Bulletin of the Atomic Scientists | Kelly Wadsworth | 13 October 2015
The historic agreement between Iran and six world powers to curb the former’s nuclear development, concluded over the summer and expected to be adopted this month, relies heavily on verification. The foreign powers are keen to make sure that Tehran doesn’t acquire enough plutonium or uranium to build a nuclear weapon, and Tehran wants to demonstrate good behavior in order to get sanctions relief. That raises questions about the imperfect verification methods used by the International Atomic Energy Association (IAEA), the organization charged with the task under the Iranian nuclear deal, and the International Monitoring System (IMS), a global network that detects nuclear explosions worldwide. Are they reliable enough? Some would argue no.
There may be, though, a new option for verification on the not-too-distant horizon. Antineutrino detection is an existing technology that, if political and diplomatic hurdles are overcome, could be put in place before the 10-year ban on Iranian enrichment R&D is lifted. And fully developed over the long-term, it holds great promise for monitoring similar deals in the future, and for reinforcing nuclear non-proliferation worldwide. Difficult to evade, antineutrino detection technology could allow the international community to reliably monitor a country’s nuclear activities in real-time, potentially without setting foot in the country. Similar in cost and technological scale to the space-borne reconnaissance methods governments use for detection today, antineutrino detection could not only help identify undeclared nuclear reactors, but could monitor nuclear facilities and detonations throughout the Middle East and beyond. More research and development could make this technology a viable nonproliferation verification option.
The problem with verification today. Current far-field verification methods have been evaded in the past. Even with technology and policy improvements since the Iraq war, in the absence of immediate onsite inspections, the IAEA cannot reliably detect facilities outside its jurisdiction that may be producing weapon-grade uranium or plutonium. To monitor for suspicious activity outside its jurisdiction, the IAEA relies on environmental sampling and US electro-optical and radar satellites, such as the one that discovered Iran’s secret nuclear facility in 2009. Environmental samples are likely to be highly diluted if collected far from the expected site, and reactors can be hidden from satellite reconnaissance via underground facilities and cooling mechanisms to divert their thermal signature. In short, the current IAEA far-field verification system isn’t foolproof.
The IMS, developed by the Comprehensive Test Ban Treaty‘s Provisional Technical Secretariat, uses seismic, hydro-acoustic, infrasound, and radionuclide monitoring technologies to detect nuclear explosions around the globe. Not only are these methods inaccurate in pinpointing the exact detonation location due to signal interference, but there is also evidence that countries can decouple and disguise their nuclear test yields to make them difficult for the IMS technologies to detect. For example, a determined proliferator could decouple (or muffle) a nuclear explosion in a large underground cavity, which might appear to a seismic monitor as an earthquake or mining explosion. Radionuclide monitoring is highly susceptible to weather, and releases could even be captured to obscure detection. Antineutrino detectors do not have any of these problems. Because it is impossible to hide or fake the antineutrino signal that a reactor sends out, as long as the detector itself has not been interfered with, it cannot be evaded.
The pioneering technology of antineutrino detection could change the game, providing real-time, accurate, remote monitoring of nuclear endeavors, giving international agencies unprecedented access to knowledge about a particular state’s nuclear activity. And the technology’s effects could go further, for example, by motivating Tehran to be a responsible player in the nonproliferation sphere, and perhaps one day helping to develop a Middle East nuclear-weapon-free zone and with it greater regional stability.
How it works. Antineutrinos are emitted during all fission nuclear processes. Since they are not electrically charged, they pass right through nearly all forms of matter in a straight line. They cannot be blocked or shielded. In fact, an antineutrino could pass through a piece of lead more than a light-year thick (6 trillion miles) before showing any sign of interaction. The concept of using antineutrinos to detect nuclear activities is not new; antineutrinos from a reactor were first detected in 1956. However, technology has only recently caught up to the science, and we now have the ability to build antineutrino detectors at various sizes and costs that could potentially aid in nonproliferation efforts.
Antineutrino detectors are categorized into three different monitoring classes: Near-field (hundreds of meters), mid-field (tens of kilometers), and far-field (hundreds of kilometers). The first category is the most fully developed, and could even be deployed today for verification purposes with a host country’s permission. Near-field antineutrino detection could supplement current IAEA safeguard methods and provide an independently-verified, real-time picture of what’s happening to the nuclear material in a reactor core. The detectors—metal boxes about the size of refrigerators—could catch frequent reactor shutdowns, alerting the IAEA to dubious behavior, and tell inspectors exactly what’s in the fuel mix, showing whether a facility is trying to over-enrich plutonium. Unfortunately, near-field detectors have struggled to gain acceptance in the safeguards community. (Some experts attribute this to a fear that the technology is so good, states won’t allow it on their soil.) Incorporation of such a technology into the IAEA inspections regime would likely be interpreted as an act of “western aggression” against Non-Aligned Movement (NAM) states. It is unlikely that Iran, or any other NAM state, would allow monitoring measures beyond what they have already agreed to without being offered sufficient additional incentives. Still, it is possible that Iran could be persuaded to adopt the technology. The opportunity to host a large-scale project with major economic, scientific, and geopolitical impact could serve as an enticement.
Mid-field antineutrino detectors, meanwhile, have been proven able to monitor the presence or absence of 10 megawatt reactors from up to 10 kilometers away, and with further research and development, could be useful for detecting covert activities outside of the IAEA’s agreed-upon jurisdiction. A country might be amenable to allowing the technology on its soil because of the prestige inherent in hosting a world-class antineutrino observatory, a center that might employ hundreds of scientists with a commensurate physical and economic footprint. Certainly, if Iran were to host one, it would ease international proliferation fears while indemnifying Tehran for any loss in international status caused by curtailing its nuclear program, and could motivate the government to become a responsible player in the nonproliferation sphere.
Though it is farther away, the greatest potential for nuclear verification lies with far-field antineutrino detectors. A far-field observatory could monitor the presence or absence of reactors from up to hundreds of kilometers away, and thus, like the methods employed by the CTBTO, would not have to be based in-country. A decade ago, a team led by John Learned, a University of Hawaii physics professor and pioneer in the antineutrino detection field, developed a plan for a far-field, deep-ocean, 9,000-ton antineutrino observatory that could be used for deterrence monitoring. A far-field detector is estimated to cost in the range of $500 million to $1 billion—which is comparable to the price of the flagship technology, space-borne reconnaissance, currently used by non-proliferation monitors. With sufficient funding, a far-field, deep-ocean observatory could be built now, and could provide nuclear verification from outside a country’s borders that would be very difficult to evade.
Far-field detectors would be the ideal means of verifying compliance with nuclear agreements, as they don’t require the monitored state’s approval; however, their development lacks funding. On the other hand, a mid-field observatory placed within Iran’s borders would promise a consistent and reliable method of verification.
Getting Iran on Board. Near- and mid-field detectors face the disadvantage of having to be installed within the borders of the state being monitored, thereby requiring its approval. This poses a problem when a country like Iran holds a historically hostile attitude toward the United States and international control regimes. Antineutrino observatories, though, could eventually transform 21st century counter-proliferation efforts as dramatically as radar transformed modern warfare in the early 20th century. A single one could have incredible implications for the future of covert proliferation as well as nuclear weapons test monitoring.
While a far-field detector is still a ways away, can Iran be convinced to host a mid-field antineutrino detector? Iranian leadership may well entertain the idea of a world-class antineutrino observatory within the country’s borders, as it would significantly repair the international isolation caused by its non-compliance, bringing with it increased economic activity and international prestige. The presence of an observatory could bring the Iranian nuclear program into full transparency and compliance with the Nuclear Non-Proliferation Treaty, to which it is already a signatory. The prospect of highly effective verification would decrease liability for countries interested in investing in Tehran’s growing power industry. And, a major scientific center may give Iran the opportunity to reverse some of the brain drain that has plagued it in recent years.
In short, one of the main things Iran wants from the nuclear deal is to repair the self-inflicted damage caused by well-documented non-compliance with internationally imposed nuclear safeguards, and hosting an antineutrino observatory would help it get there. It would attract scientists from around the world, while reassuring the agreement’s other signatories that Tehran cannot develop a “breakout capability,” or ability to quickly build nuclear weapons.
Let’s get started. A mid-field antineutrino observatory holds the answer to the Iran deal’s verification woes. It has the potential to provide real-time, non-disguisable monitoring of Iran and allow Tehran to continue to develop its nuclear power sector, while offering peace-of-mind for the international verification community. And eventually—in perhaps 10 to 20 years—a far-field antineutrino observatory could hold the key to establishing a Middle East nuclear-weapon-free zone, providing the ability to monitor nearly all nuclear reactors and detonations in the Middle East. There should be no debate over further investment in the research.