During severe accidents

Salts with the same structure have been put forward to explain the detonations or ignitions that were observed during several accidents involving DMSO and sodium hydride, sodium isopropylate and potassium tert-butylate. However, it is known that the last-named base causes the ignition of nearly all organic compounds. 

The design characteristics that are related to mitigation of accident consequences are identified in the descriptions in relation to the safety functions that they must assure during severe accidents. 

Radionuclides are released to the containment as gases and as aerosol particles by a variety of processes during severe accidents. Modem, mechanistic analyses of these radionuclide releases and the subsequent behaviour of aerosols and vapours under reactor accident conditions strive to be realistic. This realistic approach contrasts with the deliberate attempt to be conservative (which may not have been successful) in the definition of radionuclide behaviour for the design of nuclear power plant safety systems. A discussion of the various radionuclide release processes during severe reactor accidents is presented in Chapter II. Of primary interest in these discussions of release is the potential magnitude of radionuclide release and the radionuclides of most concern. Factors that most affect radionuclide release but can also be affected by accident management measures are discussed. 

S-17. D A. Powers, A re-examination of the steam explosion source term during severe accidents p.391. Source Term Evaluation for Accident Conditions, International Atomic Energy Agency, Vienna Austria, 1986. 

This report discusses analyses of the source term consequences of air ingression into the reactor coolant systems during severe accidents. 

This report provides a comprehensive survey of experimental data and models available to predict the retention of radionuclides within the reactor coolant system during severe accidents. 

Weber, C.F., Kress, T.S., Beahm, E.C., Shockley, W.E., Darsh, S.R, "TRENDS A Code for Modelling Iodine Behaviour in Containment During Severe Accidents", In Proceedings of the International Cent. Heat Mass Transfer, 30,665-674 (1990). 

E.C. Beahm, Y.M. Want, S.J. Wisbey, W.E. Shockley, Organic Iodide Formation During Severe Accidents in Light Water Nuclear Reactors , Nuclear Technology, 78,34, (1987). 

C-7a. R. Borkowski, H. Bunz, and W. Schock, Resuspension of Fission Products During Severe Accidents in Light Water Reactors, XII/978/84-EN, Kemforschungszentrum Karlsruhe, Karlsruhe, Germany, November 23, 1984. 

Assessing the severity of an accident can be a complicated task. Procedures should be in place to allow an assessment based on simple and available measurements of processes, such as reactor core temperature, radiation inside the plant, and availability of major process and safety systems. During severe accidents, difficulties usually arise when some instrumentation becomes unavailable or out of range. This should be taken into account in the accident assessment procedures. 

Contaiiunent thermal hydraulic (T/H) response during severe accident progression... 

CS 3 Need for containment and confinement integrity during severe accidents (India, Jcpan, RepiMic of Korea, Russian Federation, USA)... 

Alternative primary feed during severe accidents in PWR s K. Neu, G. Herbold, B. Putter NURETH-5 Salt Lake City September 1992. 

The ALWR design will achieve exeellence in safety for protection of the public, on-site personnel safety, and investment protection. It places primary emphasis on accident prevention as well as significant additional emphasis on mitigation. Containment performance during severe accidents will be evaluated to assure that adequate containment margin exists. 

Despite all current advances in nuclear power, NPPs have the following deficiencies (1) Generate radioactive wastes (2) Have relatively low thermal efficiencies, especially water-cooled NPPs (up to 1.6 times lower than that for modern advanced thermal power plants see Tables 1.5 and 1.6) (3) Risk of radiation release during severe accidents and (4) The production of nuclear fuel is not an environmentally friendly process. Therefore all of these deficiencies should be addressed. 

The TMI-2 accident led to increased emphasis on the importance of containment survival during severe accidents.. While the changes to containments were not as numerous as the changes to other plant systems, additional hydrogen control measures were implemented for some plants. These changes are discussed in more detail in Module 4. 

Characterize the usefulness of hydrogen recombiners during severe accidents. 

Likelihood of Containmeiit Failure During Severe Accidents... 

W. Luangdilok, R.J. Hammersley, J. Scobel, Analysis of diffusion flames on the IRWST vents of the Westinghouse AP600 during severe accidents. International Meeting on Advanced Reactors Safety - ARS 97, Orlando, 1-5 June 1997... 

The SCDAP/RELAP5/M0D3 computer code is designed to describe the overall reactor coolant system (RCS) thermal-hydraulic response, core damage progression, and fission product release and transport during severe accidents up to the point of reactor vessel or system failure The... 

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