[en] In July 1986 the US Nuclear Regulatory Commission issued a Policy Statement on the Regulation of Advanced Nuclear Power Plants. As part of this policy advanced reactor designers were encouraged to interact with NRC early in the design process to obtain feedback regarding licensing requirements for advanced reactors. Accordingly, the staff has been interacting with the Department of Energy (DOE) and its contractors on the review of three advanced reactor conceptual designs: one modular High Temperature Gas-Cooled Reactor (MHTGR) and two Liquid Metal Reactors (LMRs). As a result of these interactions certain safety issues associated with these advanced reactor designs have been identified as key to the licensability of the designs as proposed by DOE. The major issues in this regard are: (1) selection and treatment of accident scenarios; (2) selection of siting source term; (3) performance and reliability of reactor shutdown and decay heat removal systems; (4) need for conventional containment; (5) need for conventional emergency evacuation; (6) role of the operator; (7) treatment of balance of plant; and (8) modular approach. This paper provides a status of the NRC review effort, describes the above issues in more detail and provides the current status and approach to the development of licensing guidance on each

[en] This draft safety evaluation report (SER) presents the preliminary results of a pre-application design review for the standard modular high-temperature gas-cooled reactor (MHTGR) (Project 672). The MHTGR conceptual design was submitted by the U.S. Department of Energy (DOE) in accordance with the U.S. Nuclear Regulatory Commission(NRC) 'Statement of Policy for the Regulation of Advanced Nuclear Power Plants' (51 FR 24643), which provides for early Commission review and interaction. The standard MHTGR consists of four identical reactor modules, each with a thermal output of 350 MWt, coupled with two steam turbine-generator sets to produce a total plant electrical output of 540 MWe. The reactors are helium cooled and graphite moderated and utilize ceramically coated particle-type nuclear fuel. The design includes passive reactor-shutdown and decay-heat-removal features. The staff and its contractors at the Oak Ridge National Laboratory and the Brookhaven National Laboratory have reviewed this design with emphasis on those unique provisions in the design that accomplish the key safety functions of reactor shutdown, decay-heat removal, and containment of radioactive material. This report presents the NRC staff's technical evaluation of those features in the MHTGR design important to safety, including their proposed research and testing needs. In addition this report presents the criteria proposed by the NRC staff to judge the acceptability of the MHTGR design and, where possible, includes statements on the potential of the MHTGR to meet these criteria. However, it should be recognized that final conclusions in all matters discussed in this report require approval by the Commission. Final determination on the acceptability of the MHTGR standard design is contingent on receipt and evaluation of additional information requested from DOE pertaining to the adequacy of the containment design and on the following: (1) satisfactory resolution of open safety issues identified in this report and possible additional safety issues that may become identified at later stages of review; (2) satisfactory completion of final design and licensing reviews by NRC; (3) conformance with applicable NRC rules, regulations, and other guidelines current at the time of any future licensing action; (4) successful completion of required research and development activities, including design, construction, testing, and operation of a prototype reactor before design certification. (author)

[en] A new selection method for analysing high-fold coincidence data from large gamma-ray arrays, called gamma-ray filtering (GRF), is presented. The method abandons the conventional concepts of gating and gate boundaries and instead calculates merit functions for detected gamma-ray energies to determine the relative value of incrementing them into the desired spectra. Results show that the selection power and limit of sensitivity are increased approximately by a factor of two when using the new filtering method, something that would be very costly to achieve by an improvement in detector hardware. Results show that for future arrays, capable of collecting higher-fold data, the new method will further increase detection sensitivity over current methods, possibly by a factor of four or more. To implement the new method requires only a modest increase in disk storage and CPU-time requirements

No abstract available

[en] A nuclear reactor shut-down system is described which comprises a fluidic vortex valve for releasably maintaining a liquid neutron poison outside of the reactor core, the poison being contained by a reservoir and biased by pressure for flow into poison tubes within the reactor. The upper ends of the poison tubes communicate with the supply port of the vortex valve. A continuous gas flow into the control port maintains normal controlled operation. Shut-down is effected by interruption of the control input. One embodiment comprises three groups of poison tubes and one vortex valve associated with each group wherein shut-down is effected by poison release in two out of the three groups. Preferably, each vortex valve comprises three control ports which operate on a ''voting'' or two-out-of-three basis. (Official Gazette)

[en] The shape of U.S. nuclear licensing and regulatory philosophy and process has already changed. The new process requires NRC review and approval of the vendor's designs before a customer purchases the design and begins construction. The new philosophy has resulted from lessons learned through extensive operating experience. In April 1995, the NRC published two proposed design certification rules that would certify the ABWR (Advanced Boiling Water Reactor) and System 80+ designs, if approved

[en] The Nuclear Regulatory Commission (NRC) is reviewing three applications for design certification under its new licensing process. The U.S. Advanced Boiling Water Reactor (ABWR) and System 80+ designs have received final design approvals. The AP600 design review is continuing. The goals of design certification are to achieve early resolution of safety issues and to provide a more stable and predictable licensing process. NRC also reviewed the Utility Requirements Document (URD) of the Electric Power Research Institute (EPRI) and determined that its guidance does not conflict with NRC requirements. This review led to the identification and resolution of many generic safety issues. The NRC determined that next-generation reactor designs should achieve a higher level of safety for selected technical and severe accident issues. Accordingly, NRC developed new review standards for these designs based on (1) operating experience, including the accident at Three Mile Island, Unit 2; (2) the results of probabilistic risk assessments of current and next-generation reactor designs; (3) early efforts on severe accident rulemaking; and (4) research conducted to address previously identified generic safety issues. The additional standards were used during the individual design reviews and the resolutions are documented in the design certification rules. 12 refs

[en] This paper presents the substance of a proposed policy statement for nuclear power plants issued by the United States Nuclear Regulatory Commission for public comment. The focus is on reactor accidents which may release radioactive materials from the reactor to the environment. Proposed qualitative goals and associated numerical guidelines for nuclear power plant accident risks are presented. The qualitative goals state that the risk of a nuclear power plant accident not be a significant contributor to a person's risk of accidental death or injury and that a limit be placed on the societal risks posed by reactor accidents. The significance of the goals and guidelines, their bases and rationale, and their proposed mode of implementation are indicated

[en] An automatic flow injection system is described for the determination of uranium in ore leachates. Following injection from an autosampler, the leachate is extracted with a solution of tributyl phosphate in heptane, which removes uranium, and the organic phase is separated. The extract is reacted with an ethanolic solution of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (BrPADAP) and benzyldimethyltetradecylammonium chloride (zephiramine) and the resulting ternary complex with U(VI) is measured spectrophotometrically at 579 nm. The lower limit of determination is 0.1 p.p.m. of uranium and up to 50 samples per hour can be analysed. In terms of speed and sensitivity this improves significantly on published procedures using segmented flow systems. The technique is ideal for process control and can be applied to the analysis of ores following mineralisation. (author)

[en] This paper presents the substance of a proposed policy statement for nuclear power plants issued by the United States Nuclear Regulatory Commission for public comment. Proposed qualitative goals and associated numerical guidelines for nuclear power plant accident risks are presented. The significance of the goals and guidelines, their bases and rationale, and their proposed mode of implementation are indicated. (author)