Review finds flaws in new radiation monitor program

A National Research Council committee identified flawed testing, faulty cost–benefit analyses, and other problems with the Domestic Nuclear Detection Office’s program to develop and deploy improved radiation monitors for the screening of cargo at US ports. The NRC review also found that vendors of the Advanced Spectroscopic Portal (ASP) monitors had failed to deliver a system that meets DNDO’s specification for modularity, with the result that the agency is unable to match the best-performing hardware with the optimal data-analysis algorithms, or to allow upgrades as experience is gained with the system.

The findings deal another blow to a program that has been bedeviled for years by performance issues. First planned as a replacement for the network of polyvinyl toluene (PVT) detectors that are currently installed at the nation’s ports and border crossings (as shown here), the ASP system has since been relegated to a secondary role, scanning the shipping containers that set off the PVT portal monitors. The NRC panel, chaired by retired University of California president Robert Dynes, endorsed last year’s determination by Department of Homeland Security secretary Janet Napolitano that ASP monitors haven’t performed well enough to supplant PVTs. DNDO is a unit of DHS.

Ironically, the major motivator for ASP’s development was the inability of PVT monitors to distinguish the radiation signatures emitted by threat materials, principally highly enriched uranium (HEU) or plutonium, from those of harmless, naturally occurring radioactive sources such as cat litter or bananas. As a result, PVT monitors at US ports are tripped hundreds of times each day by containers that pass through them. Each false alarm necessitates a secondary, time-consuming inspection by customs agents, who must clamber with handheld radiation detectors through the containers. Like ASPs, handhelds can identify the isotopic source of radiation.

More expensive, less effective

With a life-cycle cost of about $1.2 million each, ASP units are twice as expensive as PVTs, according to the NRC report. But tests have shown that ASPs, while better at detecting moderately shielded HEU, have performed worse than PVTs at uncovering plutonium or HEU that is masked by the radiation emanating from some other—possibly benign—radioactive material in the container. Noting that physical testing couldn’t be carried out for every possible configuration of materials, nuclear contraband, and shielding inside shipping containers, the NRC reviewers recommended that DNDO add a significant modeling component to counter that limitation.

In performing its cost–benefit analysis of ASP, DNDO also should have considered the alternative of deploying improved versions of handheld detectors, known as radioisotope identification devices, that employ sodium iodide, germanium, or lanthanum bromide technologies, the committee said. Instead, DNDO’s analysis dismissed RIIDs out of hand as unsuitable for external inspection of containers. Nor did it consider advances in RIID software that could improve their performance. According to DHS, advanced RIIDs would cost about $40 000 apiece over a 10-year lifetime, compared with $27 000 for current versions—well below the cost of either ASPs or PVTs.

The panel also admonished DNDO for the agency’s ill-conceived effort to devise a single figure with which to summarize and compare ASP performance against other detection technologies. The number, or “figure of merit,” was used as input to the ASP cost–benefit analysis, but it represented aggregated test data “in ways that are incorrect and potentially misleading,” it said.

Congress had called for the NRC to review the ASP program in 2008, after acquisition of the new monitors was delayed several times over performance issues. The Government Accountability Office has produced several reports in recent years sharply critical of the ASP program, finding among other problems that vendors had inappropriately been involved in DNDO’s qualification tests. Congress expressly forbade acquisition of the new monitors until after the DHS secretary personally certified ASP’s readiness. In a May 2009 report, the GAO reported that the monitors “have a limited ability to detect certain nuclear materials at anything more than light shielding levels.” That report also identified multiple problems with integrating ASPs into customs operations at US ports.

David Kramer