“Not for Distribution, Internal Use Only”: US Energy Dept. estimated Fukushima release up to 10,000 times larger than nuclear regulators predicted — ‘Supercore’ scenario an underestimate?

Published: September 9th, 2014 at 1:00 am ET
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Ocean Plume Modeling for the Fukushima Daiichi Event (pdf) — US Dept. of Commerce, NOAA, National Weather Service, Sept. 2013:

> Estimates of contamination

  • “Coastal releases ignored. According to TEPCO estimates, coastal releases are 1% of atmospheric… Not important for far-field estimates (i.e., exposure for US territories)”
  • “Scenarios used [are] NRC source scenario [and] DOE Supercore source scenario”
  • Regarding Cs-137 release estimates, “NRC and DOE differ by three orders of magnitude” [i.e. DOE estimate is 1,000 to 9,999 times more than NRC]
  • “Enormous uncertainty in total amount of contamination released at FDNPP”
  • “Differences between NRC &  DOE sources are crippling from a scientific perspective”
  • “DOE much too high at… JAMSTEC observation line 30km offshore [and] overestimates Cs-137 by order of magnitude [predicting a] maxima of around 100 Bq/L for Cs-137… JAMSTEC realistic contamination levels would be factor 10 smaller (10 Bq/L).”

Is DOE’s 100 Bq/L an ‘Overestimate’?

  • The above report by the federal government claims to use ‘realistic’ data from the JAMSTEC line (Japan Agency for Marine-Earth Science and Technology) of 10 Bq/L for Cs-137. However, JAMSTEC measured a maxima of 186 Bq/L for Cs137 at 30km off the Fukushima coast — nearly double the DOE ‘overestimate’.
  • The Science Council of Japan: “Oceanic monitoring… identified that 100 Bq/L or more of 137Cs had been diffused to the north and south.”

DOE’s estimate based on the ‘supercore’ scenario came rather close to predicting actual Cs-137 levels observed in samples from the Pacific Ocean — if anything, it appears to be an underestimate.

The reactor conditions assumed in DOE’s ‘supercore’ scenario have been redacted from FOIA documents. However it’s likely that the ‘supercore’ was among the worst-case scenarios discussed by the US government. As reported by Echo News,  around 5 different worst-cases were in play — “I still won’t let anybody use the word ‘worst case’ in the room here because there’s about five worst cases.” -NRC’s Director of Nuclear Security & Incident Response

See also: "There is spent fuel and pellets and whatever all over the place around the plant" -NRC's Top Man in Japan -- Trying to clean it up, but dose still going to be incredible

Published: September 9th, 2014 at 1:00 am ET
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