The Opening Kick: Contaminated Water Discovered mid July near the Inner Harbour
- 11 July: TEPCO (Tokyo Electric Power Company) reports a potential radiation leak from Unit 3. Elevated levels of radioactive caesium, strontium and tritium are discovered in a groundwater testing well approximately 30 metres (100′) from the shoreline to the Fukushima inner Harbour, of approximately 10-20,000 Bq/L, 100x the expected amount of 100-200 Bq/L, where 1 Bq = one radioactive disintegration per second.
- For comparison, you have a constant internal activity of 5000 Bq and an average of about 42 L of total body water, for about 120 Bq/L.
What is the Contaminated Water Source?
- 11 July: TEPCO initially suspects the source is a pit which had been implicated in a leak into the inner harbour in April 2011. The Nuclear Regulation Authority (NRA) directs TEPCO to expedite completion of a coastal containment wall to prevent radiation from leaking into the inner harbour, initially slated for completion in March 2015.
- 29 July: TEPCO and NRA suspect source may be trapped water from the initial accident in the cabling trenches that run between the reactors. NRA orders water drained.
- 6 Aug: Ground water levels are noted to rise after ground solidification is complete. NRA on-site official declares a “state of emergency” citing a “rather high possibility” of water spillover into the inner harbour.
- TEPCO announces increased radiation in another sampling well
Is Contaminated Water Leaking into the Inner Harbour?
- 18 July: TEPCO reports to NRA increased tritium detected in the inner quay but no Strontium or Caesium.
- 22 July: TEPCO announces to the press, delaying the announcement until after the general election, swept by the pro-nuclear Liberal Democrats. Foreign consultants are not amused, and TEPCO president announces pay-cuts over the delay, including to himself, states intention to fully disclose henceforth.
Mitigation Efforts Commence for Rising Groundwater Near Shoreline
- 7 Aug: Government official estimates 300 tonnes of ground water reaching “the sea.” No clear discrimination in press reports between inner harbour and open ocean. Levels of Cesium and Strontium essentially unchanged in outer harbour since April ’13.
- TEPCO begins pumping groundwater away from shoreline
- 12 Aug: Japan’s Industry Minister says statement of contaminated water flowing to sea is an assumption.
- 15 Aug: TEPCO releases details of groundwater pumping system. Overall plan is to filter cesium/strontium out of ground water and store in above ground tanks
- 16 Aug: Hanford Engineer Works, which purified the plutonium for the Nagasaki bomb, is approached by TEPCO for assistance in contaminated water handling
- 20 Aug: Cesium stripped water storage tank leaks 300 tonnes of tritium and strontium contaminated water
- 27 Aug: The leak is stopped and defective tank contents are pumped into other tanks
Did Contamination Leak into the Outer Harbour?
- The Fukushima inner harbour is separated from the outer harbour by a large break wall and silt dam which extends to the sea floor and has been closed for over a year, to prevent water mixing.
- 1 Aug: Measurements comparing inner and outer harbour water indicate no contamination is reaching the outer harbour.
Did it Leak Into the Pacific?
- 10 Aug: Radioactivity is undetectable at Nakoso Beach, 65 km south of the power plant and Yotsukura Beach, 40 km south
- 23 Aug: Fukushima prefecture opens Yotsukura beach for the first time since 11 Mar 2011.
- 27 Aug: Rainwater channels that originate at a ditch near the storage tanks and meet the sea showed no detectable Cs-134 and 18 Bq/L of Cs-137, less radioactivity per litre than found in one banana
Is it in the Food Chain?
- Radiation levels in fish sampled outside Fukushima port (1-3 km offshore but within 20 km) show 96 samples in 100 which meet Japanese regulatory requirements
- Fish inside the port show higher radiation levels, but these appear unchanged since April ’13 (cf. Schlegel’s black rockfish).
Is there Human Contamination?
- 22 Aug: 18 child thyroid cancers are reported in 210,000 children in Fukushima prefecture, with 25 more suspected.
- This is much lower than in the US, where 500 cases would be expected in a sample of 200,000 children
What happens now?
- TEPCO intends to resume operation of the ALPS (Advanced Liquids Processing System) in September which will remove all nuclides except tritium
- The national government intends to take a direct, active role in ongoing decontamination
- Post-processed water containing only tritium could be diluted and released into the Pacific
Much of the information in this site has been compiled at the excellent Hiroshima Syndrome, and I am grateful for Leslie Corrice’s ongoing efforts rationally documenting the unfolding saga. My errors are mine alone.