Tonight we take you to one of the most toxic places on earth. The still crippled fukushima nuclear plant. It's closed to the public, and for the few who gain access, it's still a place you can only... See More
Tonight we take you to one of the most toxic places on earth. The still crippled fukushima nuclear plant. It's closed to the public, and for the few who gain access, it's still a place you can only visit with the upmost precaution. Covered head to toe in protective gear, lichlted time because any more than an hour there could cause permanent damage. Our sbep pid team suited up to find out what's happening now. Here's ab . My alarm is going off telling me we're being exposed to radiation right now. I'm about to enter one of the most toxic places on the planet. Not one inch of skin exposed. The darngs here, dangers here, radiation you can't see or smell. But the threat is all around me. This is japan's fukushima daiichi power plant. This is the site of one of the worst nuclear catastrophes in history. The closer we get, these things are just skyrocketing. 2 1/2 years after this country was crippled by an earthquake and tsunami that triggered the meltdown, we gained rare access to examine the fallout by land and by sea. To find out if fukushima is still a threat to japan and the rest of the world. They suspect some of the most contaminated water lies right there on that sea floor. Let's see if I'm contaminated with radiation. Our journey to find answers takes us through a nuclear danger zone, even inside a damaged reactor. A place few people ever dare to go. March 11, 2011, that massive 9.0 earthquake, the largest ever to rock japan. The tsunami that followed engulfed entire villages. Then the triple whammy, giant waves flood the fukushima plant, knocking out power and causing a melt doup that spewed radiation across the country side and into the ocean. Tokyo electric power company -- at first, tepco, the plant's operator and largest energy company in japan down played the severity of the disaster. Now at the start of an unprecedented and treacherous clean-up, tepco has agreed to open up the doors and show us the progress they've made. But getting there isn't easy. A 12-mile evacuation zone teeming with radiation hot spots surrounds the plant. Deep in flalout territory, masked guards only allow those with official government permission to pass. In the middle of one of the most developed nations on earth, we find what looks like a post apocalyptic landscape. Ghosts town, abandoned and overgrown. Locals ks call this the no-go zone. Here, cattle graze in the shadows with hundreds of bags of irradiated soil that no one wants to collect. In all, 80,000 people were forced to evacuate their homes. Most won't be able to return for years. Some, maybe never. At this elementary school, it was graduation day when the disaster struck. Probably in the middle of class here. And time just stood still. Every trip to the no-go zone requires one mandatory stop. A radiation inspection station. To see if I'm contaminated with energy after spending an hour in an evacuation zone. Our car, inside and out even our camera equipment are scanned. This is something we don't want to know the answer to. Safe? We're safe? You can go. Reporter: Safe for now. But the riskiest part of our journey still lies ahead. We are boarding tepco's bus, on our way to a private tour of the power plant, but it comes with restrictions. We can't film part of the grounds for security reasons. The final checkpoint, ear just a few hundred meters from the power plant and they want us to turn our cameras off. We can't film past this part. They just told us we can turn our cameras back on. We are now inside the fukushima daiichi power plant property. The alarm is going off, telling me we're being exposed to some radiation right now. Comforting. Our first stop is a building on the edge of the property. The gate way to the most dangerous parts of the plant. We're on our way to get suited up. This buildi everything in this building has got to be covered. Final pair of gloves. Just in case they need to identify my body? Yes. Reporter: She said yes. Oh, my gosh. I was joking. We have put this on in order not to breathe the radiation particles outside the power plant. Finally, we're ready to venture deep into the heart of this disaster. Our final destination -- inside a damaged reactor. It's amazing what an intricate process this is. They want no contamination anywhere. Tepco told us we can only spend one hour inside the plant. Any more time and we risk harmful radiation exposure. It's so hot in the this suit. My nose itches and I can't track it. I'm trying not to think about it. You have bigger problems. Reporter: Our radiation detectors climb. They're going off again. Found another hot spot. We are heading to one of the four reactors that was devastated during the accident. The radiation right here alone, about 2,000 times higher than outside of fukushima. We shouldn't be doing interviews in a hot spike that. This is unit four right here, the gray one. As we get closer, these radiation detectors get higher. We're going to go inside and see what kind of progress tepco has made on this clean-up. We are inside the building for reactor four. The world is watching and many fear what lies beneath this murky water. 1,500 highly radioactive fuel rods inside this pool. They've got to move them outside of this reactor into a safer location. Some say that this is an exceptionally delicate, very dangerous dance for tepco. This is a vital first step to decommission the plant. In all, it will take workers an entire year just to clean up this reactor. But so far, they've done it safely. A welcomed victory for a company with enormous challenges ahead, including three additional damaged reactors. So con stam nate contaminated we couldn't get anywhere near them. We also have to deal with possible radioactive water leaks. There's a chemical barrier. These fuel tanks here, another barrier. And that orange buoy over there is a silt fence, another barrier, three right here in this area alone to keep contaminated water from going into the ocean. Tepco is convinced these measures have helped stem the flow of radiation. But what about the damage that's already been done? Will you ever know how much contaminated water has made its way from the power plant into the ocean? He tells me it is very difficult to give an accurate number. Scientists say a trace amount of radiation is expected to reach american shores soon, but how dangerous will it be? We join a team of independent scientists on the hunt for answers. Is it worse than we thought? After the break, our unauthorized expedition to the choppy seas outside fukushima daiichi. But first, japan is no stranger to extreme weather. These winds are up to 90 miles an hour. Does mother nature still pose a threat to the crippled plant?
This transcript has been automatically generated and may not be 100% accurate.