Nikkei Shinbun's Interview of Haruki Madarame (4/7): The Worst Case Would Be "High-Pressure Melt Through", Politicians Thought Recriticality Was Nuclear Explosion

(Continued from Part 1, Part 2 and Part 3, from Nikkei Shinbun: Testimony of Dr. Madarame, in the third year of the accident: "Worst case scenario was possible for Fukushima" by Junichi Taki, editorial board member)

■「食い違いがあることに気づかず議論をしていた」

"We were talking past each other, and we didn't even know it."


――12日午後に１号機で爆発が起きたとき、どう思ったのか。

--What did you think when an explosion happened in Reactor 1 in the afternoon of March 12, 2011?

「映像を見た瞬間に水素爆発だと思った。その時の記憶はあいまいだが、下村健一・内閣審議官（当時）の書いたものよると、私は『建屋に水素が漏れて、建屋には水素があるので爆発した』と淡々と説明したとされている。多分、事実だろう」

"I thought it was a hydrogen explosion the moment I saw the image. I don't remember clearly, but according to what Kenichi Shimomura, who was a cabinet counselor at that time, wrote, I calmly explained that "hydrogen leaked into the building, and since there is hydrogen (sic) [probably "oxygen"] in the building an explosion happened." I think it is probably true."

「この爆発を機に、首相は私の言うことを信用しなくなった。『安全委員会にはほかに専門家はいないのか』と問われたので、『久木田豊委員長代理（当時）も詳しい』と答えると、『すぐに呼べ』と言われたので、久木田さんに来てもらい、私はオフィスに戻った」

"From this explosion on, Prime Minister stopped believing me. He asked me if there were other experts at the Nuclear Safety Commission. I answered that Acting Chairman Yutaka Kukita was also knowledgeable. He told me to "call him here immediately". So I had Mr. Kukita come, and I returned to my office."


――１号機の爆発のあった時間帯は、海水注入の議論をしていたころでもある。

--Around the time of the Reactor 1 explosion, the debate was ongoing on seawater injection [into the reactors].

「（海水注入の議論の中で）『再臨界の可能性はあるか』と首相から問われたら、『可能性はある』と答えたとしてもおかしくない。私には尋ねられた記憶がない」

"In discussing the seawater injection, it would not be odd if I had been asked by Prime Minister whether there was a possibility of recriticality and I had answered there was a possibility. I have no memory of being asked."

「実は水素爆発の前の時点から、海江田万里・経産相（当時）が議長になって海水注入の問題点を総理応接室（官邸５階）で話し合っていた。塩が析出し腐食も問題になるので長期間は無理だが、いまは炉心を冷やすことを何より優先し海水を入れろと私は主張していた。首相が海水注入を止めるよう言うはずはないと思う。海水注入中断の問題は、国会事故調査委員会などが指摘するように東電の武黒一郎フェローの勝手な判断が介在していたように思う。いずれにしても、吉田昌郎所長（当時）の判断で注入の中断はなかった」

"Even before the hydrogen explosion, Minister of Economy Banri Kaieda was chairing a meeting in the PM Reception Room (on the 5th floor of the PM Official Residence), and we were talking about the potential problems of seawater injection. I insisted that seawater be injected as cooling the reactor core was the first priority, even though it was not a long-term solution because of salt deposition and corrosion problem. I don't think Prime Minister would order a halt in seawater injection. The issue of halting the seawater injection arose, as pointed out in the National Diet accident investigation commission, from an arbitrary decision by TEPCO's Fellow Ichiro Takekuro. In any way, there was no halt thanks to Plant Manager Masao Yoshida."

「後に福山哲郎・官房副長官（当時）はじめ、政治家の人たちの著書を読んで気がついたのだが、みなさん再臨界イコール核爆発だと思っていたらしい。再臨界が仮に起きても核爆発とは違うことは、ＪＣＯ事故などからも明らかだ。食い違いがあることに気づかず議論をしていた」

"I realized later when I read books by politicians including Mr. Tetsuro Fukuyama (then-Deputy Chief Cabinet Secretary) that everyone had thought recriticality meant nuclear explosion. It is obvious from accidents like the JCO accident that even if criticality happens that's different from nuclear explosion. But we were talking past each other, and we didn't even know it."

――その日は深夜に自宅に戻るが、すぐにまた官邸に呼ばれる。

--You went home late that night, but was called back soon to the PM Official Residence.

「ほとんど寝ていない。ただ13日になると、いろいろな専門家から見解を聞く余裕が出てきた。とくに久木田さんとの意見交換は貴重で、その時点で最も怖いのは高圧溶融物放出（ＨＭＴ=High-pressure Melt Through）という現象だと意見が一致していた。これは溶融燃料によって圧力容器の壁が溶けて薄くなった末、圧力容器内と格納容器の圧力差によって燃料が容器を突き破って外に飛び出す現象だ。格納容器の壁まで貫通してしまう恐れがある」

"I hardly slept. But on March 13, I began to have more time [or "peace of mind"] to listen to other experts. Discussion with Dr. Kukita was particularly valuable, and we both agreed that the most frightening possibility at that time was the phenomenon called "High-pressure Melt Through" (HMT). HMT happens when the melted fuel melts the Pressure Vessel wall thin, and the melted fuel gets ejected through the Pressure Vessel due to the difference in pressure between the Pressure Vessel and the Containment Vessel. It is possible that the melted fuel could pierce through the wall of the Containment Vessel."

「14日の３号機の水素爆発の後、２号機の逃がし安全弁を急いで開くように助言したのは、２号機でＨＭＴが起きるのを心配して、圧力容器と格納容器の圧力を均一化した方がよいと考えたからだ。吉田所長はまずベントの準備を整えてからと主張していた。安全弁を開くと圧力容器内の水が水蒸気となって格納容器に流れ出し、燃料が空だきになる恐れがあるので、注水の備えがないと安全弁を開けない。難しい判断だ」

"After the hydrogen explosion of Reactor 3 on March 14, I advised that the relief safety valve of Reactor 2 should be opened quickly. I was worried that HMT might happen in Reactor 2, so I thought it would be prudent to equalize the pressure in the Pressure Vessel and the Containment Vessel. Plant Manager Yoshida insisted that preparation for the vent be done first. If the relief safety valve is opened, the water inside the Pressure Vessel becomes water vapor and flows into the Containment Vessel, leaving the fuel heated without water. So you cannot open the relief safety valve without preparation to inject water. It is a difficult decision."

――そう考えると、原子炉の底部から溶融燃料が落ちたのは不幸中の幸いと言えるか。

--In that sense, it was lucky that the melted fuel dropped from the bottom of the reactor.

「そうとも言える」

"You could say so."

班目氏の行動（３月13日）
3:40ころ 自宅で原子力安全委事務局からの電話
5:00ころ 官邸へ（官邸到着前に安全委オフィスで他の安全委員らと意見交換）
この間、３号機の高圧注水系停止などの事態が進む
10:04 原子力災害対策本部の会議
13:55 安全委オフィスに戻り、官邸の状況を説明
14:35 官邸へ
この間、保安院の安井氏らも加わって、３号機の水素爆発の可能性を議論
15:30 官房長官記者会見に同席（これ以降、数回）
21:35 原子力災害対策本部の会議
久木田委員長代理と最悪のシナリオを議論。政治家にメルトスルー後のコンクリート反応を説明

Dr. Madarame on March 13, 2011:
3:40AM received call at his home from the secretariat of the Nuclear Safety Commission
5:00AM went to the PM Official Residence (after speaking with other commissioners at the Nuclear Safety Commission office)
The situation at the plant grew more serious as Reactor 3's high-pressure core injection system stopped.
10:04AM meeting of the Nuclear Disaster Response Headquarters
1:55PM went back to the Nuclear Safety Commission office, and explained the situation at the PM Official Residence
2:35PM went back to the PM Official Residence
Discussed the possibility of a hydrogen explosion in Reactor 3 with others including Mr. Yasui from NISA
3:30PM accompanied Chief Cabinet Secretary [Edano] in the press conference (would do a few more times later)
9:35PM meeting of the Nuclear Disaster Response Headquarters
Discussed the worst case scenario [high-pressure melt through] with Deputy Chairman Kukita of Nuclear Safety Commission. Explained the core-concrete reaction after the melt through to the politicians

It is interesting to note that, according to Dr. Madarame's March 13, 2011 schedule, he was debating with another nuclear expert (Kukita) about the worst case of "high-pressure melt through", in which the melted core (corium) will eject from the Pressure Vessel at a high speed, possibly piercing through the Containment Vessel, while telling the politicians a more "benign" core-concrete reaction scenario.

If HMT had happened in Reactor 2, as Dr. Madarame and Dr. Kukita feared, it may have been an immediate evacuation from the plant. The worst case that PM Kan says he received (but decided to sit on it for months and deny the existence of the report) may have come true then.

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#Fukushima Nuclear Accident: "Worst Case Scenario" Involved Evacuation of 500,000 People, Says Government Minister

Remember the "worst-case scenario" that the Kan administration withheld in March last year and was disclosed only in January this year? Yes that one, thanks to the mis-translation by Mainichi Daily, which morphed into articles that screamed "the Japanese government are creating blueprints for forcibly removing 39 million people from the Tokyo metro-area".

Now, Koichiro "Let's all cheer for TEPCO" Genba, Minister of Foreign Affairs in the Noda administration who was the minister in charge of national strategy under the Kan administration, claims he was the one who "ordered the worst-case scenario", and that the plan was to evacuate about a half million people from the areas inside the 50-kilometer radius from Fukushima I Nuclear Power Plant.

It is still a significant number, about a quarter of the population of Fukushima Prefecture and about 5 times the number of residents who actually evacuated. But it is nowhere near 39 million people inside the 250-kilometer radius. The 50-kilometer radius evacuation was what the top management at the plant had expected after the explosion of Reactor 1 building, and they were surprised when they learned that only the residents inside the 20-kilometer radius were evacuated, according to the article by Shukan Asahi in July last year.

Mr. Genba is elected from Fukushima Prefecture. He said "Let's all cheer for TEPCO" right after he got the "worst-case scenario" from the Atomic Energy Commission of Japan.

From Asahi Shinbun (5/10/2012):

幻の５０万人原発避難計画　福島事故直後、官邸が想定

Prime Minister's Office's plan right after the Fukushima accident to evacuate 500,000 people, but the plan wasn't executed

昨年３月の東京電力福島第一原発事故の発生直後、首相官邸内で原発から半径５０キロ圏の住民約５０万人を避難させる計画を立てていたことがわかった。原発が制御不能になる最悪の事態を想定したもので、結果的には幻に終わった。

It has been revealed that there was a plan at the Prime Minister's Official Residence right after the Fukushima I Nuclear Power Plant accident started in March last year to evacuate about 500,000 residents inside the 50-kilometer radius from the plant. The assumption was the worst case where a reactor would become uncontrollable. In the end, the plan was never executed.

　事故当時、国家戦略相だった玄葉光一郎外相が朝日新聞の取材に対して明らかにした。衆院福島３区選出の玄葉氏は、事故翌日の３月１２日の原子力災害対策本部会議で「メルトダウン（炉心溶融）の可能性がある」と指摘。３月１５日には、内閣府原子力委員会に「最悪の事態」を想定した対応を指示した。

Minister of Foreign Affairs Koichiro Genba, who was the minister in charge of national strategy at the time of the accident, told Asahi Shinbun. Mr. Genba, who is elected to the Lower House from the 3rd district of Fukushima Prefecture, says he pointed out the possibility of meltdown (core melt) in the meeting of the nuclear disaster response headquarters on March 12, 2011, one day after the start of the accident. On March 15, he instructed the Atomic Energy Commission of Japan (JAEC) under the Cabinet Office to come up with the response [to the accident] based on the "worst-case scenario".

　原子力委は、原子炉の一つが制御不能になってメルトダウン状態になり、作業員が撤退して周囲の原子炉も制御不能に陥る連鎖が起きるシナリオに基づいて計画を作成。玄葉氏は当時の菅直人首相に提言した。

JAEC crafted the plan based on the scenario where one of the reactors would become uncontrollable and have a meltdown, triggering the chain reaction of other reactors becoming uncontrollable as the workers would evacuate from the plant. Mr. Genba proposed [the plan to evacuate 500,000 residents] to then-Prime Minister Naoto Kan.

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Chief Cabinet Secretary Edano on March 12, 2011: "We Should Consider Evacuation of Tokyo, Ibaraki"

Tokyo Shinbun reports that according to information they obtained through the Japanese equivalent of the FOIA, the Kan administration did talk about wide-area evacuation in the Tokyo Metropolitan areas even before the Atomic Energy Commission's chief handed the worst-case scenario to then-Prime Minister Kan on March 25, 2011.

It was Yukio Edano, then-Chief Cabinet Secretary (and current Minister of Economy, Trade and Industry), who mentioned the wide-area evacuation, while other unnamed ministers were worried about the stock market, in the evening of March 12, 2011 after Reactor 1 blew up.

... Stock market?

From Tokyo Shinbun evening edition (4/13/2012):

東京、茨城の避難検討　福島１号機　水素爆発直後に官邸

Prime Minister's Office was contemplating evacuation of Tokyo and Ibaraki, right after the hydrogen explosion of Fukushima Reactor 1

東京電力福島第一原発１号機の原子炉建屋が水素爆発した昨年三月十二日、首相官邸で開かれた原子力災害対策本部の会合で、福島県だけでなく、東京都や茨城県も含めた広域避難が必要になるかもしれない、と議論していた。十三日、本紙が情報公開請求で得た政府のメモ書きなどから分かった。

On March 12, 2011 when a hydrogen explosion took place in the Reactor 1 building at Fukushima I Nuclear Power Plant, a meeting of the nuclear disaster response headquarters was held in the Prime Minister's Official Residence where a wide-area evacuation including Tokyo and Ibaraki Prefecture was being discussed, this newspaper learned on April 13 from the memo by the government officials obtained via the information disclosure request.

　このメモは、十二日午後十時七分から開かれた第四回会合の発言をまとめたもの。この日は午後三時半ごろに１号機原子炉建屋で水素爆発が起き、３号機でも緊急冷却装置が不安定な動きをみせるなど、深刻な状況が相次いで起きていた。

The memo is the summary of remarks during the 4th meeting that started at 10:07PM on March 12, 2011. That day, a hydrogen explosion occurred in the reactor building of Reactor 1, and the emergency cooling system of Reactor 3 was becoming unstable, and the crisis was deepening.

　会合では、玄葉光一郎国家戦略担当相（当時）が「最悪の事態想定を」と求めると、菅直人首相（同）が「チェルノブイリ型（の放射能汚染）はありえるのか」などの懸念を示した。菅氏は福島第一は原子炉の形式が全く異なるとの説明に納得はしたが、とにかく格納容器を守り抜く重要性を強調した。

In the meeting, Koichiro Genba, then-minister in charge of national strategy [and current Minister of Foreign Affairs] wanted to have "the worst-case scenario", to which then-Prime Minister Naoto Kan responded with worries about whether it was possible to have radiation contamination like in the Chernobyl accident. Mr. Kan accepted the explanation that the reactors at Fukushima I Nuclear Power Plant were of totally different type [from the Chernobyl reactor], but emphasized the importance to secure the Containment Vessels at all cost.

　各閣僚から停電や食品、株式相場への悪影響への懸念が出される中、枝野幸男官房長官（当時）は「広域避難もそろそろ考えるべきだ。東京、茨城も」と発言したという。

Ministers expressed worries over blackouts, [availability of] foods, and negative effect on the stock market. Then-Chief Cabinet Secretary Yukio Edano said, according to the memo, "We have to start thinking about wide-area evacuation. Including Tokyo, and Ibaraki."

　原災本部など震災関連の会合をめぐっては、議事録が作成されていない問題が発覚。批判を受け、政府は先月議事概要を公表した。

It has been recently discovered that the minutes of the meetings related to the March 11, 2011 disaster, including those of the nuclear disaster response headquarters, haven't been created. Responding to the criticism, the government published the summaries of the meetings last month.

　広域避難発言などは議事概要には含まれていなかったが、発言の意図が十分に確認できなかったためとみられる。

[Edano's] remark on the wide-area evacuation was not included in the meeting summary. It was probably because the intent of his remark couldn't be ascertained when the summary was created.

I wish Tokyo Shinbun published the actual memo in its entirety.

So these ministers were having the meeting on the upper floor of the Official Residence, while in the basement the real information was being transmitted: SPEEDI simulations that showed the potential wide-area contamination. Somehow they didn't reach the upper floor, and the ministers forgot to turn on the teleconferencing system on the dedicated line.

The Kan administration on the first few days of the nuclear accident did the full-on propaganda of "everything was under control", as if all people needed to worry about was the earthquake and tsunami devastated Tohoku. The administration even sent out the female minister in charge of consumer affairs to scold those selfish Tokyo residents who were trying to hoard bottled water and food. "Don't buy them, because they are more needed in the disaster areas!"

That was just after Reactor 3 blew up in a spectacular fashion. Then one day later Reactor 4 blew up. And something happened in Reactor 2. The government didn't warn residents in Tohoku and Kanto about the possible radioactive fallout from the explosions, and people were still very trusting of their government. Chief Cabinet Secretary Edano was being praised for his "hard work".

Radioactive plumes from Fukushima I Nuclear Power Plant reached Tokyo, and 210 becquerels/kg of radioactive iodine was detected from the tap water in Tokyo on March 22. The Tokyo Metropolitan government didn't have enough bottled water to give to the residents with babies and infants.

Ah. Those bad old days. Makes me mad.

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