According to the eMARS report (see references), the accident investigation identified several causes, mostly related to the inadequacy of the operational measures to early spot anomalies and to learn from them. The findings can be cluster as follows. DESIGN SHORTCOMING(1) Catalyst activation was not taken into account during the reactor design: (2) There was no automatic trip in case of trespassing of the maximal reactor temperature. NEAR MISSES which were not taken into account (1)During initial plant start-up in 1991 and catalyst activation at 400 degrees Celsius an exothermic was experienced. Its cause was identified as a hydro cracking reaction of the paraffins in the treat gas, but no further action was taken; (2)In 1994 during a preliminary hot de-waxed treatment at 430 degrees Celsius, temperature indicators were seen to be out of range. No investigation was made. The settings of the temperature indicators was 410 and 450 Celsius although the instruments had a potential maximum of 1000 Celsius. All alarms were set at 405 Celsius. RISK ASSESSMENT SHORTCOMING(1)The original risk assessment did not consider the catalyst activation stage and dismissed the possibility of a runaway exothermic reaction.(2)The reactor installation was provided with an emergency shut-down control which was manually activated and required operators to respond correctly to the situation. (3)In May 1994 a new catalyst had to be activated. A temperature 430 Celsius was planned, instead of the 400 C originally used, but there was no risk assessment on this change in operating conditions. (4)During the activation stage 3 people went out onto the reactor ladders and platforms at various times, if they had been present when the reactor ruptured they would have been caught by the fire.LESSON LEARNED - ORGANISATION: A.Near misses are an important indicator of the potential for accidents. The plant organization has to record and assess them, and act upon. B.Operation process parameters cannot be changed without performing a new (partial) risk assessment C.Management of changes is a critical tool which should be adopted. It was not in the present case. LESSON LEARNED TECHNICAL KNOWLEDGE: At the time of the accidents, very little published information on runaway exothermic in continuous reactors was available. A case report in Safety Digest of American Petroleum institute, Publication 758 Section 2 1979 Chapter 5 is similar to this incident. Also "Chemical Reaction Hazards - A Guide" Editors Barton and Rogers published by IChemEng 1993 and IChemSymposium Series No. 85 "Protection of Exothermic Reactors and Pressurized Storage Vessels" could have been used to identify the chemical process on going in the reactor.Since then, hydro cracking and thermal cracking of paraffins at the temperatures experienced in this reactor are widely reported in standard text books.