Shortcomings in the “Stress Test” for UK nuclear power stations following Fukushima

Tim Deere-Jones, January 2012

The December 2011, post Fukushima, “Stress Test” report published by the Office for Nuclear Regulation, the UK’s independent nuclear safety regulator, claims that UK sites have identified and made improvements to safety by learning from events in Japan.

The Office for Nuclear Regulation (ONR) report is based largely on the conclusions of the “Weightman Inquiry” set up by the actively pro-nuclear UK Government in the immediate aftermath of the Fukushima disaster. This inquiry invited submissions of evidence from various parties in the UK, and the Inquiry has been run by Dr. Michael Weightman, Chief Nuclear Inspector.

One of the parties submitting major tranches of evidence to Weightman was the Nuclear Free Local Authorities.

Acting on the behalf of the Nuclear Free Local Authorities (NFLA), the marine radioactivity consultant Tim Deere-Jones submitted 32 pages of evidence and recommendations arising from a review and study undertaken by Mr. Deere-Jones of the ongoing, massive radioactive pollution of the marine environment at Fukushima which arose following the huge, uncontrolled use of Emergency Cooling Water as plant workers struggled to respond to the breaches of containment and subsequent loss of cooling water at three reactors and one spent fuel cooling pond at the Fukushima Diaiichi site. As result of the loss of coolant accidents (LOCA), fuel in the reactors and the cooling pond began a runaway “melt down”, and the only way to prevent a total meltdown was to apply vast quantities of Emergency Cooling Water.

However because the three reactors and the spent fuel cooling pond had been breached, the Emergency Cooling Water (ECW) could not be contained and, after running over the molten radioactive fuel, the ECW escaped from reactors and cooling ponds, and ran off the site into adjacent waterways and the nearby sea.

The Nuclear Free Local Authorities (NFLA) submission to the Weightman Inquiry concluded that:

  1. In the initial stage of the Fukushima disaster, loss of containment at 3 reactors and one spent fuel cooling pond occasioned loss of primary coolant liquids which were then released, initially into the immediate plant site environment and subsequently into the off site environment (water courses and marine)
  2. Following the application of Emergency Cooling Water (ECW), the ECW was also released into immediate plant environments and subsequently into watercourses and marine environments.
  3. The available evidence demonstrated that, at first, ECW was applied in un-quantified volumes to reactors and spent fuel cooling pond. Later attempts to quantify the use of ECW on a daily basis, over a period of many months, confirmed flow rates of up to 432 tonnes per day.
  4. TEPCO (Tokyo Electric Power Company) press releases imply that the company had managed to retain on site only approximately 195,000 tonnes of highly radioactive water which had passed through shattered reactors and spent fuel cooling ponds .
  5. No data has been provided for the actual (or estimated) volume of the highly radioactive water, which had entered adjacent watercourses and the marine environment.
  6. In the absence of definitive and verified data, the Nuclear Free Local Authorities (NFLA) submission concluded that the total volume of Highly Radioactive Water thus discharged to the marine environment ranged from between several, to many, hundreds of thousands of tonnes.
  7. In September (2011) the IRSN (Institut de Radioprotection et de Sûreté Nucléaire — the French public expert in nuclear and radiological risks) estimated that during the period from late March to the end of April about 27 PBq (Peta Becquerels) of radioactivity from the radio-isotope Caesium 137 alone, had entered the Pacific coastal waters as a result of the escape of primary and emergency cooling waters from the Fukushima disaster.NB 27 PBq =27,000,000,000,000,000 Becquerels : 27 thousand million million Bqs : or 27 thousand trillion BqsThis figure represents about 245 times the amount of total radioactivity discharged to sea by the Sellafield site in 2010.
  8. It is undeniable that such water — having been applied to the molten fuel and core material of several reactors and the highly radioactive “hot” spent fuels in ruptured cooling ponds — had become highly contaminated with the entire range of 50 to 60 isotopes found within such environments, including several isotopes of plutonium and similar substances (americium. curium etc).NB the figure given above in paragraph g. (for Cs 137 alone) only applies to the first five or six weeks of the incident weeks of the incident. Large scale use of emergency cooling water continued for many months beyond that date, estimates of the amount of radioactivity released to the sea in this period has not been provided.

NFLA note that massive use of ECW is also recorded at the Windscale and Chernobyl events following loss of coolant accidents (LOCA) which, of course, also involved significant loss of Primary Coolant. LOCA incidents also occurred at 3 Mile Island, Pennsylvania, USA, and at Mayak/Kyshtym in the Urals during the USSR era, and also at a number of lesser incidents such as that at the Hanford plant in the USA.

All of these involved uncontrolled escape of both Primary and Emergency Cooling Water from the sites into adjacent watercourses (rivers and seas). Most of them were even more poorly quantified, monitored and sampled than the Fukushima event. However the Fukushima example gives us some inkling of the potential radiological significance of such an event.

In the context of the UK’s relatively enclosed sea areas, with their attendant relatively slow flushing/dispersion/dilution rates, plus the fact that most of the UK sea areas flush/disperse into another one of the UK sea areas, this is a really significant issue which should be taken as seriously as are the considerations given to the prevention and management of LOCA (loss of coolant) events themselves.

The NFLA submission made a series of preliminary recommendations for the construction of bunding, storage tankage and site drainage control in order to manage, capture and store escaped coolant following LOCA events, and similarly to manage, capture and store ECW and thus provide robust safeguards against the pollution of marine environments as an impact of LOCA events.

The Nuclear Free Local Authorities (NFLA) also noted that under the UK Generic Design Assessment process for new-build reactors, site drainage issues were to be left largely to the discretion of site operators, and would be addressed on a site by site basis. NFLA has argued strongly that, in the light of the outcomes of ECW (emergency cooling water) use at Fukushima, such drainage issues need firm control, and the application of nationally agreed standards for the control of ECW and the prevention of subsequent marine pollution. Drainage issues should therefore not be left to individual site operators and local planning applications, but rather should become a national generic safety and anti-pollution issue.

In the context of the evidently deeply inadequate, very rushed and ineffective post Fukushima marine monitoring programmes initiated by Japanese government and industry agencies, the Nuclear Free Local Authorities have also made outline recommendations about the need to prepare, in advance, post-disaster marine monitoring programmes in order to supply detailed and appropriate information to coastal populations and marine industries both within and “downstream” of affected zones.

NFLA is now deeply concerned by the contents of the (post Fukushima) ONR Stress Test Report and its recommendations. NFLA note that the only releases of radioactivity which the Office of Nuclear Regulation (ONR) discusses in the context of accidents is “release of radioactivity into the atmosphere” (Chapter 6.4.1 : Radioactive Releases after Loss of Containment Integrity). This is an astonishing conclusion in the context of the massive marine pollution that has arisen as a result of liquid/aqueous leaks and the ensuing marine pollution at Fukushima

Among its main text and the recommendations, the ONR Report makes many references to ensuring the supply of Emergency Cooling Water (ECW) for reactors and spent fuel cooling ponds that may be undergoing loss of coolant accidents (LOCA).

Among main text and recommendations, the ONR Report makes many references to ensuring that sites can drain freely after flooding events (ingress inundations such as heavy rainfall, tsunami, storm surge etc)

Nowhere in either main text or recommendations is there any reference to the management, or behaviour and eventual fate, of used ECW (emergency cooling water), which would have gone through damaged reactors and spent fuel cooling ponds.

The NFLA notes that the ONR Report references Probabilistic Safety Analyses (PSA) as part of safety assessments and specifically states that “Level 3 PSA is the assessment of offsite consequences, leading, together with the results of Level 2 PSA, to estimates of Public Risk”

The NFLA conclude that the ONR Report specifically fails to ensure that “Level 3 PSA assessment of offsite consequences, leading, together with the results of Level 2 PSA, to estimates of Public Risk” is, and/or will be, enforced in respect of loss of Primary Coolant and ECW following Reactor and Cooling Pond LOCA events at both existing Nuclear Power Plants and new build Nuclear Power Plants.

It is on these bases, that the Nuclear Free Local Authorities have concluded that both the Weightman Inquiry and the Office of Nuclear Regulation have failed to learn and respond to the most crucial outcomes of the Fukushima disaster: i.e.

  1. Loss of Coolant Accidents are generally responded to with high volume use of Emergency Cooling Water, and
  2. Unless both primary and secondary coolants and ECW (emergency cooling water) can be contained they will inevitably escape, by gravitational flow, into the UK’s relatively enclosed, highly interlinked coastal marine environments, where
  3. Major significant radioactive pollution will be caused, and concentrations of radioactivity and subsequent derived doses are likely be higher than those seen in the marine environment around Fukushima because flushing/exchange mechanisms will not be as significant in UK waters as they have been on the open Pacific coast of eastern Japan.

Author: Tim Deere-Jones. January 2012.

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