In the morning hours, the worker was asked to fill up a poliethylene container (IBC type, capacity of 1 m3) with a nitric acid. The smaller quantities of acid were used to correct the reaction and the amount of carbonates in the chemical mixture. Essential quantities of nitric acid (as raw material) are being pumped to the reactors from the storage tanks. The worker loaded an empty container on a fork-lift truck and drove to the storage tanks located 200 m from the installation. After filling the container and screwing the cap, the tank started to bulge. The worker slightly unscrewed the cap which brought back the normal shape to the container. The worker repeated this activity twice while transporting the container. Then the container was put on a ground in the production hall/room (a place where potassium nitrate was produced). At 9:20 a.m. the container bursted causing release of the acid. The room started being filled with vapours and nitric oxides.

The rescue actions performed by the external units included the following activities:
– evacuation of 30 workers present in the room/hall and the the close vicinity.
– localization of the leakage location,
– neutralization and sorption of the acid,
– performance of the measures of the acid’s concentration,
– establishment of the dangerous zone,
– ventilation of the rooms,
– protection of the place where accident occurred.

Seven workers felt bad so were taken to the hospital for examination. There were released home after 3 days of hospitalization. Nobody was burned by the acid. No damage to the environment reported. The majority of the released acid flowed to the holding tank (installed in the ground). The material damage was estimated on several hundreds of Euro. The production was resumed at 10:00 p.m. and was preceded with the analysis of the concentration of N2O in the air.

The analysis showed that the container used was not designed for acids. The worker (by mistake and not obeying the instruction) took the wrong container. The properly labeled container was left inside the hall/room. The container which was used contained some residual quantities of hydrogen peroxide. During filling operation with nitric acid a reaction occurred resulting in formation of gases which caused the pressure increase inside the tank (bulging of the container’s walls). The investigation revealed that: – the container ruptured/bursted along whole length one of its bottom edges (between side wall and bottom), – the side walls were dented towards inside, – the container frame (made of steel pipes) was dented towards outside.

In order to prevent recurrence the following activities have been taken:
– for the storage of acid, the containers designed for 60% concentration can only be used including their proper labeling and actual legal proofs,
– transport of the containers with acid can only be carried out when supervised by the worker leading the shift.
– the instructions and procedures connected with different operations like: loading, distribution, storage and internal transport have been updated,
– training of the workers.

The operator was obliged to update the Major Accident Prevention Policy and to get acquainted all of the workers with it.
The operator fulfilled this obligation.