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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

GIF Supercritical Water Cooled Reactor: Proliferation Resistance and Physical Protection White Paper

This report is part of a series of six white papers, prepared jointly by the Proliferation Resistance and Physical Protection Working Group (PRPPWG) and the six System Steering Committees (SSCs) and provisional System Steering Committees (pSSCs). This publication is an update to a similar series published in 2011 presenting the status of Proliferation Resistance & Physical Protection (PR&PP) characteristics for each of the six systems selected by the Generation IV International Forum (GIF) for further research and development, namely: the Sodium-cooled fast Reactor (SFR), the Very high temperature reactor (VHTR), the gas-cooled fast reactor (GFR), the Molten salt reactor (MSR) and the Supercritical water–cooled reactor (SCWR). This white paper represents the status of Proliferation Resistance and Physical Protection (PR&PP) characteristics for the Supercritical Water-cooled Fast reactor (SCFR) reference designs selected by the Generation IV International Forum (GIF) SCWR System Steering Committee (SSC). The intent is to generate preliminary information about the PR&PP features of the SCWR reactor technology and to provide insights for optimizing their PR&PP performance for the benefit of SCWR system designers. It updates the SCWR analysis published in the 2011 report “Proliferation Resistance and Physical Protection of the Six Generation IV Nuclear Energy Systems”, prepared Jointly by the Proliferation Resistance and Physical Protection Working Group (PRPPWG) and the System Steering Committees and provisional System Steering Committees of the Generation IV International Forum, taking into account the evolution of both the systems, the GIF R&D activities, and an increased understanding of the PR&PP features. The white paper, prepared jointly by the GIF PRPPWG and the GIF SCWR SSC, follows the highlevel paradigm of the GIF PR&PP Evaluation Methodology to investigate the PR&PP features of the eight proposed GIF SCWR designs. Two small modular reactors, the Canadian SSR and the Canada/China/Europe ECC-SMART are also mentioned. An overview of the fuel cycles for the GIF designs are provided. For PR, the document analyses and discusses the proliferation resistance aspects in terms of robustness against State-based threats associated with diversion of materials, misuse of facilities, breakout scenarios, and production in clandestine facilities. Similarly, for PP, the document discusses the robustness against theft of material and sabotage by non-State actors. The document follows a common template adopted by all the white papers in the updated series.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Safety Analysis for Accident-Tolerant Fuels with Increased Enrichment and Extended Burnup

The ERP research and development efforts in FY22 focused on the safety analysis of ATF with increased enrichment and extended burnup to provide scientific knowledge of the ATF fuel performance, failure mechanism and source term analysis during severe accident of the NPP. FeCrAl clad ATF was selected as basis of the reactor fuel. An optimized equilibrium cycle was developed for 24-months extended burnup operation. A 4-loop PWR model under loss-of-coolant accident (LOCA) was assessed and the behavior of the major source term from failed ATF has been analyzed. The result showed that grace to enhanced mechanical characteristics of ATF, the fuel failure starts up to 200~500 seconds later than conventional Zr clad fuel. This time gives sufficient buffer until low pressure safety injection (LPSI) of the emergency core cooling system (ECCS) restarted by the operator which reduces fuel fragmentation, relocation and dispersal (FFRD). As a consequence, the total amount of major radioactive materials released from FeCrAl clad fuel into the reactor containment was found up to three times less compare to Zr clad fuel.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Multi physics simulation on Reactor Pressure Vessel (RPV) subjected to Pressurized Thermal Shock (PTS) by using Cardinal

The structural components that comprise nuclear reactors and their supporting structures are subjected to harsh operating environments that can challenge their integrity, especially after exposure for extended durations or under accident condition. As one of the most significant components of a Reactor, the Reactor Pressure Vessel (RPV) is exposed to an aggressive environment during the operation time (e.g. more than 40 years). Ageing degradation mechanisms (e.g. thermo-fatigue) could grow initial defects up to a critical size, increasing the susceptibility to failure in the RPV. The conventional methods are mostly based on simple crack and structure geometries. Very limited studies consider the real conditions of the RPV subjected to a thermal shock due to a Loss of Coolant Accident (LOCA). During a LOCA event, the most severe conditions take place when the emergency core cooling (ECC) water is injected inside the cold legs filled initially with hotter water and/or steam. The rapid cooling of the down-comer and the internal RPV surface followed probably by re-pressurization of the RPV causes large temperature gradients and variation of pressure which induces thermal-mechanical stresses. In order to develop the model for integrity assessment of a reactor pressure vessel (RPV) subjected to pressurized thermal shock (PTS), a multi-physics simulation, which includes the thermo-hydraulic, thermo-mechanical and fracture mechanics analyses is necessary.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2026

Reassessing Double-Ended Guillotine Break Requirements: Evidence-Based Analysis of Regulatory Assumptions After Five Decades of Nuclear Operation

After five decades of nuclear power operation encompassing more than 20,000 reactor-years across 35 countries and 647 reactors, zero double-ended guillotine breaks (DEGBs) have been documented in commercial reactor coolant systems—despite DEGB being the fundamental design-basis assumption driving Emergency Core Cooling System (ECCS) sizing, structural protection requirements, and containment design specifications. This report examines the basis for DEGB requirements in nuclear power plant design. The DEGB postulate assumes the instantaneous, complete circumferential severance of the largest diameter pipes in reactor coolant systems, driving major design requirements under 10 Code of Federal Regulations 50.46, General Design Criterion 4 and containment design specifications. The United States (4,880 reactor-years) and France (2,505 reactor-years) contribute the largest operational datasets. Probabilistic assessments estimate direct DEGB occurrence probabilities with extremely low event frequencies, far below the 10-5/reactor-year thresholds typically used to define non-credible events in nuclear-safety analyses; i.e., events with probability this low fall into beyond-design-basis events. Current material-science knowledge demonstrates that the ductile steel materials used in nuclear piping systems exhibit stable crack-growth behavior fundamentally incompatible with instantaneous severance. International regulatory experience, particularly Germany’s comprehensive break-preclusion implementation, and successful leak-before-break (LBB) applications in almost all of U.S. pressurized water reactor units validate that alternatives can maintain safety performance while reducing economic burden. Current DEGB protection systems impose estimated lifetime costs of hundreds of millions of dollars per unit, over the life of a plant across the nuclear industry (including ongoing costs), representing substantial resource allocation toward scenarios with extremely low probability. Although this report acknowledges uncertainties regarding long-term aging effects, potential synergistic degradation mechanisms, and site-specific seismic considerations that warrant continued evaluation as regulatory policy evolves, there remains no documented evidence that a DEGB has occurred as a consequence of the conditions or mechanisms described in this report. This report acknowledges the Nuclear Regulatory Commission’s (NRC’s) recent efforts—outlined in the draft Interim Staff Guidance (ISG) NRC-DSS-ISG-2025-XX (“Treatment of Certain Loss-of-Coolant Accident Locations as Beyond-Design-Basis Accidents Draft Interim Staff Guidance”)—to reduce overly conservative requirements for large-break loss of coolant accidents through technical justifications and exemptions. However, extensive operating experience and validated methodologies—such as LBB and in-service inspection programs—demonstrate that the probability of a DEGB in reactor coolant-loop piping is extremely low, even under seismic conditions. The authors and reviewers of this report recommend that DEGB be removed as a design-basis event through formal rulemaking, rather than case-by-case exemptions, to better reflect credible failure modes, align with current data, and align with modern, risk-informed safety analysis.

22 - GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2026

Tethered Balloon System Ozone Profiles during CoURAGE Summer Intensive Operational Period Field Campaign Report

During the summer IOP, the small ARM field campaign CRGTBSO3 collected measurements to gain an improved understanding of differences between the atmospheric composition in and just above the marine layer at the CoURAGE TBS site near the eastern shore of Chesapeake Bay. CRGTBSO3 included guest instrumentation with ozone (O 3 ) profile measurements on the TBS and surface O3 and meteorological measurements at the TBS site. An En-Sci 2Z electrochemical cell (ECC) ozonesonde (Komhyr 1969, 1986, Witte et al. 2018) was included on the TBS. The ozonesonde was connected to an InterMet iMet-4RSB radiosonde, and the overall data collected included vertical profiles of ozone, relative humidity, temperature, pressure, and altitude. The CRGTBSO3 iMet-4 radiosonde data is identical to that of the iMet in the Tethered Balloon System Merged Data Product (TBSMERGED; Gaustad and Dexheimer 2025). The TBSMERGED data product also includes meteorological data from a different sensor, the iMet XQ2. In some cases, the iMet XQ2 relative humidity (RH) data may be more accurate than the iMet-4, such as for some instances when the iMet-4 RH data stays at 100% for an extended period throughout a profile.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

TRACER-Tethersonde Ozone data

TRACER-Tethersonde, a sub-campaign of TRACER, took place during the TRACER June-September 2022 intensive operating period (IOP) at the S3 Ancillary site (29.33°N, 95.74°W) near Guy, TX. The Tethered Balloon System (TBS) operated during the first two weeks of each month during the TRACER IOP, making multiple (~4) up and down vertical profiles each day that could reach as high as ~1 km. TRACER-Tethersonde included an En-Sci electrochemical cell (ECC) ozonesonde on the TBS. The ozonesonde was connected to an iMet-4RSB radiosonde, and the overall data collected included ozone, relative humidity, temperature, and altitude.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

CRGTBSO3 TBS Ozone Data

The Tethered Balloon System (TBS) operated for two weeks during a summer IOP of the CoURAGE campaign. This dataset includes data collected from an En-Sci electrochemical cell (ECC) ozonesonde on the TBS. The ozonesonde was connected to an iMet-4RSB radiosonde, and the overall data collected included ozone, relative humidity, temperature, and altitude. The data from the iMet is the same as that found in the TBSMERGED data product. The TBS also had another instrument (iMet XQ2) that collected meteorological data, which may have more accurate relative humidity (RH) data. This ozonesonde data set is intended to complement the TBSMERGED data product, the CRGTBSO3 surface ozone measurements, and the CoURAGE SWARM ozone lidar (TOLNet) measurements from other locations.

Atmospheric relative humidity↗
NASA NTRS1974

Ozone measurement systems improvements studies

Results are summarized of an initial study of techniques for measuring atmospheric ozone, carried out as the first phase of a program to improve ozone measurement techniques. The study concentrated on two measurement systems, the electro chemical cell (ECC) ozonesonde and the Dobson ozone spectrophotometer, and consisted of two tasks. The first task consisted of error modeling and system error analysis of the two measurement systems. Under the second task a Monte-Carlo model of the Dobson ozone measurement technique was developed and programmed for computer operation.

Thomas, R. W.↗
NASA NTRS1979

Total ozone determination by spectroradiometry in the middle ultraviolet

A method has been developed to determine total ozone from multispectral measurements of the direct solar irradiance. The total ozone is determined by a least squares fit to the spectrum between 290 nm and 380 nm. The aerosol extinction is accounted for by expanding it in a power series in wavelength; use of the linear term proved adequate. A mobile laboratory incorporating a sky scanner has been developed and used to obtain data to verify the method. Sun tracking, wavelength setting of the double monochromator, and data acquisition are under control of a minicomputer. Results obtained at Wallops Island, Virginia, and Palestine, Texas, agree well with simultaneous Dobson and Canterbury spectrometer and balloon ECC ozonesonde values. The wavelength calibration of the monochromator and the values for the normalized ozone absorption are the most important factors in an accurate determination of total ozone.

Garrison, L. M.↗
NASA NTRS1981

RAWINPROC: Computer program for decommutating, interpreting, and interpolating Rawinsonde meteorological balloon sounding data

The FORTRAN computer program RAWINPROC accepts output from NASA Wallops computer program METPASS1; and produces input for NASA computer program 3.0.0700 (ECC-PRD). The three parts together form a software system for the completely automatic reduction of standard RAWINSONDE sounding data. RAWINPROC pre-edits the 0.1-second data, including time-of-day, azimuth, elevation, and sonde-modulated tone frequency, condenses the data according to successive dwells of the tone frequency, decommutates the condensed data into the proper channels (temperature, relative humidity, high and low references), determines the running baroswitch contact number and computes the associated pressure altitudes, and interpolates the data appropriate for input to ACC-PRD.

Staffanson, F. L.↗
NASA NTRS1982

Equatorial ozone characteristics as measured at Natal (5.9 deg S, 35.2 deg W)

Ozone density profiles obtained through electrochemical concentration cell (ECC) sonde measurements at Natal were analyzed. Time variations, as expected, are small. Outstanding features of the data are tropospheric densities substantially higher than those measured at other stations, and also a total ozone content that is higher than the averages given by satellite measurements.

Kirchhoff, V. W. J. H.↗
NASA NTRS1983

GSFC optical ozonesonde results during the Gap, France, intercomparisons, June 1981

O3 soundings made with balloon-borne optical sensors during the French Intercomparison Ozone Campaign in June, 1981, are reported. The GSFC four-channel UV-filter-photometer ozonesonde designed for the Super Loki rocket was attached to the gondola roof for redundant O3-density measurements at altitudes of 22-32 km, using the 300 and 303-nm filters. Sensor calibration, data processing, input constants, and vertical O3-distribution calculations are discussed. The density profiles for three legs of the flight, calculated using Bass or Vigroux cross sections, agreed within a standard error of 1.4 percent for each channel, but showed a consistent 4-5 percent (significant) difference between channels. Total average O3-column amounts determined by combining the GSFC data with ECC measurements for altitudes below 21 km were in good agreement with bias-corrected TOMS data from Nimbus-VII and with ground-based data from the Observatoire de Haute-Provence at Mt. Chiran, when the latter were computed using the pre-campaign calibration. A 9-percent discrepancy arose when the Chiran data were corrected for a post-campaign recalibration of the Dobson spectrophotometer.

Krueger, A. J.↗
NASA NTRS1983

Equatorial ozone characteristics as measured at Natal (5.9 deg S, 35.2 deg W)

Ozone density profiles obtained through electrochemical concentration cell (ECC) sonde measurements at Natal were analyzed. Time variations, as expected, are small. Outstanding features of the data are tropospheric densities substantially higher than those measured at other stations, and also a total ozone content that is higher than the averages given by satellite measurements. Previously announced in STAR as A82-29798

Kirchhoff, V. W. J. H.↗
NASA NTRS1985

Ozone intercomparisons from the Balloon Intercomparison Campaign

Intercomparisons of remote and in-situ techniques used to measure stratospheric ozone are made using results obtained on the Balloon Intercomparison Campaign of 1982 and 1983. Two in-situ and four remote instruments participated. These included ECC ozonesondes, a UV absorption photometer, and microwave emission, IR emission, and absorption spectrometers. Differences are generally less than 15 percent, and are within the quoted error bars. Flights which involved different sets of instruments were made on four separate days, and results are intercompared in plots of ozone density versus altitude. A careful assessment of errors was made for each instrument, and a plot of absolute errors versus altitude is given.

Robbins, D.↗
NASA NTRS1987

Crystallization behavior of a melt-spun Fe-Ni based steel

Whether Fe-Ni-based alloys solidify with a bcc or fcc structure has been observed by many investigators to be a stronger function of kinetics and undercooling than strictly free-energy minimization. Such behavior has been observed in an Fe(52.8)Ni(28.7)Al(3.4)Ti(6.1)B(9.0) alloy. The alloy was cast as ribbons about 45 microns thick using a dual free-jet variation of chillbock melt spinning against a Cu wheel. Optical, X-ray, and electron analyses of the as-cast and annealed ribbons were performed. A microstructure of at least four layers containing combinations of ecc, bcc, and amorphous phases in differing proportions was observed in the as-cast ribbon. The midthickness layer had the most unusual features, containing fcc grains about 75 nm in size encompassing spherulitic regions as large as 15 microns comprised of fcc grains about 25 nm in size. The crystallization sequence responsible for the as-cast microstructure is discussed in terms of the competition between the formation of bcc and fcc phases as influenced by undercooling, recalescence, and variations in cooling rate experienced by the as-cast ribbon.

Michal, G. M.↗
NASA NTRS1988

Atmospheric ozone at South Pole, Antarctica, in 1986

Results of NOAA's measurements of the ozone vertical distributions at the South Pole and of the annual course of total ozone, conducted in 1986 with balloon-borne electrochemical concentration cell (ECC) ozonesondes and a Dobson spectrophotometer, are described. The major finding was that the stratospheric ozone decreases abruptly between September 20 and October 15, with the bulk decrease occurring between 12 and 21 km. In this period, the column ozone and ozone volume mixing ratio at 16 km (the altitude of the normal ozone maximum at South Pole) decreased by 78 percent, and column ozone between 12 and 21 km decreased by 50 percent. The results of these measurements are compared with data obtained in 1971, and the changes observed in the ozone vertical distributions and in the temporal variations of atmospheric ozone are discussed.

Komhyr, W. D.↗