Date: 2011/8/9
Subject: TEPCO Fukushima Information Update on August 9: Unit 3 second meltdown ?
To: Kenji Matsuo <matsuo.kenji@tepco.co.jp>
Dear Friends,
In the Asahi Shimbun article titled “Report suggests second meltdown at reactor at Fukushima plant”, it is reported that Unit 3 might have melted twice. TEPCO’s position is shown below:
(Excerpt)
“A second meltdown likely occurred in the No. 3 reactor at the Fukushima No. 1 nuclear power plant, a scenario that could hinder the current strategy to end the crisis, a scientist said.
In that meltdown, 10 days after the March 11 Great East Japan Earthquake, the fuel may have leaked to the surrounding containment vessel, according to a report by Fumiya Tanabe, a former senior researcher at what was then the government-affiliated Japan Atomic Energy Research Institute. “
(TEPCO’s comment)
- As for the status of the reactor core around March 21, even though water injection was not sufficient, we do not believe additional large amount of radioactive materials were released into the PCV from damaged fuels based on the fact that indication of CAMS in the drywell had been decreasing during this period.
- On May 24, we have reported reactor core status in the “Analysis and evaluation of the operation record and accident record of Fukushima Daiichi Nuclear Power Station at the time of Tohoku-Chihou-Taiheiyou-Oki-
- The result of the analysis and plant parameters indicated majority of the reactor core was damaged and moved downward from its original position but we believe most of the fuel is under stable cooling.
(Excerpt)
“Between 1 a.m. and 3 a.m. on March 21, the pressure within the pressure vessel of the No. 3 reactor core increased sharply to about 110 atmospheres, likely caused by an explosion within the pressure vessel due to a lack of cooling of the fuel. That was probably the start of the second meltdown, Tanabe said.”
(TEPCO’s comment)
- In our plant parameter release as of 5:00 on March 21, as we described “at 3:58 reactor pressure indicator switched from B to A due to malfunction of the pressure indicator”, we do not think the pressure increase to 110 atmospheres was actual pressure response.
(Excerpt)
“As for the sudden pressure increase, Tanabe points to the possibility that the clump of melted fuel in the pressure vessel may have fallen apart due to a lack of cooling. The magma-like substance with high temperatures may have leaked out of the vessel and emitted large amounts of steam when it came in contact with water. “
(TEPCO’s comment)
- If “clump of melted fuel ・・・ leaked out of the vessel ・・・” was correct, very large increase of radiation level in the PCV is expected. However, we do not see any such increase from the drywell CAMS data. The CAMS data shows decrease during this period.
(Full article)
Contacts:
TEPCO Washington Office: 202-457-0790
Kenji Matsuo, Director and General Manager
Ikuo Nishimura, Deputy General Manager,
Masayuki Yamamoto, Manager, Nuclear Power Programs
- TEPCO English website
- METI(Ministry of Economy Trade and Industry)
- NISA(Nuclear and Industrial Safety Agency)
- JAIF(Japan Atomic Industrial Forum Inc.)
- FEPC(The Federation of Electric Power Companies of Japan)
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