After half an hour or so Pentecue suddenly said, without looking round, ‘That chicken was a big high, wasn’t it?’ And Dick said yes it was, and they got on fine after that.
Frank Gresham fumbled in his pockets and found the tiddlywinks that had so annoyed the Director earlier on. Seff had gathered the ash-trays from around the table, and now arranged them in a straight line in front of his blotter. Before he could proceed with the game, however, he had to cope with Manson, who had just returned from the Coffeesnacks factory and wanted to tell everyone how thoroughly ‘the boys downstairs’ were working on the samples, leaving ‘no stone unturned’ and would be reporting ‘in double quick time’. The Director said that was splendid and what did he think of the theory that Seff was about to demonstrate, and Alec sat down at last.
‘The object of the game,’ said Seff, ‘is to try to make the discs land in the ash-tray farthest from the end I’m flicking them from.’
Gatt was screwing up his face, staring very intently at the objects of attention. ‘The ash-trays, I take it,’ he said slowly, ‘represent the sugar bins at Gould’s refinery?’
Seff moved his eyes only. ‘That’s right. As you see, there are six of them. The tiddlywinks represent the specks of radioactive dust. Now watch’ He concentrated once more on the game. ‘We’ll start with one of the small “winks”. Let’s see how far I can flick it.’
The first few times the little disc went flying in the wrong direction. But at the fourth try he succeeded in shooting it into the fifth ash-tray along. Another one of the same size volleyed into the sixth. ‘Now let’s see what happens with the bigger ones.’ He had to make a few preliminary shots, but eventually he bracketed on the target and scored a bit on the nearest ashtray. The next shot was more successfuclass="underline" it went into the third. But after fishing them out and trying again, he could not flick the larger discs into the two farthest ash-trays.
Gatt said: ‘Very clever, Jack!’ Manson still looked puzzled. The Director didn’t reveal whether he got the point or not. But Gresham said: ‘I’m not going to guess, jack! So, for heaven’s sake, tell me what it’s all about!’
Seff smiled. ‘It’s quite simple, really. Gould had no filters on the inlet side of his air-conditioning… So he was sucking in dust at one end, and probably blowing it out the other — though that isn’t important. But we know that the air was contaminated, don’t we, with two different sorts of radioactive dust? Now, what were they?
‘First let’s consider what we started off with. Essentially, they must have been two different isotopes of reasonably long half-life, one of which radiated beta particles and the other gamma rays. Well, we know, almost for certain, that the first was radio-strontium. My guess is that the second was caesium — a fairly plentiful fission-product. What happened to them? Well, they wouldn’t have been in their pure state. In some way they would almost certainly have combined with other substances — don’t forget they had been lying about for quite some time, exposed to water when it rained, and so on. I’m not a chemist, and I can’t suggest what chemical reactions might have taken place between the time the particles of dust escaped from the reactor and when they finally entered Gould’s refinery, as it seems certain they did. But the chances are that had they formed chemical compounds with other substances the resulting two types of dust would be of different mass — due to the difference in atomic weight of the isotopes: strontium has an atomic weight of 90, and the “hot” isotope of caesium is the heavier at 137. In my little game of tiddlywinks, the large discs represented the compound of caesium, and the small ones played the role of the strontium. As you saw in my “experiment”, the heavy ones (caesium) landed in the nearest ash-trays (sugar bins) and the little ’uns (strontium) dropped into the ones farthest away. Ergo, the sugar became unevenly contaminated, as were the bags of sugar that were delivered eventually to Spigett’s factory. No doubt a new lot of tomato sauce was made for each day of manufacture of the beans; so the uneven distribution would have been passed on to the tins themselves.’
Frank Gresham stared in undisguised awe. ‘Marvellous, old boy!’ he exclaimed. ‘Sort of atomic tiddlywinks!’
‘As you say — marvellous,’ said Manson, ‘but where, exactly, does it get us? I mean, is it anything much more than an interesting illustration of something that isn’t really important any more? We know that uneven distribution did take place — but does it matter how?’
‘I think it does,’ said Gatt, ‘and for a very good reason. We’ve got to know what to look for and how many places to look. To me, at any rate, it didn’t seem feasible that the two kinds of radioactive material could have got into the sugar in the same way. If Self’s explanation is right, it now seems possible that they could have done so. Which in turn suggests two conclusions: first, that despite the uneven distribution all the dust came from the same place; and second, both types must have got into the sugar at the same time. Well, we know that this sugar was manufactured approximately six months after the accident, at the time when Gould’s filters were removed. So what we’ve got to find out is what those fission products that got loose were doing for the period between, undetected and inert.’ He lit a cigarette. ‘Any suggestions, anybody?’
There was silence for a while, until Hargreaves said: ‘Let’s look at the map of the area.’ He went to a drawer of his desk and produced a rolled-up ordnance survey map of Glennaverley and District. ‘What’s the prevailing wind in those parts — does anybody know?’
Seff said: ‘The Met Office should have a record of wind directions at about that time. But I think… let’s see… yes, it usually tends to blow from the south.’
‘Mm. The south, eh? The Marsdowne Establishment is roughly west of the town.’
‘Well, I could be wrong about the wind.’
‘Yes. But supposing you’re not?’ He looked back at the map again. ‘What we want is something roughly south of Glennaverley, so that the wind would blow the dust in the general direction of the factory. Something pretty near at hand, too, I should think. Well, of course, there’s the loch. Loch Logie.’
Gatt said: ‘God, yes! Isn’t that where the water is pumped from?’ He leaned back in the chair so that it creaked, his hands thrust deep in his pockets. ‘On the other hand, I checked it immediately after the accident.’
‘Besides,’ said Manson, ‘surely if there was some “hot” dust on it, it would stick to the surface of the water?’
Hargreaves looked up at Seff. ‘Is there any way,’ he asked him, ‘is there any way contaminated water could seep back into the loch?’
Seff grinned. ‘Not in my book,’ he said. ‘Of course it might eventually get past the non-return valves if some bloody fool left the inlet cock open. But that couldn’t have happened, because the day before we tried to start up Project 3, Peter Selgate and myself filled the steam system to the required level and closed the cock ourselves. And of course the water could only get back to the loch if there was any left in the heat-exchanger system — Which of course there wasn’t, because Alec went straight to the pumping-room and opened the outlet cock, to empty said water into the underground tanks.’