atw - International Journal for Nuclear Power | 02.2020

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atw Vol. 65 (2020) | Issue 2 ı February ENVIRONMENT AND SAFETY 82 | Fig. 1. Embedded system block diagram. preset thresholds for the sensors are exceeded. The information collected by the system is transmitted to a dedicated central database server that can be accessed by authorized users across the responsible bodies via a secured network. The ES allows the tracking and inspecting of the casks throughout their life cycles in storage, transportation, and disposal. The software provides easy-to-use graphical interfaces that allow access to all vital information once the security and privilege requirements are met. 3.1 Sensor modules As a prototype, the ES sensors include safety sensors (e.g. radiation and temperature), security sensor (e.g. the status of seals), and driver v iolation detector (e.g. the speed of the truck). In this paper, the Evolutionary/European Power Reactor (EPR) Spent Fuel (SF) is selected as a hypothetical source for NM. p Safety sensors are used to indicate the radiation and temperatures levels statues of the NM cask. The ORIGEN [6] computer code is used to calculate the thermal and radioactivity loads of the cask which will be used to determine the sensor threshold level. The ORIGEN computer code flowchart is shown in Figure 2. The preparation details of the ORIGEN input file based EPR fuel are stated in [7]. The radiation and temperature sensors threshold level are determined as follows. 1. Radiation: As will be proven later, when EPR SF (5 % enriched) is placed in a real cask system, the dose rate on the external surface of the cask will be lower than 1,000 mrem/hour. Therefore, the ES prototype will be used the PIN diodes to detect the increasing in gamma level, where the 1,000 mrem/hour is sufficient to excite the PIN diodes. Any gamma detector PIN diode circuit consists of a low noise amplifier and comparator, Figure 3. The photodiode circuit stated in [8] was used for the gamma ray detection. The advantage of using a photodiode is its small sensitive area; therefore, it is suitable to the high dose rate of the cask and it is not affected by the low background rate due to cosmic rays. 2. Temperature: EPR SF can be loaded into MPC-24 baskets. Using the stated equation [7] of Peak Cladding Temperature (PCT) given Decay Heat (DH), when the DH is 1.050 kW/assembly, the error free PCT is 307.12 °C in normal condition operations. The 24 PWR SF assemblies storage cask system with a burn-up of 55 Giga Watt Day/Metric Ton Uranium (GWD/ MTU) and 25.2 kW DH load, the normal temperature for long-term events (e.g. onsite and offsite transportations, and storage) are 302 °C, 64 °C and 67 °C for PCT, overpack outer surface and air outlet; respectively [9]. Therefore, for the EPR SF, the normal temperatures are 307 °C, 69 °C and 72 °C for PCT, overpack outer surface and air outlet; respectively. The normal temperature limits for overpack outer surface and air outlet are 98 °C and 72 °C; respectively. For prototype, the circuit used two digital temperature sensors, where their positions are in overpack outer surface (near the top air outlet) and air outlet, the temperature alarm SMS will delivered to the control unit (or to an emergency specified telephone number) if the temperature exceeds 98 °C and 72 °C for overpack outer surface and air outlet; respectively. p Status of Seals: The seal sensor can be located under one or two of the seal bolts of the cask overpack. The seal sensor is a short circuit wire warped around the bolt of the cask overpack. When the bolt is loosened, the short circuit wire will open the circuit. Therefore, the microcontroller trigger an alarm, the alarm is broadcasted by SMS to the responsible bodies. 3.2 Online cask monitoring and tracking The designed and implemented ES is used for receiving location data from satellites (via GPS module) and monitoring data (via sensors), then transmitting the received data to the desired web servers using a General Packet Radio Services (GPRS) connection (via GSM module). | Fig. 2. ORIGEN computer code flowchart. | Fig. 3. Gamma detector PIN diode circuit block diagram. Environment and Safety Design and Implementation of Embedded System for Nuclear Materials Cask in Nuclear Newcomers ı M. I. Youssef, M. Elzorkany G. F. Sultan and Hassan F. Morsi
atw Vol. 65 (2020) | Issue 2 ı February | Fig. 4. Embedded system frame construction. | Fig. 5. Embedded system operation flowchart. p GPS Module: The ES used the recommended minimum specific GPS/Transit data ($GPRMC) frame. This frame contains information about the locations of the cask and the cask speed over ground. The speed can be used as a driver violation, if it exceeds a predefined value (e.g. 80 km/ hour). Also, it can be used as a motion detector for the cask in storage, if greater than zero km/ hour. p GSM Module: The ES used GSM and GPRS international communications standard to provide wireless communications capabilities. The sending of the SMS messages are the functions of the GSM module. The connection of the ES to the internet is through the mobile operators GSM/GPRS. p Web servers: The server functions are receiving data from the ES, securely storing it, and serving this information on demand to the user. There are two servers. The first is for secret data, e.g. the cask monitoring data, while the second server is for tracking data. 3.3 Microcontroller The microcontroller used in ES is a Programmable System-On-Chip Cypress chip. The chip includes CPU core, configurable blocks of analogous and digital logic, and programmable interconnects. This architecture allows the user to create customized peripheral configurations for each application. 3.4 Proposed Frame Format Data is sent to the main servers as frame format. All data are grouped in a frame with a special format as shown in Figure 4. Frame fields contain; cask identification number (ID), cask tracking location, seal status, and cask monitoring sensor data. The microcontroller takes the location data from the GPS module and put it in its field in the frame. 3.5 Proposed Embedded System Operation The ES operation methodology is shown in Figure 5. When the ES starts, it reads the sensors statues and sends theses data for monitoring and tracking servers by GPRS. In addition, if any one of the sensor values exceeds the limit, the ES sends instantaneous SMS to the predefined telephone number; and the monitoring and tracking are instantaneous. For power saving, in normal operations (i.e. radiation level, T1 and T2 temperatures lower than limits, and the seal is not opened) the system is programmable to wait a time between each reading process (e.g. in a casks storage site, the waiting time will be about ten minutes). 4 Results The ORIGEN computer code simulation results of the EPR SF radiation source terms and the practical results of the ES operation will be stated in the next subsections. 4.1 Gamma Source Terms Calculation Radiation source terms of SF are photons and neutrons. In this paper, the photon source of the EPR SF is calculated using the ORIGEN code based on the EPR parameters, where the photons are the source term of gamma. The EPR SF photon source decay of the activation products, actinides and daughters, and fission products are calculated, Figure 6 (a). As shown, the main gamma source term is the fission products photons. The radioactive characteristic of the EPR SF has previously been calculated, but for a burnup and enrichment of 60 GWD/MTU and 4 % [10], respectively. To make sure that our calculations of the gamma sources (i.e. 5 % enriched EPR) correspond to that calculations (i.e. 4 % enriched EPR), we compared our results with the reference results, Figure 6 (b) shows the photon sources decay comparison of the results. From Figure 6 (b), beyond five years of SF cooling, the differences between the two curves are small. For example, at the cooling value of 20 years, it is found that the percentage difference is about (0.078393 %, providing that, the values of the fluxto-dose conversion coefficients for (a) 5 % enriched fuel (b) 5 % enriched and 4 % enriched fuels | Fig. 6. EPR spent fuel gamma source decay. ENVIRONMENT AND SAFETY 83 Environment and Safety Design and Implementation of Embedded System for Nuclear Materials Cask in Nuclear Newcomers ı M. I. Youssef, M. Elzorkany G. F. Sultan and Hassan F. Morsi
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atw - International Journal for Nuclear Power | 02.2020

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