Risk assessment existing plant

Transportation should be considered when assessing risks associated with planned or existing plants. The design of new chemical processing units should include at the earliest opportunity a qualitative or quantitative risk assessment of the whole system including production, use, and transportation in order to minimize overall risk. A brief discussion of the inherent safety aspects of transportation is included in Chapter 5. 

Capital Project Review and Design Procedures (for new or existing plants, expansions, and acquisitions) Appropriation request procedures Risk assessment for investment purposes Hazards review (including worst credible cases)... 

The harmonization of the regulation of plant protection products throughout the EU has resulted in harmonized data requirements for occupational, bystander and worker exposure assessment. These requirements are outlined in Annex III of Council Directive 91/414/EEC. This annex lists product-related exposure data requirements and, consistent with the tiered approach outlined above, provides some advice as to when different data are required (Harney, 2000). An estimation of operator exposure, using, where available, a suitable calculation model, must always be made and reported. Actual exposure data must be provided where the risk assessment indicates that a health-based value is exceeded or where no appropriate calculation model exists to estimate exposure. 

Recommendation 5. The Army should maintain conservative chemical demilitarization exhaust stack and in-plant airborne agent exposure thresholds. If current limits for exposure to stockpiled chemical agents are further reduced, the Army should not further reduce existing monitoring thresholds unless chemical agent monitors can be made both more sensitive and more specific so that lower thresholds can be instituted without significant increases in false positive alarm rates or unless health risk assessments demonstrate that lower thresholds are necessary to protect workers or the public. 

Birds and mammals may be exposed to toxic effects of active substances following the field use of plant protection products. In current ecotoxicological risk assessments for pesticide registration endpoints, of toxicity tests are compared with estimations of the expected exposure of wildlife species in the field. From the data on toxicity and exposure, a risk quotient (e.g., TER Toxicity Exposure Ratio) is calculated and compared to safety factors (e.g., 10 for acute risk). If the quotient is larger than the safety factor, the risk is considered to be acceptable. On the other hand, if the quotient is below the safety factor, a possible risk is indicated and further refinement of the input parameters is necessary to show that no risk for wildlife species will exist when the substance is applied under practical field conditions. 

All employed dryers must be equipped with clear and comprehensive operating manuals prepared jointly by the equipment supplier and the plant operating management. The manual should be learned by the operators, who are to be trained in recognition of hazardous situations and risk assessment with the material being dried. Very useful techniques, known as Hazop (hazard and operability studies) and Kazan (hazard analysis), may be applied successfully in both new and existing processing plants [39,40]. 

Probabilistic safety assessment (PSA) results of new nuclear power plants (NPP) show much lower risk compared to risk of existing nuclear power plants. 

The above deals with risk assessment in respect of existing plant and premises. However, risk assessments at the design stage are becoming increasingly demanded. These require specialist knowledge of and experience in the operation of the particular plant and are often carried out by multi-discipline teams. 

For an existing plant, the PSA should be carried out either as part of a periodic safety assessment or to support the safety case for proposed modifications. Although the requirements for the PSA remain the same, the database may be different. Moreover, depending on the age of the facility, the remaining operational lifetime, the cost of proposed modifications and other related considerations, there will be differences in what changes it would be reasonable to implement to reduce risk. 

The results of 74 Level 1 probabilistic risk assessments for operational events at U.S. nuclear power plants are summarised in this report. The summary provides a good indication of the frequency dominant accidents in existing power plants and the ranges of predicted vulnerabilities to these accidents. There is an analogous effort now underway to address risk from events initiated by so-called external events such as earthquake, fire, and flooding. Such comprehensive studies of risk during shutdown and low power operations are not now planned. 

Task-based risk assessments be made of existing equipment, as directed by the Plant Safety Review Board. 

Even though the assessment of aspects of the human factor in SCOR is preliminary (it focuses on degraded operation but similar analysis is required for normal operation, maintenance and testing), the results confirm that design options for the SCOR concept may lead to a considerable simplification of operation and to a possible improvement in human reliability in operation. This result appears particularly valuable since probabilistic safety assessments (PSA) point to the major contribution of human failures to the global risk in existing nuclear plants. 

---