Table 1: Unit 1 Reactor: Fukushima Daiichi Nuclear Power Plant - 11 May 2011

1. 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 of
reactivity
- 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
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2. 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 55
Confining 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, 55–63
Limiting 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