Table 4: Unit 4 Reactor: Fukushima Daiichi Nuclear Power Plant - 18 May 2011

TABLE 4. UNIT 4 REACTOR, SPENT FUEL POOL: 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 and TEPCO Roadmap Observation Evaluation of state conditions countermeasures Spent fuel pool shall be subcritical - According to TEPCO statement and to its PARTIALLY ACHIEVED: Maintaining the geometry of spent Keff < 0.95 (design value), and sub- assessment from the water sampling of the spent CAUTION fuel pool (including aftershocks) criticality shall be demonstrated fuel pool, TEPCO assumes that the fuel - Risk of criticality a priori excluded reinforce by countermeasure 20, Control of reactivity and maintained assemblies are ‘intact’ (sampling 26 April 2011) by TEPCO (provided that 21, 26 - New sampling performed (280 mL on 7 May). geometrically safe configuration is Make-up/cooling of spent fuel pool The activity concentrations (Cs-134/Cs-137) are maintained, etc.) by external water injection increasing compared with previous - Further assessment needed (countermeasures 18, 22, 28) measurements. Analysis by TEPCO is - In order to avoid any potential No borated water injected continuing problem due to further aftershocks, No countermeasure explicitly - Only fresh (non-borated) water is being sprayed make-up with borated water to avoid mentioned into the spent fuel pool (120 tonnes on 11 May) any risk of criticality is advised - Hydrazine is being continuously injected - Monitoring of neutrons and short - No neutron flux measured reported lived isotopes to be considered Stable cooling shall be assured Latest temperature reported: 81 °C after spraying PARTIALLY ACHIEVED: Cooling of spent fuel pool by - Spent fuel pool temperature on 9 May (no updated data available) CAUTION external water injection should be similar to the spent (countermeasures 18, 22, 28) fuel pond design values Sampling of steam/pool water and Residual heal removal Make-up (with borated water) to be (approx. 30 °C) continued measurement of radioactive - To recover the spent fuel pool Spent fuel pool temperature is not materials (countermeasure 19) water level adequately with reported on May 16 Circulation cooling of spent fuel (borated) water to about 7 m pool above the top of active fuel. (countermeasures 23, 24, 25, 27) - To restore spent fuel cooling[Type text]

Necessary safety function and TEPCO Roadmap Observation Evaluation of state conditions countermeasures - To recover the spent fuel pool - Fuel assemblies are covered by water ACHIEVED: - Cooling of spent fuel pool byConfining radioactive material water level adequately to CAUTION external water injection ensure some form of shielding - to continue spraying and/or make (countermeasures 18, 22, 28) above the top of active fuel. up - Circulation cooling of spent - to continue monitoring of major fuel pool (countermeasures 23, spent fuel pool parameters 24, 25, 27) (temperature, water level) - Sampling of steam/pool water - to improve radiation protection and measurement of radioactive materials (countermeasure 19) - Reactor building cover (countermeasures 5, 50, 54, 55) - Releases shall be only within - Uncontrolled release are not expected so far PARTIALLY ACHIEVED: - Nos 10, 12, 29–46 cooling of the agreed allowed legal limits - Radiation monitoring positions are available CAUTION spent fuel pool by external - Radiation monitoring - According to a TEPCO statement, fuel - Radioactive releases to be prevented water injectionLimiting effects of releases measurements shall be assemblies are assumed to be ‘intact’. by sufficient water make-up (countermeasures 18, 22, 28) available However, further assessment by TEPCO of - Reactor building cover to be pursued - Circulation cooling of spent - Leakages from the spent fuel the latest sampling should confirm this fuel pool (countermeasures 23, pool should prevented or statement 24, 25, 27) controlled, or if not shall be - Sampling of steam/pool water confined and measurement of radioactive material (countermeasure 19) - Reactor building cover (countermeasures 5, 50, 54, 55)

Table 4: Unit 4 Reactor: Fukushima Daiichi Nuclear Power Plant - 18 May 2011

by International Atomic Energy Agency

Accessibility

Upload Details

Usage Rights

Statistics