Table 3: Unit 3 Reactor: Fukushima Daiichi Nuclear Power Plant - 18 May 2011

TABLE 3. UNIT 3 REACTOR: FUKUSHIMA DAIICHI NUCLEAR POWER PLANT: 18 MAY 2011 ASSESSMENT OF STATUS IN TERMS OF FUNDAMENTAL SAFETY FUNCTIONS FOR ACHIEVING A SAFE STATE Necessary safety function Evaluation of safe TEPCO Observation and conditions state Roadmap countermeasures Reactor is subcritical and - No power spike or power increase ACHIEVED Boric acid was injected on May 15 as a precautionary sub-criticality is - No significant neutron flux measured and reported measure to preclude criticality a conditionControl of WITH CAUTIONreactivity demonstrated and - Short lived fission products (e.g. La-140) are not Caution: maintained reported at present - Continue detection of neutrons and short-lived isotopes Stable cooling shall be - Continued injection of fresh water through both fire NOT ACHIEVED Nos 1, 3, 4, 7, 8, 9, 13, 14, 16 and 17 assured: extinguishing lines at a rate 9.0 m3/h and feedwater Establishment of a - Keep the coolant system at a rate 6.0 m3/h long term closed-loop Preparation for injection of water through the temperature - Further temperature decrease is observed: 137.5 oC on heat removal circuit is feedwater system is continuing: sufficiently below the May 16 at the feedwater nozzle (141.3 °C on 15 May; - The water from the condenser was transferred to Residual heal removal advised. boiling point at 218.7 °C on 11 May); 129.5 °C on 16 May at the low the basement of the turbine building on 9 May atmospheric pressure head (136.2 °C on 15 May; 152.5 °C on 11 May); - Cover the damaged - Reactor pressure vessel pressure and containment core adequately with pressure reported are about atmospheric; however, the water pressure measured on 16 May in the wet well is 1.92 - Off-site and back-up atm, showing slight increase (from 1.83 atm on 12 power supply shall be May) available - Off-site power supply and backup power from portable - Achievement of long diesel generators are available term closed-loop heat - Fresh water injection is provided; however, closed- removal capability loop heat removal is not yet established[Type text]

Necessary safety function Evaluation of safe TEPCO Observation and conditions state Roadmap countermeasures - Containment is leak- - The latest measurements show the reactor pressure PARTIALLY Nos 2, 6, 11 and 15 tight vessel pressure and containment pressure to be around ACHIEVED - Containment pressure atmospheric pressure - Measures to make is maintained below - On 20 March a sudden significant drop in pressure in the containment Containment integrity design limits the reactor pressure vessel and a decrease in the leak-tight should - Hydrogen explosion containment pressure occurred. The reasons for this are be pursued must be prevented unknown. One possible explanation is a loss of - Pressure and H2 containment integrity; however, the pressure in the concentration of containment was decreasing slowly and at present the containment remains stable at around 1.03 atm. In addition water on to be further the turbine building floor of Unit 3 does not show high monitored level radioactivity - Images of Unit 3 show a crack in the primary containment and steam being released from the reactor building - Reactor pressure - Reactor pressure vessel is assumed to be leaking, PARTIALLY Nos 5, 10, 29–46, 50, 54 and 55Confining radioactive vessel (including most probably through the connected recirculation ACHIEVED (See also Annex) connected systems) system (a pump seal loss of coolant accident); leak Construction of a should not leak; or if elevation is about −1500 from the top of the active cover above the material so the leakage shall be fuel (level of ejectors of reactor coolant pumps) reactor building confined - Containment is believed to be damaged; latest should be pursued - Leakages from the measurements show the containment pressure is containment should be about atmospheric pressure prevented, controlled or shall be confined

Necessary safety function Evaluation of safe TEPCO Observation and conditions state Roadmap countermeasures - No additional releases - Intermittent releases have been observed PARTIALLY Nos 12, 47–49, 51–53, 55–63 shall be anticipated - Radiation monitors are available ACHIEVED - On May 16 TEPCO reported on the plans to - Radiation monitoring - Reactor pressure vessel and pressure containment Measures to prevent transfer highly contaminated water accumulated inLimiting effect of releases measurements shall be vessel are assumed to be leaking radioactive releases the basement of the Turbine Bld. to High- available - White smoke is observed emanating continuously should be further Temperature Incinerator Bld.(in addition to from the reactor building pursued RadWaste Treatment Facilities) - NISA reviewed TEPCO’s report on the transfer and determined the transfer was necessary to prevent radiation hazards. In addition, NISA asked TEPCO to carry out the plan and since the original purpose of these buildings is not the storage of accumulated water, TEPCO shall consider ceasing their utilization based on installation progress of treatment facilities. SPENT FUEL POOL OF UNIT 3On 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 plantusing 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.Amounts of about 106 tonnes of fresh water and 0.88 m3 of hydrazine were injected on 16 May into the spent fuel pool of Unit 3 via the fuel poolcooling and clean-up system. 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

Table 3: Unit 3 Reactor: Fukushima Daiichi Nuclear Power Plant - 18 May 2011

by International Atomic Energy Agency

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