Accident at Hanford

[this article was originally published on blog.safecast.org. We thank the author and the editors.]

 

Above: Photo showing the 20ft x 20ft hole which resulted from the collapse of a PUREX storage tunnel at Hanford (Image: Hanford Emergency Information page)

News wires have been buzzing about a tunnel cave-in at the Hanford nuclear facility in Washington State. The Hanford facility is extremely large, 580-square miles, or about half the size of the state of Rhode Island. It produced the plutonium used in the bomb dropped on Nagasaki, and during the cold war facilities were greatly expanded for weapons production. The last reactor at Hanford was shut down in 1987, and decommissioning and cleanup operations have been ongoing since 1989. The site has been fraught with problems stemming from the storage of radioactive waste, and because of the risk of releases of radioactive material to the environment, particularly the nearby Columbia River,  it is closely watched by environmental groups.

The accident yesterday involved the collapse of a small (20 x 20 foot) section of a storage tunnel built as part of the Plutonium Uranium Extraction Facility (PUREX), detected by workers on the morning of May 9th. These tunnels, constructed in the 1950’s and 1960’s, hold rail cars loaded with contaminated discarded equipment. They were constructed of wood and concrete and covered with approximately 8 feet of soil. The collapse is probably due to the degradation of wood used in construction.

Tunnel construction

(From Hanford facility dangerous waste permit application, PUREX storage tunnels)

Railcar-by-railcar breakdown of what’s stored in the PUREX underground tunnels at the Hanford Site and how radioactive it is, c/o Stephen Schwartz‏  @AtomicAnalyst.

Hanford Challenge twitter feed; this group has represented Hanford workers for the past 20 years.

Because the Hanford site is so large, only very large radioactive releases can be detected off site. This makes it difficult if not impossible to verify official data regarding releases. Official reports so far have indicated that no airborne releases of radiation have been detected due to the tunnel collapse. Nevertheless, an emergency was declared, and personnel were evacuated from nearby areas of the site and required to shelter indoors in others. As of 8pm on May 9th, work had begun to stabilize and fill the opening of the collapsed section.

Cheryl Rofer, formerly of the Los Alamos National Laboratory, posted an informative blog at Nuclear Diner, in which she concluded that the risk of large releases due to this accident are small.

At the same time, the tunnel collapse should call attention to the greater risks posed by deteriorating infrastructure at Hanford. The Washington Post notes:

“An August 2015 report by Vanderbilt University’s civil and environmental engineering department said the PUREX facility and the two tunnels had “the potential for significant on-site consequences” and that “various pieces of dangerous debris and equipment containing or contaminated with dangerous/mixed waste” had been placed inside the tunnels.”

(Update) Our colleagues at the NRDC communicated the following to us:

— NRDC assessment is that this accident does not pose a risk off site but will create increased risk for Hanford Site workers dealing with the accident, with substantial increased cleanup costs;
— This accident illustrates the difficulty of the cleanup of the US Cold War legacy of nuclear weapons production — the largest environmental cleanup project in the world costing over $6B a year (nearly $2 billion per year alone at Hanford) – every nation that has made nuclear weapons has hurt its own people and natural environment in the process – it further illustrates some complicated regulatory problems (lack of EPA and State authority over the site, where NRDC has long pushed for transparency).
— Continued risk at Hanford is greatest from the 56 million gallons of toxic, liquid high level-radioactive waste held in 177 very large tanks some of which are leaking – this underground plume threatens the Columbia River.

To summarize, this particular accident appears to be quite small and localized, but that may just be luck. In this instance, Safecast is concerned about the lack of independent monitoring at the Hanford site to confirm official statements about radiation releases.

No, radiation levels at Fukushima Daiichi are not rising

[this article was originally published on blog.safecast.org. We thank the author and the editors.]

This grating inside Daiichi Unit 2 was likely melted by falling fuel debris (TEPCO photo)

 

— Yes, TEPCO has measured very high radiation inside Daichi Unit 2.

— No, it does’t mean radiation levels there are rising.

In response to visual investigation results and high radiation measurements recently taken by TEPCO inside Fukushima Daiichi Unit 2, many news outlets have published stories with headlines like “Fukushima nuclear reactor radiation at highest level since 2011 meltdown.” (The Guardian, Feb. 3, 2017).

https://www.theguardian.com/environment/2017/feb/03/fukushima-daiichi-radiation-levels-highest-since-2011-meltdown

http://mainichi.jp/english/articles/20170202/p2g/00m/0dm/087000c

https://www.japantoday.com/category/national/view/record-radiation-level-detected-inside-damaged-fukushima-reactor

This has led to a number of alarming stories claiming that radiation at Daiichi has “spiked” to unprecedented levels. That’s not what the findings indicate, however. In addition, Safecast’s own measurements, including our Pointcast realtime detector system have shown radiation levels near Daiichi to be steadily declining. As described in the Safecast Report, Vol.2, Section 2.1.4, TEPCO and its research partners have been developing robots and remote visualization devices to search for melted fuel debris deep inside the Daiichi reactor units, and to help plan for its eventual removal. On January 30th, 2017, a long telescoping device with a camera and radiation measurement device attached was inserted through an existing opening in the reactor containment of Unit 2 for the first time, and successfully extended approximately 8 meters into in an area known as the “pedestal,” to measure and take images from immediately below the damaged reactor pressure vessel (RPV). In addition to finding the area covered with molten material likely to be fuel debris, radiation levels of 530 Sieverts per hour were detected, which would be fatal to a person exposed for only a few seconds.

The recent investigation used existing openings in the Unit 2 reactor to obtain images an measurements inside the pedestal area.(TEPCO image)

The telescoping arm (in yellow) was designed to reach inside the pedestal area to obtain visual imagery and radiation measurements.(TEPCO image)

It must be stressed that radiation in this area has not been measured before, and it was expected to be extremely high. While 530 Sv/hr is the highest measured so far at Fukushima Daiichi, it does not mean that levels there are rising, but that a previously unmeasurable high-radiation area has finally been measured. Similar remote investigations are being planned for Daiichi Units 1 and 3. We should not be surprised if even higher radiation levels are found there, but only actual measurements will tell. Unit 4 was defuelled at the time of the accident, and though the reactor building exploded and the spent fuel pool was dangerously exposed, it did not suffer a meltdown, so similar investigations are not being conducted.

The “Scorpion” crawler robot is designed to be inserted through a pipe and to fold for operation. It’s deployment is likely to be further delayed.(IRID photo)

Under a consortium called IRID, TEPCO and its research partners have been developing robots and other devices to assist in investigations inside the damaged reactors, where radiation levels are too high to allow humans to safely enter. The recent investigations at Unit 2 were intended to help plan the travel path of a folding crawler robot called the “Scorpion.” This device is designed to crawl around on the metal grating deck inside the pedestal and gather further imagery and measurements. The recent investigations, however, have revealed a 1×1 meter section of the deck to be melted through, and much of the rest may be impassable for the robot. In addition, the high radiation levels will likely limit the amount of time the robot will be able to operate before malfunctioning to about 2 hours, instead of the planned 10 hours. Much more melted fuel debris is assumed to have settled beneath the pedestal grating on the concrete basemat of the reactor. It was hoped that the Scorpion would be able to provide imagery of this. Not surprisingly, TEPCO is once again revising its plans based on the recent findings. These investigations are technically quite impressive, but they have already been delayed for over a year due to the need to more adequately decontaminate the area where human workers must operate and to solve other technical problems. This recent imagery is extremely informative and helpful, and had been eagerly awaited by many concerned people, including Safecast. If nothing else, we have learned to be patient as TEPCO proceeds slowly and cautiously with this work.  The process of removing melted fuel debris from the damaged reactors at Fukushima Daiichi is expected to take decades, and these recent findings remind us once again that TEPCO has little grounds for optimism about the challenges of this massive and technically unprecedented project.

Stitched vertical panorama showing conditions underneath the Unit 2 RPV. (TEPCO photo)

For more information:

TEPCO Reports:

Pre-investigation results of the area inside the pedestal for the Unit 2 Primary Containment Vessel Investigation at Fukushima Daiichi Nuclear Power Station(examination results of digital images)

Images Inside Fukushima Daiichi Unit 2 Need Further Examination Including The Possibility Of Fuel Debris

TEPCO Photos:

http://photo.tepco.co.jp/en/index-e.html

http://photo.tepco.co.jp/en/date/2017/201702-e/170202-01e.html

http://photo.tepco.co.jp/en/date/2017/201701-e/170130-01e.html

Video here:

NHK Video (in Japanese)

Mainichi Shimbun: