Accident conditions

The origins of potential accidents include but are not limited to the following  

Design deficiencies that render the incineration system unable to overcome the difficulties caused by thermal, mechanical, chemical or radiological failures Introduction of materials into the waste feed that lead to excessive temperatures, overpressurization and/or explosive conditions within the incineration 

Loss of critical utility supply (e.g. electric power, air, fuel and water) Human error  

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Model Validity Probabilistic failure models cannot be verified. Physical phenomena are observed in experiments and used in model correlations, but models are, at best, approximations of specific accident conditions. 

Rodgers, S. J., Udaveak, R. J. and Mausteller, J. W. In International Symposium of Fission Product Release and Transport under Accident Conditions, Oak Ridge National Laboratory, TN, USA, 1965, pp. 1204 1215. 

Calculates impact of gaseous releases under routine or accident conditions. 

HAZSEC generates two types of records. The first page is the log sheet with the time, date, rc% ision number, team leader, and team members. This page also contains a section that describes the part of the plant design under investigation, and a statement of the design intent, i.e., the expected equipment performance under normal and accident conditions. The pages that follow repeat this... 

Function event trees are developed to represent the plant s response to each initiator. The function event tree is not an end product it is an intermediate step that provides a baseline of information and permits a stepwise approach to sorting out the complex relationships between potential initiating events and the response of the mitigating features. They structure plant respoases to accident conditions - possibly as time sequences. The transition labels of function event trees (usually along the top of the event tree) are analyzed to provide the probability of that function occurring or not occurring. 

The data suggest that iodine will be released, predominantly, as cesium iodide under most postulated light water reactor accident conditions. However, formation of more volatile iodine species (e.g., elemental iodine and organic iodines) is not impossible under certain accident conditions. 

Of these phenomena, the first three in particular, involve thermal hydraulics beginning with the pre-accident conditions. Items 4 through 7 address the meltdown of the core and its influence on (1) hydrogen production, which affects containment loads, (2) fuel temperatures, which affect in-vessel fission product releases, (3) thermal-... 

It should be mentioned that boiling within a liquid metal-cooled reactor (such as a sodium-cooled reactor) is an accident condition and may give rise to rapid fuel failure. In designing a reactor core, on the other hand, sodium boiling should... 

Topic 5 Hazard Analysis and Categorization Topic 11 Analysis of Accident Conditions... 

Sequence of operations or steps to derive accident conditions... 

Henry, R. E., and McUmber, L. M. (1977). Vapor explosion potentials under LWR hypothetical accident conditions. Proc. Light Water React. Saf. Meet., 1977, Sun Valley, Idaho. CONF-770708, pp. 414-425. 

The adiabatic case is the most common for accident conditions. The process is treated as an isentropicfree expansion of an ideal gas using the equation of state ... 

For several months before the accident, conditions at the plant had been deteriorating. Procedures were not carefully followed and several mechanical features were either shutdown or compromised. Examples include the refrigeration circuit that was depleted of coolant and the vent gas scrubber that was out of service. The temperature indicator on one tank was defective. The temperature in one of the tanks had been allowed to exceed the maximum limit by as much as 15°C with no corrective action. 

Ref 3) give at best qualitative results. Although these results may be adequate for comparing the leach rates of various waste forms, they tend to be unsuitable for extrapolation to final repository or accident conditions. This deficiency has been pointed out by Mendel( 3) and Sheffler et at, (15), among others. 

Campbell, D.O. (1979) Behaviour of iodine under accident conditions at Three Mile Island. The Accident at Three Mile Island (Kemeny Report). Reports of the technical assessment task force, Vol II, Appendix F. U.S. Govt. Printing Office, Washington D.C. 

Osborne, M.F., Collins, T.L., Lorenz, R.A. Strain, R.V. (1986) Fission product release and fuel behaviour in tests of LWR fuel under accident conditions. In Source Term Evaluation for Accident Conditions, IAEA, Vienna, pp. 89-104. 

Type B packaging means packaging which meets the standards for Type A packaging, and, in addition, meets the standards for hypothetical accident conditions for transportation (1). 

Tritium is one of the main source terms in accident scenarios for ITER and to meet some of the key requirements for limitation of worker and public dose in accidents, limits need to be placed on the tritium inventory. Due to the ease of mobilization of tritium retained in co-deposited layers (co-deposited films in tokamaks start to decompose, releasing tritium, when exposed to air at temperatures > 520 K, [65-69]), a limit of 350 g is currently set for the in-vessel co-deposition inventory (and 120 g in the cryo-pumps). These limits are set to allow the full release of this inventory, under hypothetical accident conditions, without the need for public evacuation under the worst weather conditions. 

In all, 193 experiences nucleaires (nuclear tests and safety trials) were conducted at the French nuclear weapon test site at Mururoa and Fangataufa atolls. Of these, 178 were nuclear tests , in which a nuclear device was exploded with a large release of fission and, in some cases, fusion energy and 15 were safety trials in which more or less fully developed nuclear devices were subjected to simulated accident conditions and the nuclear weapon cores were destroyed by means of conventional explosives, with no or—on a few occasions—very small releases of fission energy. 

Rodgers, S.J., Udavcak, R.J., and Mausteller, J.W. (1965). Development of medium flow rate, high-purity, particulate, and iodine filters. Intern. Symp. Fission Prod. Release Transport Accident Conditions, Oak Ridge, Tenn., 1204-15. 

Numerous experimental and theoretical efforts have been made to examine the plateout distribution of fission products in the primary circuit both under normal operating and accident conditions. Different in-pile and out-of-pile deposition loops were operated in Germany, Japan, France, the UK, and the USA to study systematically the ad-/desorption behavior of fission product on metallic surfaces as a function of temperature and gas... 

Different categories apply to the hydrogen issue in nuclear reactor containments. During normal operation, small quantities of H2 are generated by radiolysis of the coolant, 44 H2 and 22 O2 molecules per 10 eV of neutron radiation energy. Under accident conditions, significant amounts of hydrogen could be produced due to radiolysis and corrosion reactions. 

The Sandia code HECTR (Hydrogen Event Containment Transient Response) is a lumped parameter analysis code for modeling the containment atmosphere under accident conditions involving release, transport, and also combustion of hydrogen [37]. It can handle saturated and supe eated conditions and it covers both short-term transients and long-term convection up to several hundred days. 

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