An accelerated schedule for spent fuel removal, high thyroid doses among workers and more revelations from the early days of the crisis marked the news from Fukushima Daiichi this week.Recent developments at the Japanese nuclear plant blacked out following last year's earthquake and tsunami include:Unit 4 Spent Fuel to Come Out EarlierTokyo Electric Power Co. plans to finish removing fuel assemblies from unit 4 a year earlier than planned. All 1,535 assemblies were in the unit's spent fuel pool at the time of the earthquake and subsequent hydrogen explosions that damaged the reactor's shield building. On Monday the utility revealed plans to begin the removal operation in November of next year, Kyodo reported, a month earlier than originally planned. Work should finish in 2014 on a timeline accelerated partly by the success of debris removal at the SFP to date.High Thyroid Doses Found Among Fukushima WorkersAmong tests of 522 Fukushima workers suspected of receiving high whole-body internal doses, 163 showed thyroid doses greater than 200 millisieverts. The Asahi Shimbun reported that a forthcoming report by the World Health Organization using the data from TEPCO also will indicate two workers had thyroid doses in excess of 10,000 millisieverts. One of them, a man in his thirties that TEPCO said did not report negative health effects, had a thyroid dose of 11,800 millisieverts, with a whole-body external and internal dose of 678.8 millisieverts. High doses in the thyroid are not as dangerous as high whole-body doses but can increase the risk of cancer in that organ.Plant Chief Made Repeated Pleas, Warnings to TEPCO HeadquartersJapanese reporters witnessed Fukushima Daiichi's plant manager becoming increasingly desperate for manpower and monitoring equipment in another batch of crisis teleconference footage released by TEPCO. Media representatives were allowed to see the teleconferences recorded March 16 to March 23 and March 30 to April 6, 2011, but were forbidden from taking their own video or audio recordings. Some of the most salient moments observed by Asahi Shimbun reporters came in plant General Manager Masao Yoshida's conferences with TEPCO executives in Tokyo. In one exchange, he pleaded for more men and bluntly refused to send his workers – who at that point had grappled with the crisis non-stop for eight days – back into high-radiation areas, noting that all plant workers were approaching or had exceeded the 200-millisievert dose limit.Two weeks later, Yoshida again showed his frustration with TEPCO's leadership as contaminated water flooded four units at the plant and threatened to overflow into the sea. His request for cameras to remotely monitor water in turbine halls was deferred until after workers discovered a leak April 2 in a nearly overflowing outdoor pit, the Asahi reported. The leak released an estimated 520 cubic meters of highly radioactive water into the ocean before crews sealed it off. On March 30, three days after rising water was detected in the pit, Yoshida told TEPCO headquarters, "I can't help but feel that we are idly waiting for death."
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Could somebody interpret the difference between a "thyroid dose" and the whole body dose. How can the former be greater than the whole body number?
Good question. The thyroid concentrates iodine, including radioactive isotopes like iodine-131, from the bloodstream. As a result, radiation doses measured within that organ can be much higher than doses in the tissues surrounding it.
From World Nuclear News: www.world-nuclear-news.org/RS_WHO_on_Fukushima_doses_2405121.html
"While contamination from caesium isotopes raises a person's general level of exposure, iodine-131 presents a special concern because it accumulates in the thyroid gland and this can lead to cancer in growing children. This is potentially fatal, although proper monitoring and treatment will cure over 95% of cases.
In the most affected areas of Fukushima prefecture thyroid doses from iodine-131 were estimated as between 10 and 100 mSv apart from one area which was lower, at 1 to 10 mSv, and one that was higher for infants at 100-200 mSv. In the rest of Fukushima, adults received 1 to 10 mSv to their thyroids while children and infants received 10 to 100 mSv, the study estimated.
For comparison, young people in the vicinity of the Chernobyl accident received on average doses of 300 to 1400 mSv to their thyroids."
Nuclear Street News Team
Thanks. So I take it that the whole body dose does not include the continuing effects of isotopes such as I-131 that do their damage after they are ingested and accumulate in the body..
The thyroid dose is an organ specific dose and the whole body dose can be calculated a weighted average of organ doses.
I'm the Anonymous of the first and third postings here, and i feel like I've fallen through the looking glass. Would it be clearer without introducing if the term "whole body gamma count" were used?
I must have somehow bumped the post button with my thought incomplete. Would adding the word "gamma" to whole body count help clarify the confusion pointed out in the first question? (I'm relying on Wikipedia here for the definition of the whole body count.)
For more information, the CDC offers a more thorough explanation of the factors that affect thyroid dose here: www.atsdr.cdc.gov/.../csem.asp
Anonymous - I commend you for putting in the work to try and understand the terminology of nuclear radiation. There is a lot to learn, and I encourage you to stick with it until you find answers. they are there, but they require some digging.
Although frustrating, it is actually better that you look and find this information from credible third party sources (such as the CDC as Nuclear Street News suggests), rather that relying exclusively on industry direct or industry related sources. Please understand, the information you get from industry is largely reliable and accurate, and I do not mean to imply otherwise. But a rightfully skeptical and questioning general public needs to verify the information industry provides through reputable independent sources.
We in the nuclear field believe passionately in this source of energy, and that it can be a huge solution for the worlds energy needs. But nuclear is obviously not completely benign. It MUST be managed and controlled properly to safely reap its huge energy benefits. Most of us in the nuclear fields recognize our own human fallibility, to design, to operate, to maintain these units. So we require, design in, implement multiple layers of protection. But multiple layers of protection can lead to complacency even among the best of us.
That's why it is so very important to have a knowledgeable public watching and monitoring, constantly checking and verifying the accuracy and adequacy of what the industry tells you.
I'd just like to know that we were using the same language so that I would know what you mean when you use a common word like dose.