The face mask and three radiation monitors1) I’m wearing here are grim reminders that I’m at the site of the worst nuclear accident in history. On April 26, 1986, 1:23:44 A.M. local time, explosions destroyed reactor No. 4 at the Chernobyl nuclear power plant, releasing approximately 400 times more radioactive fallout2) than the atomic bomb dropped on Hiroshima3), according to the International Atomic Energy Agency.
Now, 25 years after the disaster, the Ukrainian government has officially opened the area up for tourism. But just how safe is the zone now?
Radiation
After the explosions, it was unclear how contaminated4) the surroundings were, so the authorities declared an arbitrary 30-kilometer distance from the reactor off-limits5), and roughly 115,000 people were evacuated6) from the area. This “exclusion zone” is now open to tourism.
I drove to Chernobyl with health physicist Vadim Chumak at the Research Center for Radiation Medicine at the Academy of Medical Sciences of Ukraine and his colleagues. A car shuttles there every week to collect stool samples from workers to test for any plutonium7) they might have accidentally absorbed.
The world is normally bathed in a low level of radiation. In Kiev8), where I started my trip, one normally receives 0.1 millionths of a sievert9) every hour. This is pretty much the level of radiation we saw on the road on the roughly two-hour, 150-kilometer drive into the exclusion zone, but readings on our dosimeter10) temporarily climb up to 4.76 millionths of a sievert per hour when our car passes through the old path of the radioactive plume11) from the destroyed reactor.
How safe this area is now after the accident depends on what radioactive material was released and where it went. There are four kinds of radionuclides12) or radioactive isotopes13) that are of special concern at the site. Iodine14)-131 is rapidly absorbed by the thyroid gland15) and increases the risk of childhood thyroid cancer. Cesium16)-137 mimics potassium17) inside the body, seeking out muscle. Strontium18)-90 acts like calcium19), attracted to bone. Plutonium-239 and other isotopes can stay in the body indefinitely, irradiating organs.
Iodine-131 decays20) rapidly, and was virtually gone from the environment after only three months, Chumak says. However, cesium-137 and strontium-90 both have approximately 30-year half-lives, meaning they each take roughly three decades for half their material to decay, and plutonium-239, one the main isotopes in nuclear reactors, has a half-life of more than 24,000 years.
After the disaster, both emergency workers dubbed “liquidators” and natural forces helped to reduce airborne levels of radiation. The liquidators sprayed detergents21) and latex22)-like binding solutions23) from helicopters and automobiles to bind contaminants. The roads were paved to cover radioactive dust, while ploughs24) flipped soil over to bury polluted soil. Meanwhile, rain helped contaminants migrate down into the ground.
The exclusion zone was possibly safe for tourism “about five years after the accident”, Chumak says. Still, just because one can tour the area does not mean everywhere here is safe to tread25). There are hot spots that remain highly contaminated, especially in the path of the radioactive plume, where tourists are allowed to go and how long they will be allowed to stay will be strictly controlled to keep their risks of exposure down.
And there are some places here that remain too dangerous for tourists to go, such as the sarcophagus26).
Inxide the Sarcophaqus
Soon after firefighters extinguished the blazes from the explosions at Chernobyl, workers quickly built a structure of steel and concrete technically known as the Shelter Object but commonly known as the sarcophagus to entomb27) the remains of the damaged reactor and keep any more contaminants from escaping. It remains one of the most radioactive areas in the zone.
Nowadays, workers here maintain the corroding sarcophagus, monitor the radioactive material inside, and decontaminate what they can. To enter the structure with them, I strip down to only my underwear in a “clean room” and walk in a hospital gown and slippers into a “hot room”, where I put on the pure white outfit given to everyone on site—scrubs28), a jacket, trousers, a scrub cap, socks, gloves and a mask with the highest-grade filter available for dust. On top of that I don an overcoat, a hardhat and crusty boots. In addition, I am carrying the radiation badge I had when I entered the 30-kilometer exclusion zone, a second radiation badge I was given when I entered the area of the plant, and a personal electronic dosimeter to tell me exactly how much radiation I am receiving.
The maximum dose of radiation that workers here are generally allowed on a daily shift is 0.1 thousandths of a sievert, the level of radiation one gets from a 90-minute transatlantic flight or from four hours watching a plasma29) screen television. When I am standing right in front of the sarcophagus, the readings leap up to 0.12 thousandths of a sievert per hour, or 1,200 times that seen in Kiev.
After passing an electronic checkpoint, I find myself in the dark, gutted remains of the control room for reactor No. 4. Here engineers made the fateful errors that poisoned the Earth.
Life and Wildllfe
Although Chernobyl might be safe for a day of tourism, living there is another question. The Ukrainian government did allow people who originally lived in the exclusion zone to resettle on an individual basis. For instance, some areas within 30 kilometers of the explosions are relatively clean, and the elderly would probably not absorb unhealthy levels of radiation in what time they had left, Chumak says.
However, some places remain too dangerous for resettlement. “People might be allowed to live in the 30-kilometer zone, but I don’t expect anyone to live within the 10-kilometer zone, ever,” Chumak says. “There’s some plutonium there.”
The disaster’s impact on wildlife in the zone remains hotly contested. For instance, radiation biologist Ron Chesser at Texas Tech University in Lubbock and his colleagues suggest the area is thriving with life now that humans have left, finding that the wild boar population there has grown 10 to 15 times than what it was before the accident, and that other fauna30) are often seen in the area, such as wolves, rabbits, red deer, black storks31) and moose32). Their genetic work suggests that any effects of radiation are subtle enough to not lead to any mutations33) passed down across generations. As bad as the radiation is, the effects of humans on the environment might have been worse, Chesser concludes.
On the other hand, biologist Tim Mousseau at the University of South Carolina at Columbia and his colleagues have found that species richness34) of forest birds was reduced by more than half when comparing sites with normal background levels of radiation to sites with the highest levels in the exclusion zone, and the numbers of bumblebees, grasshoppers, butterflies, dragonflies and spiders decreased too. Analysis of more than 7,700 barn swallows35) in Chernobyl and other areas in Ukraine and Europe suggested ones from in or near the exclusion zone had higher levels of abnormalities and recent work also suggests that birds living in areas with high levels of radiation around Chernobyl have smaller brains.
Both teams stand by their own work and suggest the other made errors related to geographic variability.
Tourist Attraction?
So what can tourists see at Chernobyl? One can often see and feed giant catfish in the 22-square-kilometer nuclear power plant cooling pond. In the distance, one can also see a giant radar grid roughly 150 meters high—taller than the Great Pyramid of Giza’s current height.
The city of Pripyat, abandoned after the accident, is frozen in time. Nature is reclaiming the area, with white birch and green pines hiding many of the blocky Soviet buildings.
Despite the official announcement, tourism to Chernobyl is nothing new—trips have been going there for about a decade. “There is this motivation there to do what can be done to return some of this land to productive use,” Mousseau says.
Among those who lived through the disaster, the idea of tourism to Chernobyl brings up strong emotions, just as it might for New Yorkers dealing with 9/11. “If we are wise, we will make Chernobyl a museum for humankind just like Hiroshima and Nagasaki,” Chumak says.
Among the younger generation in Kiev, there is real interest in visiting. “My son really wants to go, as do a couple of young students here,” Chumak says.
Still, for others, tourism to Chernobyl holds no attraction. “Personally, every trip I make there is not a positive one,” says physicist Elena Bakhanova at the Research Center for Radiation Medicine in Kiev. “It was a human error, a sign of human foolishness.”
我脸上的面罩和身上的三个辐射监测仪都是严峻的提示，提醒我正身处历史上最惨痛的核事故现场。1986年4月26日，当地时间凌晨1点23分44秒，爆炸摧毁了切尔诺贝利核电站的四号反应堆。根据国际原子能机构的估算，爆炸释放出的放射性物质大约是广岛坠落的原子弹所释放物质的400倍之多。
如今，在灾难过去25年后，乌克兰政府正式开放了这一地区，以供游客参观。但是，现在这里的安全情况到底如何呢？
辐射
核事故发生后，人们并不清楚周围环境受污染的程度，因此乌克兰当局发布了一项强制性规定：反应堆30公里以内的地方禁止任何人入内，同时，大约有11.5万人撤离了该区域。现在，这一“禁区”已对游客开放。
我驱车前往切尔诺贝利，随车同行的还有乌克兰医学科学院辐射医学研究中心的健康物理学家瓦季姆·丘马克及他的同事。每周，都会有一辆车前往切尔诺贝利采集工人的粪便样本，以检测他们有没有意外吸入钚。
地球通常处于低剂量的辐射中。在基辅，也就是我此次切尔诺贝利之行的出发地，一个人每小时受到的辐射量通常为0.1微西弗。在我们驱车前往禁区的约两小时、150公里的旅途中，我们检测到的辐射量差不多就这么高。但是，当我们驾车经过爆炸核反应堆的放射性烟羽曾经过的区域时，测定器上的读数突然上升到每小时4.76微西弗。
核事故发生后，这一地区目前的安全情况取决于爆炸时都释放了哪些放射性物质以及这些物质都扩散到了哪里。在这一地区，共有四种放射性核素(或放射性同位素)值得格外关注。碘-131能够被甲状腺迅速吸收，增加儿童患甲状腺癌的风险。铯-137在体内与钾的功能类似，积聚在肌肉组织内。锶-90的作用与钙类似，沉积在骨骼中。钚-239和其他放射性同位素则会无限期地存于体内，对体内器官造成辐射。
丘马克说，碘-131会迅速衰变，只需三个月的时间差不多就能从环境中完全消失。然而，铯-137和锶-90的半衰期都为三十年左右，也就是说，它们需要大约三十年的时间才能衰减到原来的一半。而核反应堆中主要的同位素钚-239的半衰期则超过24, 000年。
核灾难发生后，在绰号为“清理者”的救险工作人员和自然力量的双重作用下，空气中的核辐射量有所降低。清理者从直升机和汽车上喷洒净化剂和橡胶状的胶合溶液，用以凝固污染物。道路被重新铺过，用来覆盖放射性尘埃。土地也被翻了一遍，以便将受污染的泥土掩埋在下层。与此同时，在雨水的作用下，污染物逐渐转移至大地的深层。
丘马克介绍说，“事故发生五年之后”，在禁区旅游可能会比较安全。但是，能在这里旅游并不意味着这里所有的地方都安全，可以随便涉足。这里依然有被高度污染的热点地区，尤其是放射性烟羽曾经扩散的区域。这一区域允许游客入内参观，但游客在此停留的时间会受到严格限制，以防他们过多地暴露在核辐射下。
但这里还有些地区仍然太危险，游客是不能入内参观的，比如石棺。
石棺内部
当时，在消防员扑灭切尔诺贝利爆炸引起的大火后不久，工人们迅速建起了一座钢筋混凝土建筑，技术上称为核保护罩，但人们通常叫它石棺。石棺用于掩埋被损毁反应堆的残留物，以阻止更多的污染物泄露。目前，这里依然是禁区内辐射量最高的地点之一。
如今，工作人员在这里维护着这座正在遭受腐蚀的石棺，监测内部的放射性物质，尽其所能地去除污染。为了和工作人员一起进入石棺，我在“净室”内脱到只剩下内衣，然后穿着病号袍和拖鞋走进了“热屋”，在那里，我穿戴上了现场发给每个人的纯白装备——防护衣、夹克、裤子、防护帽、袜子、手套和配有最高级别的防尘过滤设备的面具。在这套装备外面，我又穿了件外套，戴了顶安全帽，还套了双硬皮靴子。此外，我还带着进入30公里禁区时戴的那个辐射徽章和进入核电站区域时发给我的第二个辐射徽章，而且还携带一台个人电子测定器，以精确地检测自己受到的辐射量。
这里的工作人员每天允许接受的最大辐射量通常为0.1毫西弗，相当于一个人跨洋飞行90分钟或者观看四个小时等离子电视所受到的辐射量。当我站在石棺前时，测定器上的读数一下跳到每小时0.12毫西弗，这是在基辅所测读数的1200倍。
通过一个电子检查站后，我就站在四号反应堆控制室那昏暗、破落的残骸里了。就是在这里，工程师们犯下了致命的错误，污染了地球。
生命和野生动物
在切尔诺贝利游玩一天也许还算安全，但在这里长期生活可就是另外一回事了。乌克兰政府确实允许原先住在禁区的居民按个人意愿回迁。例如，一些距离爆炸点30公里内的区域相对安全些，而且老人在剩余岁月里所吸入的辐射量不足以危害他们的健康，丘马克如此介绍道。
然而，有些区域仍然非常危险，不能回迁居住。“30公里内的区域大概还能住人，但我想十公里内的区域就不能住人了，永远都不行，”丘马克说，“那里有钚。”
关于灾难对该地区野生动物所造成的影响这一问题，一直存在着激烈的争辩。例如，来自位于拉伯克市的得克萨斯理工大学的放射生物学家罗恩·切瑟和他的同事们认为，由于人类的离开，这里的野生动物生机勃勃，野猪的数量已达到灾难前的10～15倍，而且，这里还经常能看到其他动物，比如狼、兔、赤鹿、黑鹳和驼鹿。这些动物的遗传状况显示，辐射的影响非常小，还不足以导致遗传基因的变异。因此，切瑟的结论是，尽管辐射很糟糕，但人类对环境的影响可能更糟。
然而，来自位于南卡罗来纳大学哥伦比亚校区的生物学家蒂姆·穆索和他的同事们发现，与辐射量正常的区域相比，在禁区内辐射量最高的区域中，森林鸟类的种类减少了一半以上，大黄蜂、蚱蜢、蝴蝶、蜻蜓、蜘蛛的数量也有所减少。对切尔诺贝利及乌克兰和欧洲其他地区7700多只家燕的分析数据也表明，来自禁区或禁区附近的家燕发生畸变的数目更多。近期的研究还表明，生活在切尔诺贝利附近高辐射区域的鸟类的大脑比同类的小。
上述双方都坚称自己的研究是对的，认为对方的数据在地理变量因素方面出现了误差。
旅游胜地？
那么游客在切尔诺贝利能看到些什么呢？在占地22平方公里的核电站冷却池中，你常常可以看到体型庞大的鲶鱼，你也可以拿食喂鱼。在远处，你还可以看到一座约150米高的巨大的雷达网格——比吉萨大金字塔目前的高度还要高。
核灾难后，普里皮亚季城成了一座空城，时间在这里仿佛凝结了。大自然正在回收这座城市，白色的桦树和翠绿的松树将许多方方正正的苏维埃建筑掩埋于其中。
尽管官方近来才正式宣布切尔诺贝利对外开放，但来切尔诺贝利旅游却早已不是什么新鲜事了——大约十年前就开始有人来这里游览了。“来这里的人抱着这样一个动机：尽自己所能做点什么，让这片土地重新发挥效益。”穆索说道。
对于那些亲身经历了这场灾难的人来说，在切尔诺贝利搞旅游业的想法引起了他们强烈的情绪波动，大概正如纽约人在提到9·11事件时的情绪一样。“如果我们够明智，就会把切尔诺贝利建成一座人类纪念馆，像广岛和长崎那样。”丘马克说。
基辅的年轻人确实有兴趣来看看切尔诺贝利。“我儿子真的想来，还有些年轻学生也是一样。”丘马克说。
然而，在其他人看来，去切尔诺贝利旅游没有任何吸引力。“就我个人来说，每次去那里都让我感觉很不舒服，”基辅放射医学研究中心的科学家叶连娜·巴哈诺娃说，“那是人类犯的一个错误，是人类愚蠢的标志。”