Chernobyl

Chapter 5

The Chernobyl Power Station contains four units, each of them an RBMK-1000 "pressure-tube" reactor. The RBMK is not the Soviet Union's only nuclear power generator, but it is the favorite. Across the USSR nearly two dozen such units are installed and operational, and the 1000-series models, each of them rated at 1000 megawatts of electricity, are the largest and newest in operation, though even larger ones are beginning to appear.

The fuel is uranium dioxide, which is encased in steel and zirconium tubes and inserted into a huge mass of graphite blocks. (The purpose of the graphite is to be a "moderator." Nothing is needed to make uranium atoms fission — that is to say, break apart — and when they do that they produce atomic energy in the form of heat. They do it naturally all the time; that is why uranium is called "radioactive." As each atom fissions, it releases neutrons which strike the cores of other atoms and cause them to fission too. However, the naturally released neutrons whisk through so fast that they only rarely cause fission in another atom; they need to be slowed down to make a reaction go at the right speed to be of use to human beings. Graphite, along with a few other materials, has the capacity to "moderate" or slow down these escaping neutrons, and so in a reactor the speed of the reaction can be controlled.)

Along with the fuel tubes, the slab of graphite is pierced by nearly seventeen hundred pipes containing water. As the uranium fissions, it gives off heat. The water carries away this heat, thus preventing a runaway meltdown of the uranium, and also providing the steam that turns the turbines that generate the electricity. Like every other nuclear reactor in the world, the RBMK-1000 is designed to be totally safe. And it is, as long as nothing goes wrong.

At ten o'clock that Friday night Bohdan Kalychenko was also trying to get to sleep, under circumstances less favorable than Leonid Sheranchuk's. He was in a bunk in the fire department of the Chernobyl Nuclear Power Station. Kalychenko had borrowed the bunk from a fireman friend — well, definitely a fireman and at least a sort of a friend — named Vissgerdis, who was a member of the plant's Fire Brigade No. 2. The bunk had been constructed for someone a lot shorter than a man with Lithuanian blood like Kalychenko — or like Vissgerdis himself for that matter. Kalychenko had difficulty in composing himself comfortably in it. It wasn't merely the bunk; it was his job, his boss, his boss's bosses like Khrenov, his girl, his approaching wedding — it was also the fact that before being allowed to get to sleep he had been wheedled into two hours of cards with the rest of the firemen. Now he was eight rubles fifty kopecks poorer than he had been that afternoon, and his fiancee, Raia, was sure to find out that he had been gambling again.

He pulled the thin, sweaty blanket over his head to shut out the noise from the card game. It didn't work. It made it dark for him, but also hot; it did not keep out the men's voices from the next room, or even the reek of tobacco smoke from the game. It was Kalychenko's pride that he did not, at least, smoke. In fact, he was quite intolerant of people who did, like his fiancee — except that in her case it was useful to have her possess at least one vice he did not. It would be particularly valuable after they were married, he thought gloomily. At least, that was when he would need it most.

The idea of getting married was not all joy for Bohdan Kalychenko, Sooner or later, of course, it was what one did. But he was not ready for that sort of surrender, especially since he considered that it was entirely Raia's fault that she had become pregnant. Of course, he reminded himself, when they were married and had a room to themselves in the families' hostel, it would be quite nice to share a bed together every night — at least until the baby came, when one room would no longer seem quite enough for the three of them. And even in Pripyat there was a three-year waiting list for flats. To be sure, first there would be the honeymoon. . But even that, Kalychenko told himself sourly, would not be without its drawbacks. Raia was determined to go to the Black Sea. Neither of them had enough standing to get the plant or the union to get them into one of the special "sanitoria," so that meant paying seven rubles a day to some Crimean robber, and lucky if they didn't have six other beds in their room anyway.

He pounded the pillow, threw the blanket off, and sat up angrily.

How could these other men sleep so soundly here? There were at least half a dozen bunks filled, and gentle snores coming from most of them. From the nearest bunk, not so gentle; Kalychenko knew that the fireman there was the football player they called "Summer," the best scorer of the Four Seasons.

Kalychenko was still trying to make up his mind whether it was worthwhile to lie down again, when Vissgerdis poked his head in the door. "Kalychenko? Telephone," he said. When Kalychenko mumbled a question about who would be calling him here, Vissgerdis only looked upward and jerked a thumb toward heaven before returning to his card game.

That could mean one of two things, either God himself or the organs — the GehBeh. And what in hell could he want? Sure enough, the voice on the other end belonged to the Personnel and Security chief, Khrenov. "Operator Kalychenko," he said, voice warm and intimate, "how nice that you sleep alone for a change, but if you can bring yourself to report to work a bit early, we need you. The thermal output on Reactor Number Four is dropping fast."

"With pleasure," snarled Kalychenko, looking at the clock. It was not even eleven yet! As he dressed he helped himself to half a cup of the concentrated tea the firemen kept for times they needed to wake up in a hurry. He pulled his clothes on rapidly. How like Khrenov to seek him out himself, instead of letting the shift chief do it! It was not that Khrenov interfered in the technical work of the power station — exactly — he was careful, always, to stay within his own sphere of authority.

But where did that sphere end?

Kalychenko didn't waste time resenting Khrenov's issuing orders, or in wondering how the Personnel man had known where to find him; of course Khrenov knew where to find anyone, all the time. What he did resent was Khrenov's continuing nagging little jokes about Kalychenko's relationship with the woman whom he was pledged to marry. Surely that was none of even the GehBehs' business!

It did not occur to Kalychenko to complain to anyone about Khrenov's actions. Who was there to complain to about the KGB?

Vissgerdis took time out from the game to look in on Kalychenko again. "What's up?" he asked. "There's a story that they're doing something strange with the Number Four Reactor tonight."

Kalychenko paused as he pulled a boot on. "Oh, of course," he said, remembering. "No, it is nothing strange, simply a test of a new energy conservation measure." They were friends, of a sort — Vissgerdis was half Lithuanian, like Kalychenko himself, and so they both stood out as tall and pale among the stubby Slavs, which had made them at least acquaintances. Nevertheless Kalychenko never forgot that he was an accredited power operator, while Vissgerdis was only a fireman. So he said, in rough comradeship, "A technical matter. Nothing important." But, he reflected, the trouble was that when something like that was going on, they would be busy all night. That was a nuisance. Normally Kalychenko actually preferred night duty. After all, the Chernobyl power plant pretty well ran itself. All the operators drowsed off from time to time on the midnight shift; oh, they were careful to see that there was always someone watching the boards and listening for the telephone in case of any messages from the load dispatcher in Kiev, but, really, there was not that much to do at night, when the bosses were all tucked away.

But tonight would be different, he thought glumly.

Reluctantly he left the fire department's comfortable little quarters, waving thanks to Vissgerdis, already back at the card table. The power plant was not quiet — it was never that, with the turbine scream always in everyone's ears wherever they were in the structures — but it was almost deserted. There were hardly more than a hundred people anywhere in the vast expanse at this time of night; construction had stopped for the weekend, and the three thousand workers who swarmed around the plant in the daylight hours were all back in their homes.

When Kalychenko got to the control room for Reactors 3 and 4, it did not look deserted. It was full. The four-to-midnight shift was still there, so were some of those who would take over at twelve, though it was only eleven-thirty by the big clock. And so was Khrenov, gazing thoughtfully at Kalychenko as he came in, and so, for a wonder, was the Chief Plant Engineer, Vitaly Varazin.

The Security chief gave him one of those intimate, understanding looks. "Are you just out of bed, then, Kalychenko?" he asked — it was his way of showing he was in a good humor, but what was he in a good humor about? "Did you also manage, this time, to get a little sleep?"

With someone like, say, Smin, Kalychenko would have managed some sort of retort to the effect that it was none of anyone's business whom he slept with, or when. Not with Khrenov. In a quite civil tone Kalychenko said, "Thank you, yes." He did not prolong the conversation. He relieved the other operator and took his seat before the big board, frowning as he saw that the main pumps were still disconnected. He called to the shift chief, "Shouldn't we turn these on again?"

It was Chief Plant Engineer Varazin who answered. "Not at all, Kalychenko. We've been allowed to take Number Four off line after all, so now we are able to proceed with the planned experiment."

And Khrenov, standing behind Kalychenko, said pleasantly, "Aren't you pleased?"

Kalychenko didn't answer. He didn't have to, because two more men were coming into the main control room. They were strangers to Kalychenko, but obviously not to Khrenov, who turned away at once to greet them.

Kalychenko scowled at the board. The best things about his job were that there was so little, really, to do, and that little could be done in comfort, without people standing around to watch you. This night was all different. Another stranger had just come hurrying in, looking as rumpled and sleepy-eyed as the first two. The shift chief whispered to Kalychenko that they were observers — from the turbine factory, from other power stations — but, whoever they were, they were not welcome to Kalychenko. Nor was Khrenov, who certainly had no business being present at this purely technical matter. As for Chief Plant Engineer Varazin, well, certainly the man had every right to be anywhere in the plant he chose, at any time. Still, Kalychenko had never before seen him in the control room after midnight before. With all these people present there would be no good chance to disappear for half an hour or so for a little rest from his duties.

Both Khrenov and the Chief Engineer looked freshly washed and shaved, and humorously apologetic to their guests for getting them out of bed at this uncultured hour. "Still, now you can see how hard we work here at Chernobyl," Varazin said affably. "In any case, you're just in time. We've already begun to reduce power on Reactor Number Four."

"Excellent," said one of the visitors politely, glancing around. "And the Director and Deputy Director?"

"The Director has left the entire matter in the hands of Chief Plant Engineer Varazin." Khrenov smiled. "As to Smin, I tried to call him, but he is off on some private errand. So when they come in to work on Monday, we will be able to give them both a pleasant surprise."

"Exactly," Varazin agreed, rubbing his hands together. "Now, as designated test leader, I must give a briefing." He stepped toward the board and raised his voice. "May I have your attention, please? As provided by the regulations, it is my duty to brief you all on the experiment we are conducting. But don't stop what you are doing. Continue to reduce the power; we don't want to be here all night!"

Kalychenko listened with half an ear. Most of his attention was on the tricky business of lowering, the temperature of Reactor No. 4, though what the Chief Engineer was saying was certainly interesting. Kalychenko almost forgot to be sleepy as he heard the plan.

The basic intention of this experiment, Varazin announced, was to see if useful power could be generated from the heat usually wasted while a nuclear reactor was down for maintenance. The reactor never stopped being hot, of course; it never would until at last the plant was finally decommissioned, somewhere in the next century, and probably not for some time even then. But it was not the practice to try to use that heat while the reactor was being serviced. Now, perhaps Chernobyl could lead the way to new practices.

By the time he got to the new practices, more of the observers were drifting in, looking sleepy. Varazin nodded affably to them, and added, "This is how we will lead the way for our colleagues all over the Soviet Union. Also," he went on, looking serious, "these measures could be of great importance under catastrophic conditions. They could insure a steady supply of power to keep our operations stable until, for example, the auxiliary diesels could be started. Are there any questions?"

The shift chief raised his hand. "I do not quite understand what 'catastrophic conditions' we are preparing for, Vitaly Aleksandrovitch," he called.

"Who can say?" smiled the Chief Engineer. "A very bad storm? An earthquake? Or" — he frowned meaningfully at them—"a sudden nuclear attack from our enemies, perhaps."

"Ah," said the shift chief, enlightened. "Of course. But there is still a question in my mind. Why don't we simply shut down the reactor instead of trying to lower the output?"

"Because," said the Chief Engineer severely, "we must be quite sure. We will do this test a number of times, keeping careful record of the results each time. It is a matter of safety, after all — and we can't be too careful in a matter of the safety of the Chernobyl Power Plant!"

Kalychenko groaned silently. A number of times! They would be at this all night! — and, likely enough, well into the Saturday morning shift, too, the way things were going. With resignation he bent to his work.

The normal night shift in the control room was only half a dozen men, just a skeleton crew to keep things going. There was not much need for electrical power in the late night hours in the Soviet Union. Good Soviet citizens went to bed at night so they could rise, bright-eyed and refreshed, for the next morning's work.

Tonight was different. Besides Kalychenko's own crew, there were four men left over from the late evening shift, looking oppressed at being kept on overtime for which they were not likely to be paid, plus the observers, the Chief Engineer, and the Personnel man, Khrenov.

To lower the power on a reactor like the RBMK is not like turning down the gain on a radio set. To shut it off entirely is much easier. You simply thrust home all the boron rods, two hundred and eleven of them, piercing the graphite core from top and bottom and in all its parts. The element boron is poisonous to nuclear reactions. Boron soaks up neutrons; they cannot go on to make another atom fission, and so the reaction stops; that is the easy way.

To slow the nuclear reactor down is another matter entirely. There are three separate ways to do it. First, for a rough approximation, you shove a few additional rods into the core. Not too many; you don't want the reaction to die. (Once the reactor stops waste products begin to accumulate — the element xenon is the worst of them, since it is a worse poison to nuclear reactions even than boron. Then it is impossible to start again until weeks have passed and the xenon has decayed away.)

Then there is a certain measure of fine control that can be attained by varying the mixture of gases in the sealed space surrounding the core. Some of the gases soak up neutrons in the same way that boron does, though not as strongly; to slow the reaction a bit, you simply add more of those gases to the mix.

Finally, there is water. The water that flows up through the core to turn to the steam that drives the turbines also has the neutron-absorbing characteristic — as long as it is water. Once it has turned into steam, which is less dense, it soaks up fewer neutrons, and thus the nuclear reaction picks up speed. This condition is called a "positive void coefficient," a technical term which means only that the more steam there is in the tubes the faster the reaction will go. This also means that the faster the reaction goes, the more steam will be generated— consequently adding to the "voids" — consequently adding to the speed of the reaction — consequently adding to the steam…. It is a delicate balance to keep a reactor, any reactor, poised between dying and running away, and so controlling a power reactor is a constant dance of rods and pumps.

When things were going well, Kalychenko enjoyed his part in the dance. Most of it was automatic, anyway. There were heat sensors all through the reactor core. The optimum running temperature of the one hundred eighty tons of uranium fuel was hundreds of degrees hotter than the ignition temperature of the graphite slabs. Graphite is carbon. Carbon burns. But it couldn't burn without oxygen, and oxygen was carefully excluded from the mix of gases in the surrounding jacket. If the temperature of the reactor climbed too high or fell too low, there would be a signal from the expensive imported Western instruments that monitored it. Then the operator would engage the motors that thrust a few rods farther in or took them a bit less deep. If it climbed drastically high, the operator would not be involved at all; automatic pumps would rush floods of new cold water into the core to cool it down.

That could not happen this night, because the automatic system had been turned off hours before, but then, no one ever wanted to let things get so far that the automatics were tripped anyway.

Another thing no operator wanted — at least, Kalychenko certainly didn't want it! — was to try to lower the temperature slowly. That was a sweaty business, because at low power levels the RBMK was notoriously hard to control. The trouble was that it was so big. The temperature sensors could not be everywhere. One part of the core could be at exactly the temperature desired, while another, an arm's length away, could be soaring to dangerous levels without warning. So Kalychenko did sweat, and swore under his breath, because the bitch was obstinately rising and falling, down to ten percent power, then up to thirty, slowly down again as they inched a few rods back in — then almost dying on them, down to the range where xenon began to form, until they had withdrawn all but six of the rods entirely and were coaxing it back to life.

When Kalychenko took his eyes off the board long enough to glance at a clock it was only one a.m.! He wasn't sleepy any more. He was simply exhausted. Only one, and he had worked harder than he usually did in a full shift. And everyone else was on edge too.

Even the GehBeh, Khrenov, had lost his warm, hooded look. Just behind where Kalychenko sat at his board, Khrenov was quarreling softly with the Chief Engineer. "What is the matter, Varazin?" he demanded. "Can't you control this thing? Must I find Smin and bring him here?"

Varazin flushed, glancing at the observers. "I am Chief Engineer, not Smin," he whispered fiercely.

"And I am responsible for Personnel. Perhaps I have been deficient in my duties. It may be that I have not screened this plant's personnel with sufficient care."

Varazin flinched, but said sturdily enough, "If you have complaints in that respect, Comrade Khrenov, there will certainly be time to discuss the matter. This is not the time. May I remind you that I am in charge here?"

Khrenov looked at him thoughtfully for a moment, then gave a long sigh. He turned to the observers with the smile back on his face. "What a pity," he said genially, "that this operation should take so long. Since most of you are, after all, more interested in the turbines and the steam generation than in the nuclear aspects of the operation, perhaps we should take a look at some of the other systems?"

"Can we take a look at something to drink?" one of the visitors grinned.

"We can do our best. Let me see, it's one o'clock. If we come back, say, at two, I think things will be in order. Don't you think so, Comrade Varazin?"

"I hope so," said Varazin.

At least with Khrenov gone everyone breathed a little more freely, but the job didn't get easier. It got worse. With great difficulty they managed to stabilize the power output of Reactor No. 4 at 200 megawatts electric, a fifth of its normal capacity. Kalychenko called out the reading and reached for the switch that would maintain that level. "Shall I engage the automatic systems?" he asked, finger poised.

"Certainly not," snapped Varazin, looking frayed. "It is far too high. Cool the reactor a bit."

"There are six pumps already going," the shift chief reported.

"Engage a seventh!"

Kalychenko marked the time when the seventh pump was cut in, three minutes after one. And indeed the temperature of the core began to respond; it was not the cooling of the water that made it happen, but the added liquid water in the system absorbing a few more neutrons.

The atmosphere in the control room was excited now, with the engineers and operators calling the numbers back and forth to each other, like spectators at a football game. Even old Varazin was shifting from one foot to another as he watched the readouts with them, and Kalychenko began to think about what all this meant. If this experiment succeeded, it could well be a model for every nuclear power plant in the Soviet Union. There would be commendations, perhaps cash awards — perhaps they would be written up in Literaturna Ukraina, even in Pravdal Well, no, he cautioned himself, that was not likely; this sort of thing one did not advertise in the open press, since the West had no business knowing what went on in critical Soviet industries. But it would be in the records! Even Khrenov would not fail to list all the people who had contributed to such a success somewhere in his file folders. .

"It is still too high," Varazin announced. "Add another pump!"

It was seven minutes after one. And all of a sudden, without transition, Kalychenko's bright mood vanished. He began to worry.

The first indications of trouble were the pressure readings in the water system. "Pressure is dropping in the drying drum," reported one of the engineers.

The shift chief glanced at Varazin, who said impatiently, "Yes, of course. Carry on." But he looked nervous too. With two extra pumps forcing water into the system, the steam generation had slowed; there was more water coming in than the core could boil into vapor at once, and so in the great drum, where the steam was extracted to feed into the turbines and the remaining water pumped back into the circulation system, pressure had begun to fall. Paradoxically, that meant more steam there, as the water that had been squeezed liquid found room to expand. Kalychenko listened and thought he could hear, in the distant throb of the pumps, a laboring sound as they tried to pump vapor instead of liquid water.

Then the state printout computer flashed a warning: Reactor should be shut down at once.

"Chief Engineer Varazin!" Kalychenko cried. The old man was looking strained now, but he said:

"Yes, of course. We are operating under unusual conditions, which the program is not designed for."

"Then shall I—"

"Certainly not!" said Varazin, biting his lip. "Comrade Khrenov and our guests will be back at two, and I don't want to have a dead reactor for them." He glanced at the clock. It was twenty minutes after one. "Close the stop control valve," he ordered.

Kalychenko looked at the shift chief for confirmation before he obeyed, but the man only nodded. His face was pale. Reluctantly Kalychenko switched the stop control valve off; it was the last of the automatic safety features. ..

Then it all went sour.

"Temperature's rising!" screamed the shift chief. And everyone stared at the thermal readings — from seven percent of normal power, already at fifteen.. twenty… in ten seconds it went to a full fifty percent of normal power. And in Kalychenko's mind, as he gazed awestruck at what was happening, there flashed a picture of the interior of the reactor core, with each of the 1,661 tubes filled with water. . only the pressure was dropping. . and the water turned prematurely into steam, steam that was not dense enough to soak up neutrons, that let the reaction pick up speed. .

There was a distant thud.

"What was that?" Varazin cried, and then in the same breath: "Insert rods! Fifty percent rods, immediately!"

But the rod operator was reporting that the control rod motors were not responding; the rods would not penetrate the core. "Emergency shutdown then! At once!" Varazin shouted, and held his breath.

But the rods would not go in. "Something is blocking them!" the rod controller shouted, his voice shaking. Kalychenko heard the words incredulously, for that was impossible! There was nothing to block the rods in their sockets — why, it would mean that the interior of the reactor itself had suddenly become warped, or shrunken, or broken—

The next explosion was much louder. The walls shook. Dust sprang out from the walls, hanging like a sudden shimmer of ice fog in the air. The lights went out — all of them, even the lighted meters and dials on the full-wall instrument board.

"Oh," moaned Varazin, "my God."

"Emergency circuits!" cried the shift chief, and the man next to Kalychenko, muttering oaths, reached for the switch.

At least then the instrument lights went on again, but what they said was insane. Temperature readings simply off the scale, radiation levels that could not be believed. And the noise did not stop with the explosion. There was a rumbling thunder of walls going down, a patter of something hard falling on the roof, a crackle that could only be flame.

"Go and see what has happened to the reactor," ordered Varazin.

It was at least an instruction to follow. Most of the men in the main control room jumped up to comply. Even Kalychenko rose from his useless board, but as he started through the door he caromed off one of the other hurrying men, who swore and thrust him out of the way. Kalychenko fell heavily. By the time he got up, most of the men had rushed out to peer down at the reactor chamber.

Kalychenko's arm hurt where he had fallen on it. He hesitated, rubbing the arm, then turned and went the other way. It was unquestionably a cowardly act. It also saved his life.