SCE Responses to Surfrider Questions (October 4, 2017)
San Onofre Nuclear Station
October 24, 2017
Thank you for your questions. Please find responses below.
1. To reduce the threat of canister corrosion due to salt exposure, why isn’t SCE planning to construct a building around the Holtec UMAX storage system?
Response: The NRC has determined licensed dry storage designs provide reasonable assurance of adequate protection for the public without the use of an environmentally controlled building; the dry cask storage systems are designed for the open air environment. This determination is supported by over 30 years of safe ISFSI operation in the U.S. In addition, none of the dry storage systems currently licensed and available in the U.S. include a building housing the ISFSI within the licensing basis. SCE has elected to take additional actions, beyond those required by regulation, to mitigate potential corrosion caused by the marine environment, such as specifying a more corrosion-resistant grade of stainless steel and a thicker canister shell.
2. How many security staff will be onsite 24/7 once the first canister gets filled and placed in the storage system?
Response: Safety is a core principle of Decommissioning and SCE is dedicated to protecting the health and safety of the public. SCE security staffing will remain at San Onofre with officers onsite 24 hours/7 days a week as long as spent fuel is stored onsite. ISFSI Security will remain regulated by the NRC, which includes approval of the security measures, periodic inspections and regular training and exercises, throughout decommissioning and as long as the spent fuel remains onsite. The exact number of officers is classified as “Safeguards Information” and is not publically available.
3. Will the fence constructed around the property (once decommissioning is complete) continue to automatically set off an alarm if touched?
Response: Yes, the intrusion detection and assessment systems around the perimeter of the dry cask storage system will continue to be maintained and will be monitored 24/7. An alarm would automatically sound in the security alarm station if the fence sensed motion nearby or is touched.
4. What are the wave heights/storm surges that would result in ocean water reaching the Holtec UMAX storage system (accounting for the current seawall) in the following circumstances?
a. Current sea level on a king tide (~8 foot tide)
b. 0.05 feet above the 1990-2009 mean sea level on a king tide (~8 foot tide)[1]
c. 1 foot above the 1990-2009 mean sea level on a king tide (~8 foot tide)[2]
Response: The wave heights and storm surges with respect to the Holtec UMAX dry cask system are important questions and similar to the ones discussed in the California Coastal Commission Staff report (https://documents.coastal.ca.gov/reports/2015/10/Tu14a-10-2015.pdf, starting on page 338). The report provides a thorough analysis of the various conditions considered and provides a comprehensive overview.
5. Based on the permits already received by SCE, what is the highest radiation level and concentration of water (from cooling pools) allowed to be released into the ocean?
Response: The same federal NRC regulations for radioactive discharges - while San Onofre Units 2 and 3 were in operation - still apply as a decommissioning plant. NRC regulations require precise monitoring of effluent releases within very strict limits and releases would be stopped automatically by sensitive radiation monitors well below any Federal limits. A required environmental monitoring program includes periodic samples of ocean water, marine life (e.g. fish and crustaceans), kelp, ocean bottom and shoreline sand, all of which are analyzed for radioactivity. Additionally, two annual reports are submitted to the NRC which detail (1) the radioactive eluent discharged from the site, and (2) the effects (if any) on the environment.
These reports, the Radioactive Effluent Release Report contains facility monitoring data and the Radiological Environmental Monitoring Report contains the results of the environmental monitoring program. The reports are publically available and can be found on the NRC’s website. The link to the San Onofre reports are as follows: http://www.nrc.gov/reactors/operating/ops-experience/tritium/plant-specific-reports/sano2-3.html)
At San Onofre, the plant discharges only a fraction of that maximum allowable limit of its regulatory permits. The NRC regulatory allowance is 3 millirem per year total body from nuclear power plant liquid effluents. The EPA has a 4 mrem/year drinking water limit. While San Onofre was operating, the annual dose to a member of the public from SONGS Units 2 and 3 liquid releases during past power operations averaged about 0.001 to 0.002 mrem, about 0.06% of the limit. This is less than 1/100,000 of the annual dose from natural sources and less than 1 millionth of the international annual limit for radiation workers. Additional information can be found from the following website: http://www.nrc.gov/about-nrc/radiation/around-us/doses-daily-lives.html
Water from the spent fuel pools would be cleaned and processed using resin filters and ion exchangers to reduce and limit radioactivity and discharged through monitored effluent pathways – and is expected to be even less than when the plant operated.
6. Is SCE required to notify the public when releases of contaminated cooling pool water occur?
Response: No, the public is not notified when releases are made from the plant. All effluent releases are monitored and must comply with NPDES (National Pollutant Discharge Elimination System) permits for non-radioactive releases, and with NRC criteria for radioactive releases. As mentioned in response #5, annual reporting to the NRC of effluent discharge is provided in the Radiological Environmental Monitoring Program Report, and is publically available on the NRC website.
Also, as mentioned in response #5, water from the spent fuel pools will be processed using resin filters and ion exchangers to reduce and limit radioactivity and discharged through monitored effluent pathways. This material has been in the past and will continue to be released well below the regulatory limits during the Decommissioning of SONGS.
7. A 50-mile planning radius is frequently used for operating nuclear power plants, what are the safety planning radii for decommissioned plants in dry storage? Is this based on the potential release of a specified amount of radiation from one canister? Please explain.
Response: There are two emergency planning zones around operating nuclear power plants to facilitate a preplanned strategy for protective actions during an emergency. The 10-mile zone is designed to avoid or reduce dose from potential exposure of radioactive materials, and 50-mile radius to avoid or reduce dose from potential ingestion of radioactive materials such as contaminated food. At decommissioning reactors such as San Onofre, neither of these planning zones is required because there’s no credible accident scenario that would result in a radioactive release that would exceed EPA Protective Action Guidelines. This evaluation applies to permanently defueled nuclear plants that have received NRC approval of emergency planning exemptions.
8. From the Oct 4 Meeting: Is the aluminum material of the “baskets” in the canisters was the same design the Japanese use?
Response: No, the aluminum alloy baskets used by some Japanese plants in the dry storage canisters are not the same as the aluminum alloy used by Holtec. The material of baskets used at San Onofre is Metamic-HT, which is manufactured from AA1100 (99.4% Al), a pure aluminum alloy and uses a different manufacturing process, compared to the aluminum alloy used in Japan
Specifically, Metamic-HT material lacks phase transformation mechanism that would modify properties when material is exposed to high temperatures. Metamic-HT was tested and qualified using a severe testing regime approved by NRC, including extensive aging and creep testing, that demonstrate that it meets all properties required for the safety evaluations under storage and transport.
The Areva NUHOMS canisters use stainless steel baskets.
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[1] The estimated sea level rise expected to occur near La Jolla by 2030. Citation: Griggs, G, Árvai, J, Cayan, D, DeConto, R, Fox, J, Fricker, HA, Kopp, RE, Tebaldi, C, Whiteman, EA (California Ocean Protection Council Science Advisory Team Working Group). Rising Seas in California: An Update on Sea-Level Rise Science. California Ocean Science Trust, April 2017. pp. 27.
[2] The estimated sea level rise expected to occur near La Jolla by 2050. Citation: Ibid.