Engineering is the application of principles in mathematics and physics in order to design, analyse and manufacture systems. It is crucial for an engineer to consider the ethical implications during every stage of creating a system, therefore it is vital to understand the definition of Ethics: a system of moral principles that govern people’s behaviour and decision-making. For example, prior to the design, production and operation of a nuclear power plant, there are numerous environmental, economic and social impacts that must be carefully evaluated and taken into consideration. From an environmental perspective, there are advantages and disadvantages to the use of nuclear power. On one hand, nuclear energy does not emit greenhouse gases and seems a suitable alternative for fossil fuels which are diminishing in supply whilst demand for energy increases. However, nuclear energy also involves mining of radioactive raw materials and disposal of radioactive waste which damages the environment and poses health threats to nearby residents (Xiang and Zhu, 2011). The Chernobyl Power plant incident (See Figure 1) is an example of the social, economic and environmental consequences when engineering decisions are carried out without ethical implications adequately taken into account. Figure 1: Photograph of an aerial view of the damaged Chernobyl Nuclear Power Plant, taken by Wojtek Laski in May 1986, a few weeks after the disaster. (Taylor, 2019)
On the morning of April 26, 1986, the Unit 4 Reactor at Chernobyl Nuclear Power Plant in northern Ukraine exploded, spreading “50 million curies of radiation” into the atmosphere, “the equivalent of 500 Hiroshima bombs” (Serhii Plokhy, 2019). The accident occurred during a test designed to assess the reactor’s safety margin in a particular set of circumstances. The test was scheduled to coincide with a routine shut-down of the reactor because it had to be performed at less than full operation power (Chernobyl > ENGINEERING.com, 2006). This essay will outline the factors during testing that lead up to the incident as well as discuss the ethics behind decisions that were made from the perspective of the Soviet State and from the operation of the reactor that was used in Unit 4 and its unsuitable design.
The Test
Nuclear power stations whilst producing electricity also consume electricity, for example to power the pumps that circulate the coolant. This power is usually supplied by the grid or by the reactor’s own production. However, when the reactor is in operation but not producing power, for example when shutting down, other supply is required usually in the form of generators which have a time delay while they are started (Chernobyl > ENGINEERING.com, 2006).
“The test carried out at Unit 4 was designed to demonstrate that a coasting turbine would provide sufficient power to pump coolant through the reactor core while waiting for electricity from the diesel generators. The circulation of coolant was expected to be sufficient to give the reactor an adequate safety margin” (Chernobyl > ENGINEERING.com, 2006).
Energy produced by nuclear reactors is in the form of thermal energy, measured as megawatts thermal, MW(t) (Chernobyl > ENGINEERING.com, 2006). For this test, the power should have been stabilised at around 700-1000 MW(t) prior to shutdown. However, it was decided by management that testing should be carried out at just 200 MW(t), as long as the minimum permissible Operating Reactivity Margin (ORM) of 15 control rods was fulfilled. “The ORM is essentially the number of control rods of nominal worth remaining in the reactor core” (RBMK Reactors - World Nuclear Association, 2019). Calculations performed after the accident proved that during the test the ORM was equal to 8 control rods (Chernobyl Appendix 1: Sequence of Events - World Nuclear Association, 2019).
These violations of operating regulations display a disregard for utilitarian ethics, actions were taken to proceed with testing despite multiple conditions being suboptimal and therefore the consequences of the increased probability of the test failing had not been accounted for. Ultimately this led to uncontrollable increases in steam generation and the rupture of fuel elements which caused two explosions in Unit 4, initially a steam explosion followed several seconds later by another explosion due to an accumulation of hydrogen during the reactions. Consequently, ejecting fuel and structural materials and leaving the destroyed core exposed to the atmosphere (Chernobyl Appendix 1: Sequence of Events - World Nuclear Association, 2019).
The Reactor
“The Soviet designed Reaktor Bolshoy Moshchnosty Kanalny (RBMK), displayed in Figure 2, is a pressurised water reactor with individual fuel channels and using ordinary water as its coolant and graphite as its moderator” (Chernobyl > ENGINEERING.com, 2006). The design had several shortcomings which are likely contributors to the accident in 1986, including the positive void coefficient nature of the reactor.
[image: A Light Water Graphite-moderated Reactor (LWGR/RBMK)]In a water-cooled reactor such as the RBMK, steam accumulates to form voids and therefore excess steam production creates excess voids, disturbing the operation of the reactor because water is a more effective coolant than steam and the water acts as a moderator and neutron absorber while steam does not. A positive void coefficient reactor increases power generation when excess steam voids are present, which can lead to rapid uncontrollable increases in power. This is because excess power production causes additional heating of the cooling circuit, producing more steam which results in reduced neutron absorption and more chain reactions occurring in the reactor (Chernobyl > ENGINEERING.com, 2006).Figure 2: Diagram of the components of the RBMK Reactor (RBMK Reactors - World Nuclear Association, 2019)
Additionally, due to the nature of the RBMK design as shown in Figure 2, the different materials used for the moderator and the water coolant means that excess steam production reduces the cooling of the reactor, but the moderator remains intact allowing for the chain reaction to continue at an increasing rate (RBMK Reactors - World Nuclear Association, 2019).
Following on from the accident in Unit 4, there were some immediate changes carried out to the RBMK reactor’s design. Most importantly, measures were taken to reduce the magnitude of the positive void coefficient by: installing 80 additional absorbers in the core to inhibit operation at low power, increasing the effective number of control rods from 30 to 45 to improve the ORM and finally increasing fuel enrichment from 2% to 2.4%. These measures were successful, reducing the size of the positive void coefficient by 84%. Further changes were made to reduce the time taken to shut down the reactor including cutting the scram rod insertion time, where control rods are rapidly inserted to shut down the reactor, from 18 to 12 seconds as well as redesigning the control rods (Chernobyl > ENGINEERING.com, 2006).
These sudden changes following the disaster raise the question as to whether the incident could have been prevented had the engineers designing the RBMK reactor carried out their ethical duty to analyse the design flaws with thorough testing and devise solutions to improve these technical problems. Furthermore, the engineers had failed in their duty to warn of perceived danger as the operators of the reactor at the time had not been informed that “the test could have brought the reactor into an explosive condition” (Chernobyl Appendix 1: Sequence of Events - World Nuclear Association, 2019).
The Soviet State
After 24 hours since the explosion, there was still no public announcement that the reactor had exploded releasing radioactive substances into the atmosphere. This was due to the fact that engineers at the power plant had been prohibited by their superiors from sharing news of what had happened to friends and family (Serhii Plokhy, 2019). However, the rapid spread of rumours about the meltdown suggests that despite orders, the engineers had considered the ethical implications of their actions and concluded that the morally correct action was to undermine these orders and to secretly alert friends and relatives about the incident, therefore this decision was made taking into account the public safety and the duty of an engineer to warn the public about danger.
Armen Abagian, director of one of the Moscow nuclear-power institutes, demanded for the city to be evacuated immediately following inspection of the plant. However, this demand was rejected by the deputy head of the Soviet Government, Boris Shcherbina, as government regulations at the time stated that an evacuation was not necessary unless the dose accumulated had reached 75 roentgens, the current measured intake was around 4.5 roentgens a day (Serhii Plokhy, 2019). However, the dosimeters used had a limited maximum measurement that could be taken, the actual dosage in some areas was as high as 20000 roentgens per hour (Medvedev, 1992).
Consequences
The Chernobyl incident had significant environmental, economic and social impacts among the majority of Europe. “Release of radionuclides continued for ten days and contaminated more than 200000 square kilometres of Europe.” Current environmental concern involves the content of radiocaesium present in agricultural produce including milk, meat and some plants however concentrations fall within safe levels except for a few exceptions. Animals and vegetation in forests had high absorption of radiocaesium, with persistent high levels in mushrooms and berries. The effects of radiation included increased mortality of coniferous plants and mammals and reproductive losses in plants and animals in high exposure areas of a 20-30 km radius from the site. However, numerous successful measures were taken to reduce the harmful impacts of the radiation on the environment and agriculture, including removing contaminated pastures from animal diets, monitoring milk for radiation levels and treating land for crops (Chernobyl: the true scale of the accident, 2005).
Description automatically generated]The economic cost is estimated to be several hundred billion dollars including costs of: direct damage, resettlement of people, social protection and health care, research on the environment, radiation monitoring and further examples of expenditure which have placed a large drain on the budgets of countries affected. Agriculture in the local economy had taken the most significant impact, making 784320 hectares unavailable for production, and even where farming is safe there is a stigma associated with Chernobyl leading to falling revenues and the closure of some farming facilities. Combined with the collapse of the Soviet Union and recession, the economy suffered resulting in lower living standards, unemployment and increased levels of poverty (Chernobyl: the true scale of the accident, 2005).
Estimations place the total number of deaths attributable to Chernobyl at around 4000. Figure 3 displays a rising rate of thyroid cancer among children, as a result of milk consumption from cows who had eaten contaminated grass. This caused iodine to concentrate in the thyroid gland and led to the increase in cases of thyroid cancer in children shortly after 1986 (Chernobyl: the true scale of the accident, 2005).Figure 3: Graph showing increased frequency (per 10000 inhabitants) of thyroid cancer in children in relation to radiation levels in Belarus (circles) and Ukraine (squares) before and after the Chernobyl incident (MOLLER and MOUSSEAU, 2006).
Conclusion
There are clear advantages to nuclear power, which is a substitute for fossil fuel energy, including the fact that it does not release greenhouse gases and provides a solution to the diminishing supply of fossil fuels. However, the Chernobyl disaster is a clear demonstration of the environmental, economic and health consequences that are borne by society when engineering decisions about the design and operation of a nuclear power plant are not carried out ethically, in the best interests of society as a whole. The disregard for the duty of the engineer to ensure public safety has led to catastrophic repercussions that were experienced for decades, leading to the question of whether the advantages of nuclear power outweigh the potential economic and environmental costs of a meltdown. This emphasises that the role of an engineer exceeds the sole knowledge of physics, mathematics and processes, it is crucial for engineers to adhere to the code of ethics throughout every stage from design to operation of a system in order to maximise the benefits and minimise the possibility of a recurrence of a disaster like Chernobyl.
References
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