STATUS OF THE FUKUSHIMA DAIICHI SITE AND THE REMAINING RISKS

Transcription

1 STATUS OF THE FUKUSHIMA DAIICHI SITE AND THE REMAINING RISKS NURIS st INRAG Conference on Nuclear Risk BOKU, Vienna Dr. G. Kastchiev Member of INRAG 1

2 STATUS OF THE FUKUSHIMA SITE /1/ 2

3 FUEL DEBRIS The fuel containing masses in units 1-3 блок include total about 257 t HM /2/ - more than Chernobyl: - More than 2800 кг isotopes of Pu; - - Almost 540 кг Cs-137; - About 362 кг Sc-90; - About 1280 кг other long lived isotopes; The solidified fuel containing masses continue to generate heat, air cooling is still not possible; The water cooling cycle is semi open, every day 320 m3 water /2/ are injected in units 1 3, after cleaning half of it is reused; Fuel debris create very high radiation fields in units 1-3, assess of personal in the buildings is limited; Geometrical shape and physical properties of debris unknown, as well as their locations containing. Re-criticality? February 2015, unit 1 experimental use of muon detection device, that could detect how much of the debris remains in the vessel; The basements of units 1 3 contain huge amount (about m3) highly contaminated water; No real plans for their removal. 3

4 SPENT FUEL IN SPENT FUEL POOLS IN UNITS 1-4 Before the accidents the amount of spent fuel in the spent fuel pools: Unit spent fuel assemblies (about 40 tons HM) Unit spent fuel assemblies (about 97 tons HM) Unit spent fuel assemblies (about 63 tons HM) Unit spent fuel assemblies (about 219 tons HM) Removal of spent fuel from unit 4 completed in December Removal of spent fuel from unit 3 (planned) - first half of 2017 /3/. Severe radiation fields. Works to remove the large pieces of debris that fell into the pool in an accident August 2014; Removal of spent fuel from unit 3 plans unclear; Removal of spent fuel from unit 1 (planned): Dismantling of the existing cover scheduled March Application of an anti-dispersal agent; 4

5 RADIOACTIVE WATER IN THE BASEMENTS OF UNITS 1-3 To cool fuel debris every day about 320 tons water is injected /4/ in reactors 1-3. Part of injected water is in direct contact with the debris and becomes highly radioactive. In addition during typhoons and heavy rains rain water goes inside the buildings; In the end of March 2015 approximately m3 water is accumulated in the basements of units 1 3 /1/; The total activity of the accumulated water is huge, but not known. An assessment /5/ shows that the activity of Cs-137 in the water accumulated in the basements of units 1-3 could be more than 1 E17 Bq. This is more than Chernobyl releases of Sc-137 (about 8,5 E16 Bq) to the atmosphere /3/. If this radioactive inventory would be released to the environment this will represent another INES Level 7 accident; The water in the basements of units 1 3 contains sea salt, boron acid, oil and other chemicals and is chemically aggressive. Metal and other structures subject to corrosion. 5

6 RADIOACTIVE RELEASES TO THE ATMOSPHERE Radioactive waters, contaminated surface and equipment, removal of debris and other activities generate aerosols, containing Cesium, Strontium, Tritium and other radioactive nuclides; End March the rate of Cs emissions - hundreds to thousand billion Bq/h /10/; March the rate of Cs emissions from damaged units - about 10 million Bq/h /11/; NGO /12/ - the present rate of Cs emissions is about 10 million Bq/h (quoting TEPCO); Even with a rate 1 million Bq/h the annual release of Cs would be 8,76 billion Bq; In 2003 the total annual release of long-lived aerosols including Cs from 42 operating reactors in Germany, Spain, Switzerland, Belgium and Finland was 0,4 billion Bq /13/; Fukushima site is a source of continuous and long term tremendous contamination of the ocean. 6

7 RADIOACTIVE LEAKAGES TO THE OCEAN The site is at the bottom of the hills, every day tons of underground water drain down to units 1-4. At least 300 tons /4/are going into the basements of units 1-3 through cable/pipe penetrations and small cracks, mixing with the heavily contaminated water used to cool the debris. Part of the radioactive water is leaving the buildings in similar ways to the port causing high levels of contamination to be found in the test wells near the sea; During typhoons and heavy rains the underground water flow and its activity is increasing, rain water is also contaminated. Highly contaminated water flows from buildings into the trenches on the sea side. TEPCO failured to stop the flow of contaminated water; Following typhoon Uifa, on the record activity (isotopes of cesium, strontium, tritium) measured in the underground water (east unit 2) 1,3 million Bq/l /7/. After two weeks heavy rains on the activity measured in the sample of groundwater (east unit 1 and 2) 267 thousands Bq/l /8/ (accuracy of measurements questionable); In addition there are leakages of radioactive water stored in the thanks ( peaks of the iceberg - August about 300 tons, 9 October about 10 tons); Samples of water taken from the Pacific Ocean of the U.S. and Canada West Coast already contain Cesium /14/, even in very small amount, far below the limits; 7

8 RADIOACTIVE LEAKAGES TO THE OCEAN TEPCO - activity of Strontium, Cesium and Tritium in the daily radioactive releases to the sea (2013 and the projection for 2014 and 2015) is in order of billions Bq/day (see the figure on the right). No data about releases of Barium, Molybdenum, Technetium, etc.; In 2013 the total annual release of Strontium- 90 and Cesium-137 to the sea - about 13 TBq (using TEPCO data); According to TEPCO the difference between last year (2013) and this year (2014) is due to the movement of the survey point; Even after start of operation of sub-drain system, wall of frozen soil and sea-side wall TEPCO plans to release about 325 billion Bq of Cesium and Strontium to the ocean; Fukushima site is a source of long term tremendous contamination of the ocean. INES scale doesn t consider radioactive releases to the ocean. 8

9 RADIOACTIVE WATER STORED AT THE SITE The total volume of water with different activity stored at the Fukushima site all the time is steadily increasing; In the end of 2013 г. more than tons are stored in more than 1000 tanks; In March 2015 the total amount of stored water with different activity is more than tons, the total storage capacity is about tons /6/; TEPCO demonstrated insufficient ability to manage the contaminated water. 9

10 STORAGE OF RADIOACTIVE WATER 10

11 STORAGE OF RADIOACTIVE WATER The thanks are sitting on poor concrete foundation too close to each other. In case of strong earthquake and collapse of one thank domino effect is possible; Still some thanks are made from bolted steel sheets and have to be replaced with welded thanks; Still some thanks are without level measuring devices; Every 1-3 days a new 1000 tons tank has to be installed and connected to the system. There are too many joints, pipes, pumps, etc. System too big to be effectively controlled and managed; Leakages of contaminated water from the thanks. Last incident March 2015, leak of more than 700 m3 highly contaminated water. 11

12 CLEANING OF CONTAMINATED WATER Every day about 320 tons water are injected in units 1-3 to cool the debris; Water is contaminated, much of it is pumped out and passed through Cesium cleaning systems; Water contaminated with other radioactive nuclides is cleaned with Advanced Liquid Processing System (ALPS), capacity 250m3/day x 3 systems; Additional expanded high performance ALPSs (250m3/day x 3 systems) and high-performance ALPSs (500m3/day) installed /7/ with government subsidies; ALPS removes all radioactive nuclides without tritium. The waste water is stored on the site; After installing the new systems approximately 2000 tons of water a day could be processed /6/; In addition several strontium removal systems; End of about m3 already treated. TEPCO plans to clean highly contaminated water till the end of May 2015; The problem with the treatment of salt water (about m3) is not resolved; 12

13 OTHER FACILITIES Groundwater bypass system Groundwater is pumped from 12 wells inland from units 1-4 and stored in thanks. This system could reduce the ingress of water to the basements by 100 tons per day. The activity of released water must be below 10 Bq/l. From April 2014 till February 2015 about m3 released; Sub-drain system Set of wells on the site to decrease the level of underground water. Damaged in March 2011 and restored, new pits installed (total42). Includes collecting, purification and transfer equipment. Could capture m3 water per day with subsequent cleaning. Start of pumping August TEPCO expects that this will reduce groundwater inflow into the buildings by up to 150 m 3 per day. No final decision about disposition or discharge of treated water. Difficult to prevent radioactive contamination of wells as well as the water in them; Seaside Impermeable Wall Barrier between units 1-4 and the port in order to prevent leakages of contaminated water. Steel pipe sheet pile wall constructed, m deep inside the seabed, about 5 m from the coast. Total length about 780 m, and 4-5 m above the sea level. Initially planned to close it in the end of September 2014 (postponed till May 2015). 13

14 ICE WALL The approved plan is to isolate units 1-4 from the flow of the groundwater and to prevent leakages by freezing the soil around the damaged units; 1549 chiller pipes will be installed (approximately 30m deep underground) at 1m intervals /7/. The total length of the wall would be about 1500 m, the volume of frozen soil would be about m³ ; The soil-freezing technology used in tunnel and mining industry, but never in such large scale; No feasibility studies; Vulnerable to earthquakes and accidents with heavy equipment; Potential negative consequences not thoroughly evaluated; In April 2015 the ice wall will be partially frozen, overall freezing in the mountain side to be started in May after approval from the NRA. Very small progres on the sea side; Initial investments more than $ 320 million (with government subsidies); 14

15 OTHER PROBLEMS Metal and other structures in the buildings are subject to corrosion processes; Buildings are vulnerable to earthquakes, typhoons, heavy rains and combinations of extreme external events; The site territory is contaminated, radiation dose rates above the natural background. Protective measures needed; The port is heavily contaminated; Long-term management of generated radioactive waste with different activity not resolved, only temporary storages on the site; Big amount of treated water that contains tritium; Lack of skilled workers because of dose limits; Lack of trust between the main shareholders TEPCO, Japanese nuclear regulator, public; It looks that Japanese government, TEPCO and IAEA underestimate the severity of the situation. 15

16 S0URCES 1. TEPCO, Status of the Fukushima Daiichi Nuclear Power Station Nuclear Power Station, January The National Diet of Japan Fukushima Nuclear Accident Independent Investigation Committee (NAIIC) Report 3. Nuclear Regulation Authority, Japan, Measures for Mid-term Risk Reduction at TEPCO s Fukushima Daiichi NPS, Situation of Storage and Treatment of Accumulated Water including Highly Concentrated Radioactive Materials at Fukushima Daiichi Nuclear Power Station (194th Release), March 27, Errico Cazzoli, Estimate of Consequences from the Fukushima Disaster 6. TEPCO, Schedule of Main Targeted Events at Fukushima Daiichi Nuclear Power Station, March TEPCO Nuclear Safety Reform Plan Progress Report, February 3, Estimation of radioactive release resulting from Fukushima Dai-ichi NPS accident, , Hiroya SHIRAKI, TEPCO Current Status of Fukushima Dai-ichi NPS, Masaya Yasui, International Experts Meeting on Reactor and Spent Fuel Safety in the Light of the Accident at the Fukushima Daiichi Nuclear Power Plant, March 2012, Vienna, Austria 12. Current State of Post-Accident Operations at Fukushima Daiichi, Hajime Matsukubo, March 31, National Reports to the Convention on Nuclear Safety, Fukushima Daiichi NPS Prompt Report (Nov 11,2014), Efforts to ensure ocean protection, TEPCO, August 11, 2014, 16