Many people are filled with anxiety whenever nuclear reactors are mentioned. There has been heated debate over setting up of nuclear reactors. The heated debates confirm the fear that people have over a nuclear hazard. Memories of Chemobyl and Three Mile Island nuclear reactors accidents are still fresh and none would wish to have a repeat of the same. Although nuclear reactors are a major solution to energy problem in the world, it poses high risks. Nuclear hazard occurs in four main forms: criticality, direct radiations, inhalation and ingestion. Criticality nuclear hazard occurs in the procedure of nuclear reactor leading to massive release of radiation. Criticality accident can lead to massive destruction of life. Direct radiation nuclear hazard is the case an individual is exposes to radiations without the necessary protective gears. Inhalation or ingestion of radioactive substance also poses high risk to health. Nuclear hazards are threat to health and human existence, thus every effort should be made to avoid them.
Nuclear life cycles are associated with many radioactive emissions. Alpha rays, beta rays and gamma rays radiations form the distinguished bands of emissions from power plants. Gamma rays have very short wavelength usually dependent on electric field and magnetic field of its particles in a free atmosphere. The ionizing radiation nature of gamma rays makes it easy for the atoms associated with its propagation to undergo radioactivity in expose to light. In this assessment, we will explore the potential hazards and threats that people may encounter while working in a nuclear plant. Based on the study of Pressurized Water Reactor, We will also assess the various risks involved in conducting inspection and maintenance exercise in the plant (Pentreath, 1980, p. 23). By identifying and assessing the risks involved in servicing the plants, observations made on operating in dusty conditions is unusually entered and such areas form the basis of risk assessments. Inferring to the risk informs the mitigations strategies considered against international standards in the final part of this assessment (Trudeau, 1991, p. 1-5).
A Pressurized Water Reactor needs to be shutdown periodically to replace fuel and to undertake essential inspection and maintenance activities, this is done approximately after two years. During this time, a large team of specialist workers will be brought onto the site and these workers will enter areas of the plant that are not normally accessible. The mode of conduction of outages is an indicator of the general performance of a nuclear plant. An outage process involves inspection of the turbines, generators, transformers and doble testing, reactors and cooling systems are also checked. A look into the refueling operations at Arkansas Nuclear One (ANO) plant in the US reveals that the operation is preceded by two years of preparation; preparation for the next outage process begins as soon as the company completes the current one. The equipment used during an outage must be reliable and must be examined continually prior to the exercise since failure can lead to huge losses, both human and financial.
The refueling operation is a very subtle process as several risks are involved. The staff working in the rarely accessed areas of the plant is under a high risk of being exposed to harmful radiations and to avoid this, several practices have been put in place. Companies have designed robots to handle the refueling process; an example is the Leningrad Nuclear Power Plant (LNPP), a nuclear plant located in Russia. The machine undertakes online refueling unlike the human-operated procedure that is done after every two years, this is much safer and more efficient than the human-operated exercise. Use of gas masks by the staff during the procedure also reduces exposure to radiations.
Pressurized Water Reactor exploits nuclear sources to generate energy used in a variety of industries. Despite its significant contribution to development of different economies, the reactor needs careful handling during operations just as it demands many precautions to carry out occasional inspections and maintenance services. Since the first Pressurized Water Reactor (PWR), developed by Westinghouse Bettis Atomic power in 1982, several companies have embarked on similar projects of building PWR to complement the ever-growing energy demands in a rapidly industrializing world with a continuously narrowing technology gap. A typical Pressurized Water Reactor consists of three distinct cooling systems. In the Main Steam System are the Condensation Feeder water System and Reactor coolant although only the Reactor coolant inhabits radioactivity. The main challenges faced by these plant operators include nucleate boiling and thermodynamic pressure which must be mitigated for higher efficiency. The loops in the containment of a PWR normally transmit water at high temperatures and pressures; this justifies the constant monitoring and maintenance of these components done to minimize the degree of potential risks that may occur in the plant. In the PWR, water plays a critical role as a coolant and steam pressure that turns the turbines, which in turn drives an external generator, it therefore important to avail adequate water to control potential risks and hazards (Radioisotope Power System Committee, 2009, p. 16).
The multinational companies that build PWR include Siemens, Framatome and Mitsubishi. Upon installation they offer after sale services such as monitoring the productivity of the plants for their clients as they understand their technology better; this helps in their durability, maintenance, efficiency and modification aimed at conforming them to the new technologies. However, the experts are usually required to highly regard precaution measures to curb against the wide range of possible risks. Some of these risks, which predispose people to adverse health conditions, follow in the discussion bellow:
The operations of a PWR greatly depend on nuclear heating as the main input in its power production. In the entire nuclear life cycle, nuclear reactor forms just a small proportion of the full and half-atomic lifespan. In the reactor, uranium, coal and lithium undergo fusion through thermal decomposition. Over time, reprocessing of radioactive Uranium 238 and Uranium 239 isotopes may decompose in the reactor chamber resulting into gamma ray emissions by reflection on dust constituents. The air contaminated with this objects even in tiny sizes pose serious threats to the human gaseous system (Organization for Economic Co-operation and Development, 1997, p. 33). Therefore, specialists who enter the containment area of the reactant risks charred bodies if they lack highly protective covering. Safety equipment is therefore compulsory in any event of entering the processing room. Evidently, such environments inhibit proper air circulation because Uranium isotopes and Carbon compounds in the local atmosphere creates dense impure oxygen. This calls for the use of protective devices which are expected to mitigation inhalation of gases in the environment (OECD Nuclear Energy Agency. 2001, p. 1-7).
In recent studies conducted to determine the levels of contaminants on the surrounding of Coolant system reactants, high levels of arsenic and lead showed in the gradual degradation of the containment area posed the risks associated with exposure to gamma radon rays radiation. In the event that workers in the PWR expose themselves to these radiations in highly concentrated areas, it has the potential of denaturing their body cells. In particular, exposure to gamma rays often results into cancerous blood cells. The condition of the victim may worsen as the patient develops sickle cell anemia. Due to the complexity of managing these kinds of illness, the workers require precautionary measures to enable them ward off the fatal risks such as this in the plant. Since, uranium and carbon concentration in the concrete wall may gradually diffuse into the external areas of the containment, the possibility of inhaling air contaminated by the radioactive substances in particulate forms instantaneously suspended in the most accessible areas of the reactor, pose the potential risks of choking the workers. In the areas of high lead, cobalt, uranium and carbon particles concentration, choking may result into blood dehydration and unusual clotting then fatal death because the patient lacks oxygen threshold for effective survival. In minor cases, the specialists working in the PWR risk respiratory infections due to oratory exposure to gaseous contaminants in the plant most sensitive areas (Soares, 1997, p. 11).
Due to their frequency and wavelength, gamma rays can penetrate the reactor chamber and cause harmful effects upon close range radiation on the workers. In particular, exposure to these rays in a Pressurized Water reactor may result into serious health hazards such as development of cancerous cells. Any leak from the reactor chamber would allow gamma ray emission to the accessible areas where the plant specialists are operating. In the event of such an occurrence, the plant poses a potential risk hazard on the body parts of the workers exposed to the particular environment. So that thick materials such as concrete, water and stock bocks make the most suitable protection against the rays.
Gamma rays comprise of ionizing radiation that may pose threats even in the absence of major industrial activities. Therefore, in the absence of protective material that may protect the workers against any eventualities, negligible impurities may infiltrate any faulty components of the reactor and ionize the surrounding atmosphere leading to adverse effects to workers. In particular, it may produce foam in the reactor and impair vision as well as blind the workers. Exposure or contact with the ionized air formed by disassociation of the radioactive lead, zinc and carbon from coal readily combines with the air to form oxide compounds of the substances. The compounds then pose great danger to the specialists as they cause irritation and blisters on the body whenever contact occurs.
Prior to the entry of the workers in the site, the PWR owners need to take precautions to ensure that no fuels leaks or pores are left to remains carelessly in the operation area. This is particularly important in minimizing the risks of fire outbreaks. The chances of all the workers dying in case of an outbreak while they are in the plant are very high. In addition, an ambulance with adequate first aid equipment and health facilities must be availed at the site to facilitate the process of taking care of any emergencies and persons who may be injured in the process (National Academy of Sciences, 1980, p. 12).
Gamma rays have subatomic particles which have the potential of presenting grave risk hazards to humans when they get in contact with the body at the reproductive areas. Hence, according to research on exposure to the substances, the chemicals may cause genitival disorders in the lineage of the victim. The workers therefore risk life long illness with far reaching effects on their families, in the event that they make themselves obliviously exposed to the dusty chemicals in the coolant reactor room. Research shows that inhaling air contaminated with constituents of nuclear material such as uranium and zinc would inevitably lead to blood conditions such as leukemia. The company should also take care to desist from calling the same workers to come and conduct check up for plant each time it closes for inspection instead they should alternate to reduce the exposure time for the specialists.
Mineral elements of uranium, lead and carbon used in the plant sometimes contain traces of arsenic impurities. Over time, the impurities may infiltrate the reactor chamber and synthesize themselves on the irregular pores in the housing unit. Therefore, exposure to the dust material in the uncommonly accessed areas bears the potential risk of contaminating the blood of the workers. This may further lead to poor blood circulation system as the respiratory system inhibits oxygen flow because of inhaling impure air that has carbon impurities (OECD Nuclear Energy Agency, 2000, p. 103).
In addition, burns and scalds form a large proportion of the risks in nuclear reactors leading to death. Any slight exposure to coal in highly sensitive but accessible areas usually require adequate protection and extreme care in order to avoid contact with highly poisonous chemical reactors in the coolant reactor that also has the potential to tarnish the skin. Moreover, any possible leak from the reactor in the containment because of cumulated heat or pressure due to sudden changes in temperature may also constitute a serious threat. For example, in past incidences of nuclear reactor accidents, just some slight leak led to the exposure of workers to gamma ray radiation particularly from uranium 238 and carbon materials. In the case of specialists inspecting a PWR in order to a certain whether it would suit further human and economic activities, their conditions of possible dangers while working in the site may greatly increase due to combination of radioactive gamma ray radiation and heavy metals impurities in the air. Therefore inhaling the air may result into fatal death due to congestion of the respiratory tract by mineral elements present in the dust particles and the surrounding air (Wilson & Crouch, 1982, p. 44). There are different types of nuclear hazards that can occur during operations in nuclear plant; these include criticality accidents, direct radiation, inhalation and ingestion.
- Criticality hazards- this arises when a self-sustaining neutron chain reaction occurs without anticipation, this leads to an increase in neutron radiation. Such radiation is very harmful to workers and brings about induced radioactivity in the nearby areas. This hazard is not common since it can only be caused by few nuclear materials, e.g. enriched Uranium and Plutonium. A criticality accident leads to the release of harmful products (fission products) and include heat, radiation and radioactive matter. In the history of use of nuclear accidents, there have 21 deaths mostly caused by exposure to radioactive substances. Examples of such accidents include accidents at Los Alamos, New Mexico in June 1945 that occurred when enriched Uranium came into contact with water. Another accident occurred in 1999 in Japan at a nuclear facility in Tokai when plant operator accidentally placed Uranyl solution in a precipitation tank that was not meant for this solution. This led to the death of two workers from exposure to harmful radiation.
- Ingestion- this occurs when harmful nuclear materials enter the body through the mouth by eating or drinking food containing radioactive substances. Such material may occur in food materials or water. Food materials can be exposed to nuclear substances when they are harvested from an area or land previously containing such substances, an example is the presence of radioactive material in sheep that live around the Chernobyl area. The sheep were only recently declared free of radioactive substances, 24 years after the accident, the sheep fed on the grass around this area. Radioactive chemicals can also come into contact with water systems through surface run-off or the leaching process.
- Direct Radiation- this could occur if one is exposed to radioactive materials released in the atmosphere because of an accident, natural causes or those attributed to man e.g. terrorism activities. The released material could be deposited on a person’s body or clothing, such a person can be contaminated by these substances internally if the radiations enter the body. Precautions must be taken when handling radioactive material to avoid direct radiation, this can be achieved through use of robotics or special clothing and storage in specially made double-walled containers that prevent radiation leaks.
- Inhalation- this occurs when radioactive elements enter the body through the nose or mouth and in to the lungs. Exposure to such harmful substances can be through an accident, natural causes or man-made causes. Airborne radioactive substances are inhaled through nose and travel to the lungs where they cause mitotic deaths of cells. Higher doses of radiation can cause disintegration of cells within the lung tissues. Radiation through inhalation can be avoided by use of radiation masks.
Since production of electricity has to continue and the plant specialists must carry out regular refueling operations, observing mitigation measures is essential as it would minimize the risks that may be encountered. Usually, the workers consider the various ways through which they can remain safe during and after the exercise.
The first precaution involves proper dressing to protect the body from the risks of any exposure to the contaminated air and dusty conditions in the plant. Specialists take good care since they understand risks involved and that the dust presents a potential hazard that may cause serious dangers to the workers. Clearly, wearing heavy jackets with cotton lining to absorb the gamma chips in the non-accessible sections of the plant may absorb dust containing harmful radiation. Hence, the dressing has to take into consideration, protection from misty conditions as the carbonic gases mixed with zinc and uranium particles can end up accumulating inside the plant. The activity gear worn by the engineers on this particular exercise ranges from gas masks, helmets, overalls, boots and multi-layered jackets. The attire setup must include portable oxygen gas, as the workers may need to supplement a failed individual (Roberts, Green & Graham, 1991, p. 132).
Other protective measures include gloves and goggles that still form suitable defensive roles. These are important in safeguarding oneself from the harmful effects of chemical radiations of radioactive material such as Zinc and Uranium commonly used in PWRs.
Moreover, the workers can never ascertain whether all the heat has been dissipated completely when the plant is closed for refueling until the time of the actual exercise. Therefore, testing for high temperatures requires that the workers keep some safe distance from the coolant reactor system and in particular the reactor. In the process, they can use metal linkages to coordinate the test for heat and pressure consistent with the processes of the plant normal operation. The safe distance is important for two important reasons; to keep the workers from burns and scalds that my result from underestimating the temperature of the coolant system and the pressure of the reactor. Again, this keeps the workers against confusion and errors resulting from anxiety in the event of risks in the loops faults. In addition, the workers need to ensure that all the fire extinguishers disposable for the exercise can best suit the activity in the event of fire.
Another precautionary measure during the refueling operation emphasizes the need to minimize the time of refueling the plant. In case of any slight exposure, this measure would serve in limiting the risk of contacting diseases such as cancer and respiratory infections. Naturally, as specialists, sometimes one may find himself or herself exposed to the dusty conditions in the plant while refueling the PWR. However, with limited time for exposure to the prevailing condition, the workers can only inhale a small proportion of the contaminated air (International Atomic Energy Agency, 1988, p. 2).
Safety is given a very important place in design of the reactor. Reactor Protection System is designed to ensure that any potential risk is identified at the right time in order to allow hazard mitigation to be implemented. Engineering Safety Features Actuation System is designed using logic circuit that allows potential risks to be identified and avoided in good time. The logic circuit is able to activate various components whenever potential risks are senses. For instance, loss of coolant would activate.
Before undertaking a refueling process, Radiation Protection Agencies (RPAs) must first inspect the site to check whether the radiation levels are harmful to the workers. Apart from checking the radiation levels, RPAs train staff on how to reduce the risks involved in the refueling operation. International bodies such as the Health and Safety Executive (HSE) must accredit agencies that offer advisory services.
Features of International Standards in the effectiveness of Mitigation Measures
International guide has significantly informed the threshold distance precaution in dealing with heat and pressure intensities in a nuclear reactor. Such guides have incorporated the ALARP (AS Low As Reasonably Practicable) policies to lessen the risks of radiation exposure or any other risks that may occur during the refueling procedure. The ALARP principle acknowledges that some exposure levels are acceptable in nuclear plant operations but this must be as minimal as possible. It is based on the fact that any level of exposure can negatively affect the health of the workers through such diseases as cancer and that the chances of occurrence of such negative effects increase with cumulative lifetime doses. Major strategies of minimizing radiation exposure during refueling include use of shielding clothing, minimizing the time spent in the plant and increasing the distance between radioactive elements and the workers. However, the principle fails to forecast the consequence of direct exposure to minimal radiation. For instance, it claims that when the risk of exposure occurs to a lesser degree, the negative effects would also be less (Okrent, 1981, p. 67). The ALARP principle is outlined under the HSE (Health and Safety Executive) safety act and is normally referred to as ALARA (As Low As Reasonably Achievable) in some publications.
Regulation limits have been set by the ICRP (International Commission on Radiological Protection) and other organizations on the allowable radiation levels on PWR workers. Radiation level is measured in Sievert (Sv) which is equivalent to 1 J/Kg (gray) or 1 m2s-2. The exposure limits for one calendar year for nuclear plant workers are as outlined below:
- For the whole body, the maximum radiation levels should be 0.05 Sv;
- For the hands and forearms, maximum levels are 0.50 Sv;
- For the skin on the body, maximum levels are 0.50 Sv; and
- The maximum dose on the eye is 0.15 Sv.
Special groups for whom the maximum radiation levels will be lowered are pregnant workers and those below the age of 18. The exposure levels must be minimized in relation to the ALARP principles.
The measure recommending for availability of sufficient firefighting equipment and additional protective gear for protection against heavy metal suspensions inside the reactor all improve the efficiency of the refueling operation. The Nuclear Regulatory Commission (NRC) which ensures safety of workers from the harmful radiations in nuclear plants recommends the use of protective clothing and the use of respiratory apparatus during the refueling procedure. The policy on protective clothing is a reinforcement of the ALARP Act aimed at minimizing workers’ exposure to radiations during refueling operations (Primack, 1975, p. 15).
Another mitigation procedure set by the international guidelines is that of proper storage of spent fuels after the refueling operation. Spent fuels have the highest radiation levels among all nuclear wastes and must be safely stored to reduce exposure to the plant workers. This includes extremely radioactive byproducts of the fission process. The NRC recommends that such fuel should be stored in specially made pools located next to the reactor, these pools are filled with boric acid which absorbs part of the radiations. The fuels must be monitored since as they may be placed close to one another and create a criticality accident as earlier discussed, neutron-absorbing materials can be placed between the rods to reduce such a risk. Another storage method is the dry storage mechanism where the rods are placed in thick casks or underground concrete tunnels. These are normally used when the fuel rods have been cooled in the boric acid pools for roughly 5 years (Cho, & Jones, 1995, p. 23).
Risk and safety management
In order to remove the valve safely, the following eight steps would be followed logically.
- Workplace hazards
In the process of removing the valve, we have to recognize the hazards posed by inappropriate procedure of handling the system. For instance, haphazard removal may result into the pilferages leading to fuel ignition thus causing fire accidents. At high temperatures, combination of oxygen and disulphide may result into explosion due to the fusion energy involved in combining the two chemicals. While the presence of oil hydro carbon may lower the temperature of combustion, it cannot stop the combined substances from burning completely. In case of the risk occurring as the reaction of disulphide on oxygen at reactor temperature may cause fire, determining the likelihood of the inflammatory substances causing explosion forms the first step accompanied by regulating the number of technicians getting into the reactor to fix remove the valve. This way, it becomes practical to apply the techniques of risk assessment.
- Systems for the control of workplace hazards
Systems control of the hazards involves using the assessment criteria in the first step to establish the level of control required for a worst case scenario of the risk. So that removing the valve under lathered or cushioned channel at the point where it occurs would prove more ideal than valve substitution techniques. In addition, using engineering controls accompanied by personal reduction methods to minimize exposure to fumes from the chemicals chambers would constitute another set of suitable control in this kind of closed environment.
- Task Risk Assessment
Depending on the level of risk assessment, the matrix used would suffice to fix the inflammable scale of the substances with the correct assessment. Conventionally, such an assessment would make use of security 3 based on the 3rd column likelihood. In the this matrix, the likelihood of leaks creating explosion is matched with security measure such as lathering and intensive foiling while minimizing the concentration of oxygen in its channel. Similarly, the protection devices must take into consideration the viscosity of the two primary chemicals.
- Permit to Work
Due to the number of fatalities and risks involved in a reactor system of this nature, work permits are critical at this stage in addressing the potential problems of machine failures. To a great extent, mitigating against the potential accidents involved in the valve replacement exercise that is classified thus as maintenance work makes it necessary to take permit to work. Permit to work usually proves the organizational competency to meeting standards set out by international standards for mitigation measures. Because the valve replacement involves access into risky and uncommon places in the chamber, PTW validates the actions of plant operator in authorizing individual technicians to enter into some restricted areas such as the oil tank pipe and assess the connection tube.
- Behavioral safety systems
Since PTW may be prone to error, adopting behavioral safety systems help to back up the systems control techniques and the requirement of PTW. Behavioral training that forms the primary stage in behavioral safety help to encourage people to take professional responses to unsafe conditions while removing the valve. Since it is normal to escape danger, Behavioral safety would use some definite criteria of averting any possible crisis in the machine. For instance, Behavioral training increases individual response mechanisms.
- Hazardous Chemicals / Goods
Such practices also increase the individuals’ natural capacity to predisposed risks in working environments such as valve removal and replacement. All hazardous chemicals /goods have international labeling that can easily understand by technical experts. To avoid explosive substances from causing accidents in the process of removing the valve, the technicians need to understand the flow of the elements in the chambers and keep in mind always. The hazardous chemicals go together with the final temperature of the chamber. On the other hand, the shelf life of the chemicals used in any way while removing and replacing the valve matters in the event of reactivity as the disassociation of disulphide in the presence of condensing oxygen.
- Personal Protective Equipment (PPE)
The personal protective equipment component of the exercise forms a critical aspect of the experts undertaking to replace the valve. The equipment protects against corrosive material that has the ability to destroy skin. Even eye contacts with some of the materials that may concentrate the area inform of foams and fumes necessitate adequate protective equipment.
- Hazardous area classification
Hazardous area classification applies to the knowledge of areas with high concentration of chemical channels bypasses in the environment. The likelihood of causing an accident while operating in such areas is high due to the chemical composition of the substances used. In hazardous area classifications, it is important to note that some of the chemicals may have passed their days of exposure to open air. Such chemical pose higher reactivity to the liquid substances flowing through the processing chambers.
Companies involved in the manufacture of PWRs have made commendable efforts in inspecting and maintaining the plants. These efforts create safe working conditions in the plants favorable for working as they minimize possible panics of the employees due to risks occurring. Regular inspection to seal all the possible leaks that would cause adverse health effects on the workers by the plant specialists however should not expose the specialists’ lives to the dangers of polluted air in from the coolant reactor system. The specialists must ensure that they observe the standard requirements on their attire the exercise (Jaeper, 2001, p. 89). Lathered jackets should be included to mitigate exposure to the harmful effects of radioactive gamma rays. In as much as the lives of the specialists are concerned, the management has to confirm that all the loops are leak proof to minimize risks of death due exposure of the workers to gases contaminated with radioactive substances such as lithium, uranium and titanium used in the plants. While this assessment concentrates on the risks and risks involved in the use of PWR it should be noted that radioactive materials only pollutes water in the primary loop and not the one in secondary loop; this is because the primary loop is completely separate from the turbine loop (National Research Council (U.S.) & Committee on separation Technologies, 1996, p. 1-9). The risk hazards associated with PWR are grave, they can cause cancer, sickle cell, and genetic disorders that can last through generations, it is there fore imperative that exposure of the gases is minimized and exposure time of the specialists reduced by alternating them. Otherwise, they are of great importance in the contemporary world which requires regular propulsion for their aircraft carriers and should be maintained regularly to contain hazards (Mannan, 2005, p. 4).
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