Another safety incident has shaken the Pelindaba nuclear facility outside Johannesburg, resulting in the total shutdown of the NTP Radioisotopes plant which produces vital supplies of nuclear medicine and radiation-based products.Senior NTP staff point fingers at parent company the South African Nuclear Energy Corporation (Necsa).The sudden halt in production, which can be lifted only once the National Nuclear Regulator gives the all-clear, threatens global medicine supply.amaBhungane understands that the NTP facility was shut down after a dangerous spike in hydrogen gas levels was detected last Thursday. This, according to a senior technical employee, "could have resulted in an explosion".Necsa group chief executive Phumzile Tshelane, speaking on behalf of Necsa and NTP, ignored most questions put to him, saying: "We cannot disclose classified information". He did, however, attempt to downplay the incident.'Minor incident'"This was a minor incident followed by vigilant safety protocols which ensured that there is no danger as alleged by your source."Tshelane cautioned against what he called "dangerous and alarmist allegations".This is the latest in a string of setbacks for NTP, the owner of the plant. In November last year, the plant was shuttered by the nuclear regulator after faulty calibrations in an instrument for analysing hydrogen levels.Several employees claimed that since the November incident the new acting management brought in to get the plant restarted has bungled the recovery process and created unsafe work conditions.After the November incident, state-owned Necsa hurriedly placed a number of NTP senior managers on special leave, including managing director Tina Eboka.Necsa then announced that one of its executives, Thabo Tselane, who is also an NTP board member, would act in Eboka's place.The employees described how, after the shutdown last year, staff seen as aligned to Tselane and Necsa effectively took over operations but have struggled to get the plant up and running again.A protected disclosure by "concerned staff of NTP", written in February and addressed to the minister of energy, alleges that Necsa-deployed acting managers "inappropriately assembled teams in NTP that are not suitably qualified or experienced in what it takes to restore the plant integrity and safe operability".'Manipulating the crisis'Two senior technical employees claimed that Necsa and Tselane have been manipulating the crisis, bringing in their favoured employees who are underqualified and unfamiliar with NTP systems, while side-lining experienced NTP technicians."I've been twiddling thumbs in my office for months," said one.Necsa's Tshelane, citing an inability to disclose "classified information", did not respond to specific questions about allegations that it was side-lining experienced staff in favour of those less qualified."We will answer your – and other – media questions in full in a media statement as soon as possible," said Tshelane. In February, amaBhungane reported on alleged attempts by Necsa to exploit the ongoing shutdown for its own ends. Necsa was accused of purging senior management in an attempt to make a grab at NTP's funds and its coveted intellectual property.READ: Is a nuclear success story about to be snuffed out?Tshelane, the Necsa chief executive, was said to have wanted tighter control over NTP.More than six months after the November incident, a disciplinary case against Eboka, the suspended NTP boss, has not progressed. It is understood that she rejected a settlement offer from Necsa. As the only profit-making entity in the Necsa stable of companies, NTP – which is autonomously-run with its own mandate, management team, and board – allegedly became the target of its ailing parent company, which needed to plug holes in its own finances.Necsa at the time denied that it was threatening NTP's viability by attempting to siphon funds away from NTP and into its own accounts. The company said that "this is simply part of the optimisation of group assets and intra-group liquidity management. This will never be done irresponsibly either to the detriment of the Group or in contravention of any Act that governs us."The signatories of the protected disclosure allege that the Necsa-deployed team – despite assurances that its role would be temporary and limited to issues of safety and the resumption of production – is overstepping its mandate and "actively influencing the direction of the entire business group".They claim that the new management has amended the Strategic Business Plan 2018-2019 "while excluding participants who were part of the process of designing it".Soon after the November incident Tshelane took to the media to insist that the shutdown would likely only last weeks. Since then Necsa has been keen to claim successes in getting NTP back on its feet, but staff have pointed out that attempts to kickstart production have stuttered.In February, NTP claimed that the plant had restarted production. However, the nuclear regulator only gave permission for a limited number of return-to-readiness runs while corrective action was implemented and the plant was subject to continuous monitoring.The regulator told amaBhungane that "From February through to mid-April 2018, Necsa was required to provide weekly reporting on production undertaken."In May, media reports trumpeted a return to full production at NTP. Again, however, permission for production was conditional.Breakdown of safety cultureamaBhungane is in possession of correspondence between the regulator and Necsa/NTP from February to May that suggests that the recovery process has been far from smooth.The correspondence paints a picture of a breakdown of safety culture at the plant, where those working on returning the facility to full production are out of their depth.In their communications with Necsa/NTP, the regulator flags among other things: the submission of falsified results; inaccuracies in tables submitted; the failure to demonstrate repeatability of tests; the unsuitability of a particular individual to provide theoretical training to NTP staff; a lack of due diligence in calibration; failure to submit hydrogen calibration schedules; and a repeated failure to address the poor quality of graphs.In a letter from March, the regulator writes: "Noting the falsification of information, highlighted by the regulator… and recognising that that similar issue (sic) was previously raised by the regulator… Necsa/NTP Management is required to confirm what action(s) have been taken with regard to this matter."The protected disclosure also notes two separate incidents that were incorrectly handled by Necsa deployees.According to the disclosure, on 28 December the concentration of hydrogen in one of the reactor's cells exceeded the permissible limit. The safety manager attempted to log the incident but was reprimanded by new senior staff members, including the newly-deployed nuclear facility manager who was installed by Necsa and "has never worked with or been exposed to the Radiochemicals Facility".The incident was belatedly reported to the regulator on 19 January.Hydrogen levels could have resulted in an explosionOn 2 February, another violation took place when modifications were made to the plant without following proper processes. The nuclear facility manager allegedly did not deem it necessary to log the changes until being forced to after an inspection by the regulator.The protected disclosure also notes that "due to several known unauthorised changes that were made to the plant and the culture of hiding safety issues and concerns… the state of the plant at the moment is questionable and various discrepancies have been picked up by experienced personnel.""Currently when safety concerns are raised people are told they are being obstructive and are removed from the project."In the latest incident last Thursday, two senior technical specialists told amaBhungane that hydrogen levels reached 120% of what is termed the "lower explosion level"."You shouldn't get to 100 or even 80 percent," said one, adding that the concentration of hydrogen could have resulted in an explosion if there was a spark or even sufficient static.The incident appears to have begun with a cooling error, which led to the rise in hydrogen levels.The manager and operator on duty failed to monitor the graphs tracking the gas levels until it was too late.The sources described this situation as far more dangerous than the November incident, where readings were faulty but actual gas levels were not dangerously high.They explained that an explosion would not have resulted in nuclear fallout, but that the lives of employees at the plant would have been at risk and the facility could have suffered serious damage. Lives are at riskA less hypothetical threat, however, is the impact this will have on crucial medical supplies.NTP produces life-saving nuclear medicine, in particular molybdenum-99, or "Molly" - a key radiochemical that is used in the diagnosis of a range of ailments including cancer and heart disease.South Africa usually supplies up to 20 percent of global demand for the product, while the entire South African nuclear medicine industry, including 14 public hospitals, relies on NTP as the baseline supplier.Lives are at risk if supplies from South Africa dry up.An international industry insider that amaBhungane spoke to expressed concerns about the latest disruption in production.The insider said that after the November shut down international clients started receiving supplies in February, March and April, but at a reduced level. In May things started to look up with the resumption of supply a "pretty much" normal level.Now, however, they are anticipating further disruptions to international markets. amaBhungane's NTP sources are pessimistic that they would be allowed an immediate restart to production.The supply chain for Molly is extremely delicate as the product has a very short half-life and must be used within days of being produced at the facility.As soon as it comes out of the reactor it is flown to the various NTP clients around the world.As one of only four major global suppliers in a complex supply chain, if South Africa is knocked out of production other suppliers will struggle to make up shortfalls. This is complicated further by contractual obligations between suppliers and clients.Said the insider: 'Things are very tight and [during the previous shut down] there were shortages in various markets, with Japan being hit particularly hard."