1. TABLE 3. UNIT 3 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 TEPCO
Observation Evaluation of safe state
conditions Roadmap countermeasures
Reactor is subcritical and sub- - No power spike or power increase ACHIEVED No additional
criticality is demonstrated and - No significant neutron flux measured and reported Caution: countermeasures reported
Control of
reactivity
maintained - Short lived fission products (e.g. La-140) are not reported at present - Continue detection of
neutrons and short-
lived isotopes
Stable cooling shall be - Injection of fresh water at a rate 9.0 m3/h (as of 9 May) NOT ACHIEVED Nos 1, 3, 4, 7, 8, 9, 13, 14, 16
assured: - The temperature has risen significantly since 5 May: on 10 May it Establishment of a long and 17
- Keep the coolant was 218.7 °C at the feedwater nozzle (122.6 °C on 5 May); the term closed-loop heat
temperature at the low head did not change (152.5 °C)
Residual heal removal
temperature sufficiently removal circuit is Preparation for injection of
below the boiling point at - Water level in the reactor slightly increased: −1750 mm (A) and −2000 advised. water through the feedwater
atmospheric pressure mm (B) (on 5 May: −1850 mm (A) and −2250 mm (B)) from the top of system is continuing:
- Cover the damaged core active core - The water from the
adequately with water - Reactor pressure vessel pressure and containment pressure are about condenser was
- Off-site and back-up atmospheric pressure transferred to the
power supply shall be - Off-site power supply and backup power from portable diesel generators basement of the turbine
available are available building on 9 May
- Achievement of long term - Fresh water injection is provided; however, closed-loop heat removal is
closed-loop heat removal not yet established
capability
- Containment is leak-tight - The latest measurements show the reactor pressure vessel pressure and PARTIALLY Nos 2, 6, 11 and 15
- Containment pressure is containment pressure to be around atmospheric pressure ACHIEVED
maintained below design - On 20 March a sudden significant drop in pressure in the reactor pressure - Measures to make
Containment integrity
limits vessel and a decrease in the containment pressure occurred. The reasons the containment
- Hydrogen explosion must for this are unknown. One possible explanation is a loss of containment leak-tight should be
be prevented integrity; however, the pressure in the containment was decreasing pursued
slowly and at present remains stable at around 1.03 atm. In addition - Pressure and H2
water on the turbine building floor of Unit 3 does not show high level concentration of the
radioactivity containment to be
- Images of Unit 3 show a crack in the primary containment and steam further monitored
being released from the reactor building
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2. Necessary safety function and TEPCO
Observation Evaluation of safe state
conditions Roadmap countermeasures
- Reactor pressure vessel - Reactor pressure vessel is assumed to be leaking, most probably PARTIALLY Nos 5, 10, 29–46, 50, 54 and
Confining radioactive
(including connected through the connected recirculation system (a pump seal loss of ACHIEVED 55
systems) should not leak; coolant accident); leak elevation is about −1500 from the top of the Construction of a cover (See also Annex)
material
or if so the leakage shall active fuel (level of ejectors of reactor coolant pumps) above the reactor
be confined - Containment is believed to be damaged; latest measurements show the building should be
- Leakages from the containment pressure is about atmospheric pressure pursued
containment should be
prevented, controlled or
shall be confined
- No additional releases - Intermittent releases have been observed PARTIALLY Nos 12, 47–49, 51–53, 55–63
Limiting effect
shall be anticipated - Radiation monitors are available ACHIEVED
of releases
- Radiation monitoring - Reactor pressure vessel and pressure containment vessel are assumed to Measures to prevent
measurements shall be be leaking radioactive releases
available - White smoke is observed emanating continuously from the reactor should be further
building pursued
SPENT FUEL POOL OF UNIT 3
On 8 May 2011 TEPCO took approximately 40 mL (40 cm3)of water from the spent fuel pool of Unit 3 at Fukushima Daiichi nuclear power plant
using the concrete pumping vehicle to check the condition in the pool.
The results of the radionuclide analysis of the pool water are shown in Table 4. TEPCO will further evaluate the situation.
TABLE 4. RESULTS OF ANALYSIS OF WATER FROM THE SPENT FUEL POOL OF UNIT 3
Main radionuclide detected Activity concentration
(Bq/cm3)
Caesium-134 140 000
Caesium-136 1600
Caesium-137 150 000
Iodine-131 11 000