Preliminary assessment of the safety factors in K-DEMO for fusion compatible regulatory framework.

We open an avenue for discussing how we can pave the way for compliance with existing regulations is a far-reaching factor for settling nuclear fusion technology. Based on a model of the Korean Fusion Demonstration Reactor (K-DEMO) with a target fusion power of 2.2 GW, we assess the intrinsic safety determinants of internal energy sources, the expected radioactive waste, and the tritium management. Regarding these safety factors, we scrutinize the compatibility of the current legislative environment in Korea with K-DEMO and envisage foreseeable obstacles, such as licensing of the nuclear facilities and acceptability of the radioactive waste. Based on precedent licenses for the Korean Superconducting Tokamak Advanced Research (KSTAR) and lessons learned from the International Thermonuclear Experimental Reactor (ITER), we examine hazardous factors that would threaten regulatory compliance of K-DEMO. This approach can help shape a fusion-compatible framework for consolidating the necessary technical provisions and regulatory baselines reflecting social acceptance with a sense of safety. Fusion-compatible aspects in the regulatory environment are discussed, from fusion philosophy to subordinate administrative and technical guidelines, facility classification, and detailed methods guaranteeing integrity and safety. This paper will contribute to the timely settlement of fusion demonstration facilities and subsequent commercial plants.

Forward projection matrix derivation through Monte-Carlo ray-tracing of KSTAR infra-red imaging video bolometer (IRVB).

The infrared imaging video bolometer (IRVB) as a foil bolometry technique can be an alternative solution to the conventional resistive bolometer due to its electro-magnetic immunity and 2D plasma profiles. The plasma profile of the IRVB cannot be directly derived from the foil images due to the difference between the foil pixel number and the plasma pixel number and the line integrated nature of the incident rays on the foil. So, it needs tomography such as the Phillips-Thikhonov algorithm. The projection matrix constructing the foil image from the plasma very directly influences the tomography. So, the projection matrix needs to be constructed precisely. For the technique calculating the precise projection matrix, a forward Monte-Carlo ray-tracing method is proposed here, and this technique can provide the detailed descriptions of the foil image. And it can give enhanced performance in the reconstructions of the plasmas with spatially localized power.

Reconstruction of radiation profiles near the plasma boundary using an infrared imaging video bolometer in KSTAR.

An infrared imaging video bolometer using tomographic inversion can provide the total radiated power and 2-D radiation profiles, which are crucial information for impurity seeding experiments. Because large amounts of impurities exist at the plasma edge, accurate reconstruction of the radiation profiles near the material boundary is an important issue. In this study, two methods of boundary condition treatment are compared. One involves the exclusion of plasma pixels outside the boundary before reconstruction, whereas the other excludes these pixels after reconstruction. Phantom reconstruction tests are performed with D-shaped and divertor radiation profiles, and the second method shows an improvement in the boundary-reconstruction results compared with the first method. Using the second method, the radiation profiles of krypton (Kr) seeded H-mode plasmas in KSTAR are reconstructed. A significant amount of input power is dissipated through the Kr radiation. The 2-D reconstructed radiation profiles show that Kr mostly accumulates at the plasma core rather than at the edge.

Hepatic iron overload in the portal tract predicts poor survival in hepatocellular carcinoma after curative resection.

BACKGROUND & AIMS: Hepatic iron overload is associated with liver injury and hepatocarcinogenesis; however, it has not been evaluated in patients with hepatocellular carcinoma (HCC) in Asia. The aim of this study was to clarify the degree and distribution of intrahepatic iron deposition, and their effects on the survival of HCC patients. METHODS: Intrahepatic iron deposition was examined using non-tumorous liver tissues from 204 HCC patients after curative resection, and they were scored by 2 semi-quantitative methods: simplified Scheuer's and modified Deugnier's methods. For the Scheuer's method, iron deposition in hepatocytes and Kupffer cells was separately evaluated, while for the modified Deugnier's method, hepatocyte iron score (HIS), sinusoidal iron score (SIS) and portal iron score (PIS) were systematically evaluated, and the corrected total iron score (cTIS) was calculated by multiplying the sum (TIS) of the HIS, SIS, and PIS by the coefficient. RESULTS: The overall prevalence of hepatic iron was 40.7% with the simplified Scheuer's method and 45.1% with the modified Deugnier's method with a mean cTIS score of 2.46. During a median follow-up of 67 months, the cTIS was not associated with overall survival. However, a positive PIS was significantly associated with a lower 5-year overall survival rate (50.0%) compared with a negative PIS (73.7%, P = .006). In the multivariate analysis, a positive PIS was an independent factor for overall mortality (hazard ratio, 2.310; 95% confidence interval, 1.181-4.517). CONCLUSIONS: Intrahepatic iron deposition was common, and iron overload in the portal tract indicated poor survival in curatively resected HCC patients.

Coordinated underground measurements of gamma-ray emitting radionuclides for plasma physics research.

Forty-eight samples made of CaF2, LiF and YVO4 were placed inside the KSTAR Tokamak and irradiated by neutrons and charged particles from eight plasma pulses. The aim was to provide information for plasma diagnostics. Due to the short pulse durations, the activities induced in the samples were low and therefore measurements were performed in five low-background underground laboratories. Details of the underground measurements, together with data on the quality control amongst the radiometric laboratories, are presented.

Expression profile and prognostic value of glypican-3 in post-operative South Korean hepatocellular carcinoma patients.

Hepatocellular carcinoma (HCC) patients commonly experience poor overall survival (OS) and disease-free survival (DFS) after curative surgical resection. Glypican-3 (GPC3) has been suggested as a prognostic biomarker for post-operative survival. However, few to none of these studies have included South Korean patients. This study aimed to determine GPC3 expression rate, clinical correlation, and post-operative prognostic value in South Korean HCC patients who underwent curative surgical resection. Surgically resected tissues from 185 HCC patients were collected and assembled into tissue microarrays (TMAs), which were stained for GPC3 by immunohistochemistry. GPC3 expression rates were correlated with clinicopathological information, and survival analyses were performed to assess the prognostic value of GPC3. GPC3 expression was present in 153 patients (82.7%). GPC3-positive patients were younger with higher frequencies of microvascular invasion and higher AFP levels than GPC3-negative patients. There was no significant difference in survival between GPC3-negative and GPC3-positive patients. Based on multivariate analysis, GPC3 expression was not a prognostic marker for post-operative survival. In South Korean HCC patients, GPC3 expression was more frequent in HCCs with aggressive features, but it was not an independent prognostic biomarker.

Prevalence and outcomes of extrahepatic primary malignancy associated with hepatocellular carcinoma in a Korean population.

BACKGROUND: With advances in hepatocellular carcinoma (HCC) screening and treatment, the incidence of diagnosing a case of extrahepatic primary malignancy (EHPM) in patients with HCC has increased. This study aimed to elucidate the prevalence and clinical outcomes of EHPM in patients with HCC who underwent curative resection in Korea. METHODS: The clinical data of 250 patients with HCC who underwent curative resection in our hospital from May 2003 to December 2011 were retrospectively analyzed. The clinical features, overall survival, and causes of death were compared between patients with HCC with or without EHPM. RESULTS: The prevalence of EHPM among the 250 patients was 13.2% (n = 33). The most common site of EHPM was the colorectal (n = 10), followed by the stomach (n = 9), breasts (n = 4), and kidneys (n = 3). Patients with EHPM were significantly older, and they presented with higher rates of comorbidities, a different etiology of HCC, and better liver function than patients without EHPM. Interestingly, overall survival was significantly lower in the EHPM group, which more frequently displayed extrahepatic causes of death. Moreover, the presence of EHPM was an independent factor for overall survival in the study population. CONCLUSIONS: The prevalence of EHPM in patients with HCC who underwent curative surgical resection was 13.2% in Korea, with colorectal and stomach cancers comprising most EHPMs (88%). The patients with EHPM displayed significantly worse survival because of extrahepatic causes of death, which should be considered in the management of HCC in the future.

Prediction of risk for hepatocellular carcinoma by response of serum α-fetoprotein to entecavir therapy.

BACKGROUND AND AIMS: Serum α-fetoprotein (AFP) is frequently elevated in patients with chronic hepatitis B (CHB) who do not have hepatocellular carcinoma (HCC). Entecavir (ETV) treatment reduces AFP levels in these patients, but the clinical significance of AFP response to ETV has not been fully studied. The aims of this study were to elucidate the temporal response of AFP to ETV therapy and to determine the relationship between AFP response and the subsequent development of HCC. METHODS: All consecutive nucleos(t)ide-naïve CHB patients who started ETV therapy between March 2007 and February 2009 were selected from an electronic medical record database at a tertiary referral center (BESTCare). Clinical, biochemical, and virologic parameters were evaluated in relation to the serial AFP levels tested during ETV treatment. RESULTS: Among the 244 enrolled patients, 66 had elevated AFP levels before ETV therapy. Low serum albumin was a significant predictor for elevated AFP. During 12 months of ETV therapy, AFP levels normalized in approximately three fourths of these patients. The decrease in AFP was delayed in patients with high baseline hepatitis B virus titers and in patients who subsequently developed HCC during ETV therapy. Incidence of HCC was similar regardless of baseline AFP levels. Among patients with elevated AFP, however, HCC developed exclusively in the subgroup where elevated AFP persisted for more than 6 months of ETV therapy. CONCLUSIONS: Delayed AFP response to ETV may serve as an indicator of high HCC risk.

Probe diagnostics in the far scrape-off layer plasma of Korea Superconducting Tokamak Advanced Research tokamak using a sideband harmonic method.

Plasma characteristics in the far scrape-off layer region of tokamak play a crucial role in the stable plasma operation and its sustainability. Due to the huge facility, electrical diagnostic systems to measure plasma properties have extremely long cable length resulting in large stray current. To overcome this problem, a sideband harmonic method was applied to the Korea Superconducting Tokamak Advanced Research tokamak plasma. The sideband method allows the measurement of the electron temperature and the plasma density without the effect of the stray current. The measured plasma densities are compared with those from the interferometer, and the results show reliability of the method.

Development of a particle injection system for impurity transport study in KSTAR.

A solid particle injection system is developed for KSTAR. The system has a compact size, compatibility with a strong magnetic field and high vacuum environment, and the capability to inject a small amount of solid particles with a narrow injection angle. The target flight-distance of 10 cm has been achieved with a particle loss rate of less than 10%. Solid impurity particles such as tungsten and carbon will be injected by this system at the midplane in KSTAR. The impurity transport feature will be studied with a soft X-ray array, a vacuum ultra-violet diagnostic, and Stand Alone Non-Corona code.

Treatment outcomes of transcatheter arterial chemoembolization for hepatocellular carcinoma that invades hepatic vein or inferior vena cava.

PURPOSE: We aimed to elucidate the treatment outcomes of transcatheter arterial chemoembolization (TACE) and survival-associated factors in hepatocellular carcinoma (HCC) patients with hepatic vein (HV) and/or inferior vena cava (IVC) invasion. METHODS: The subjects were consecutively enrolled, newly diagnosed HCC patients with HV/IVC invasion who underwent TACE (n = 62) at the Seoul National University Bundang Hospital from May 2003 to October 2012. Clinical characteristics, treatment responses, overall survival, and survival-related factors were analyzed. RESULTS: The mean subject age was 56.6 years, 82.3% were hepatitis B surface antigen-positive, and 76.2% were classified as Child-Pugh class A. The tumor volume was ≥50% of the liver in 64.5% of patients, and 79, 41.9, and 9.7% of patients had accompanying portal vein, IVC, and right atrial invasion, respectively. TACE response rates for primary tumors and tumor thrombi in HV or IVC were 55.6 and 13%, respectively. Median overall survival was 10.9 months (range 0.1-23.0 months). Multivariate analysis showed that Child-Pugh class A (hazard ratio [HR] = 0.31; 95% confidence interval [CI] 0.14-0.72; p = 0.007), tumor volume <50% of liver (HR = 0.31; 95% CI 0.11-0.83; p = 0.019), alpha-fetoprotein (AFP) response (HR = 0.28; 95% CI 0.11-0.69; p = 0.006), and tumor thrombi treatment response (HR = 0.09; 95% CI 0.01-0.77; p = 0.027) were independent survival-related factors. CONCLUSIONS: TACE seems effective for HCC with HV/IVC invasion, especially in patients with preserved hepatic function, a treatment response for tumor thrombi, and an AFP response.

Studies on formation of carborane film prepared by using a deuterium glow discharge method.

Carborane powders (C2B10H12) were deposited on silicon substrates and the physical properties of the films were investigated as functions of the distance of the sample from the electrode, the carborane mass, and the plasma-pulse. To obtain the optimum thickness of the films, three silicon substrates were positioned at 6.5, 16.5, and 36.5 cm from the electrode, and the thickness of the samples was analyzed by using XRD, TEM, and SEM. For the deposition, the carborane powder was warmed to 80 degrees C in 10 minutes and was applied a DC-power pulse of 900 W (150 volts, 6 amps) for 2 hours. The mass of carborane and the on-time sequence were varied during the deposition. The combined results of XRD and TEM studies revealed that the structure of the deposited film is an amorphous phase. A careful analysis of the SEM images show that the thickness of the carborane films increased as increasing the mass of the flown carborane while it remained constant when a plasma-pulse time was varied. The thickest film of 353 A was achieved from the samples placed closest to the carborane inlet and the thickness became thinner as farther from the source suggesting that the density of the evaporated carborane powder in a chamber decreased as increasing the distance of the sample from the carborane inlet.

First results on disruption mitigation by massive gas injection in Korea Superconducting Tokamak Advanced Research.

Massive gas injection (MGI) system was developed on Korea Superconducting Tokamak Advanced Research (KSTAR) in 2011 campaign for disruption studies. The MGI valve has a volume of 80 ml and maximum injection pressure of 50 bar, the diameter of valve orifice to vacuum vessel is 18.4 mm, the distance between MGI valve and plasma edge is ~3.4 m. The MGI power supply employs a large capacitor of 1 mF with the maximum voltage of 3 kV, the valve can be opened in less than 0.1 ms, and the amount of MGI can be controlled by the imposed voltage. During KSTAR 2011 campaign, MGI disruptions are carried out by triggering MGI during the flat top of circular and limiter discharges with plasma current 400 kA and magnetic field 2-3.5 T, deuterium injection pressure 39.7 bar, and imposed voltage 1.1-1.4 kV. The results show that MGI could mitigate the heat load and prevent runaway electrons with proper MGI amount, and MGI penetration is deeper under higher amount of MGI or lower magnetic field. However, plasma start-up is difficult after some of D(2) MGI disruptions due to the high deuterium retention and consequently strong outgassing of deuterium in next shot, special effort should be made to get successful plasma start-up after deuterium MGI under the graphite first wall.