Sensitivity analysis of the reactor safety study

Originally presented as the first author's thesis, (M.S.) in the M.I.T. Dept. of Nuclear Engineering, 1979.The Reactor Safety Study (RSS) or Wash-1400 developed a methodology estimating the public risk from light water nuclear reactors. In order to give further insights into this study, a sensitivity analysis has been performed to determine the significant contributors to risk for both the PWR and BWR. The sensitivity to variation of the point values of the failure probabilities reported in the RSS was determined for the safety systems identified therein, as well as for many of the generic classes from which individual failures contributed to system failures. Increasing as well as decreasing point values were considered. An analysis of the sensitivity to increasing uncertainty in system failure probabilities was also performed. The sensitivity parameters chosen were release category prob- abilities, core melt probability, and the risk parameters of early fatalities, latent cancers and total property damage. The latter three are adequate for describing all public risks identified in the RSS. The results indicate reductions of public risk by less than a factor of two for factor reductions in system or generic failure probabilities as hignh as one hundred. There also appears to be more benefit in monitoring the most sensitive systems to verify adherence to RSS failure rates than to backfitting present reactors. The sensitivity analysis results do indicate, however, possible benefits in reducing human error rates.Final report for research project sponsored by Northeast Utilities Service Company, Yankee Atomic Electric Company under the M.I.T. Energy Laboratory Electric Utility Program

Sensitivity analysis of the reactor safety study

Originally presented as the first author's thesis, (M.S.)--in the M.I.T. Dept. of Nuclear Engineering, 1979Includes bibliographical references (p. 232-233)Final research project reportFinal report for research project sponsored by Northeast Utilities Service Company, Yankee Atomic Electric Company under the M.I.T. Energy Laboratory Electric Utility Progra

Reactor core thermal-hydraulic analysis ; improvement and application of the code COBRA-IIICMIT

Several improvements have been made to COBRA-IIIC/MIT. All of the improvements, except for one, have been made in response to the recommendations of past research. The improvements are included in a new version of the code as new modeling options. The new modeling options overcome limitations and disadvantages of old modeling options. The improvements are as follows: 1. Addition of a new fuel pin conduction model which includes temperature dependent properties and burnup dependent gap heat transfer coefficient. 2. Addition of a new heat transfer package which covers a broad range of flow regimes and contains more consistent logic. 3. Addition of a quality dependent mixing model for two-phase flow. 4. Addition of new correlations for BWR, CHFR and CPR calculation. 5. Addition of new options for calculating transverse momentum coupling parameters use for the single pass method.The improvements have been tested individually and during application of the improved code to transient PWR and BWR test cases. Testing mainly involved comparison of the predictions of different modeling options and in some instances, comparison of predictions with experimental measurements. MDNBR, MCPR and MCHFR predictions showed only small sensitivities to the fuel rod and heat transfer modeling options used for the test cases analyzed. Differences in predictions of the old and new heat transfer models resulted in different clad temperature predictions. Clad temperature varies more smoothly in the axial direction when the new heat transfer model is used. The new heat transfer model predictions vary smoothly from one time step to the next with changing coolant conditions. Discontinuous change in old heat transfer model predictions caused failure of the flow solution to converge during transient BWR analysis. Fuel rod surface heat flux predictions of the old and new fuel rod models were close even though fuel rod temperature predictions showed some differences. The new mixing model did not improve subchannel flow and enthalpy predictions for BWR conditions. However, some improvement was seen in predictions for sub-cooled conditions. The CISE-4 MCPR predictions were in agreement with experimental CHF measurements. Hench- Levy MCHFR predictions were conservative for the CHF test cases. The new transverse momentum parameters had no significant effect on steady state hot channel predictions of the single-pass method

Towards More Precise Survey Photometry for PanSTARRS and LSST: Measuring Directly the Optical Transmission Spectrum of the Atmosphere

Motivated by the recognition that variation in the optical transmission of the atmosphere is probably the main limitation to the precision of ground-based CCD measurements of celestial fluxes, we review the physical processes that attenuate the passage of light through the Earth's atmosphere. The next generation of astronomical surveys, such as PanSTARRS and LSST, will greatly benefit from dedicated apparatus to obtain atmospheric transmission data that can be associated with each survey image. We review and compare various approaches to this measurement problem, including photometry, spectroscopy, and LIDAR. In conjunction with careful measurements of instrumental throughput, atmospheric transmission measurements should allow next-generation imaging surveys to produce photometry of unprecedented precision. Our primary concerns are the real-time determination of aerosol scattering and absorption by water along the line of sight, both of which can vary over the course of a night's observations.Comment: 41 pages, 14 figures. Accepted PAS

The Long Life of Birds: The Rat-Pigeon Comparison Revisited

The most studied comparison of aging and maximum lifespan potential (MLSP) among endotherms involves the 7-fold longevity difference between rats (MLSP 5y) and pigeons (MLSP 35y). A widely accepted theory explaining MLSP differences between species is the oxidative stress theory, which purports that reactive oxygen species (ROS) produced during mitochondrial respiration damage bio-molecules and eventually lead to the breakdown of regulatory systems and consequent death. Previous rat-pigeon studies compared only aspects of the oxidative stress theory and most concluded that the lower mitochondrial superoxide production of pigeons compared to rats was responsible for their much greater longevity. This conclusion is based mainly on data from one tissue (the heart) using one mitochondrial substrate (succinate). Studies on heart mitochondria using pyruvate as a mitochondrial substrate gave contradictory results. We believe the conclusion that birds produce less mitochondrial superoxide than mammals is unwarranted

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

The Apache Point Observatory Galactic Evolution Experiment (APOGEE), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three-year observing campaign on the Sloan 2.5 m Telescope, APOGEE has collected a half million high-resolution (R ~ 22,500), high signal-to-noise ratio (>100), infrared (1.51–1.70 μm) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design—hardware, field placement, target selection, operations—and gives an overview of these aspects as well as the data reduction, analysis, and products. An index is also given to the complement of technical papers that describe various critical survey components in detail. Finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity, and abundance patterns across the Galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III Data Release 12 and later releases, all of the APOGEE data products are publicly available

The CMS Phase-1 pixel detector upgrade

The CMS detector at the CERN LHC features a silicon pixel detector as its innermost subdetector. The original CMS pixel detector has been replaced with an upgraded pixel system (CMS Phase-1 pixel detector) in the extended year-end technical stop of the LHC in 2016/2017. The upgraded CMS pixel detector is designed to cope with the higher instantaneous luminosities that have been achieved by the LHC after the upgrades to the accelerator during the first long shutdown in 2013–2014. Compared to the original pixel detector, the upgraded detector has a better tracking performance and lower mass with four barrel layers and three endcap disks on each side to provide hit coverage up to an absolute value of pseudorapidity of 2.5. This paper describes the design and construction of the CMS Phase-1 pixel detector as well as its performance from commissioning to early operation in collision data-taking.Peer reviewe

A study of liquid mass transport in annular air-water flow

Massachusetts Institute of Technology. Dept. of Nuclear Engineering. Thesis. 1967. Sc.D.One unnumbered page inserted. Vita.Bibliography: leaves 281-284.by William Dean Hinkle.Sc.D

Water tests for determining post voiding behavior in the LMFB : final report

The most serious of the postulated accidents considered in the design of the Liquid Metal Cooled Fast Breeder Reactor (LMFBR) is the Loss of Pipe Integrity (LOPI) accident. Analysis models used to calculate the consequences of this accident assume that once boiling is initiated film dryout occurs in the hot assembly as a result of rapid vapor bubble growth and consequent flow stoppage or reversal. However, this assumption has not been put to any real test. Once boiling is initiated in the hot assembly during an LMFBR LOPI accident, a substantial gravity pressure difference would exist between this assembly and other colder assemblies in the core. This condition would give rise to natural circulation flow boiling accompanied by pressure and flow oscillations. It is possible that such oscillations could prevent or delay dryout and provide substantial post-voiding heat removal. The tests described in this report were conceived with the objective of obtaining basic information and data relating to this possibility. To accomplish this objective a natural circulation test loop was designed to simulate LMFBR geometry and flow conditions predicted to exist at the time boiling is initiated in a LOPI accident. The test loop included: (l) a vertical tube test section, (2) upper and lower plenum tanks, (3) an external down-commer, (4) sight flow indicators and (5) instrumentation. The test section was an electrically heated tube designed with a hydraulic diameter and length similar to current LMFBR (FTR) design. The upper and lower plenum tanks were provided with means for controlling liquid subcooling above and below the test section. The down-commer was large enough to eliminate down-commer hydraulics. Water at a pressure of 1 atmosphere was used to simulate sodium. Sight flow indicators were provided to observe flow conditions at the test section inlet and exit. Instrumentation was provided to measure test section pressures, inlet and exit temperatures, tube wall temperatures, heat flux and oscillation frequencies. Steady state tests were conducted for subcooled flow boiling, saturated flow boiling, CHF and post CHF conditions. Subcooled flow boiling was observed for heat fluxes below 1 x 104 BTU/hr ft2. For this condition, both pressure oscillations and temperature oscillations at the heated surface were observed; but the pressure oscillations were not observed continuously. Saturated flow boiling was observed for heat fluxes between 3 x 104 BTU/hr ft2 and CHF. For this condition, pressure oscillations were observed continuously. As the CHF condition was approached, a periodic downward expansion of vapor from the heated section was observed at the bottom sight flow indicator and the flow regime appeared to be annular at the top sight flow indicator. CHF was observed at the top of the heated section when the heat flux reached 6.4 x 104 BTU/hr ft2, but rewetting occurred after a few seconds. As the heat flux was increased further, the maximum surface temperature reached before rewetting increased; until, at a heat flux of 7.15 x 104 BTU/hr ft2, the maximum temperature exceeded 9000 F and rewetting no longer occurred. A transient test was conducted for a post CHF condition. The heat flux was 7.3 x 104 BTU/hr ft2. The oscillations observed under steady state conditions developed within a few seconds after the power was turned on. The equilibrium tube wall temperature upstream of the CHF location was reached in 10 seconds. The equilibrium tube wall temperature at the CHF location was reached in about 135 seconds. A similarity analysis was done in order to scale the test results to LMFBR LOPI conditions. The results of this analysis indicate that the CHF for the LMFBR (FTR) would be at least 6 x 104 BTU/hr ft2. This corresponds to a critical average linear power for the hot assembly of 1.06 kw/ft compared to an estimated 2.55 to 5.1 kw/ft being transferred to the coolant at the time boiling begins during a LOPI accident. On the basis of this analysis, the results of the water tests indicate that CHF would occur. But, this conclusion is conservative for a number of reasons and further experimental work on a more prototypical system is suggested.Union Carbide Corporation, Nuclear Division under Subcontract no.4450 of Contract no.W-7405-eng-26 with the U.S. Energy Research and Development Administratio

An Eight-Year-Old Girl Presents With Two Weeks of Vision Loss and Nightly Headaches

Intraocular medulloepithelioma is a rare congenital tumor that arises from the nonpigmented epithelium of the ciliary body. It is the second most common primary intraocular neoplasm during the first decade of life. It may present with an iris mass or cyst (56%), glaucoma (48%), cataract (26%), leukocoria (18%), decrease in vision (41%), or pain (30%). Here, the authors present a case of a medulloepithelioma investigated with multimodal imaging, including the first characterization with intraoperative optic coherence tomography. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:314-317.]