This study was conducted to review the safety and appropriateness of PSV (Pressure Safety Valve) installation in the supply tank, which is a pressure vessel included in supply systems dedicated to supplying the acid/alkaline substances used in the Korean semiconductor manufacturing process. Three aspects of design, risk assessment, and regulations were reviewed to determine if there is a source of pressure higher than the maximum allowable working pressure (MAWP) of the supply tank that could cause fires, explosions, and overpressure. In the case of the design review, all 17 overpressure scenarios described in API Standard 521, i.e., pressure-relieving and depressuring systems, were reviewed, and there was no overpressure scenario above the maximum allowable working pressure (MAWP). Then, the risk assessment, i.e., the Hazard and Operability Study (HAZOP) technique, was used, and as a result of reviewing all possible risk situations, we can state that there were no overpressure scenarios that can exceed the design pressure of the supply tank; thus, we decided that the installation of a PSV on top of the supply tank is unnecessary. Finally, accident prevention measures against overpressure, such as the KS B 6750-3 system design and the Korean Industrial Standard, were reviewed from a legal point of view. It was confirmed that the hazardous chemical supply system for the semiconductor industry designed in this study has several protective functions to prevent fires, explosions, and overpressure. As a result of reviewing the above three aspects, it can be said that there is no need to install a pressure safety valve in a pressure vessel storing hazardous chemicals.

As the size of the chemical industry increases, chemical accidents continue to occur as the handling volume of chemicals also increases. Currently, in the case of a chemical accident, the prediction of the scope of influence mainly analyzes the scope of the impact on a single substance in the accident and does not consider the scope of the decomposition and reaction products. Nitric acid, one of the many chemical accidents, produces nitrogen dioxide, which is harmful when decomposed. In this research, we at first assumed an outflow accident of nitric acid. After conducting our research using the Chemical Accident Response Information System (CARIS), we discovered that the impact range and breakdown of nitric acid were comparable to that of nitrogen dioxide. Furthermore, we were able to identify the potential ramifications associated with such occurrences. In this study, the impact scenarios were evaluated according to the worst-case scenario, the alternative scenario, the size of the leak hole diameter, atmospheric temperature, atmospheric wind speed, and atmospheric stability. The results showed that the end point concentration distance of nitrogen in ERPG-1, 2 and 3 was larger than nitric acid in most conditions, with differences of up to 5.45 times in the worst-case scenario, 5.96 times in the alternative scenario, up to 6.952 times in the leak hole diameter scenario, up to 10 times in the atmospheric temperature scenario, up to 13 times in the wind speed-specific scenario, and up to 4 times in the atmospheric stability scenario. In the event of a nitric acid spill chemical accident, the response agency should set up a boundary area at a greater distance in consideration of the impact of nitrogen dioxide when setting up a boundary area such as the Hot zone and the Warm zone. Nitric acid handling sites should install additional detectors for nitrogen dioxide, which is decomposition products, to monitor the diffusion of decomposition products into the atmosphere when installing detection alarm equipment in preparation for leakage accidents. It is believed that the government should continuously secure and study data on other decomposable chemicals besides nitric acid to provide material information and disaster prevention methods to chemical accident response agencies and communities for effective and early treatment of chemical accidents.

The process safety management (PSM) system was introduced in South Korea in 1996, wherein a company voluntarily organizes and manages a chemical accident prevention system, which contributes to reducing chemical accidents. However, large- and small-scale chemical accidents occur frequently. This trend necessitates analysis and improvement of the PSM systems. This study aimed to analyze the correlation between major industrial accidents, their main causes, the status of accidents by company size and industry, and the PSM evaluation grade through an analysis of 130 accidents that occurred in the past 17 years (2005–2021). The results showed that small- and medium-sized enterprises (SMEs) with fewer than 100 employees accounted for 36% of all accidents, indicating a higher occurrence rate than large companies. Additionally, the proportion of companies with inadequate PSM levels, rated as M-grade (M+, and M−), were 67.0%, suggesting a high probability of major industrial accidents. The results of this study show that a company’s voluntary safety management can be induced by an improved PSM system and management plan, which is expected to prevent major industrial accidents.