Oct 3, 2018 in Case Studies

Background

In the last week of November, when the naval staff was enjoying a holiday dinner on Thanksgiving Day on board of a nuclear-powered submarine USS Mazeltov, an explosion was heard near the reactor control room. The reactor was shut off immediately by the automatic control system but it could not prevent the leakage of contaminated coolant water that spilled out containing unspecified amount of unspent fuel, Plutonium-239. There were associated fire breakouts in the coolant system but they were immediately controlled. The explosion caused radiation leakage in the bay area and though there were no on the spot fatal casualties on board, but the next day there was a reported death of 10 sailors and one civilian though the cause for the death was not officially declared.

The automatic cooling system flushed out the debris at the site but there was no doubt that the fumes of the explosion spewed out radioactive material to the atmosphere. Emergency naval operations were initiated to isolate the explosion area and remove the contaminated components that were exposed to contamination and were immediately sealed in safe chambers. The immediate concern was to assess the extent of the danger posed to bay area and to the city of San Diego and how to contain or minimize the effects of the radiation hazard.

Defense Department took charge of safeguarding the USS Mazeltov and towed her to safe area but refused to comment on the further dangers posed to the civilians. However, the Environmental Protection Agency confirmed that the radiation has spread to bay area. In response to this confirmation and the related death of ten sailors and a civilian the local authorities called for estimating the extent of the danger posed to the civilians and ways for minimizing the damages. A task force from San Diego Science and Technology Commission is assembled to study the fallouts of the nuclear accident and comes out with recommendations for procedures to be adopted to counter the threat.

Assessment of the Accident

Task force of SDSTC set upon scientifically determining the extent of the damage and thereby the severity of the risk as the first priority as it determines the nature and the scope of counter measures to be adopted.

The submarine was built with reactor using Plutonium-239 as fuel. Plutonium-239 has half life of 24,100 years which means that it takes 24,100 years for the amount of radioactive material to be reduced to harmless material of half of its initial weight. This means that the bay will remain contaminated for many generations to come. But fortunately, the leaked material is no more in the lumped form as it has become a part of dust and a part of it is swept away washed to the safe waste disposal container. Still it remains to be seen whether the concentration of the radio active material poses any danger before it is diluted to negligible concentration. It is not commonly known that radioactive materials are naturally found in soil, air and ocean waters. In fact, on an average a person receives radiation of 600 mrem per year in the USA from natural sources like inhaled air, cosmic radiation and from artificial sources like medical and industrial environments and even from monitors of TV and computers! So it is necessary to realistically estimate the danger posed by the above nuclear incident to the civilian population in terms of the actual radiation level increases from various sources in the area.

Extent of Leakage Determined by the Nature of Accident

The task force took the stock of the incident by on-the-spot study of the accident and checked the records of data from the instruments. The statements of the operating staff and the recorded data running up to the minute of the incident were studied. The photographs of the damaged components and records of shut down procedure were requested.

The result of the study showed one redeeming fact that the automatic control system had shut down the reactor smoothly and safely and there was no chance of nuclear meltdown which would have been very serious accidents, almost akin to a nuclear disaster of Chernobyl. Certainly the incident had no parallel to the Fukushima plant accident where the cooling system itself was damaged in the aftermath of killer Tsunami. In case of USS Mazeltov, reactor control system acted to switch off the reactor and force cool the reactor with parallel standby cooling system. All the damage was due to the explosion at the outside of the core of the reactor which had damaged the fuel carrying pipes but even that supply was cut off automatically. The core of the reactor had held out with no internal damage. This resulted in minimal leakage of the radioactive fuel to the environment but all that was leaked out was due to the fumes at the time of explosion and due to the fact that cooling system had washed out the leaked fuel to the waste disposal compartment.

Assessment of Danger Posed to Public

The main difficulty was in assessing the actual amount of the leaked radioactive material to the ocean and to the atmosphere. The USS Mazeltov was powered by medium sized nuclear reactor of 80 MWe. Like all other US nuclear submarines, the shield ensures that the radiation at the nuclear reactor site is less than the natural radiation one can be subjected on a beach due to the natural radiation. Immediately after the accident the radiation levels measured in all areas of the submarine showed no abnormal radiation except in the reactor cabin.

Conclusion

The nuclear accident in itself was not as disastrous as it could have been if it involved ripping off the reactor or meltdown. This explains low fatalities and injuries caused but those who inhaled the fumes directly in the aftermath were unfortunate victims of the accident. The eyewitness accounts of the control room operators corroborated the extent of the explosion and the thick fumes were flushed out by HVAC system. This does not, however, imply that the accident is not serious enough to be ignored. Immediate actions must be taken to minimize the risks to inhabitants living in the vicinity of the bay and to 1.2 million population of San Diego County.

Recommendations

The recommendations of SDSTC are based on the findings of the committee on the extent of the damage. The committee has limited the scope of the study only to take actions to safeguard the population of San Diego from the radiation risks but not look in to the design aspects of the reactor that led to the accident. The study of flaws in design, lack of maintenance, human error or mechanical failure was taken up by the Navy and the suppliers of the reactor. The information obtained from the defense department was for the purpose of estimating the extent of radioactive material leaked to environment in the form of fumes and water contamination.

Many environmental groups have already embarked upon taking up this accident to organize protests and propose that the city must be fully evacuated to prevent the radioactive fallout comparing to the meltdown of Chernobyl and Japan’s Fukushima plant accident. But the facts do not support such an action as the studies by Geiger records showed slightly heightened levels of radioactivity around the city but these are not considered hazardous to human health. But in the vicinity of the bay of San Diego, the radiation levels were observed to have crossed the tolerable limits even on the second day of the accident and it is prudent to evacuate the residents only from this area. However, even in these areas, the levels are rapidly falling down due to the winter storm that recently swept off the radiation from the atmosphere. The demand for complete evacuation has no scientific basis as the accident has no comparison to Chernobyl meltdown or Fukushima nuclear disaster. There is no cause for alarm as the accident was minor in nature and there are no more reported cases of radiation related cases reported in hospitals. More than the extent of damage, the fact that nuclear reactor was involved bringing the often quoted examples of Chernobyl, Fukushima and Three Miles Island to comparisons can make people over react. There is no doubt that the public believe that one can not survive a nuclear (threat) or accident due to the highly sensationalized reporting of the accidents and their portrayal in movies.

But it is always possible to survive nuclear accidents if proper precautions are taken. This involves monitoring of the situation by periodic inspection of the radiation levels in atmosphere and oceanic environments. The most important step is also having clear knowledge of the disaster and its effects. This also involves disposing off wrong notions and unscientific predictions which are easily believed by the public. It is the duty of the civic administration to ensure that everyone in the community is aware of the accident and the resultant poisoning of air and water. All mass media must be employed to ensure the propagation about the risks and dispel any exaggerated scenarios presented which are based on pure speculation having no scientific or factual basis.

It is also recommended to follow up of radiation level measurements every month and ensure that radiation has contacted by entering the food and water chain. 

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