Original Design Criteria Research Articles

Seismic individual plant examination of external events of US nuclear power plants: insights and implications

As part of the implementation of the severe accident policy, nuclear power plants in the US are conducting the individual plant examination of external events (IPEEE). Seismic events are treated in these IPEEEs by either a seismic probabilistic risk assessment (PRA) or a seismic margin assessment. The major elements of a seismic PRA are the seismic hazard analysis, seismic fragility evaluation of structures and equipment and systems analysis using event tree and fault tree analysis techniques to develop accident sequences and calculate their frequencies of occurrence. The seismic margin assessment is a deterministic evaluation of the seismic margin of the plant beyond the design basis earthquake. A review level earthquake is selected and some of the components that are on the success paths are screened out as exceeding the review level earthquake; the remaining ones are evaluated for their seismic capacity using information from the original plant design criteria, test data and plant walkdown. The IPEEEs of over 100 operating nuclear power plants are nearing completion. This paper summarizes the lessons learned in conducting the IPEEEs and their applicability to nuclear power plants outside of the United States.

Common Causes of Retaining-Wall Distress: Case Study

Poor performance of cantilever retaining walls has been observed at many sites in Southern California during postconstruction investigations. It was found that, in many cases, distress occurred because the walls were constructed outside of the original design criteria. Our studies indicate that during mass grading development projects, walls are frequently designed using soil parameters obtained during a preliminary soil investigation. When actual construction of a given wall begins, conditions encountered sometimes vary dramatically from what was originally expected or intended. Unless the soil design criteria are reevaluated and modifications made to the original wall design, an inadequate wall may be constructed and over time according distress will occur.

Equity of water distribution along secondary canals in Punjab, Pakistan

Equity in the distribution of irrigation water has long been an operational objective for the management of the large canal systems in the north and west of the Indian subcontinent. How well that operational objective continues to be met is the central concern of the research reported in this paper. Detailed studies of canal operations were conducted on three distributaries in the Lower Chenab Canal system in Punjab Province, Pakistan. Mananwala and Lagar Distributaries off-take in the head reach of the Gugera Branch Canal and Pir Mahal Distributary is at the very tail of this Branch. Flow conditions for these distributaries and of selected outlets served by each were measured daily throughout 1988, and data were converted to discharges. These field observations show that discharge variation at the head of distributaries greatly exceeds the original design criteria. The data also indicate that two design assumptions for outlets are no longer valid: continuous full supply water level in the distributary and outlet modular flow conditions. Field measurements confirm that the distribution of surface water among the outlets of all three distributaries is substantially inequitable. Outlets in the channels' head reaches commonly draw 3 to 6 times greater share of total supplies than do tail outlets. Although all three selected distributaries are perennial canals, some outlets remained dry for up to 90% of the total operational days in a year. Finally, evaluation of field data also shows that better operational procedures at the distributary level can substantially improve water supply conditions in the tail reaches.

Development of geotechnical experience on the North West shelf : Khorshid, M S E D Aust GeomechN19, Dec 1990, P11–21

This paper describes the development of geotechnical experience on the North West Shelf, from the early 70's when natural gas was first discovered; to 1989 at the completion of the Goodwyn A (GWA) foundation design. The development of the original foundation design criteria for the North Rankin A (NRA) platform is outlined along with the realisation that a significant remedial programme was needed with the adoption of a solution based on end bearing. The logic for adoption of drilled and grouted piles for the GWA platform and the development of design criteria for these piles is also discussed

RIPRAP DESIGN DOWNSTREAM OF STRAIGHT DROP SPILLWAYS

ABSTRACT Tests made to determine the scour downstream of the straight drop spillway stilling basin and the size and placement of riprap to ensure stability of the structure are described in this article. The problem and the need for making the tests are discussed. Results are presented on the performance of the spillway with square and rounded abutments at the entrance to the stilling basin and with basins shorter than those recommended by the original design criteria. Criteria are presented to select the size and placement of riprap downstream of straight drop spillway stilling basins to ensure the integrity of the structures.

Distributed fermenter control with central supervision and data collection

This article looks at the original design criteria and the final product for a laboratory system to control a number of fermenters. The design uses general principles which are applicable to other areas of control besides fermenters.

Acoustic design of an anechoic chamber

This paper describes the acoustic design of an anechoic chamber built mainly for the measurement of the acoustic properties of electrical equipment. In order to reduce background noise the anechoic chamber was built on a ‘box within a box’ principle and mounted on an isolating foundation which consisted of 50 spring vibration isolators. To extend the free field and to obtain the lowest possible low cut-off frequency, absorbing wedges of 1150 mm long were used in the chamber, spaced 150 mm from the wall. Measurements conducted after the completion of the anechoic chamber indicated that all the original acoustic design criteria had been reached, some even surpassed. The anechoic chamber showed excellent acoustic characteristics during its use after completion in the following year.

Design and Operational Considerations for Unsupported Offshore Pipeline Spans

Summary Design and operational considerations have been examined in determining the significance of unsupported offshore pipeline spans that may develop during pipeline installation or field operation. Allowable unsupported span lengths determined during design are generally based on strict code compliance and a design foundation encompassing the worst possible environmental and operational loads. During operation, however, unsupported spans develop beyond the allowable limits, perhaps as a result of various unforeseen local conditions. Applying original design criteria is likely to result in cost-prohibitive repair predictions, while lack of action may result in loss of production. Without the design code requirements of an existing or a proposed pipeline system being violated, realistically safe design can be approached through evaluation of the sensitivity of the key design parameters. Priorities for remedial repair of the unsupported spans can be established for the pipelines in service while operating constraints, budget, and schedule are recognized. On the basis of periodic surveys, properly formatted survey data, and reanalysis of the design parameters, pipeline span repair cost estimates and schedules can be appreciably reduced. Similar principles can be applied to a pipeline in planning and design stages to ensure a safe operating design and to eliminate an uneconomically conservative design. These design and operational considerations are illustrated through a case study.

BOX WORD and LIST‐ED: a Case Study in Designing Software for Adult Students with Learning Difficulties

Abstract In order to produce a suite of computer software for adult students with learning difficulties, the authors used a technique of ‘intensive, consultative design’ characterized by iterative consultations between team members. The technique resulted in a suite of software which met the original design criteria. Initial results with the software are described. The exercise supported the value of the design technique used, highlighted different priorities of team members, revealed the potential of modular software construction for software development, and snowed a need for further work on the presentation of learning records. It is hoped that others will describe their approaches to design in detail so that the complex and costly process of designing special‐educational software can be better understood.

Five years experience with ceramic-metal-composite hip endoprostheses

The results of the complete and detailed clinical evaluation are compared with the original design criteria. It is shown that most of them stood the test. Those aspects which did not meet the expectations are discussed in detail: The occurrence of very little and biologically tolerable wear during the initial running-in period will be further reduced by a considerable improvement of the material properties. The few cases of severe wear had been associated with clinically exceptional situations, the analysis of which allows for suggestions to avoid such situations. The material improvements and all other steps taken to increase the safety margin considerably against fractures of the ceramic ball are described in detail. In addition, the attention is paid to some necessary clinical precautions.

Experimental verification of operation of the indium-doped infrared-sensing MOSFET

Verification demonstrating operation of the indium-doped silicon infrared-sensing MOSFET (IRFET) is provided. This is a new type of detector for the 3-5-µm infrared wavelength regions, and the detector has been found to operate according to the original design proposal and criteria.

A New 1000°C Double Tilt Stage for the Hitachi 650 kV Microscope

A new 1000°C specimen holder has been developed for the Hu-650 electron microscope and is interchangeable with other holders for the recently designed orthagonal drive tilting stage. The requirements for the high temperature device were as follows: 1. An orthogonal double-tilt stage with all original design criteria maintained(1). 2. Capability of heating standard (3mm. dia.) metallurgical specimens to 1000°C. 3. Geometry and materials should be such that stage and microscope components shall not be damaged by heat from the specimen holder. 4. The electric current to the heating element shall impart a minimum effect upon the microscope electron beam. 5. Heating and cooling rates to be as rapid as possible.

Acoustical Performance of Two Music Buildings

Music buildings at Washington State University and Central Washington State College, completed 2 and 4 yr ago, respectively, were the subject of an acoustical study involving measurements and user judgments. Although the two buildings are similar in size and facilities, the acoustical performances are not the same. Each building contains a 400-seat recital hall, but the acoustics of the two are quite different (one is almost twice the volume of the other, 171 000 vs 93 000 cu ft). Data are presented on reverberation time, sound-transmission loss, and background-noise measurements made throughout each building. The teaching staff of both buildings were asked to rate their impressions of the acoustics by completing brief questionnaires. On the basis of questionnaire responses, the original design criteria are examined and some proposals offered.