concern of a nuclear engineer.'
Captain Vanislav turned to Ravi and smiled. 'You see, I teach him priorities, months ago. And he never forget. You got a good man here, General. Young Ben Badr. I like him. Make no mistakes, hah? That's the trick, you wanna stay alive.'
'Yes. I've often found that myself,' said Ravi, smiling back. 'But I'm afraid you'll have to be more patient with me. I know very little, and I have to learn fast.'
'Right here's a very good place to start,' replied the Russian Captain. 'These screens show you the quality and temperature of the water flowing into the reactor. But I think Ben should be your professor. That way I can listen to him, make sure he's learned everything good.'
Commander Badr nodded, and stepped up to his task. 'Okay, Ravi,' he said in English. 'I start by telling you the danger of sodium chloride. It's just salt, of course. Seawater is full of it, and we have to get rid of it because it's probably the most corrosive stuff on the planet. You get that stuff in our water system, it seeks out little crevices, maybe in the joints, or the welding, and it builds up, weakening the steel, until one day, under the terrific pressure, it blows. Blows a damned big hole, and a blast of pressurized scalding water rips out of the fracture into the room, flashes off into wet steam of terrific heat.'
'Unbelievable,' said Ravi.
'You know what happens then?'
'Not really.'
'Well, remember the whole system works on stability. Inside the nuclear reactor, the core consists of these cleverly shaped and machined slugs of highly active uranium, and in general terms, the neutrons split away, millions of them, and if they were allowed to just get on with it, they'd collide with U-235 atoms, hitting and splitting, causing a too-rapid chain reaction, generating colossal heat, until you had, in a very few minutes, a core meltdown. However, we don't allow this… '
'Oh, good,' said Ravi.
'No. We have a system of rods inside the reactor. They're made of some stuff called hafnium, which absorbs the neutrons, stops the reaction running out of control. So when all these rods are down, deep in the uranium, the activity is neglible. Just a quiet, scarcely active, hunk of machinery.
'Then we want to get going, right? So we begin to 'pull the rods'—lifting first one group and then another out of the uranium core. And as we do so the neutrons have more and more freedom to split and cause further fissions. And as this happens, the system gets wanner. But we have total control of the process, and we create the heat precisely as we wish — a self-sustaining critical mass.'
'Okay,' said Ravi. 'I'm with you.'
'But remember,' said Ben Badr. 'This is a circuit. The pressurized water is pumped out of the reactor, into a simple steam generator, and this surges off down the pipeline to drive the turbines. The whole thing is just a steam engine. But we control how much steam goes to the turbines, and we control how much turns back into water and surges around the circuit, back into the reactor to begin the process all over again. It's called the Carnot Cycle, the difference between water temperature coming out of the reactor and going back into the reactor… this is the power factor driving the ship.'
'When the water flows into the reactor, does it actually touch the uranium?'
'Oh, yes,' replied Ben. 'It flows right over the solid U-235, and the temperature of the water is absolutely critical. If it's a little too cold, the neutrons react, speed up, and get hotter. And in my view the really scary thing about a nuclear reactor is that the hotter it gets, the hotter it wants to get.'
'So we get a corrosion leak, like you just said,' asked Ravi, 'and the pressure drops and the water cools, and comes in at too low a temperature, we have big trouble?'
'With a leak like that in the prime circuit, the core loses its water flow and rapidly starts to overheat.'
'I imagine you have some kind of 'fail-safe' in there, right?'
'Absolutely. The rods crash straight back in, all of them, immediately reducing the activity of the core. But in a submarine, you have a problem right there. The rods actually stop the reactor. It's called a reactor SCRAM. But at that moment the submarine's power plant is dead. That means we soon have no propulsion, no fresh water plant, no fresh air system, and no heat. Should we be one thousand feet below the surface this is relatively bad news.'
'There's an emergency system, I suppose?' said Ravi.
'Yes. One to keep the now inactive reactor cool, and a diesel engine, which we immediately fire up, once we get back to periscope-depth or on the surface.'
At this point Captain Vanislav interrupted. 'Remember, General,' he said. 'Ben is speaking to you as a submarine officer, not a scientist. And you don't need to be a scientist to command an SSN. But you do need to understand the system, and you need to know what those screens are telling you. But most of all, you need the ability to recognize a problem and to know what action to take. You will have very knowledgeable nuclear engineers down here in this part of the ship. They will keep you well informed. But you must be aware of the potential snags, and how to react to them.'
'Have you taught Ben everything during sea trials?' asked Ravi.
'Oh no. We have a superb simulator on shore, and all of our future submarine officers learn the profession in there. Ben has spent literally weeks in that simulator, just like an airline pilot studying big passenger jets. He's been right through the entire course, from the smallest emergency to core meltdown.'
'I'm not sure I like the sound of that last part,' replied Ravi.
'No,' interjected Captain Vanislav. 'That last part is bad.'
'When does it happen?'
'Tell him, Ben.'
'It is most likely caused by either a leak in the prime circuit, as we mentioned. Or by the sudden arrival in the reactor of very cold water. For whatever reason. If, for instance, there is no returning water, because of a chronic system failure, an emergency valve will open, and seawater will gush in from outside the hull. This is not good, but it's not as bad as no water at all, because no water increases the fission of the neutrons to a very severe degree in about seven seconds. Right then you have the potential for a core meltdown.
'Not a bomb, just uranium getting so hot it will eventually melt through the stainless steel floor of the reactor, maybe through the deck, and then both hulls. But this is rare. Almost unheard of.
'The most common crisis is a slug of cold water surging in through the emergency valve, which will trigger increased fission. But it's all a bit slower, in time for the rods to drop, get things back under control. Back to what we call the Negative Temperature Co-Efficient, which means the reactor is self-governing, heating the water right where we want it, self-regulating.'
General Rashood was all business right now, concentrating all of his considerable intellect on the words of Ben Badr. 'Okay,' he said. 'You say self-regulating? What changes? What's getting regulated?'
'Every time we open the throttles on the submarine, we are drawing off power, drawing off the steam, cooling off the returning water, effecting a change in the temperature of the water being received by the reactor.
'Always remember one thing, Ravi… The neutron population increases immediately to that cooling water, more fissions occur, more energy is released in the core. That gets transferred to the primary coolant, then to the secondary system. That's the water that boils to steam to drive the turbines. Thus, when you draw off more power, the reactor automatically increases its fission rate to provide it.
'Vice versa, it's a similar chain. Reduce power draw-off, increase temperature of water back into the core. Reduce neutron population, reduce fission rate.
'But that doesn't mean we all have a nervous breakdown whenever we speed up. The whole system is very largely self-regulating. Strictly hands-off. We don't do anything; we watch. We watch like fucking arctic eagles for anything that can go wrong… That's the engineering officer's task.'
'Ben's a very good student, right?' said Captain Vanislav, chuckling, and adding with a mock-serious expression, 'Of course, I had to get him into shape at first. He's a little impatient, sometimes little bit arrogant. You know, his daddy's a very big man. But he's very good. He was Russian, I give him command of nuclear ship any time.'
He placed his arm around the shoulders of Commander Ben Badr, and stated quietly, 'Right now, I can say that in thirty years in the Russian Navy, I never met a better young submarine officer.'
