On February 12, 2013, North Korea carried out its third nuclear test.  Nuclear watchdogs the world over were alerted by the three-day advance warning of testing a nuclear device of a smaller size with significantly higher yields imminent. The fact that this test was not secretive reflected the confidence of the North Korean scientists in testing a possible warhead device that could be mounted on an intercontinental ballistic missile. As revealed later, it also reflected the Korean pride in clouding a test.
This prompted a nuclear gossip in the world rife with North Korea having mastered the centrifuge based techniques to produce weapons grade HEU as a departure from the more complicated plutonium route. Some observers and nuclear scientist, like Siegfried S. Hecker, expected the latest test to be a second generation compact HEU device; in other words, a warhead design provided covertly by Dr A. Q. Khan. Like the hermit kingdom that North Korea is, the world is still guessing what it actually was? Even more, the world is left guessing about the motives, intentions and long-term goals of a nuclear North Korea.
Though earlier, North Korea had managed to test two plutonium devices, opinions over their physical size and practicability as nuclear weapons differed. The first test was termed a fizzler, a dud or a decoy explosion with huge amounts of conventional explosives till the US was able to confirm the presence of radio nuclei and Xenon 133 gas isotopes associated with plutonium devices. Yet, the test though alarming was dismissed as a potential nuclear threat associated more with its failure to trigger a higher yield. 
This test on March 25, 2009, had surprised the world for many reasons. According to Congress Research Services (CRS), the test produced seismic signals detected by at least 61 seismic stations. However, unlike the first test, no radioactive materials were, reportedly, detected. The frustration at not being able to detect the nuclear signature led Geoffrey Forden, a scientist at MIT, posit a scenario in which a room could be filled with 2,500 tons of TNT, enough to create an explosion within the yield range estimated for the 2009 North Korean test, in two months using about four 10-ton truckloads per day. Professor Paul Richards from the Lamont-Doherty Earth Observatory, Columbia University, USA, considered the scenario technically possible, but practically highly implausible. Hence, the biggest challenge for nuclear watchdogs and Comprehensive Test Ban Treaty (CTBT) protocols remained; how was North Korea able to conceal the radioactive signatures of such a big explosion?
Successful containment of the nuclear signature is of great value to North Korea. It controls radioactive fallout from reaching China, Japan, Russia or South Korea, thereby averting crises and preventing international intelligence from gathering material that could reveal information about the extent of the nuclear development, the weapon, materials and the steps involved in testing. 
Alarmingly, as posited by experts and nuclear detectives, this successful clouding could permit North Korea to host nuclear tests by other nations, such as Iran. Most it challenges the completeness of CTBT verification protocols for being ineffective without onsite verification; something that has been alluded in my columns in the past.
Soon after the second test and during a diplomatic thaw, North Korea permitted US scientist to visit its facilities in pursuit of a quid pro quo. Hecker during his many visits to Yongbyon nuclear complex, housing both plutonium production and its uranium enrichment facilities, was told by North Korean nuclear specialists that the first two nuclear devices tested used plutonium, in one unsuccessfully and the other with a measured success. In 2008, North Korea voluntarily suspended its plutonium production. Hecker estimated that it had only 24 to 42 kilograms of plutonium, sufficient for four to eight primitive nuclear devices. He was of the view that further testing in plutonium devices was imperative to producing nuclear weapons and the country’s production facilities with a prominent plume would always give away the North Korean preparations.
In my assessment, the slow and tedious route of producing plutonium cores, coupled with the inability to contain the production signatures and frequency of verifiable tests to confirm the decay rates, made the plutonium route impracticable. Hence, they chose to rely on the more secretive and bulkier HEU enrichment centrifuge designs backed by the creation of compact designs. While keeping centrifuge facilities with big reservoirs of uranium ores was never an issue, North Korean scientists worked hard on clouding the nuclear signatures for further testing. This was essential to maintaining opaqueness in a poor man’s nuclear deterrence.
So when the North Korean alert came on October 9, Hecker was quick to predict that North Korea was possibly shifting to a more reliable and secretive HEU route. Yet, he and many others questioned the ability of the country to detonate compact HEU devices with no prior experimentation with such devices. He and the entire team of nuclear watchdogs remain sceptical how North Korea was able to sidestep the experimental stages to a suspected miniaturised HEU based device of which the country has no previous experience. Finally, their fingers pointed at Dr A. Q. Khan and Iran, the proverbial scapegoats when anything goes wrong.
According to David E. Sanger, international detectives have been working in secret for two years, to track the digitised blueprints of a weapon that is relatively small and easy to hide to links of Khan’s computers in Switzerland, Dubai, Malaysia and Thailand. Though Pakistan was quick to reject these allegations and assert that Dr Khan was never involved with development of Pakistan’s nuclear weapons, the world does not believe it. They also conjecture that some of its six nuclear devices were also based on a similar HEU design and infer the designs as Pakistani. However, this explanation can be challenged on three counts.
First, that Dr Khan was only involved in the enrichment process and missile development technologies is correct. Any designs that he developed were his own or designs on his computer network came from some outside international source.
Second, other than the seismic data and nuclear signatures, Pakistan has kept the nature and extent of its nuclear testing a secret. So, the assertion that Pakistan used the same designs in its HEU testing is a mere educated guess.
Third, after 1998, Pakistan’s activities came under intense international scrutiny sharpening the focus after Libyan/Iranian revelations and the confessions of Dr Khan. The North Korean HEU programme may have begun earlier, but appears to have been accelerated after the second testing in 2009 and inspection of its facilities in 2010 by international experts.
All these allegation and arguments aside, the third secretive nuclear explosion, purportedly of a compact HEU device with no nuclear signatures, has challenged the international non-proliferation efforts on the following counts.
First, that the CTBT regime is not definitively variable. This fact has been underlined by critics due to the continued testing by USA and Russia, using terms like Cold Tests, Inertial Confinement Fusion (ICF) etc. These technologies can be effectively used by clouding and testing of elements to upgrade weapon systems. On a bigger scale, the third North Korean test has initiated a debate on the efficacy of CTBT.
Second, North Korea has shown the way to other countries toying with the idea of nuclear weapons, to concentrate on HEU centrifuge technologies and opt for bulky but reliable fission designs.
Third, as suspected by CRS, North Korea could provide testing grounds for other countries like Iran.
This development is most likely to usher in a new level of debate in nuclear proliferation and testing. Invariably, Dr Khan’s name will come in as a likely corroborator with North Korea. Pakistan ought to do well in parrying  these attacks.
The writer is a retired army officer, current affairs host
    on television and political economist.
       Email and Twitter: samson.sharaf@gmail.com