What we cannot see, nor understand, instigates more violent a response than any other. Adding weight to this hypothesis is the current chaos regarding the need for nuclear energy. Nuclear energy as an optimal alternative for fossil fuel-generated power has now come under global scrutiny as efforts to contain radioactive contamination at the disaster-hit Fukushima Daiichi nuclear plant in Japan fall short.
Nuclear safety at power plants embody three primary questions: How safe are the reactor designs? How effective are the emergency response mechanisms? And lastly, can the safety measures combat the repercussions of unprecedented events? Deliberations on these primary questions have consciously shaped nuclear safety mechanisms, especially since reactor accidents at the Three Mile Island in 1979 and Chernobyl in 1986. However, events at the Fukushima Daiichi nuclear plant have once again urged the international community to calculate the benefits of nuclear energy under the lurking shadow of a probable nuclear accident.
Amidst varied speculations, two main strands of explanations for the nuclear mayhem at Fukushima prevail. According to the first strand, the reactor design of the Mark I (Boiling Water Reactor) vessels have come under severe criticism for their single circuit mechanism which introduces the primary coolant (water) into the reactor core and then relies chiefly on its primary containment vessel (made of steel and concrete) to mitigate radiation exposure to the environment in case of any reactor accident. Concerns related to this reactor design stem from the probability of a core meltdown increase if cooling systems fail and the likelihood of the zirconium cladding (fuel assemblies and spent fuel) coming into contact with oxygen, amplifying the chances of hydrogen generation (resulting in an explosion), a situation currently unfolding at the Fukushima Daiichi nuclear plant.
The second strand focuses significantly on the emergency preparedness and response mechanisms. In Fukushima Daiichi nuclear power plant, the coolant pumps, regulated by an on-site generator would have ensured cooling of the reactor core after the control rods were inserted fully to cease nuclear fission right after the earthquake. However, when the tsunami destroyed these on-site generators, the coolant pumps fell back on battery generated power which ran out soon thereafter causing a furore to bring in mobile generators. It is this time gap between the switch from battery backup to mobile generators that has been speculated as the precipitating factor leading to the Fukushima nuclear accident. The point to be noted is that although the Fukushima nuclear plants had a multi-layered safety mechanism in place, operational difficulties catalyzed the mayhem.
In light of this evidence, it is important to once again turn towards the three fundamental questions regarding nuclear safety that formed the base of the deliberations in this article. The first question raised concerns about the safety of the type of reactor designs installed. In this regard even the IAEA asserts that the reactor designs should be such that they ensure that the nuclear installations are suited for reliable, stable and easily manageable operation, with its prime goal aimed at the prevention of nuclear accidents. However, the case of Fukushima Daiichi and that of Chernobyl add weight to the claim that in addition to safe reactor designs, operational verification and consistent assessment procedures cannot be ignored.
The second question dealt with the efficacy of emergency response mechanisms at nuclear installations. Nuclear installations have an array of overlapping safety measures to provide optimal protection against any untoward event. However, an inference drawn from the Fukushima Daiichi case stipulates that despite having multiple back-up systems in place, operational inadequacy catalyzed escalation. This incident draws attention to what the IAEA identifies as the ‘systematic consideration of the man-machine interface’ wherein human factors form an important aspect of the development of operational requirements.
The third question deals with the viability of the safety measures against the probability of unprecedented events. While selecting a particular location for installing a nuclear plant, the history of the seismic activity particular to that region along with the region’s propensity towards natural disasters form a key factor which affects the final decision. Thus, most nuclear plants are built in a way so as to endure natural disasters. The case of the Kakrapar nuclear plant (which was hit by an earthquake in 2001) and that of Kalpakkam (which withstood the 2004 tsunami) in India demonstrate the above. However, in the occurrence of an unprecedented event, reactor designs and emergency mechanisms along with the efficacy of operational measures (that of the optimal manning of technical apparatus) dictate the turn of events.
Therefore, even though answers to these three questions provide an insight into the basics of safety at nuclear installations it should be remembered that ‘nuclear safety’ is not an absolute term; rather it is one that is evolving and requires constant upgrades along with the realization that the human factor is an important aspect of nuclear safety. More importantly, nuclear safety is also one that deserves a second chance.