fast. So for the Chicago experiment, the physicists used graphite to slow down the emitted neutrons, via multiple scattering processes. The idea was to increase the neutrons’ chances of being absorbed by another uranium nucleus.

To make sure they could safely control the chain reaction, the team rigged together what they called “control rods.” These were simply sheets of the element cadmium, an excellent neutron absorber. The physicists interspersed control rods through the uranium-graphite pile. At every step of the process Fermi calculated the expected neutron emission, and slowly removed a control rod to confirm his expectations. As a safety mechanism, the cadmium control rods could quickly be inserted if something started going wrong, to shut down the chain reaction.

They called this 20x6x25-foot setup Chicago Pile Number One, or CP-1 for short – and it was here they obtained world’s the first controlled nuclear chain reaction on December 2, 1942. A single random neutron was enough to start the chain reaction process once the physicists assembled CP-1. The first neutron would induce fission on a uranium nucleus, emitting a set of new neutrons. These secondary neutrons hit carbon nuclei in the graphite and slowed down. Then they’d run into other uranium nuclei and induce a second round of fission reactions, emit even more neutrons, and on and on. The cadmium control rods made sure the process wouldn’t continue indefinitely, because Fermi and his team could choose exactly how and where to insert them to control the chain reaction.

A nuclear chain reaction. Green arrows show the split of a uranium nucleus in two fission fragments, emitting new neutrons. Some of these neutrons can induce new fission reactions (black arrows). Some of the neutrons may be lost in other processes (blue arrows). Red arrows show the delayed neutrons that come later from the radioactive fission fragments and that can induce new fission reactions.

Controlling the chain reaction was extremely important: If the balance between produced and absorbed neutrons was not exactly right, then the chain reactions either would not proceed at all, or in the other much more dangerous extreme, the chain reactions would multiply rapidly with the release of enormous amounts of energy.

Sometimes, a few seconds after the fission occurs in a nuclear chain reaction, additional neutrons are released. Fission fragments are typically radioactive, and can emit different types of radiation, among them neutrons. Right away, Enrico Fermi, Leo Szilard, Eugene Wigner and others recognized the importance of these so-called “delayed neutrons” in controlling the chain reaction.

If they weren’t taken into account, these additional neutrons would induce more fission reactions than anticipated. As a result, the nuclear chain reaction in their Chicago experiment could have spiraled out of control, with potentially devastating results. More importantly, however, this time delay between the fission and the release of more neutrons allows some time for human beings to react and make adjustments, controlling the power of the chain reaction so it doesn’t proceed too fast.

The events of December 2, 1942 marked a huge milestone. Figuring out how to create and control the nuclear chain reaction was the foundation for the 448 nuclear reactors producing energy worldwide today. At present, 30 countries include nuclear reactors in their power portfolio. Within these countries, nuclear energy contributes on average 24 percent of their total electrical power, ranging as high as 72 percent in France.

CP-1’s success was also essential for the continuation of the Manhattan Project and the creation of the two atomic bombs used during World War II.

Physicists’ remaining questions

The quest to understand delayed neutron emission and nuclear fission continues in modern nuclear physics laboratories. The race today is not for building atomic bombs or even nuclear reactors; it’s for understanding of basic properties of nuclei through close collaboration between experiment and theory.

Researchers have observed fission experimentally only for a small number of isotopes – the various versions of an element based on how many neutrons each has – and the details of this complex process are not yet well-understood. State-of-the-art theoretical models try to explain the observed fission properties, like how much energy is released, the number of neutrons emitted and the masses of the fission fragments.

Delayed neutron emission happens only for nuclei that are not naturally occurring, and these nuclei live for only a short amount of time. While experiments have revealed some of the nuclei that emit delayed neutrons, we are not yet able to reliably predict which isotopes should have this property. We also don’t know exact probabilities for delayed neutron emission or the amount of energy released – properties that are very important for understanding the details of energy production in nuclear reactors.

In addition, researchers are trying to predict new nuclei where nuclear fission might be possible. They’re building new experiments and powerful new facilities which will provide access to nuclei that have never before been studied, in an attempt to measure all these properties directly. Together, the new experimental and theoretical studies will give us a much better understanding of nuclear fission, which can help improve the performance and safety of nuclear reactors.

Both fission and delayed neutron emission are processes that also happen within stars. The creation of heavy elements, like silver and gold, in particular can depend on the fission and delayed neutron emission properties of exotic nuclei. Fission breaks the heaviest elements and replaces them with lighter ones (fission fragments), completely changing the element composition of a star. Delayed neutron emission adds more neutrons to the stellar environment, that can then induce new nuclear reactions. For example, nuclear properties played a vital role in the neutron-star merger event that was recently discovered by gravitational-wave and electromagnetic observatories around the world.

The science has come a long way since Szilard’s vision and Fermi’s proof of a controlled nuclear chain reaction. At the same time, new questions have emerged, and there’s still a lot to learn about the basic nuclear properties that drive the chain reaction and its impact on energy production here on Earth and elsewhere in our universe.


Artemis Spyrou, Associate Professor of Nuclear Astrophysics, Michigan State University

Wolfgang Mittig, Professor of Physics, Michigan State University

Smithsonian Magazine 

Trump is the real nuclear threat, and we can’t just fantasise him away – Jonathan Freedland. 

Among the many terrifying facts that have emerged in the last several days, perhaps the scariest relate to the nuclear button over which now hovers the finger of Donald Trump. It turns out that, of all the powers held by this or any other US president, the least checked or balanced is his authority over the world’s mightiest arsenal. He exercises this awesome, civilisation-ending power alone.

As Trump has learned in recent months, the man in the Oval Office cannot simply issue a decree changing, say, the US healthcare system. He has to build majorities in the House and Senate, which is harder than it looks. If he wants to change immigration policy, a mere order is not enough. He can be stopped by the courts, as Trump saw with his travel ban. But if he wants to rain fire and fury on a distant enemy, bringing more fire and fury down on his own citizens and many hundreds of millions of others, there is no one standing in his way. Not for nothing does the geopolitical literature refer to the US president as the “nuclear monarch.”

The more you hear of the simplicity of the system, the more frightening it becomes. If Trump decides he has had enough of Kim Jong-un’s verbal threats, he merely has to turn to the low-level military aide at his side and ask them to open up the black briefcase that officer keeps permanently in their grasp. The bag is known as the nuclear “football”. (It gets its name from the code word for the very first set of nuclear war plans: dropkick.) Inside the bag is a menu of options, explained in detail in a “black book,” but also set out in a single, cartoon-like page for speedy comprehension. Trump has only to make his choice, pick up the phone to the Pentagon war room, utter the code words that identify him as the president and give the order. That’s it.

There is no need for consultation with anyone else. Not the secretary of state or the secretary of defence, nor the head of the military. The officer who receives the call at the Pentagon has no authority to question or challenge the order. His or her duty is only to implement it. Thirty minutes after the president gave the instruction, the nuclear missiles would be hitting their targets. There is no way of turning them back. Such power in the hands of a single individual would be a horrifying prospect even if it were Solomon himself whose finger was on the trigger. But as Bruce Blair, a former nuclear missile launch officer, and seasoned military analyst wrote during the 2016 campaign, Trump’s “quick temper, defensiveness bordering on paranoia and disdain for anyone who criticises him do not inspire deep confidence in his prudence.”

What’s more, Trump is the man who said in 2015, “For me, nuclear is just the power, the devastation is very important to me,” and who bellowed from the campaign podium, “I love war”. In last year’s election campaign, the former Republican congressman Joe Scarborough reported on a briefing a foreign policy expert had given Trump. “Three times, he asked, at one point, ‘If we have them, we can’t we use them?’ … Three times, in an hour briefing, ‘Why can’t we use nuclear weapons?’”

It turns out Hillary Clinton was right to warn Americans 14 months ago that, “It’s not hard to imagine Donald Trump leading us into a war just because somebody got under his very thin skin.” And here we are, Trump tweet-goading the North Koreans by declaring military solutions “locked an loaded”. We need imagine no longer.

Those who find themselves trembling at all this have spent the last few days grasping for a comfort blanket. A favourite has been the notion that those around Trump, especially the generals current and former, will not let him unleash nuclear Armageddon. This view holds that, yes, Trump may well be dangerously unhinged but fear not, the wiser heads of Washington will stay his hand. Indeed, this strain of thinking has been visible since Trump took the oath of office. Call it the deep state fantasy. It looks to the national security apparatus, the intelligence agencies and the permanent bureaucracy, the shadow government, to step in and do the right thing.

It hangs its hopes on a range of prospective saviours. It might be the trio of former generals made up of Jim Mattis, who heads the Pentagon, John Kelly, recently drafted in as chief of staff, and HR McMaster who serves as national security adviser. Alternatively, it looks to the loose alliance hailed this week by the influential Axios website as “The Committee to Save America”, consisting not only of the generals but also the cluster of New Yorkers that includes some of Trump’s less hot-headed economic advisers, with added reinforcements from the Republican ranks in Congress. The committee’s unofficial mission: to protect “the nation from disaster”. The ultimate deep state fantasy longs for the men in the shadows not merely to restrain Trump, but remove him from office. The designated hero of this story is Robert Mueller, the former FBI director now heading what is reported to be a swift and penetrating probe into allegations of collusion with Russia as well as Trump’s wider business dealings.

Mueller’s role may indeed prove to be critical. But the deep state fantasy itself, while comforting, is surely a dead end for Trump’s opponents. For one thing, events have reached an odd pass when liberals are dreaming of unelected generals thwarting an elected head of government: that used to be the fantasy of the militaristic right.

But it also relies more on hope than evidence. All these supposedly wise heads around Trump: what restraint have they achieved so far? Kelly was meant to impose order and discipline, and yet we still have Trump tweeting threats that could easily be misinterpreted as the cue for war. On North Korea, the US administration continues to send conflicting signals by the hour, with Trump outriders like Sebastian Gorka slapping down secretary of state Rex Tillerson on BBC Radio 4’s Today programme on Friday, creating confusion when a nuclear standoff requires calm clarity.

And we cannot escape the basic fact. All these advisers can try to hold him back, but when it comes to it, nuclear authority is Trump’s and Trump’s alone. He is the nuclear monarch.

The glum truth is that the only people who can effectively check a democratically elected menace like Trump are other democratically elected leaders. Ultimately it will be up to the men and women of Congress to do their constitutional duty by impeaching Trump and removing him from office. If Republicans won’t do it, then voters need to replace them with Democrats who will, by voting for a new House in the midterm elections of November 2018. The trouble is, it’s not clear that the US – or the world – have that much time.

The Guardian 

How Islamic State nearly stumbled on the ingredients for a ‘dirty bomb’ – Joby Warrick and Loveday Morris. 

On the day the Islamic State overran the Iraqi city of Mosul in 2014, it laid claim to one of the greatest weapons bonanzas ever to fall to a terrorist group: a large metropolis dotted with military bases and garrisons stocked with guns, bombs, rockets and even battle tanks.

But the most fearsome weapon in Mosul on that day was never used by the terrorists. Only now is it becoming clear what happened to it.

Locked away in a storage room on a Mosul college campus were two caches of cobalt-60, a metallic substance with lethally high levels of radiation. When contained within the heavy shielding of a radiotherapy machine, cobalt-60 is used to kill cancer cells. In terrorists’ hands, it is the core ingredient of a “dirty bomb,” a weapon that could be used to spread radiation and panic.

continues … NZ Herald

What Trump Doesn’t Get About Nukes – Bruce Blair. “The time to decide and act is now.” Mikhail Gorbachev

Will Trump come to his senses in time to avert an arms race and a nuclear war?

Mikhail Gorbachev, the former Soviet premier, warned in an extraordinary article late last month that the “increasingly belligerent” tone of geopolitical debates looked to him “as if the world is preparing for war.” He urged the United Nations Security Council to “adopt a resolution stating that nuclear war is unacceptable and must never be fought.”

To almost everyone, this call from a far-sighted leader may seem self-evident, but what about President Donald Trump?

Trump has suggested he is willing to launch a new nuclear arms race, despite the costs and the risks. In his phone call with Vladimir Putin last month, Trump reportedly rebuffed the Russian president’s apparent offer to extend the New START agreement that otherwise expires in 2021. This extension was a key aim of President Barack Obama, whose administration negotiated the arms deal. It would enable the United States to continue to closely monitor Russia’s strategic nuclear deployments and prevent Russia from uploading huge numbers of warheads onto those forces. Without the extension, the U.S. intelligence community would need to spend billions of additional dollars to monitor Russia. And the uncertainty and unpredictability of each side’s deployments would likely spark a costly nuclear arms race and increase the instability of a nuclear crisis and the likelihood of nuclear conflict.

After reportedly checking with his advisers to learn what treaty Putin was talking about (the White House says he was asking for an opinion), Trump apparently told the Russian leader the entire agreement was just another bad deal signed by his predecessor, even though its provisions impose identical obligations on both sides, and even though it was supported by the U.S. Senate and all the key national security players, including the U.S. Strategic Command and the Joint Chiefs of Staff. Instead of seizing upon a good offer (as well as an offer to convene talks on a range of other nuclear issues, including strategic stability, according to a former U.S. official familiar with the call) that would strengthen U.S. national security, Trump signaled a willingness to embark on an expensive, pointless new arms race that he boasts the United States would win.

This is a foolish, dangerous delusion.


January 2017

The world today is overwhelmed with problems. Policymakers seem to be confused and at a loss.

But no problem is more urgent today than the militarization of politics and the new arms race. Stopping and reversing this ruinous race must be our top priority.

The current situation is too dangerous.

More troops, tanks and armored personnel carriers are being brought to Europe. NATO and Russian forces and weapons that used to be deployed at a distance are now placed closer to each other, as if to shoot point-blank.

While state budgets are struggling to fund people’s essential social needs, military spending is growing. Money is easily found for sophisticated weapons whose destructive power is comparable to that of the weapons of mass destruction; for submarines whose single salvo is capable of devastating half a continent; for missile defense systems that undermine strategic stability.

Politicians and military leaders sound increasingly belligerent and defense doctrines more dangerous. Commentators and TV personalities are joining the bellicose chorus. It all looks as if the world is preparing for war.

It could have been different

In the second half of the 1980s, together with the U.S., we launched a process of reducing nuclear weapons and lowering the nuclear threat. By now, as Russia and the U.S. reported to the Non-proliferation Treaty Review Conference, 80% of the nuclear weapons accumulated during the years of the Cold War have been decommissioned and destroyed. No one’s security has been diminished, and the danger of nuclear war starting as a result of technical failure or accident has been reduced.

This was made possible, above all, by the awareness of the leaders of major nuclear powers that nuclear war is unacceptable.

In November 1985, at the first summit in Geneva, the leaders of the Soviet Union and the U.S. declared: Nuclear war cannot be won and must never be fought. Our two nations will not seek military superiority. This statement was met with a sigh of relief worldwide.

I recall the Politburo meeting in 1986 at which the defense doctrine was discussed. The proposed draft contained the following language: “Respond to attack with all available means.” Members of the politburo objected to this formula. All agreed that nuclear weapons must serve only one purpose: preventing war. And the ultimate goal should be a world without nuclear weapons.

Breaking out of the vicious circle

Today, however, the nuclear threat once again seems real. Relations between the great powers have been going from bad to worse for several years now.

The advocates for arms build-up and the military-industrial complex are rubbing their hands.

We must break out of this situation. We need to resume political dialogue aiming at joint decisions and joint action.

There is a view that the dialogue should focus on fighting terrorism. This is indeed an important, urgent task. But, as a core of a normal relationship and eventually partnership, it is not enough.

The focus should once again be on preventing war, phasing out the arms race, and reducing weapons arsenals. The goal should be to agree, not just on nuclear weapons levels and ceilings, but also on missile defense and strategic stability.

In modern world, wars must be outlawed, because none of the global problems we are facing can be resolved by war — not poverty, nor the environment, migration, population growth, or shortages of resources.

Take the first step

I urge the members of the U.N. Security Council, the body that bears primary responsibility for international peace and security, to take the first step. Specifically, I propose that a Security Council meeting at the level of heads of state adopt a resolution stating that nuclear war is unacceptable and must never be fought.

I think the initiative to adopt such a resolution should come from Donald Trump and Vladimir Putin — the Presidents of two nations that hold over 90% of the world’s nuclear arsenals and therefore bear a special responsibility.

President Franklin D. Roosevelt once said that one of the main freedoms is freedom from fear. Today, the burden of fear and the stress of bearing it is felt by millions of people, and the main reason for it is militarism, armed conflicts, the arms race, and the nuclear Sword of Damocles. Ridding the world of this fear means making people freer. This should become a common goal. Many other problems would then be easier to resolve.

The time to decide and act is now.

Mikhail Gorbachev