One recurring theme that has emerged after Fukushima is the tendency of nuclear experts to underestimate (publicly at least) the severity of the disaster. Today we received further proof of this when the Japanese government more than doubled the estimate for the amount of radiation released from the plant in the immediate aftermath of the crisis in March.

Government watchdog The Nuclear and Industrial Safety Agency also said that the meltdowns of the plant’s reactor cores–at least one of which we now know suffered a total meltdown—happened much more quickly than Tepco has previously suggested, making it clear that the plant operators’ desperate attempts to cool the reactors by dumping sea water on them were largely unsuccessful.

According to news reports, NISA now estimates the total amount of radiation released into the atmosphere in the first week of the crisis at 770,000 terabecquerels. This compares with NISA’s previous estimate, released on April 12, of 370,000 terabecquerels for the first month of the crisis. NISA has pointed out that most of the radiation was released in the first week.

The new estimate brings falls in line with another government watchdog, the Nuclear Safety Commission, which has projected the total radiation release at 630,000 terabecquerels, Dow Jones reported.

The latest figure is still only about 10% of the radiation released from the 1986 Chernobyl disaster, which is estimated at 5.2 million terabecquerels.. But the amended estimate further undermines the credibility of Tepco, NISA and the IAEA in the aftermath of the crisis. It’s easy to understand why in the frenzied few weeks after the earthquake those three bodies would have wanted to remain cautious when estimating the scale of the emergency—they wanted to prevent panic. But there’s a problem with that approach. The nuclear industry has long suffered from a “credibility gap” and low-level of trust from the public. The global community needs to know as quickly and as accurately as possible what’s going on in a nuclear emergency. If there is a level of uncertainty about the situation–as there was at Fukushima–officials should emphasize that.

It is often said that one of the scary things about radiation is that you can’t see or sense it. In the case of an invisible radiation leak, we should demand that national and international nuclear safety experts be highly visible, and as emphatic as possible.