Our research team has developed a gamma ray detector which can be distributed over large area through air transport. Multiple detectors (9 devices per 1 set) are distributed to measure environmental radiation, and information such as the activity and location of the radiation source can be inferred using the measured data. Generally, radiation is usually measured by pointing the detector towards the radioactive sources for efficient measurement. However, the detector developed in this study is placed on the ground by dropping from the drone. Thus, it does not always face toward the radiation source. Also, since it is a remote measurement system, the user cannot know the angle information between the source and detector. Without the angle information, it is impossible to correct the measured value. The most problematic feature is when the backside of the detector (opposite of the scintillator) faces the radiation source. It was confirmed that the measurement value decreased by approximately 50% when the backside of the detector was facing towards the radiation source. To calibrate the measured value, we need the information that can indicate which part of the detector (front, side, back) faces the source. Therefore, in this study, we installed a small gamma sensor on the backside of the detector to find the direction of the detector. Since this sensor has different measurement specifications from the main sensor in terms of the area, type, efficiency and measurement method, the measured values between the two sensors are different. Therefore, we only extract approximate direction using the variation in the measured value ratio of the two sensors. In this study, to verify the applicability of the detector structure and measurement method, the ratio of measured values that change according to the direction of the source was investigated through MCNP simulation. The radioactive source was Cs-137, and the simulation was performed while moving in a semicircular shape with 15 degree steps from 0 degree to 180 degrees at a distance of 20 cm from the center point of the main sensor. Since the MCNP result indicates the probability of generating a pulse for one photon, this value was calculated based on 88.6 μCi to obtain an actual count. Through the ratio of the count values of the two sensors, it was determined whether the radioactive source was located in the front, side, or back of the probe.

Nuclear inspection is necessary to verify nuclear activities. If North Korea takes denuclearization, North Korea’s nuclear materials should be verified through non-destructive testing and destructive testing for nuclear material production. Since destructive testing of all substances is impossible, nondestructive testing is essential. Most non-destructive tests are performed by measuring the energy of gamma rays, but the characteristics of nuclear fuel can be evaluated by measuring neutron sources when enclosed with thick shields and when shielding structures are difficult to remove. Before the neutron source evaluation of MAGNOX used by North Korea, the relative characteristics will be evaluated later by analyzing the burnup, enrichment, and cooling time of the spent nuclear fuels discharged from the domestic nuclear power plant. This study evaluated the source strength and major nuclides according to burnup for the WH17×17 nuclear fuel assembly. The depletion calculation was conducted using SCALE 6.2 ORIGEN, and 3.5wt% enrichment, 10, 20, 30, 40, 50, 60 MWd/kg burnup, and five years cooling time, the minimum requirement for transport specified in the notice of the Nuclear Safety Commission, was applied. Although the impact assessment on enrichment should be evaluated with MCNP Tally to consider the fission reaction of the generated neutrons, this study only evaluated the spontaneous fission and (a, n) reactions that occurred first because it only evaluates the burnup impact. As burnup increased, neutron generation increased, and most of the total neutron strength occurred through spontaneous fission from the 10 MWd/kg burnup step. The influence of Pu-240 nuclides was dominant in the 10 MWd/kg burnup step but most neutrons were generated in tiny amounts of Cm- 244 generated from 20 MWd/kg burnup. Since DPRK’s 5 MWe Yongbyon MAGNOX has very low burnup (about 0.7 MWd/kg), the primary neutron sources of 10 MWd/kg, Am-241 and Pu isotopes, especially Pu-240, are expected to be used as indicators for evaluating spent nuclear fuel characteristics. If only specific nuclides are evaluated as major neutron sources at lower burnup than those evaluated in this study, in that case, the accuracy of non-destructive testing can be improved. Additionally, the evaluation according to the enrichment and cooling time should be considered as well.

미국을 비롯한 국제사회는 평화와 안정을 추구하고 있다. 이러한 국제 사회의 노력에도 불구하고 곳곳에서 테러, 핵위협 등이 난무하고 있다. 미국의 對이란 경우, 부시 행정부는 이란의 아마디네자르 핵개발 계획에 대해 강경하게 대응함으로서 대결국면이 전개되었고, 아마디네자드 대통 령의 비타협적인 핵 개발 의지에 오바마 행정부는 더욱더 강한 제재를 강화하였다. 이란은 정권 교체 후, 로하니 대통령은 앞선 아마디네자드 대통령과는 달리 오바마 대통령과 협상을 통해 P5+1 방식으로 타협하게 된다. 하지만 트럼프 대통령은 이를 파기하고, 이란에 대해 강력한 경제 제재로 회귀한다. 미국과 이란의 비핵화 과정은 행위자의 선택에 따른 전략에 따른 ‘주고받기(Give and Take)’식으로 전개한다. 본 연구는 미 국의 對이란 비핵화 과정이 대결-타협-대결-타협을 거쳤음에도 불구하고 여전히 이란 핵문제를 해결하지 못하고 원점 제재체제로 복귀하는 이유 가 무엇인지 알아보고자한다. 본 연구는 미국과 이란의 비핵화 협상 과 정을 행위자 중심으로 전개하고, 비핵화에 영향을 미치는 가장 큰 요인 을 제3국의 지원이라 본다. 그리고 나아가 이란의 비핵화 문제를 해결할 수 있는 유효한 방법으로 양자주의가 아닌 다자주의 협상이 중요성을 제 시한다.

Since the 1992 ‘Joint Declaration of South and North Korea on the Denuclearization of the Korean Peninsula’ was agreed, various negotiations and policies have been conducted. There were policies such as CVID, Strategic Patience, Top-Down Approach, Calibrated Practical Approach, Audacious Initiative and the Geneva Agreement, and 9.19 Joint statement by the six-party talks were signed to denuclearize Korean Peninsula. However, starting with the first nuclear test in 2006, North Korea conducted six nuclear tests to develop atomic bombs, boosted fission bombs, ICBMs, and SLBMs to enhance its weapon capabilities. In addition, nuclear security crisis on the Korean Peninsula has been rising day by day as signs of restarting the North Korea’s Yongbyon 5MWe Graphite-moderated reactor were observed and the possibility of a seventh nuclear test have been increased. Since North Korea’s nuclear issue has a lot of influence on international security, especially on the Northeast Asian countries, a realistic denuclearization policy that reflects North Korea’s current domestic situation along with the international situation is needed. It’s been six months since Russia invaded Ukraine on February 24, 2022. The war between Russia, which has nuclear weapons, and Ukraine, which gave up its possession of nuclear weapons due to the Cooperative Threat Reduction (CTR) program known as the Nunn-Lugar program, is expected to have a significant impact on North Korea, which is considering denuclearization due to UN sanctions on North Korea. Therefore, in this study, based on the war patterns of Russia-Ukraine war, perspective on how it could affect North Korea’s denuclearization is analyzed. Also, significance and limitations of the previous nuclear negotiations, the North Korea’s political regime, the ‘five-year strategy for North Korea’s economic development’ and the ‘five-year plan for North Korea’s economic development’ were analyzed to suggest practical DPRK’s denuclearization policy.

In emergency situations such as nuclear accidents or terrorism, radioactive and nuclear materials can be released by some environmental reasons such as the atmosphere and underground water. To secure the safety of human beings and to respond appropriately emergency situation, it is required to designate high and low dose rate regions in the early stages by analyzing the location and radioactivity of sources through environmental radiation measurement. This research team has developed a small gamma probe which is featured by its geometrical accessibility and higher radiation sensitivity than other drone detectors. A plastic scintillator and Silicon Photomultiplier (SiPM) were applied to the probe to optimize the wireless measurement condition. SiPM has a higher gain (higher than 106) and lower operating voltage (less than 30 V) compared to a general photodiode. However, the electronic components in the SiPM are sensitively affected by temperature, which causes the performance degradation of the SiPM. As the SiPM temperature increases, the breakdown voltage (VBD) of the SiPM also increases, so the gain must be maintained by applying the appropriate VBD. Therefore, when the SiPM temperature increases while the VBD is fixed, the gain decreases. Thus, the signal does not exceed the threshold voltage (VTH) and the overall count is reduced. In general, the optimal gain is maintained by cooling the SiPM or through a temperature compensation circuit. However, in the developed system, the hardware correction method such as cooling or temperature compensation circuit cannot be applied. In this study, it was confirmed that the count decreased by up to 20% according to the increase in the temperature of the SiPM when the probe was operated at room temperature (26°C). We propose methods to calibrate the total count without cooling device or compensation circuit. After operating the probe at room temperature, the first measured count is set as the reference value, and the correction factor is derived using the tendency of the count to decrease as the temperature increases. In addition, since this probe is used for environmental radiation monitoring, periodic measurements are more suitable than continuous measurements. Therefore, the temperature of the probe can be maintained by adding a power saving interval to the operation sequence of the probe. These two methods use the operation sequence and measurement data, respectively. Thus, it is expected to be the most effective method for the current system where the temperature compensation through hardware is not possible.

The denuclearization of North Korea was unpredictable and resulted in radical changes. Despite the skepticism and disappointment surrounding denuclearization, it is important for certain verification technologies to establish what is technically possible or practically impossible, and how reliable these technical means are. This article presents the technical hurdles in nuclear verification by systematically categorizing them into issues of correctness and completeness. Moreover, it addresses the safety and security risks during the denuclearization process, including the radiological impact on humans, environmental effects, and the illegal transfer of material, information, and technologies.

The Republic of Korea is expected to participate in the denuclearization verification activities by the International Atomic Energy Agency (IAEA) in case any neighboring countries declared denuclearization. In this study, samples for the verification of nuclear activities in undeclared areas were selected for the denuclearization of neighboring countries, and the appropriateness of the procedures was considered. If a country with nuclear weapons declares denuclearization, it must be accompanied by the IAEA’s verification regarding nuclear materials and weapons in the declared and undeclared areas. The analysis of the process samples or on-site environmental samples and the verification of undeclared nuclear facilities and materials aid in uncovering any evidence of concealment of nuclear activity in undeclared areas. Therefore, a methodology was established for effective sampling and analysis in accordance with proper procedures. Preparations for sampling in undeclared areas were undertaken for various potential scenarios, such as, the establishment of zones according to radiation dose, methods of supplying electricity, wireless communication networks, targets of sampling according to characteristics of nuclides, manned sampling method, and unmanned sampling method. Through this, procedures were established for pre- and post-site settings in preparation for hazards and limiting factors at nuclear inspection sites.

북한은 핵·미사일 개발로 인한 경제제재, 코로나19 방역으로 인한 북· 중 국경 폐쇄, 기상이변으로 인한 식량부족 등 삼중고(triple whammy) 를 겪으며 일방적으로 차단했던 남북 연락통신선을 복구하는 등 남북관계 개선에 대한 의지를 일부 보이고 있다. 또한 미국의 바이든 대통령과 외교안보팀 고위직 대부분은 이란과의 공동포괄행동계획(JCPOA: The Joint Comprehensive Plan of Action)에 참여하였고 이 합의를 주요한 외교적 성과로 인식하고 있으며 북한과의 핵협상에서도 이를 적용해야 한다고 주장하고 있다. 본 연구의 목적은 이란의 공동포괄행동계획 사례를 DIME (Diplomacy, Intelligence, Military, Economy) 요소로 분석하여 북한 특수성에 맞는 북한의 비핵화 방안을 DIME 구상으로 모색하는 것이다. 북한 비핵화를 위해 외교적 구상으로 ‘다자주의에 입각한 단계별 비핵화 합의’가 필요하며 정보적 구상으로 북한을 NPT체제로 복귀시켜 국제 핵 비확산 체제 안에서 미확인되고 핵심적인 핵프로그램에 대한 정보에 접근하는 ‘선택적 검증’을 추진해야 할 것이다. 군사적 구상으로 북한의 핵 고도화와 핵사용에 대한 ‘전방위 억제전략(full spectrum deterrence strategy)’이 필요할 것이며 경제적 구상으로 ‘비핵화 조치에 상응하는 대북제재 완화’를 추진하며 중대한 합의 불이행시 원상복구(snap-back) 할 수 있는 조항을 포함시켜야 할 것이다.

The so-called Iran nuclear agreement, officially known as the Joint Comprehensive plan of Action, is an agreement between Iran and the five permanent members of the UN Security Council as well as Germany and the EU to ensure that Iran’s nuclear program will be exclusively peaceful. Praised as an historic diplomatic achievement that resolved a decade-long crisis, the 2015 agreement is distinctive in its comprehensive provisions and innovative solutions to various legal and technical issues. However, US President Donald Trump’s controversial decision to withdraw the US from the agreement in May 2018 has put its future in peril. This paper attempts to analyze the legal aspects of the US’ decision to withdraw from the Iran nuclear agreement with special reference to the currently on-going US-North Korea deal for the complete denuclearization of the Korean Peninsula. In the course of this study, special attention is given to the lessons learned from the Iran nuclear agreement.

북한의 거듭된 핵실험과 미사일 도발로 인해 한반도의 긴장이 고조되고 있다. 북한 핵에 대한 확실한 핵우산과 북핵의 완전한 폐기를 위해 전술핵 재배치 등 모든 옵션의 가능성을 제한하지 말아야 한다. 스포츠교류로서 2018 평창동계올림픽은 기능주의 입장에서 한반도 통일의 길에 하나의 의미 있는 이벤트라고 할 수 있다. 그러나 신기능주의 입장에서 현재의 북한 핵 위기는 한미동맹의 강화 위에서 풀어가는 것이 가장 올바르고 분명하며 강한 안보를 통해 북한 도발을 응징해야 한다. 지금은 국제사회와 함께 봉쇄와 압박에 매진할 때이다. 유엔의 제재와 미국 등 여러 국가들의 독자 제재에도 불구하고 북한의 계속되고 있는 핵실험과 미사일 도발은 북한에 대한 더욱 강한 압박이 필요하게 만들고 있다. 미국과 중국의 역할과 협력도 더욱 강조되고 있다. 오바마정부의 ‘전략적 인내정책’ 보다 적극적인 트럼프의 한반도 정책을 확실한 한미동맹을 통해 우리는 잘 대응하고 활용하여 북한의 비핵화와 민주평화통일을 이루어 내야 한다.