In this research, a detailed analysis of the decay heat contributions of both actinides and non-actinides (fission fragments) from spent nuclear fuel (SNF) was made after 50 GWd·tHM−1 burnup of fresh uranium fuel with 4.5% enrichment lasted for 1,350 days. The calculations were made for a long storage period of 300 years divided into four sections 1, 10, 100, and 300 years so that we could study the decay heat and physical disposal ratios of radioactive waste in medium- and long-term storage periods. Fresh fuel burnup calculations were made using the code MCNP, while isotopic content and then decay heat were calculated using the built-in stiff equation solver in the MATLAB code. It is noted that only around 12 isotopes contribute more than 90% of the decay heat at all times. It is also noted that the contribution of actinides persists and is the dominant ether despite decreasing decay heat, while the effect of fission products decreases at a very rapid rate after about 40 years of storage.

In South Korea, the master plan for high-level radioactive waste management, announced in 2016, suggested the construction and operation of intermediate storage facilities on a permanent disposal site and specified the adoption of dry storage in consideration of the ease of operation and expansion. As of 2021, the government is again reviewing its overarching policy on the back-end fuel cycles, including intermediate storage and permanent disposal. In the case of dry storage facilities, safety evaluation is being conducted using a combination of deterministic and probabilistic approaches, similar to that of nuclear power plants. The two methods are complementary, of which Probabilistic Safety Assessment (PSA) has the advantage of being able to identify key scenarios affecting safety, but its use in storage facilities has not been highlighted so far. However, depending on the spent fuel management phases such as loading, transportation, and storage, it may be not enough to capture effective and efficient safety evaluation only deterministically, and probabilistic methods may contribute to the evaluation of long-term operation or external events such as an earthquake. There have already been cases where PSA has been performed on a part of the nuclear fuel cycle through previous studies. This paper created the safety assessment model based on open sources such as the released EPRI reports, by targeting arbitrary intermediate storage facilities. The model considered the scenarios for loading, transportation, and storage, with human error respectively. It will be able to be modified and improved to fit domestic and specific intermediate storage facilities in the future.

The revitalization of e-business via Internet brings big changes to the postal business, and leads to a tremendous increase of heavy and large sized postal mails with continuing growth of home delivery business. Thus, even though the number of intermediate storages for mail delivery that mailmen use for picking up mails in the middle of mail delivery has been being increased, it has still many problems such as insufficient number and size of the storages as well as avoidance of mail keeping of trust agents. It is necessary that safety of mail keeping, seamless mail delivery, and individual parcel pick-up process reestablish- ment should be made through an improved counter plan for the problems described previously. This study presents the efficient and right operational plan for the intermediate storage for mail delivery with providing the number and size of intermediate storages per mail delivery sequence according to four different types of post offices.

The revitalization of e-business via Internet brings big changes to the postal business, and leads to a tremendous increase of heavy and large sized postal mails with continuing growth of home delivery business. Thus, even though the number of intermediate storages for mail delivery that mailmen use for picking up mails in the middle of mail delivery has been being increased, it has still many problems such as insufficient number and size of the storages as well as avoidance of mail keeping of trust agents. It is necessary that safety of mail keeping, seamless mail delivery, and individual parcel pick-up process reestablishment should be made through an improved counter plan for the problems described previously. This study presents the efficient and right operational plan for the intermediate storage for mail delivery with providing the number and size of intermediate storages per mail delivery sequence according to four different types of post offices.