It has been known that as oxide layer (ZrO2) forms on the nuclear fuel cladding during irradiation in nuclear power plants, the corrosion kinetics are influenced by various parameters such as chemical environments. One of those environments, crud deposition driven by coolant chemistry has an adverse effect on the formation of oxide (ZrO2) and leads to increase thickness of the layer. In this study, crud formation was performed through loop experiment equipment on the surface of intentionally-made oxide layer (ZrO2) on cladding tubes and then the composition and characteristics of cruds were examined for the investigation of nuclear power plant environment. As a result, various cruds in composition and microstructure were formed depending on the exquisite methods and conditions such as metal ion concentration.

돌나물 유전자원의 기내 활성보존을 위하여, 10mm 크기의 기내배양 shoot를 agar, Gelrite, ABA 및 sucrose 농도를 달리한 MS 배지에 치상하여, 4oC와 25oC에서 계대배양 없이 보존하였다. 배지는 0.2mg · L−1 BA를 기본으로 첨가하였고, agar와 Gelrite 배지에는 5% sucrose, ABA 배지에는 5% sucrose와 1.2% agar, sucrose 배지 에는 1.2% agar를 각각 첨가하였다. 상온 활성보존(25oC) 에서 sucrose와 Gelrite 배지는 생장억제 효과가 거의 없었고, 0.2mg · L−1 BA + 10mg · L−1 ABA + 1.2% agar, 또는 0.2mg · L−1 BA + 1.6% agar를 첨가한 배지가 효과적이었으며, 계대배양 없이 10개월까지 활성보존이 가능 하였다. 저온 활성보존(4oC)에서 12개월후 생존율은 모든 배지에서 100%였으며, 10mg · L−1 ABA, 또는 6% sucrose 첨가배지에서 계대배양 없이 18개월 이상의 활성보존이 가능하였다. 특히 고농도 sucrose 배지는 저온 활성보존(4oC)에서 돌나물 유전자원의 장기간 활성유지에 가장 효과적이었다.

To identify the new source of breeding materials for rice salt tolerance, the salinity tolerance of thirty-four varieties was evaluated under 0.5% saline condition at seedling stage. The salinity score showed highly significant correlations to dry weight and dead leaf ratio. The tested varieties were classified into three groups by visual score, reduction ratio of dry weight, and dead leaf ratio. Eighteen varieties were classified as the highly tolerant group (salinity scores of 1.3-3.7), seven varieties were fallen into the tolerant group (salinity scores of 4.2-5.8), and others were susceptible (salinity scores of 6.7-9.0). In highly tolerant group, most indica varieties including Getu, Dikwee and Kuatic Putic, didn't exsert a panicle under the Korean climate. But six varieties, Xiangcho V, Annapuruna, HP 3319-2wx-6-3-1, Giza 175, and GZ 2447-S-17, GZ 4255-6-3 were suitable to the Korean climate, and their heading date (6-16, August) and culm length (65-78㎝) were similar to the Korean varieties. Accordingly, these varieties can be utilized as crossing materials for the salt tolerance in japonica rice.

Mihyangbyeo, a new japonica aromatic rice (Oryza sativa L.) was developed by National Honam Agricultural Experiment Station (NHAES), RDA in 1998. It was derived from the three-way cross among Seomjinbyeo of the disease resistance and high yielding lines,

“Hoanbyeo” is a new japonica rice cultivar developed from a cross between Kanto149 and Milyang95 by the rice breeding team of National Honam Agricultural Experiment Station (NHAES), RDA, during 1990 to 1998. This cultivar requires about 121days of growth

“Sobibyeo” is a new japonica rice cultivar developed from a cross betw een Hwayeongbyeo and YR13604Acp22 line by the rice breeding team of National Honam Agricultural Experiment Station (NHAES), RDA, in 1999. This cultivar has a large grain and about 119

Tuberous roots of yacon (Polymnia sonchifolia Poeppig ＆ Endlicher) were stored in different temperature and relative humidity conditions after curing for 30 days. Non-decadent percentage, moisture contents, brix degree and sugars were investigated. Whether temperature and relative humidity were high or not, most of the tuberous root decayed during storage, and the decayed percentage was increased as long as the storage period. In final, only 13% of tuberous roots remain intact at 4~circC , 85% relative humidity condition to be appeared best storage condition in this experiment and all of the tuberous root decayed in other storage conditions after 6 months. Moisture contents decreased a little in the high relative humidity. Even though tuberous roots decayed when stored at 10~circC and 20~circC , most of brix degree reached about 17.0. Fructose, glucose and sucrose contents were 1.65, 1.15 and 0.35% at early storage period, and 1.6, 1.1 and 0.5% after 6 months at 4~circC , 85% relative humidity, respectively. In 3 temperature conditions, fructose and glucose increased for a month and then decreased successively afterwards, but sucrose increased gradually during 6 months. Also in 4 relative humidity conditions, fructose, glucose and sucrose contents were changed with similar to that of in temperature. Changes of fructose and glucose were the same except on 4~circC , 85% relative humidity, that was lower level than moisture of tuberous root.

Unstable seedling stand establishment of wet direct seeding culture of rice is one of the major elements preventing the extension of its culture area. In order to develop methods of seedling stand improvement in direct seeded rice on flooded surfaces, three field experiments were conducted on silty loam soil using a cultivar 'Donjinbyeo' for three years, mainly focusing on water management after seeding and seed soaking with plant growth regulators (PGRs). Under the condition of shallow flooding after seeding, seedling stand rate increased and floating seedling rate decreased in both early and normal season seeding compared to deep flooding. With earlier draining time after seeding, there was a tendency towards preferential growth of the seminal root, increase of seedling stand and decrease of the floating seedling rate. Therefore the highest seedling numbers per unit area and the lowest floating seedling numbers were found upon drainage at 1 day after seeding (DAS), while a contrary tendency was shown upon conventional drainage at 7 DAS. Seed soaking with PGRs such as Metalaxyl or mixing of Metalaxyl with gibberellic acid (GA3 ) significantly increased the seedling stand. In addition the effects of PGR treatment on seedling stand and the early growth of plants were greater under flooded conditions than under drained conditions after seeding, although draining of water after seeding improved the seedling establishment rate more when compared with the PGR treatment. These results suggest that draining management after seeding or maintaining of shallow flooding for a week is the most effective method to improve the seedling stand rate in wet direct seeding.