Minutes from SAGE update meeting 23 March 2011
Held in 35 Great Smith Street Whitehall at 10.00
Professor John Beddington, Government’s Chief Scientific Advisor and SAGE Chair
Hillary Walker (Department for Health)
Nick Gent (Health Protection Agency)
Robin Grimes (Imperial College)
Neil McColl (Health Protection Agency)
Mike Weightman (Health and Safety Executive (Chief Nuclear Inspector))
Mike Griffiths (RIMNET)
Andy Hall (Health and Safety Executive)
Robert Hunter (Civil Aviation Authority)
Janet Dixon (Defra)
David Clary (Foreign and Commonwealth Office)
Peter McDonald (Department for Energy and Climate Change)
Matt Hort (Met Office)
Paul Tossell (Food Standards Agency)
Terry Donoghue (Food Standards Agency)
Brian Baptie (British Geological Survey)
Pat Boyle (Met Office)
Miles Elsden (GO Science)
Elizabeth Surkovic (GO-Science)
Elizabeth Moore (Cabinet Office)
Chris McFee (GO-Science)
Richard Meadows (GO Science)
AGENDA ITEM 1: WELCOME AND INTRODUCTION
1. The CHAIR welcomed all to the meeting and gave a short summary of the focus of the meeting and an update of the situation.
2. The CHAIR told SAGE that they would need to consider the potential health advice for drinking water as well as the longer term implications of the incident, and that he would be holding another teleconference with UK residents in Japan to offer advice on the health and safety of food and water in Japan. He said that a number of SAGE members would be participating in the teleconference with him to provide expert advice on food and water.
3. The group was reminded of the Code of Conduct and to raise any conflicts of interest to the SAGE Secretariat.
Review of Minutes
4. The CHAIR told SAGE members that it was the intention that the Minutes of all the previous meetings would be put on the GO Science website. He asked all members to review the minutes to ensure that they were factually correct.
AGENDA ITEM 2: RECENT DEVELOPMENTS
a. Reactor Status
5. The CHAIR informed the group that he had information from French officials that the workers at the reactor had started using fresh as opposed to sea water in their attempts to cool the respective reactors and ponds.
6. The Office for Nuclear Regulation were able to corroborate this information, and also informed the group that there was some work ongoing to look at the effects of the crystallisation of boric acid.
7. The Office for Nuclear Regulation told SAGE that, although the plant was stabilising, it was still likely that small amounts of smoke would be emitted from time-to-time as machinery was restarted for the first time in around a month. They told SAGE that smoke from the site whether white, black or grey could be caused by a range of benign processes.
8. The Japanese evacuate the site when such a release happens on the assumption that it could be a radiological release, so an evacuation could not be used as an indication that there has been a release of radiological material.
9. The Office for Nuclear Regulation summarised reactor status
- Reactors 5 and 6 are in safe cold shut down status. They are physically distant from reactors 1 to 4 so there is no concern about these reactors.
- For reactors 1, 2 and 3 they now have information on pressure in the pressure vessel and the water level. This is reported as being covering around half way up the fuel assembly levels. If that is the case then half of the core will have degraded. What exactly has happened was unclear but it is likely that there will have been significant fuel cladding damage.
- Pond 4’s building is severely damaged and the inventory of the pond is reported as at 3 times more than the other ponds (1-3). The Japanese suspect fuel damage and there is a reduced water inventory which they are refilling. The group was informed of some declining trends in radiation level which would imply the situation is under control.
- ONR said that they now had good information on the level of fuel in each of the fuel ponds. These agreed with the source term levels which we had been using.
- At buildings 1, 3 and 4 they are still working to restore power. Building 2 is reported to have AC power to distribution board and the control room in reactor 2 now has power. The Japanese are now aware of problems with some of the pumps and are trying to source components and repair them.
b. Weather Forecast
10. The Met office updated SAGE about the current weather conditions in Japan. The current wind direction would take any plume off-shore. Moving towards Friday morning (GMT) the wind shifts to a southerly which would bring any potential plume towards Sendai with wet deposition possible. From Saturday onwards the wind was forecast to be persistently off-shore and there was rain forecast for Friday and Saturday.
11. RIMNET confirmed that this was consistent with the forecasts they were using to provide dose estimates for potential plumes.
c. Health, Food and Environment Implications
12. SAGE discussed the issue of a report of a reading from one water treatment plants which feeds Tokyo of having a level of Iodine-131 at over 200 Bq/l. This threshold caused the Japanese to issue a health warning to infants under 1 year. The Japanese thresholds are conservative in comparison to EU regulations considering the UK threshold for the same warning to be issued would be 500Bq/l.
13. SAGE discussed the amount of water needed to be ingested to achieve levels of dose which would be a detriment to health. SAGE members agreed that the time over which the water would need to be ingested would be several months at those levels.
14. British Nationals in Japan were getting concerned about the situation considering the Japanese advice and the effect it had on the supply of bottled water in Tokyo. The CHAIR informed the group that he would be having a teleconference call on the issue of food and water safety on Thursday morning with the Embassy, members of the business community and schools which aimed to reassure British Nationals in Japan. He asked those around the table to provide him with information to use during the teleconference.
15. DEFRA presented their updated paper on food and water safety which had been agreed with colleagues from the Drinking Water Inspectorate. The overall advice is that British Nationals should follow local instructions with regards to food and water.
16. However, DEFRA told SAGE that it would be prudent to make plain in any advice given that the advice to boil water cold was to mitigate any bacterial threat within the water and not to reduce the iodine-131 content in the water. Using water for all other purposes was not a hazard to human health.
17. SAGE discussed current levels of Iodine 131, which has a half life of ~8 days. HPA told SAGE that accepted convention is that 6 half-lives reduce the amount of radioactive material to negligible amounts (3.125% of original). This would mean that it would take 48 days before a specific release or discovery of Iodine 131 no longer caused concern. The biological half life was not known and the SAGE Secretariat was tasked with sourcing this information for the group.
Action SAGE Secretariat
18. SAGE discussed reports of Iodine 131 in the water treatment plant which feeds Tokyo. The HPA had modelled Iodine deposition into an open reservoir and told SAGE that it didn’t look plausible as a source of the Iodine 131.
19. SAGE members said that Iodine 131 is not normally found in water and therefore it was not clear how this may have happened. DH suggested that the presence of Iodine 131 could be a cross contamination of hospital waste as a result of the effects of the Tsunami and Earthquake.
20. Following these discussions, the SAGE Secretariat was tasked with releasing information on the location of reservoirs in Japan for the group to consider. RIMNET offered to plot areas where there will have been deposition and the CHAIR tasked, NII, DH + HPA + Defra with forming a subgroup to have a look at the amount of probably contamination of water.
Action NII / DH / HPA / Defra
d. International Collaboration
21. The CHAIR said that there was continuing collaboration with the United States, and also confirmed that the French agreed with the group’s assessments of the situation.
AGENDA ITEM 3: MODELLING
22. RIMNET described the current modelling, noting that it was a fully audited process giving models of 4 hour release for 6 times in a day. Previous modelling had used 1 reactor as a source term; from now on it would be 1 reactor plus 1 fuel pond.
23. The SAGE Secretariat described the 24/7 response mechanism which had been put in place earlier in the week.
Shelter and Evacuation Zones
24. SAGE discussed the evacuation zones and the science behind the Japanese decision to evacuate up to 20km from the site and to advise shelter at 30km from the site. UK criteria for evacuation are (30-300mSv effective dose) and those for shelter are (3-30 mSv effective dose).
25. The modelled doses for the reasonable worst case are consistent with the Japanese advice. The group endorsed the 20-30km zone for shelter and the 80k zone as proportionate response to these dose levels.
AGENDA ITEM 5: PROGNOSIS
Future Reactor Status
26. The news that the Japanese are supplementing salt water with fresh water meant that the situation would be expected to gradually return to normal. However, SAGE members emphasised that the reasonable worst case was still possible.
Longer Term Hazards
27. SAGE discussed whether the caesium contamination that could make its way into food and water supplies would have potential longer term impacts. They agreed that not enough information was available at the minutes and it was too soon to assess the impacts. FSA, Defra, DH and HPA were tasked with finding out more about this issue.
Action FSA, Defra, DH, and HPA
28. CEFAS The group discussed the potential for radionuclides to be found in sea water and thus enter the seafood chain. They told SAGE that there is a Japanese seawater monitoring plan being put in place. Results were to be available on Wednesday and Thursday and the system was thought to be robust, including having background readings to baseline against.
29. SAGE discussed the possibility of an international monitoring programme for international waters. CEFAS said that the IAEA was taking a close interest in seawater monitoring and could provide a good central point of international coordination on this matter.
30. BGS told SAGE that aftershocks are continuing at around the 5-6 magnitude (Richter Scale) and are distributed around the area in the Japan Trench. The probability of a 7+ magnitude earthquake in the next few days was considered to be low.
31. Questions still needed to be answered as to how the stress may have been distributed to other fault systems although BGS told SAGE that the Tokyo fault lies between two major fault lines so would be difficult to predict. BGS were asked to producing more information to inform SAGE.
32. BGS told SAGE that, while only one variable in the process, a substantial Tsunami can be triggered by a 7+ magnitude earthquake but generally a 7.5+ was considered a more reasonable assumption. There would always be the possibility of localised tsunamis from lesser earthquakes.
33. BGS told SAGE that they would be informed of a quake within minutes of it happening and that ground shaking can also be modelled. The CHAIR asked BGS to liaise with the SAGE Secretariat to be involved in the 24/7 response mechanism.
Action BGS / SAGE Secretariat
AGENDA ITEM 6: AOB
34. The Met Office raised the issue of enquiries they had received about reported measurements of Iodine 131 in Iceland. The following was submitted by RIMNET to the SAGE Secretariat as a post-hoc response
The UK’s Radioactive Incident Monitoring Network (RIMNET) has not observed any uplift above normal background levels in the ambient gamma dose rate. RIMNET maintains a network of 95 gamma dose rate monitoring stations across the UK. These stations are polled every hour and provide measurements of the UK background level 24 hours a day, 7 days a week. These measurements are exchanged with European partners on a an hourly basis. In return, RIMNET receives ~4500 readings from across Europe every two hours through this exchange mechanism (known as EURDEP). There have been no uplifts in background radiation levels observed in the measurement data received from Europe to date. Please note that Iceland exchanges measurement data with EURDEP partners and there have been no uplifts observed in the Icelandic measurements.