Why the heated attack between the pro-nuclear and pro-renewable energy experts intensifies after the Fukushima incidence? The two groups had been attacking each other for quite a long time. Pro-nuclear group claims that nuclear energy is, and will in the next decades be the cheapest and most reliable sources of power especially in the developed world. While the pro-renewable energy group sites the risk, waste disposal danger and initial high cost of plant development associated with nuclear power as enough reason to end the life of the industry. They also claim that renewable energy guaranty cheaper, sustainable and clean energy with no or less risk to both humanity and the environment.

The 3/11 Fukushima disaster has been considered among the most lethal in the last decade. While most of the nuclear energy experts believe the level of damage is not as fatal as being exaggerated and the cause of the accident can be avoided. The pro-renewable energy group claims that trillions of dollars were lost to the disaster and the radioactive effect on human life and health would definitely be seen in a very near future. Looking into situation, the magnitude of the damage done as claims by many has been based on assumption.

 Initially I have been wondering how an accident like that of Fukushima can be avoided looking into the post Tsunami condition of the nuclear plant and its entire accessories. But the technical information received in the aftermath of the disaster changed my thinking.

TECHNICAL INFORMATION

The information obtained from high speed data recorders, paper recorders in the control rooms and computer alarm printouts, the parameter plots as posted by the Tokyo Electric Power Company TEPCO and interpreted by nuclear engineers, the following points were drawn on what exactly happens in unit 1,2 and 3 during the first 80minutes after the earthquake.

UNIT3:The available information for Unit 3 does not extend long after the arrival of the tsunami, and does not extend to the point at which fuel in the reactor core was damaged by overheating. Much of the available information ends at 4:05 pm local time, about 80 minutes after the earthquake occurred at      2:46 pm. And the detail information as obtained from the plots of the parameters below indicate as follows

1. The reactor shut down around 2:46 pm local time and remained shut down.

2. Normal power supplies to in-plant equipment were lost about a minute later. It is assumed that this occurred when the operators manually tripped the turbine/generator per procedure.

3. Both emergency diesel generators on Unit 3 automatically started and connected to their in-plant

electrical buses within seconds of the power loss, restoring power to essential plant equipment.

4. The power interruption caused the main steam isolation valves to automatically close, disconnecting the reactor core from its normal heat sink and disabling the normal source of make-up water to the reactor vessel.

5. A safety relief valve (SRV) automatically opened around 2:52 pm to control rising pressure inside the reactor vessel. This SRV automatically re-closed when reactor pressure dropped. This SRV followed by two other SRVs cycled opened/closed periodically over the next 73 minutes to control pressure inside the reactor vessel.

6. The water level inside the reactor vessel steadily declined as cooling water was discharged through the open SRVs into the torus. By 4:00 pm, the water level had dropped below the bottom end of the level monitoring scale. There’s no compelling evidence that any system was used to provide makeup flow to the reactor vessel from the time that the MSIVs closed around 2:48 pm until 4:00 pm.

7. Around 3:38 pm, one of the emergency diesel generators stopped running. About a minute later, the other emergency diesel generator stopped running. It is assumed that the tsunami caused these failures.

8. Around 4:02 pm, the reactor core isolation cooling RCIC system appears to have been placed in service.

The charts 21 and 22 above show the electrical output being supplied by emergency diesel generators 3A (top) and3B (bottom) between 2:40 pm and 4:05 pm. At around 3:38 pm, emergency diesel generator 3A stopped running. Within a minute, emergency diesel generator 3B stopped running. This left Unit 3 without any power except that coming from batteries.

The RCIC system’s turbine controls and valves are battery powered. So it can operate when only battery power is available. The SRVs were being operated mechanically. The SRVs are kept closed by spring pressure, similar to how a spring coil keeps a mousetrap closed. When pressure inside the steam lines raised high enough to overcome the spring force, the pressure would open the SRV against its springs. After the open SRV lowered pressure sufficiently, the spring force would re-close it. Thus, the SRV pressure control function did not require power from the emergency diesel generators or batteries. But from the information obtained it appears that the RCIC system went in service around 4:02 pm, the water level inside the reactor vessel had already dropped below zero even before 4:00 pm. But the available information does not explain why the water level in Unit 3 dropped below zero by 4:00 pm.

The RCIC system appeared to be operable yet was apparently not operated. The high pressure coolant injection (HPCI) system apparently did not operate either.

TECHNICAL FAULT?

It appears that neither the RCIC nor HPCI systems were used between 2:52 pm and 4:00 pm. It’s not clear why they were not used to correct the steadily declining reactor vessel level after 3:35 pm.

Did the tsunami rendered the TEPCO emergency backup pumps inoperable by shorting out the electrical controls and power feeds? Is there a design flaw with the reactorscooling system? These questions need answers.

Many experts believed that TEPCO in the first place failed to take preventative measures, by building a flood wall or having water proofed the emergency water pump circulators, taking into consideration the location of the nuclear plant. Because no one can claim that the Fukushima disaster was unpredictable. It has been known for centuries that Japan is geologically right in the midst of prominent Pacific earthquake zones that habitually create tsunamis in their wake.

If the failure of both RCIC and HPCI to operate correctly was as a result of design flaws, then it is quite unacceptable. But TEPCO is one of the companies that I am guess would not be so foolish to play with sophisticated design issue like this.

CONCLUSION

The point is that Fukushima not have happened in the first place had TEPCO added some  basic technical safeguards in place to protect those reactors from the tsunami flooding. I am not a nuclear plant engineer, but I am sure such safeguards are feasible and would not have been that expensive to implement compared to the level of damages done.  It is quite unfortunate to learn from an engineer that was involved with GE's work with TEPCO on Fukushima, that there are many sad stories about TEPCO officials undermining design and safety programs GE recommended.

And if in any case such a company can erroneously commit design flaws like this, then the fate of nuclear power would be put into a more serious dilemma, considering the number of nuclear power plant manage by the company. This is in addition to the fact that, the nuclear power industry is facing fierce challenge from the promising Renewable energy counterpart. Its proliferation danger had been a matter of utmost concern by many especially with the current quest by many nations to acquire nuclear weapons, a great threat to the global peace.

Though I am more to Renewable energy than nuclear and I have been campaigning for clean, sustainable energy and climate change mitigation for more than a decade. But I am not in support of outright ending of nuclear power plants, as doing so would aggravate the global energy crises already at hand. But I am certain with the promises, and the speed at which the world is turning toward the clean, sustainable, renewable energy, Nuclear power industry is in for an unending challenge and the future of the industry looks no bright.

References:

1. TEPCO official document, http://www.tepco.co.jp/nu/fukushima-np/index10-j.html.
2. RenewableEnergyWorld.com
3. Ref: http://www.ucsusa.org/assets/documents/nuclear_power/fukushima-daiichi-ucs-analysis-unit-3-first-80-minutes.pdf