ANSI Criticality Safety Standard

Subjects for criticality safety standards may arise from any source in which a sufficient need is identified. In the past, topics for consideration have been suggested by members of ANS-8, ansi Subcommittee N16, the ANS Standards Steering Committee, criticality safety specialists, and others. To accomplish preparation of draft standards, ANS-8 utilizes work groups led by interested and dedicated group leaders. Because of direct sponsorship and support by the Nuclear Criticality Safety Division of ANS, a broad base of national and intemation criticality safety expertise is available to draw upon in accomplishing assigned tasks and developing consensus on each project... 

This joint American National SUndards Institute/Amer-ican Nuclear Society (ANSI/ANS) criticality safety standard applies to facilities constructed and operated so that personnel would be protected from the effects of aniccidental criticality if it occurred. When specified protection criteria are met, reduced conservatism in equipment design and process operation is allowed compared to operations where protection is not provided. 

Currently Active ANSI/ANS Criticality Safety Standards... 

American Nuclear Society American National Standard, Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactors, Report ANSI N16.1-1975, La Grange Park, 111. 

The ES H Manual Supplement also considers applicable ANSI standards, including the basis for criticality requirements, record keeping, assessments for potential criticality events, criticality safety control parameters, conducting criticality safety analyses, preparation of plans and procedures, requirements for criticality alarms, personnel training, posting, and operational considerations. 

In conclusion, the manager with the responsibility of ( >erating the plant must ensure that the operations wUl be canied out within the criticality control specifications. Engineered safeguards for criticality control should minimize reliance on administrative control. The ANSI N16.1 Standard On nuclear criticality safety provides the basic guidelines necessary to accomplish these jobs. 

In 1964, representatives of commercial firms emphasized the need for further safety standards and guides. It appears that they would remain unsatisfied by contents of ANSI N16.1-1969, "Nuclear Criticality Safety In Operations with Fissionable Materials Outside Reactors," as well as the two proposed standards mentioned in the table. Another standards Work Group, ANS78.9, on safe pipe intersections for fissile solution, retognizes the need for data beyond resxilts that came recently from Oak Ridge and earlier from Rocky Flats. ... 

The proposed ANSI Standard for the Validation of CalculationaJ Methods for Nuclear Criticality Safety defines a Method as the mathematical equations, approximations, assumptions, associated numerical parameters (e.g., cross sections), and calculational procedures which yield the calculated results. The proposed Standard further states,- Nuclear parameters such as cross secUons should be consistent with experimental measurements of these parameters. Care clearly is required in specifying what constitutes a Method. It is obviously not acceptable merely to specify, say, KENO. ... 

The Role of Criticality Models in ANSI Standards for Nuclear Criticality Safety,/. T. Thomas fORNL), invited... 

Fortunately, there are now criteria for acceptance of a model given in the ANSI Standard N16.9 The principal requirement for validation is the correlation of results from the proposed model with the results of criticality experiments, or with the results of another validated method, to establish a bias for the model. The bias serves to normalize the model over the applicable range of its parameters so criticality will be predicted within the ev uated uncertainty of the bias.. Following validation, (he parameters arc adjusted, or limited such that applications of the model produce specifications for systems known to. result in subcriticality. The.procedure contributes to bases for standards in the field of nuclear criticality safety. 

ANSI Standard N16.9, Validation of Calculational Methods for Nuclear Criticality Safety (1975). 

American National Standard, Criteria for Nuclear Criticality Safety Controls in Operations Where Shielding Protects Personnel, ANSI N-16.8-1975,... 

The experiments being performed under this program provide data suitable for validating calculational techniques as required by. the American National Standard—ANSI N16.1-1969 (Nudear Criticality Safety in Operations with Fissionable Materials Outside Reactors). The data from experiments completed have been widely disseminated and used. Also, from all reports to date, they appear to be in a satisfactory and usable form. 

Meeting iri May 1981, Subcommittee S of ISO/TC 85 acted to initiate a writing group that would address Standardization of Calculations, Procedures, and Practices Related to Criticality Safety. If this proposal is endorsed by the member countries participating in SC 5, it is expected that the American National Standards Institute (ANSI) will serve as convenor for this new writing group. 

ANSI/ANS-8,9>1978-Criticality Safety Pipe Intersection Standard Review and Applications,... 

Work on this standard was begun in 1968 by a woric group containing representatives of industry, research, and government organizations. The first draft was submitted for comment in June 1979. Twelve subsequent drafts were prepared over a five-year period, some in response to recommendations from the American National Standard Committee N16. Subcommittee 8 of the ANS Standards Committee approved this standard in 1974. It was then adopted by the ANSI in May 1974 as ANSI N16.8-1975/ANS 8.10, Criteria for Nuclear Criticality Safety Controls in Operations Where Shielding Protects Personnel. ... 

AMERICAN NATIONAL STANDARD for Nuclear Criticality Control and Safety of Plutonium-Uranium Fuel Mixtures Outside Reactors, Rep. ANSI/ANS-8.12-1987, American Nuclear Society, LaGrange Park, IL (1987). 

Bursting safety factor. The provisions of the American National Standards Institute standard ANSI A92.2-1969, section 4.9 Bursting Safety Factor shall apply to all critical hydraulic and pneumatic components. Critical components are those in which a failure would result in a free fall or free rotation of the boom. All noncritical components shall have a bursting safety factor of at least 2 to 1. 

All crawler, truck, or locomotive cranes in use shall meet the applicable requirements for design, inspection, construction, testing, maintenance and operation as prescribed in the ANSI B30.5-1968, Safety Code for Crawler, Locomotive and Truck Cranes. However, the written, dated, and signed inspection reports and records of the monthly inspection of critical items prescribed in section 5-2.1.5 of the ANSI B30.5-1968 standard are not required. Instead, the employer shall prepare a certification record which includes the date the crane items were inspected the signature of the person who inspected the crane items and a serial number. 

Alarm management system plays key role toward the maintenance of plant safety. ANSI/ISA-18.2 standard Management of Alarm Systems for the Process Industries" (ISA-18.2) could be considered as a foundation for successful design, implementation, operation, and maintenance of alarm systems in a process plant. Operator s response to an alarm is considered as IPL in LOPA. This is important link of ISA with LOPA as the performance of critical alarms can impact the design of the SIS also. If its performance is poor, then result from LOPA could deteriorate. 

Thompson and Beckerly, "The Technology of Nuclear Safety", Vol. 1, Chapter 5, Sections 1, 2.land 3 Standard ANS-1 (ANSI N405-2000), "Conduct of Critical Experiments" Copyright 2000 by the American Nuclear Society, LaGrange Park, Illinois (attached copy provided by permission of ANS)... 

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