Let us go straight to the primary source of all this radioactive material: the heat-producing nuclear fuel. Preventing overheating, which could lead to another huge environmental release of radioactive material, is the highest priority. So far it’s been successful, primarily due to the makeshift cooling system, which has effectively kept the melted fuel rods (as well as those in the spent fuel pools) cool and stable since the fall of 2011. Time and the laws of physics have also lent a hand—the fuel generates less and less heat with each passing day. Indeed, its potential for overheating is significantly less than it was two years ago and will continue to diminish at a known rate.

This makeshift cooling system is a conceptually simple cycle. Water is constantly pumped to the stricken reactor vessels containing the damaged fuel. Because the integrity of internal various containment units was compromised, the water not only becomes contaminated by its pass over the damaged core but also finds its way into the buildings’ basements. The water is then pumped back out of the building, processed, and pumped through the building again.

In practice, however, the system is not a neat, closed cycle; and it is here that major problems begin to appear. The entire site bristles with conduits, tunnels, and trenches, which, unfortunately, allow some of the untainted groundwater on its way to the sea to leak into these basements. This net inflow of about 400 tons of water per day, amounting to the carrying capacity of about 13 large gasoline trucks, adds continuously to the volume of contaminated water that must be processed and contained. The solution so far has been to keep building more storage tanks and reservoirs on site.

Uphill of the stricken reactors is land covered with almost 1,000 of these water storage units. After two and a half years, they already hold enough water to fill 120 Olympic-size swimming pools, and their burden continues to grow. This colossal effort is unsustainable. Not surprisingly, leaks have begun to appear.

Several of these have been reported this year, varying in their volume, how far they spread, and their radioactivity. The latter depends on the leak’s source. The water in each storage unit bears the traces of its unique history—how much radioactive matter it picked up, to what extent it was filtered of radioactive isotopes, whether it was desalinated, and so forth. One leak in mid-August was alarming enough to prompt Japan’s Nuclear Regulation Authority to issue an International Nuclear Events Scale (INES) rating of 3, just shy of what would qualify as a “nuclear accident” rating (which would be a 4 or higher). Leaks originating with the plant’s various processing systems have also been reported, but these leaks, being typically quite small and contained, are more nuisances than cause for great concern.

But the water containment woes do not stop here. Rainwater, too, is literally swelling the size of the water problem. Not only does it complicate the hunt for leaks, sending false alarms and triggering investigations by creating wet piping and puddles, but the additional water must also be monitored and controlled. For instance, in mid-September, heavy typhoon rains filled dikes around the tank farms to the brim, some of which tested as too contaminated to discharge, swelling the water storage problems further.

While these leaks and rainwater flows may contribute to the increase in contamination of Fukushima’s surroundings, they are not the primary cause of the recent spikes in ocean and groundwater radioactivity. There is something bigger.

Return to those leaking basements. There is clearly a net inflow of water, but, worse still, there is contaminated water leaking out of the basements and into the groundwater which is heading to the sea. In August, Tepco reported that this leakage appears to have been going on since the initial accident and that this continuing discharge is already the largest such release after the plants were stabilized. We now try to give a sense of the scale of this leak. The amount of contamination which has reached the sea from this basement leak is substantially higher than from any other leak observed after the initial accident phase. To give some idea of scale, this is about twice the rate of the plant’s allowable annual discharge during normal operations and thousands of times less than the estimated contamination released during the accident phase in March/April.

Once the contamination enters the sea, the concentrations of radioactivity dilute quickly – radioactive cesium has rarely been detected in samples taken beyond a third of a mile from the plant (prompting Japanese Prime Minister Shinzō Abe to state that the “influence of the contaminated water is completely blocked within the 0.3 square kilometer area of the plant’s port”). However, bottom-dwelling fish that remain local have been found with radioactive cesium concentrations exceeding food contamination standards (cesium tends to collect in and adhere to the sea bed), making some reluctant to buy fish from this region (South Korea, for instance, has recently banned its import). Even some migrating tuna far across the Pacific have presented minute cesium levels, though well within food safety guidelines.

The ongoing water problems at Fukushima are dauntingly complex, and the attempts to tackle them tend to fall under the following broad categories: preventing untainted water from being contaminated, keeping contaminated water from entering the quay and beyond, and filtering the radioactive isotopes from contaminated water. The various efforts to fulfill these goals—including building a $300 million subterranean ice wall, pumping contaminated groundwater out for treatment and storage, and diverting clean groundwater around the site on its way to the sea—are costly and of uncertain efficacy. In addition, there remains the ballooning water storage problem to resolve. Some experts argue that once the much-anticipated new water treatment system comes online, filtering out the vast majority of radioactive isotopes, the treated water could be diluted and safely discharged into the sea. Local fishermen are (understandably) opposed.

Since the ultimate goal of these efforts is to protect public health, it is useful to discuss the health risks of these water issues in more familiar terms. Radioactivity in some ways is similar to the well-known common household cleaner, chlorine (of course, this is a very rough analogy, not an exact comparison). Chlorine, like radiation, in high concentrations is fatal, while in low concentrations such as chlorinated drinking water (or natural background radiation) is innocuous. In between is a wide range of concentrations that have accordingly varied effects on our health – skin burns from a bleach spill, dry hair from swimming in a chlorine-treated pool, and a funny taste in drinking water. Such a range is similarly true of radiation. Recognizing such nuances might give us a better perspective of what radioactive water leaks and spills reported at Fukushima really mean. (Of course there are countless ways that radiation differs from chlorine—for example the ability to smell chlorine well before it is harmful—but please indulge us.)

Applying this analogy, imagine deadly chlorine gas when thinking of the stricken reactor buildings—worker access is severely limited. Think of industrial-strength and household bleach when dealing with water processing systems and storage tanks—workers risk burns or asphyxiation if handled improperly, but the situation is otherwise manageable with the appropriate precautions. The area around the reactor sea-intake pipes in the harbor could be conceptualized as a heavily chlorinated swimming pool. To continue with the analogy, the sea area within two-thirds of a mile outside the harbor periodically contains barely detectable levels, which is somewhat like chlorine in drinking water—sometimes it has a distinctive taste, other times it goes unnoticed. A chlorine spill, however concentrated, will diffuse and dilute as it goes into the ground or gets washed by rain and drains to the sea, where it further dilutes. One can draw parallels to the events occurring at Fukushima and—though we don’t yet know the long-term impacts the contamination might have on the marine environment (particularly the seabed)—the direct and immediate risks of spills and leaks are primarily to the workers and not the public at large.

Whatever the impact to public health may be, in a bid to regain people's confidence, the Japanese Government has essentially demanded that all of the plant’s contamination be contained. This is an honorable goal. However, marking every leak intolerable regardless of the risk might be unreasonable, if not impossible, to abide by. It is comforting at least to note that the most dangerous aspects of Fukushima seem to be under control. It would be nothing short of a miracle if there weren't more setbacks along the way. So, expect more headlines.