《那些古怪又讓人憂心的問題》第5期:乏燃料游泳池
SPENT FUEL POOL
Q. What if I took a swim in a typical spent nuclear fuel pool? Would I need to dive to actually experience a fatal amount of radiation? How long could I stay safely at the surface?
Q．如果我在一個普通的乏燃料（用過的核燃料）水池裏游泳會怎麼樣？我是不是要潛到水底纔會受到致命劑量的輻射？我在表面能安全地待多久？——喬納森?巴斯蒂安.菲利亞特羅A. ASSUMING YOU'RE A REASONABLY good swimmer, you could probably survive treading water anywhere from 10 to 40 hours. At that point, you would black out from fatigue and drown. This is also true for a pool without nuclear fuel in the bottom.
A．假設你的游泳技術還算不錯的話，那麼你差不多可以通過不停踩水在水中活上10～40小時，之後你就會因爲體力不支而昏迷並溺水。對於底下沒有核燃料的水池來說也是這樣……
Spent fuel from nuclear reactors is highly radioactive. Water is good for both radiation shielding and cooling, so fuel is stored at the bottom of pools for a couple of decades until it's inert enough to be moved into dry casks. We haven't really agreed on where to put those dry casks yet. One of these days we should probably figure that out.
核反應堆產生的乏燃料具有高度放射性。水在屏蔽輻射和散熱方面性能都不錯，因而乏燃料會被存放在水池底部，直到其中的放射性物質活躍程度降到一定水平後纔會被轉移到幹桶中。對於這些幹桶該儲存在哪裏，我們目前還沒有達成共識，但總有一天，我們會找到合適的地方的。Here's the geometry of a typical fuel storage pool:
下面是一個普通的乏燃料儲存池的樣子：The heat wouldn't be a big problem. The water temperature in a fuel pool can in theory go as high as 50°C, but in practice it's generally between 25°C and 35°C-warmer than most pools but cooler than a hot tub.
輻射產生的熱量不是大問題，雖然理論上來說，乏燃料池中的水溫可以達到50℃，但在現實情況下，水溫一般會介於25～35℃——這比大多數泳池的水溫要高，但比浴缸裏的熱水溫度要低。The most highly radioactive fuel rods are those recently removed from a reactor. For the kinds of radiation coming off spent nuclear fuel, every 7 centimeters of water cuts the amount of radiation in half. Based on the activity levels provided by Ontario Hydro in this report, this would be the region of danger for fresh fuel rods:
輻射水平最高的燃料棒，應該是最近才從核反應堆裏移除出來的那些。對於乏燃料裏釋放出來的輻射而言，每7釐米深的水就能讓劑量減半。根據安大略電力公司的報告中給出的輻射水平，如果把剛取出來的燃料棒放在燃料池中，那麼危險區域如下：Swimming to the bottom, touching your elbows to a fresh fuel canister, and immediately swimming back up would probably be enough to kill you.
當你潛到水底，用手肘碰一下剛拿出來的燃料罐，然後立即游回水面，所受到的輻射就極有可能讓你喪命。Yet outside the outer boundary, you could swim around as long as you wanted-the dose from the core would be less than the normal background dose you get walking around. In fact, as long as you were underwater, you would be shielded from most of that normal background dose. You may actually receive a lower dose of radiation treading water in a spent fuel pool than walking around on the street.
但若是停留在最外面的那塊區域，那麼你想待多久就可以待多久——燃料棒核心所釋放出來的輻射劑量，比你在街上四處走動時受到的背景輻記住，我只是個漫畫家。如果你打算遵循我關於核廢料安全問題的建議，那麼之後無論發生什麼都是你自作自受。射1劑量還少。實際上，只要你待在水下，那麼絕大多數普通背景輻射是不會影響到你的。你在乏燃料池裏踩水受到的輻射劑量沒準兒比你走在大街上時受到的劑量還要少。Remember: I am a cartoonist. If you follow my advice on safety around nuclear materials, you probably deserve whatever happens to you.
記住，我只是個漫畫家。如果你打算遵循我關於核廢料安全問題的建議，那麼之後無論發生什麼都是你自作自受。That's if everything goes as planned. If there's corrosion in the spent fuel rod casings, there may be some fission products in the water. They do a pretty good job of keeping the water clean, and it wouldn't hurt you to swim in it, but it's radioactive enough that it wouldn't be legal to sell it as bottled water.
以上討論完全建立在沒有出任何差錯的情況下，如果乏燃料棒的外殼發生了腐蝕，那麼水中就可能會有些裂變產物。這些物質能夠很好地清潔水質，你在裏面游泳也不會受到傷害，但它的輻射劑量已經到了讓你不能把這裏的水當瓶裝水賣出去的程度。We know spent fuel pools can be safe to swim in because they're routinely serviced by human divers.
我們知道在乏燃料池裏游泳一般來說是安全的，因爲會有潛水員定期進行保養。However, these divers have to be careful.
但是，這些潛水員也必須小心。On August 31, 2010, a diver was servicing the spent fuel pool at the Leibstadt nuclear reactor in Switzerland. He spotted an unidentified length of tubing on the bottom of the pool and radioed his supervisor to ask what to do. He was told to put it in his tool basket, which he did. Due to bubble noise in the pool, he didn't hear his radiation alarm.
2010年8月31日，一位潛水員正維護瑞士萊佈施塔特核電站的乏燃料池。突然他發現在池子底部有一段管子，不知道是什麼東西，於是他通過無線電詢問主管該怎麼辦。主管讓他把管子放到他的工具籃裏，他也這麼做了。由於水池中氣泡的聲音太大，他沒有聽到輻射警報器的響聲。When the tool basket was lifted from the water, the room's radiation alarms went off. The basket was dropped back in the water and the diver left the pool. The diver's dosimeter badges showed that he'd received a higher-than-normal whole-body dose, and the dose in his right hand was extremely high.
當工具籃被提出水面後，屋子裏頓時警鈴大作。工具籃被扔回水中，潛水員也馬上離開了水池。他身上的輻射計量器顯示他受到的全身輻射劑量比正常水平高，而他右手上的劑量更是極高。The object turned out to be protective tubing from a radiation monitor in the reactor core, made highly radioactive by neutron flux. It had been accidentally sheared off while a capsule was being closed in 2006. It sank to a remote corner of the pool, where it sat unnoticed for four years.
原來這根管子是反應堆核心中輻射監測器上的一根保護管，長時間的中子流使得它具有高度放射性。在2006年一個艙室關閉時它意外地脫落了下來，然後就沉到了燃料池底部一個不起眼的小角落，之後的4年裏也一直沒有被發現。The tubing was so radioactive that if he'd tucked it into a tool belt or shoulder bag, where it sat close to his body, he could've been killed. As it was, the water protected him, and only his hand-a body part more resistant to radiation than the delicate internal organs-received a heavy dose.
要是這名潛水員把那根管子放到工具腰帶或者揹包裏等靠近身體的地方的話，管子上的輻射物質足以使他喪命。正如前面所說的，水救了他一命，只有他的手——手比身體其他嬌嫩的內臟器官更能承受輻射——受到了大劑量的輻射。So, as far as swimming safety goes, the bottom line is that you'd probably be OK, as long as you didn't dive to the bottom or pick up anything strange.
所以說，只要你按規矩在乏燃料池裏游泳，你應該不會遇到問題，除非你潛到水底或撿了個奇怪的東西上來。But just to be sure, I got in touch with a friend of mine who works at a research reactor, and asked him what he thought would happen to someone who tried to swim in their radiation containment pool.
爲了確證，我聯繫了一位在研究用核電站工作的朋友，問他如果你試圖在他們被輻射污染的池子裏游泳會發生什麼。“In our reactor?” He thought about it for a moment. “You'd die pretty quickly, before reaching the water, from gunshot wounds.”
“在我們這裏？”他想了一會兒之後說道，“你會死得很快，甚至在你碰到水之前，警衛就一槍把你打死了。”Which is too bad - it'd make a hell of an energy D (AND WORRYING) QUESTIONS FROM THE WHAT IF? INBOX,
這很糟糕——它來當“能量飲料”可是太合適了。一那些古怪而又讓人憂心的問題合集Q. Would it be possible to get your teeth to such a cold temperature that they would shatter upon drinking a hot cup of coffee?
Q．如果把牙齒的溫度降到很低，有沒有可能在喝到熱咖啡的時候牙齒就崩碎了？ ——謝爾比?赫伯特Q. How many houses are burned down in the United States every year? What would be the easiest way to increase that number by a significant amount (say, at least 15%)?WEIRD（AND WORRYING）QUESTIONS FROM THE WHAT IF?INBOX，
Q．美國每年有多少幢房子被大火燒燬？讓這個數字大幅增長（比如上升15％）最簡單的方法是什麼？——匿名提問者
