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HYEX Safety risk contours surrounding the planned Fjord Base ammonia bunkering terminal.

Published 09.04.2024.

HYEX Safety Risk Contours Front Page in Norway #1 Tech Newspaper

On March 6, 2024, three months after a public hearing process, our client Yara Clean Ammonia received approval from the Norwegian Directorate for Civil Protection (DSB) to start construction of an ammonia bunkering terminal from Azane Fuel Solutions at Fjord Base in Florø. A key element of the application was the risk contours from a QRA performed by HYEX Safety. Today these contours could be found as top news on the front page of Teknisk Ukeblad, the main technical daily newspaper in Norway. There was however no recognition to HYEX Safety.

The reason for the news was that one neighbour, living/working well outside the outer consideration zone (fatality risk < 1E-7/y or less than once every 10 million year), was concerned that our risk assessment had not been considering the scenario with the maximum consequences. Our top event was a 2-chances-per-million-year major ship collision breaking the hull of the storage barge before rupturing the thick steel tank with refrigerated ammonia placed away from the collision zone (B/5). Our study assumed that the entire tank would quickly leak to sea with 35% evaporating and the rest being resolved in the sea. The maximum risk contour in the prevailing wind direction was 760 m, and there were no contours predicted beyond the industry base area and surrounding area at sea. As an illustration of the low risk level around the barge, it can be mentioned that residential homes would normally be allowed beyond the yellow zone (1 fatality per million years) if this were not in the middle of the industry base.

The “more dangerous scenario” proposed by the neighbour is a scenario in which the tank would break but not the barge, with all the ammonia evaporating from the barge. While this could give more ammonia evaporating into air, the evaporation rate would be at least 13 times lower than estimated for the top scenario. The ammonia toxicity is defined by a probit function from RIVM in the Netherlands, and with a 13 times lower evaporation rate, the concentrations blowing with the wind 760 m away will not represent any fatality risk of concern. CFD modelling of such releases predict that plumes will quickly lift off the ground in moderate winds due to an elevated release of buoyant ammonia gas or dilute quickly in strong winds. This has already been explained in responses to neighbours expressing concerns about exactly this “more dangerous scenario” during the public hearing process.

The Fjord Base ammonia bunkering facility is considered very safe, located well inside the base area, with few industry neighbours nearby, and the nearest residential homes well outside the outer consideration zone. With refrigerated storage (-33 ºC) and all tank penetrations on top of the tank, there should be no releases to sea outside the bunkering or loading operations, unless the tank and barge both break. Releases in gas phase will represent a limited concern due to the low storage pressure and buoyant plume. Releases during transfer operations will quickly be stopped by safety systems or crew.

Still, we understand that neighbours can have concerns about facilities nearby. The concerns were fuelled by media statements from the Statsforvalter, the regional government representative, claiming that the hazard distances for ammonia incidents should be 10 km. The 10 km safety distance was taken from a guideline for first-responders and may be a reasonable evacuation distance for catastrophic events involving ambient temperature (warm) ammonia stored at pressure, but not for a refrigerated storage tank.

With the consideration zone concept introduced in 2012 the safety requirements from the DSB are very strict. If a facility has been approved, the fatality risk for neighbours shall be negligible. Worldwide, ammonia is among the most traded and transported toxic industry chemicals and the fatality rates are low. Compared to another toxic chemical like chlorine, a 100-times higher ammonia volume concentration is required to reach fatal exposure levels.

HYEX Safety is also supporting developers of ammonia fuelled vessels with risk assessments for maritime approval processes. Our experience is that vessel design requirements are very strict related to safety, and that the risk to crew on ammonia fuelled vessels will be low. To the extent there are ammonia releases possible during operations, these will be collected and released at high elevation with low likelihood for odours and negligible toxicity concerns.