Accidents Hazard evaluation

What-If/Checklist analysis identifies hazards, possible accidents, qualitatively evaluates tlie consequences and determines the adequacy of safety levels. It is described in CCPS (1 )92 ). 

These accidents would have been prevented by 1) adequate process safety design, 2) proper-procedures to prevent the initiation, 3) hazard evaluation procedures to identify and correct Iia/.ards hc fure accident occurrence, and 4) containment systems to prevent release into the aimosphci c,... 

After tlie system has been defined, a hazard evaluation technique can be used to identify different types of hazards within tlie system components and to propose possible solutions to eliminate the hazards. This topic is treated in more detail in the next t o chapters. These procedures are e.xtremely useful in identifying system modes and failures that can contribute to the occurrence of accidents diey should be an integral part of different phases of process development from conceptual design to installation, operation, and maintenance. The hazard evaluation tecliniques tliat are useful in tlie preliminary and detailed stages of tlie design process include ... 

The purpose of a what-if analysis is to identify hazards, hazardous situations, or specific accident events that could produce an undesirable consequence. The what-if analysis is described in detail in Guidelines for Hazard Evaluation Procedures (CCPS, 1992). 

The Seveso and Duphar accidents could have been avoided if proper containment systems had been used to contain the reactor releases. The proper application of fundamental engineering safety principles would have prevented the two accidents. First, by following proper procedures, the initiation steps would not have occurred. Second, by using proper hazard evaluation procedures, the hazards could have been identified and corrected before the accidents occurred. 

Snee, T. J., "Incident Investigation and Hazard Evaluation Using Differential Scanning Calorimetry and Accelerating Rate Calorimetry," J. Occupational Accidents, 8 (1987). 

Hazard Evaluation—The analysis of the significance of hazardous situations associated with a process or activity. It uses qualitative techniques to pinpoint weaknesses in the design and operation of facilities that could lead to accidents. 

The necessary emergency measures to be taken following accidental spillage or poisoning have to be assessed, and national fire control legislation will also apply. Exceptional risks to the community surrounding a chemical plant may have to be evaluated under major accidents hazards legislation, such as the European Community (EC) Seveso Directive [4]. 

Procedures for Hazard Evaluation and Testing Accident and Loss Prevention... 

The purpose of reviewing and assessing major accident hazards is to help understand the major safety threats to the asset and to provide information to take forward for further evaluation. This is a high-level review intended to reveal the major threats to the safety of the asset and personnel. The scope of this study is to identify the principal threats to the safety of the asset in normal operating conditions. 

To prevent the undesirable consequences of accidents, hazards that can lead to accidents must be identified. Effective hazard identification and control require a systematic, comprehensive, and precise analysis of the process system and its operation. Once hazards are recognized, the adequacy of the mechanisms to control the hazards is evaluated. If control mechanisms do not exist or are inadequate, this must recognized and actions recommended. Several of the benefits of using a HAZOP are the ... 

The intention is to evaluate the potential impact of the organization s ability to control accident hazards and to ensure that there are no adverse effects on the organization s ability to deliver quality products and services to its customers. 

Structures, systems, and components (SSCs) that are important to safety and that are identified as Safety SSCs are based on criteria contained in DOE-STD-3009 (p. xix) and the results of safety analyses, which determine the safety contributions of specific SSCs. The degree of consequence mitigation is the basis for identification of Safety SSCs and associated Safety Functions". These Safety Functions are the essential performance requirements that are imposed on Safety SSC s which maintain the consequences of accident scenarios within bounds that are described in the SAR accident analysis. The use of the term Safety Function will be limited to these essential performance requirements in this SAR. While many SSCs provide a material safety benefit and could be considered to perform a safety function, SSCs that are not relied upon to effect an acceptable outcome will not have an associated Safety Function as the term is used in this S/VR. Safety SSCs and associated Safety Functions are based on the results of hazard evaluation and accident analysis described in Chapter 3, and are specifically identified in Section 3.3.2.3. The specific safety functions important to safety are described in Chapter 4, and form the basis of the derivation of Technical Safety Requirements presented in Chapter 5. 

The hazard analysis considers the complete spectrum of accidents that may occur due to operations at the facilities, analyzes potential accident consequences to the public and workers, estimates the likelihood of accidents occurring, identifies and assesses associated preventive and mitigative features, and identifies bounding accident scenarios. Subsequent accident analysis evaluates the bounding accident scenarios for comparison vwth DOE Evaluation Guidelines. The scope and format of this chapter is consistent with DOE-STD-3009-94. 

As indicated in Table 3.3-6, the risk to the public and the environment from the internal isotope production and radioactive material storage accidents was assessed to be minor or very minor, and the application of a graded approach to the accident analyses is appropriate. Since no unique accidents are assessed to be of high risk, representative accidents are chosen to bound a number of similar accidente and form as complete a set of bounding conditions as possible to represent the accident risk to the public and the environment. Accidents from the hazard evaluation with the greatest potentiai consequences to the public are emphasized in the DBA selection process. 

In all of the SCB fire scenarios, the fire was assumed to envelop the liquid dissolution cocktail in the process containers during or following UO2 dissolution and release of radioactive material to the SCB and Zone 1 ventilation systems. While dilution of combustion products is expected to preclude damage to the ventilation system, an unmitigated release bounds the scenario where the filters or the ventilation system itself have been degraded or compromised as a consequence of a fire. The frequencies per year for such an accident developed in the event tree analysis shown in Appendix 3E.3 agree with the frequency for an extraction SCB fire as assessed in event CP-7 in the hazard evaluation (Appendix 3C). 

---