By Rick Andrew
March 11, 2011 is a day that most Japanese will never forget. The massive earthquake, now known as the Great East Japan Earthquake, caused massive damage, with the resulting tsunami being responsible for most of it. In the end, over 15,000 were killed and 3,000 more are still missing. One of the most significant impacts of this event was that the tsunami, which reached an estimated 40 meters high and washed as far as 10 kilometers inland, severely damaged the Fukoshima Dai Ichi nuclear plant. The damaged plant, which likely will take decades to completely remediate, released radioactivity into the environment, including radioactive iodine.
Release of radioactive iodine in severe nuclear reactor accidents
In nuclear reactor accidents where there is not a wide dispersion of radioactive particulate (as in Chernobyl), the most common release is from the atmosphere of the containment building, as gasses and suspended particulate. During the early stages of an accident, the primary release is in the form of particulate iodine as CsI (>95 percent). After the initial release, the bulk of iodine release is from the repartitioning of iodine from liquid in the containment building.
This release is greatly enhanced if the liquid in the building is not pH controlled. As the pH drops, iodine is released into the atmosphere and can escape the containment building. The iodine is predominantly in the form of I2 (or HI) with a small fraction (<1 percent) of organic iodine (CH3I). The predominant radioactive iodine isotope present is I131. This isotope has a high specific activity and can result in potentially hazardous levels in drinking water at concentrations as low as 1 x 10 e-13 gram/liter. The iodine typically enters the water supply from rainfall, which deposits the iodine into water supplies from the airborne particulate CsI and iodine gasses.
Radioactive iodine reduction
In light of the release and potential impact of radioactive iodine in Japan, NSF and the Japan Water Purifier Association (JWPA) combined forces to develop a protocol for testing POU systems for the reduction of radioactive iodine. This protocol is officially titled, NSF/JWPA P72 Drinking Water Treatment Units – Iodine Radioisotope Reduction. The protocol covers three specific technologies identified by NSF and JWPA as most useful in treating water contaminated with radioactive iodine: activated carbon, reverse osmosis (RO) and anion exchange.
Because of safety issues associated with laboratory usage of radioactive iodine, the protocol specifies testing with non-radioactive iodine. And, because of limits in the technology used to detect iodine in water, the concentrations of iodine used for testing in the protocol are significantly higher than the concentrations of radioactive iodine detected in Japan after the earthquake and tsunami, and are significantly higher than the concentrations of radioactive iodine that can cause health effects.
Given these differences between the protocol and real world radioactive iodine contamination in drinking water, a significant effort to validate the protocol was undertaken by NSF and JWPA. Products were tested under the conditions of the protocol, as well as with actual radioactive iodine contaminated water in Japan. The results correlated very well, confirming the validity of the approach used in the protocol.
Testing at two pH values
The pH of drinking water can vary over a significant range. Also, iodine in drinking water has complex chemistry. It takes different forms with different chemical characteristics at different pH values. At a lower pH level of about 3, most of the iodine is in the form of I2 (iodine). At higher pH level around 9, most of the iodine is in the form of HOI (hypoiodus acid). Other iodine forms can be present, too, including I– (iodide), I3– (triodide), IO3– (iodate), OI– (hypoiodite), and organic iodine compounds. Because of this dependence of the form of iodine on pH, NSF/JWPA requires testing at two pH values, 6 and 8.4.
NSF/JWPA P72 also allows for evaluation of treatment trains. A treatment train consists of a combination of technologies in one single treatment device. The most common example of a treatment train would be a typical POU RO system that includes a carbon post filter. The RO membrane and the carbon post filter form a treatment train.
Under this Protocol, treatment trains can be evaluated in one of the following ways:
- If any part of the treatment train meets the requirements of NSF/JWPA for radioactive iodine reduction independently, then the whole treatment train is considered to meet the requirements.
- If the entire treatment train in series meets the requirements of NSF/JWPA for radioactive iodine reduction using all appropriate test methods for each technology, then the whole treatment train is considered to meet the requirements.
- The treatment train may be evaluated such that the first technology in series is evaluated appropriate to that technology, and then the second technology is evaluated appropriate to that technology excepting that the average effluent concentration from the first technology is used as the influent concentration for the second technology, and so on. The last technology in series must meet the requirements of NSF/JWPA for radioactive iodine reduction.
Suitability for use in the intended market
One of the unique features of NSF/JWPA P72 is its international development and application. Developed jointly between the US and Japan, the protocol is structured to allow flexibility in some requirements because the different markets have different requirements for POU products. With this in mind, NSF/JWPA P72 requires that material safety, structural integrity, product literature and other requirements must be addressed per the NSF/ANSI DWTU Standards, as appropriate, or per the local standards of the intended market. For products being sold in Japan, this means conformance to the applicable Japanese JIS Standards. NSF/JWPA P72 could be adapted for other local markets similarly. Additionally, flexibility in the inlet pressure used for radioactive iodine reduction testing is allowed, due to inherent fluctuations in typical water supply pressures in different countries and markets.
NSF and JWPA believe that this approach could be a starting point for future work to develop additional protocols intended to allow adaptation into multiple local markets, without causing conflict with local regulations and/or market conditions.
Out of disaster comes hope
The events of March 11, 2011 constituted a disaster of monumental proportions, one that will take Japan many years to recover from. However, some small but yet significant pieces of cooperation and advancement have come from it. NSF and JWPA have enjoyed a highly productive and cooperative effort to develop an international protocol to help consumers protect themselves from radioactive iodine, a highly toxic byproduct of nuclear events. NSF and JWPA plan to grow the relationship and continue to partner, paving the way for more good things to come.
Rick Andrew is the General Manager of NSF’s Drinking Water Treatment Units (POU/POE), ERS (Protocols), and Biosafety Cabinetry Programs. He previously served as Operations Manager, and prior to that, Technical Manager for the program. Andrew has a Bachelor’s Degree in chemistry and an MBA from the University of Michigan. He can be reached at 1(800) NSF-MARK or email: [email protected].