Table 1: Unit 1 Reactor: Fukushima Daiichi Nuclear Power Plant - 11 May 2011
TABLE 1. UNIT 1 REACTOR: FUKUSHIMA DAIICHI NUCLEAR POWER PLANT: 11 MAY 2011 ASSESSMENT OF STATUS IN TERMS OF FUNDAMENTAL SAFETY FUNCTIONS FOR ACHIEVING A SAFE STATE Necessary safety function and Observation Evaluation of safe state TEPCO Roadmap countermeasures conditions Reactor is subcritical and sub- - No power spike or power increase ACHIEVED No additional countermeasures reported criticality is demonstrated and - No significant neutron flux measured and Caution:Control of maintained reported - Continue detection ofreactivity - Short lived fission products (e.g. La-140) neutrons and short-lived are not reported at present isotopes Stable cooling shall be assured: - Based on available measurements: NOT ACHIEVED Nos 1, 3, 4, 7, 8, 9, 13, 14, 16 and 17 - Keep the coolant temperature • Reactor vessel temperatures are: Establishment of a long term sufficiently below the boiling 115.7 °C at feedwater nozzle and closed-loop heat removal Actions aimed to establish closed-loop cooling point at atmospheric pressure 94.1 °C at the lower head circuit is advised are in progress: - Cover the damaged core • 1. Installation of primary and secondary Residual heal removal Reactor pressure: (A) 5.7 atm / (B) adequately with water 13.8 atm) based on available closed-loop cooling systems (planned for 31 - Off-site and back-up power measurements May) supply shall be available • Water level of reactor core is below 2. Flooding of the containment to provide - Achievement of long term about −1650 mm (A) from the top water supply for the primary system closed-loop heat removal of active core capability - Off-site power supply and backup power from portable diesel generators are available - Fresh water injection is provided; however, closed-loop heat removal is not yet established - Containment pressure - Pressure in the primary containment ACHIEVED Nos 2, 6, 11 and 15 maintained below design vessel is maintained at about 1.05 atm Caution:Containment integrity limits which is well below the design operating - Pressure and H2 - Hydrogen explosion to be pressure of 4.85 atm concentration of the prevented - Nitrogen injection is maintained containment to be further monitored[Type text]
Necessary safety function and Observation Evaluation of safe state TEPCO Roadmap countermeasures conditions - Reactor pressure vessel - Reactor pressure vessel is assumed to be PARTIALLY ACHIEVED Nos 5, 10, 29–46, 50, 54 and 55Confining radioactive (including connected leaking most probably through connected Caution: systems) should not leak; or if recirculation system (pump seal loss of - radioactive releases including material so the leakage shall be coolant accident) venting operations should be confined - Exiting gap in pressure containment limited, controlled and - Leakages from the vessel is assumed (ongoing injection of monitored containment should be nitrogen has not led to increase of prevented or controlled, or pressure in pressure containment vessel) shall be confined - No additional releases shall - Intermittent releases have been observed PARTIALLY ACHIEVED Nos 12, 47–49, 51–53, 55–63Limiting effects of be anticipated - Radiation monitors are available Caution: - Radiation monitoring - Reactor pressure vessel and pressure - radioactive releases including In order to reduce air radiation levels inside the releases measurements shall be containment vessel are assumed to be venting operations should be reactor building, a filtered air circulation system available leaking. limited, controlled and and system circulating outside air through the - Opening of the airlock in the reactor monitored building have been installed building did not lead to measurable increase in the releases to the environment
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