Safety analysis of the reactivity transients resulting from water ingress into a high-temperature pebble bed reactor

Journal Article · Mon Aug 01 04:00:00 EDT 1983 · Nucl. Technol.; (United States)

OSTI ID:6276719

Nabbi, R; Jahn, W; Meister, G; Rehm, W

Analysis of extreme water ingress accidents in the pebble bed high-temperature reactor of 500-MW (thermal) power during the first few minutes shows that the temperature coefficients of reactivity limit the power increase, presupposing no action of the shutdown system and other safety devices. The rupture of all steam generator tubes with the highest ingress rate of 55 kg/s results in a power maximum of 1.8 times the initial value after about1 min. The system pressure increases from the operating value of 40 bar up to the design value of 50 bar. Fuel temperatures do not reach values that cause fuel particle damage and fission product release. Hence, special requirements on the promptness of shutdown rod actions are not needed to limit accident consequences in the core. Overpressurization of the reactor vessel will arise, however, if water ingress with the highest rate continues. Water ingress at a small rate (7 kg/s), corresponding to the rupture of a few tubes, results in a rather slow power increase up to 1.3 times the initial value and to a primary system pressure of 43 bar after 5 min.

• Research Organization: Kernforschungsanlage Julich, Institut fur Nukleare Sicherheitsforschung
• OSTI ID: 6276719
• Journal Information: Nucl. Technol.; (United States), Journal Name: Nucl. Technol.; (United States) Vol. 62:2; ISSN NUTYB
• Country of Publication: United States
• Language: English

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