Risk Management: Safety Case

Scope of the Case

There are various ways of explaining the concept of a safety case. However, a safety case may be formally defined as “A documented body of evidence that provides a convincing and valid argument that a system is adequately safe for a given application in a given environment” (Regester 2009). A safety case is often termed as a ‘live document’ precisely because in a safety case, the emphasis is more on the application of the case than on the process to develop it.

The primary objective of designing the safety case for the development of a supercompactor plant on a nuclear licensed site is to successfully demonstrate to all the concerned stakeholders that the potential hazards associated with the development of the supercompactor plant have been identified and major accident risks have been evaluated. It should be able to assure the target audience that adequate measures have already been taken in advance or will be taken to mitigate the risks of major accidents. Controlling major accidents/ hazards should be an important concern (Lambert 2008).

The safety case under consideration will further demonstrate to the relevant stakeholders including the public that all the major HSE (Health, Safety and Environment) risks associated with the operation of the supercompactor are both tolerable and reduced to as low as reasonably practicable (ALARP) (Koontz & Weihrich 2004).

Moreover, the safety case should be designed in a manner so as to ensure that it gets the necessary statutory approval for the development of the supercompactor plant.

Information required to develop the safety case

The following information has to be obtained in order to develop the safety case under consideration:

1. Understanding of the working of the different components required to develop a supercompactor plant such as the compactor press, the drum-handling mechanism, service module, liquid waste collection sump etc.
2. Information regarding the role of the supercompactor in treating radioactive wastes. Risks associated with the operation and management of the radioactive wastes must be identified (Hutter & Power 2007).
3. Information regarding the conditioning methods to be employed after treatment of the radioactive wastes for its successful management in the form of transportation, storage and final disposal.
4. Information regarding the risks associated with the management of the radioactive wastes. Here, the role of proper and elaborate packaging in averting fatal accidents related to transportation of radioactive wastes must also be considered.
5. Understanding of the major accident hazards leading to the emission of radioactive materials in large quantities that cause serious damage to human health, safety and environment (HSE) factors (Woodhead 2008).
6. Information regarding the safety considerations that must be taken into account for ensuring safe working conditions for the workforce such as fire protection and detection, communication systems, Integrated Control Systems (ICS), Closed Circuit Television (CCTV) etc.
7. A clear understanding of the concept of mobile supercompaction system which is operated manually and stationary supercompaction system which is computer controlled. Effectiveness of both the systems and the safety concerns associated with them are to be analyzed.
8. Information regarding the various statutory safety requirements and standards that need to be complied with in order to obtain permission to develop the supercompactor plant (Watson & Noble 2007).

Proposed safety documentation for obtaining safety clearance for development of the supercompactor plant

Nuclear safety is a synthesis of a number of complementary and overlapping factors. In the present scenario, the design, construction, commissioning and operation of the supercompactor plant on a nuclear licensed site would require necessary safety documents for obtaining safety clearance. The relevant safety documents, in my opinion, would include the following:

1. Description of the nuclear site where the supercompactor plant is to be developed.

This would involve a description of the concerned site in order to facilitate a better understanding of the features of the site including its present condition, the probability of the occurrence of natural evolution and the occurrence of natural and man-made events. The main objective is to assure the target audience that the site is safe and suitable for the development of the supercompactor.

2. Environment description including the external equipments to be used interfaces with the other safety cases, failure modes, hazardous or safe states of the equipments used and the potential changes (Smith 2009).

This document would be beneficial in assuring the relevant stakeholders that some of the hazards as well as hazard potentials have been identified thoroughly. Moreover, identification of the failure modes would help in eliminating and reducing the chances of failure. An analysis of the failure modes also helps in obtaining functional safety certification of the equipments used.

3. Documentation of the safety requirements which would include the safety functions to be delivered and the anticipated changes.

This document would assure the target audience that the development of the supercompactor plant is in compliance with the existing safety criteria. Furthermore, it would emphasize on some of the safety attributes like reliability, availability, maintainability etc.

4. Description of the system architecture of the supercompactor plant which would include the organization of the system, the subsystems, interconnections among them, subsystem derived functions, integrity levels, design and contents of the system and evidence. Defence in-depth strategy is to be implemented along with adequate safety margins (Regester 2009).

This would be beneficial in demonstrating that the design and contents of the supercompactor conform to good nuclear engineering practices and sound safety principles. The defence-in-depth would help in preventing accidents and if not possible, in mitigating the consequences and acceleration to more serious outcomes.

5. Designing the supercompactor plant for ensuring safety.

“This would demonstrate to the concerned stakeholders that these safety measures taken to ensure the safety of both the workforce and the public helps in reducing personal injury, loss of time, damage to property which, in turn, reduces medical costs, insurance premium and creates a positive impact on the project schedule” (Peijuan 2009).

6. Ensuring the safety of the supercompactor plant at the construction, commissioning and operation stages

This would demonstrate to the relevant stakeholders that Construction Safety, Commissioning Safety and Operational Safety of the supercompactor plant are taken care of. The issues of Construction Safety include electric shock, confined space, fire, toxic substances, vehicle traffic etc. The issues of Commissioning Safety would include lockout/ tag out procedures, energizing equipments, energizing systems, noise levels etc. Operation Safety would include issues like maintenance hazards, maintenance access, hazardous process gases, rotating equipment protection etc (Peijuan 2009).

7. Documents supporting the long term maintenance of the supercompactor plant

This document would provide evidence to support the long-term maintenance of the supercompactor plant. The factors that would support long-term maintenance like appropriate regulatory documents, like plant safety, economic viability, effect on environment in the long run, application of ageing management activities and programs would be explained in the document (Nottage 2009).

8. Review of the safety assumptions at the various stages of the development of the supercompactor with the help of the safety case tools.

This would demonstrate to the relevant stakeholders that the safety case tools have been applied to ensure that all the possible risks and hazards have been identified and assessed and proper controls and recovery measures have been adopted.

9. Document substantiating evidence of quality and safety management

This document would demonstrate to the relevant stakeholders that the aspects of safety and quality have been effectively managed with the help of QA audit results, safety audits and other evidences. The Quality Assurance (QA) audit is an effective management evaluation tool which verifies whether the implementation of the particular program is in compliance with the prescribed QA program (Lummus 2008).

Identifying the sections of one of the proposed safety documents and providing a brief summary of each

Of all the safety documents that have been proposed in this context, the document ‘Designing the supercompactor plant for ensuring safety at the job site during construction, commissioning as well as final plant operation’ is selected for further elaboration (Pickett 2008).

Designing of the supercompactor plant for safety

The design stage focuses on the reduction of the possible health and environmental hazards resulting from constant emission of radioactive elements. Its primary concern is keeping the exposure of the workforce as well as the environment to constant doses of radioactive emission within tolerable limits and to as low as reasonably practicable (ALARP). To this end, the design phase incorporates certain controls and measures to be adopted to ensure the safety of human health as well as environment. E.g.

“most of the waste handling is to be done by the operators remotely by viewing the waste through shielded windows and closed circuit television. Equipments like conveyer belts and robotic manipulator are to be employed for handling the wastes as well as sorting the contents” (Regester 2009).

These measures would considerably help in reducing human intervention in these activities.

Furthermore, this document also takes into account the administrative controls to be implemented. These include imparting training to the employees, limiting the exposure of wastes in enclosed systems and reducing the time required by the employees in handling the wastes (Peijuan 2009).

This document may be divided into the following sections

Waste retrieval

Waste retrieval forms an important part of the entire operation as it involves expert handling as well as exposure of the workforce to radioactive wastes. It, thus, involves taking a number of precautionary measures of safety.

Thus, this section would provide information on:

1. The sound engineering principles applied in designing the heavy equipments to be used for retrieval and transfer of wastes.
2. The technical knowledge and skills of the workforce essential for handling the radioactive wastes.
3. The design of the liquid waste collection sump with level alarm
4. Air extraction/ filtration systems to be used to control the emission of airborne dusts and contaminants (Nottage 2009).

Waste characterization

Waste characterization is the subsequent step of waste retrieval. During this phase, the contents of each and every box are opened for examination. Handling of the wastes and the modes of their storage are determined on the basis of the type of wastes retrieved. E.g. soil is stored in a particular area while metal debris in another area (Loosemore 2009).

This section provides information on:

1. Waste characterization equipments to be used like gamma spectrometry, headspace gas sampling etc.
2. Technical knowledge and skills of the workers involved in the handling of waste containers during the waste characterization process (Smith 2009).

Waste processing and packaging

Waste processing and packaging forms a crucial step in the entire process. Waste processing and packaging is done in an area which is divided into different zones. Zones are divided taking into account the considerations of plant operations and worker safety.

This section would provide information on:

1. The mechanisms adopted to avoid leakage of radioactive materials such as the construction of concrete walls and viewing windows
2. Glove boxes designed to ensure that there is no possibility of flow of radioactive materials
3. Packaging materials used to ensure safe packaging, transportation and disposal.
4. The electrical and mechanical designs to ensure these are leak proof.
5. Safety considerations that are incorporated to ensure safety of the workers employed at different levels of waste processing and packaging such as fire protection and alarm, access control, communication systems etc (Lambert 2008).

Summary report

“The creation of a summary report is crucial in assessing that the effectiveness of the safety concerns, the major accident hazards associated with them and suggesting design modifications as and when required” (Woodhead 2008).

This section would provide information on:

1. The hazard identification (HAZID) and risk assessment tools employed to evaluate the potential risks, hazards associated with the process and modify the design accordingly
2. The assessment of the costs to be incurred in the process
3. Design modifications and changes that have been incorporated as per the assessment (Koontz & Weihrich 2004).

Identification of three aspects of generic safety case requiring review for site specific factors

The components of a safety case vary according to the system to be applied to a particular situation. However, there are certain elements that form the basis of most of the safety cases.

Some of the essential components of a generic safety case may be subject to review as the development of a safety case is dependent on a number of factors specific to the particular application. Site specific factors are also to be taken into consideration in the formulation of a safety case. In my opinion, three aspects of a generic safety case that require review for site specific factors are as follows:

1. Conformation to the standard safety requirements including the safety functions, and incorporation of the safety attributes of reliability, availability and maintenance is likely to be site-specific.

This aspect is site specific since safety requirements and standards depend, to a large extent, on the characteristics of a site. Changes cannot be anticipated in most of the cases as natural changes are unpredictable by nature. Moreover, the features that are considered the attributes of safety in a particular case may not be considered so in some other situation. The determination of safety attributes is specific to the site. E.g. a nuclear licensed site may meet most of the requirements but may lack in the availability of water resource (Watson & Noble 2007).

2. Management of the radioactive wastes as per the design described in the approved safety case and safety assessments

Management of radioactive wastes involves the processes of storage, transportation and final disposal. Proper disposal of radioactive wastes is necessary for ensuring the health and safety of man and environment. Disposal of the radioactive wastes is largely dependent on the specific site. The features of a site as well as the facilities offered vary and hence, the design, construction and operation of the radioactive waste disposal should be in accordance with the specificities of the site.

3. The safety assessment tools incorporated in a safety case to identify the potential hazards as well as the risks of occurrence of certain major accidents can also vary according to the features of the site (Hutter & Power 2007).

The safety case needs to be assessed for identification of possible accidents/hazards and potential occurrences of risks. The safety assessment tools commonly used are hazard identification (HAZID), consequence assessment, frequency assessment through fault tree and event tree analysis, quantitative risk assessment etc. Specific tools work best in specific situations. Site specificity is a determining factor in the incorporation of specific tools. While designing a safety case for a site more vulnerable to unexpected natural events, the frequency assessment and consequence assessment tools may not be appropriate (Hutt and Speh 2008).

Proposing a high level strategy for managing the changes of one of the above-mentioned aspects to the safety case

Of the above three aspects, I would select the aspect ‘management of the radioactive wastes as per the design described in the approved safety case and safety assessments’ for proposing the change to be made based on the nuclear site and developing a strategy for incorporating this change into the safety case.

The radioactive waste management is basically concerned with the management and disposal of radioactive wastes emitted by the nuclear power plants. High level radioactive wastes are treated, conditioned before they are ready for subsequent management. “Management of the radioactive wastes includes transportation, storage and final disposal” (Woodhead 2008). High level radioactive wastes are usually stored in repositories till it decays after hundreds of thousands of years. This calls for extremely reliable geological deposition of wastes in repositories as the substances are highly poisonous (Woodhead 2008).

However, ensuring the safety of human as well as environment during the disposal of radioactive wastes is a major challenge as the disposal techniques are employed irrespective of the features of the nuclear site. As a result, the stability of the entire waste disposal process has been a matter of serious concern in most situations.

One of the serious issues that require further attention is the appropriate technique to be adopted for the release of the huge amount of heat generated from the stored nuclear power waste.

With respect to the site under consideration, this has emerged as a matter of serious concern as no proper place can be identified from where the heat generated from the stored radioactive wastes may be released. This requires a lot of research as the heat generated from these highly poisonous substances may lead to health, safety and environment (HSE) hazards (Holmes 2007).

To combat this problem, the concept of “Multibarrier Monitored Retrieval Storage” Gordon 2008) (MMRS) has been developed and has even been put to use in certain situations.

The concept of MMRS is characterized by two important features. One is that the volume of waste involved is relatively less. Another aspect is that it requires comparatively less workforce. However, the perennial problem of constant waste management cannot be addressed through this technique.

In the MMRS technique, the idea is to create multiple barriers to control the release of heat emanated from the repositories. “The cladding barrier is usually made of zirconium though stainless steels barriers are also used sometimes. The final barrier will be in the form of solid containers whose outer surface can be monitored” (Lummus 2008). Monitoring of the radioactive wastes can be done from outside with the help of automated equipments. This would a help in providing accuracy and precision in the readings by reducing the possible human errors.

This MMRS technique, if applied to this particular nuclear site, would reduce the problem of releasing huge amount of heat from stored radioactive wastes.

This change in the technique of disposing radioactive wastes released by nuclear power plants can be made to this particular safety case. This can be done by demonstrating the fact that the choice of the waste disposal technique is to be made in accordance with sound engineering principles applicable to a particular site. Since the health and safety of human as well as environment is of primary concern, it is unjustifiable to abide by a set technique when better alternatives prevail. In this context, references may be made to the nuclear site at Oklo, Gabon in West Africa, Brazil and Koongarra ore body in Australia to prove that the MMRS technique, if applied to appropriate nuclear sites, can go a long way in preventing future disasters (Lummus 2008).

Reference list

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Holmes, A., 2007. Risk Management. New York: John Wiley & Sons.

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