Analysis of Rod Withdrawal at Power (RWAP) Accident using ATHLET Mod 2.2 Cycle A and RELAP5/mod 3.3 Codes

The system code ATHLET (Analysis of THermal-hydraulics of Leaks and Transients) is being developed by the Gesellschaft für Anlagen-und Reaktorsicherheit (GRS) mbH in Garching, Germany. In the paper, an overview of activities performed at Faculty of Electrical Engineering and Computing (FER), University of Zagreb, in application of system code ATHLET in transient analyses for NPP Krško (NEK) is presented. Newly, the NEK input deck for the released ATHLET version (Mod 2.2 Cycle A) has been developed. For that purpose, the NEK data base that has been developed and maintained at FER for the last two decades primarily for development of standard input deck for RELAP5 code was used. The ATHLET model has been validated by analyzing the Rod Withdrawal At Power (RWAP) accident at nominal power. The results for steady state calculation as well as RWAP transient were assessed against the analysis performed by RELAP5/mod 3.3 code. In both ATHLET and RELAP5 calculation, the RWAP accident was simulated by constant reactivity insertion rate equal to 2.4 pcm/sec. For ATHLET analysis, two fluid dynamic options were tested for the primary side: a) base case analysis with 5 conservation equations and mixture level model and b) two-fluid model with separate conservation equations for liquid and vapour phases for all the volumes except for the pressurizer where 5 equations+mixture level model was retained. The Steam Generators (SGs) were built using basic ATHLET elements together with the dedicated separator model. For RELAP5/mod 3.3 analysis, a standard option with thermal and mechanical non-equilibrium (6 equations) was used. The results of the steady state calculation for the ATHLET model have shown a very good agreement with RELAP5 calculation. In the transient analysis very small differences for the main physical parameters between ATHLET and RELAP5 as well as between the two ATHLET models were obtained

I2S-LWR Top-Down Differential Economics Evaluation Approach

The Integral Inherently Safe Light Water Reactor (I2S–LWR) is a design concept of a large (~1000 MWe) light water reactor with integral primary circuit configuration. One of the key design features promoting inherent safety is implementation of an integral primary circuit configuration, which in turn requires a compact design of the core and primary circuit components. Assessments of the cost of I2S-LWR is an important aspect of the overall evaluation of the new reactor concept. There are several approaches to cost estimation and economics evaluation of the new nuclear power technologies. Frequently used guidelines rely on the Code of Accounts, originally developed in the U.S. Department of Energy (DOE) Energy Economics Data Base (EEDB) Program Code of Accounts, proposed as evaluation tool by C.R. Hudson, and further popularized in the guidelines for economic evaluation of bids, by The International Atomic Energy Agency (IAEA). The code of accounts allows to break down main costs (Total Capital Investment Cost, Fuel Cycle Cost, Operation and Maintenance) to individual systems and items. This work aims to implement and apply a top-down differential economics evaluation approach to the Code of Accounts based guidelines, to assess the costs of the I2S -LWR relative to a representative “standard” PWR. In this methodology, a representative PWR design was taken as a reference and the differential cost was estimated for each individual account based on the design difference (or similarity). Cost estimating techniques were applied to the accounts representing systems that differ from the ones of the reference PWR. In this manner, the cost of the common components cancels out, and the uncertainty in the estimate is reduced. While this preliminary evaluation yet needs to be completed, the indications so far are that the I2S-LWR LCOE will be economically competitive with a standard PWR

I2S-LWR Top-Down Differential Economics Evaluation Approach

The Integral Inherently Safe Light Water Reactor (I2S–LWR) is a design concept of a large (~1000 MWe) light water reactor with integral primary circuit configuration. One of the key design features promoting inherent safety is implementation of an integral primary circuit configuration, which in turn requires a compact design of the core and primary circuit components. Assessments of the cost of I2S-LWR is an important aspect of the overall evaluation of the new reactor concept. There are several approaches to cost estimation and economics evaluation of the new nuclear power technologies. Frequently used guidelines rely on the Code of Accounts, originally developed in the U.S. Department of Energy (DOE) Energy Economics Data Base (EEDB) Program Code of Accounts, proposed as evaluation tool by C.R. Hudson, and further popularized in the guidelines for economic evaluation of bids, by The International Atomic Energy Agency (IAEA). The code of accounts allows to break down main costs (Total Capital Investment Cost, Fuel Cycle Cost, Operation and Maintenance) to individual systems and items. This work aims to implement and apply a top-down differential economics evaluation approach to the Code of Accounts based guidelines, to assess the costs of the I2S -LWR relative to a representative “standard” PWR. In this methodology, a representative PWR design was taken as a reference and the differential cost was estimated for each individual account based on the design difference (or similarity). Cost estimating techniques were applied to the accounts representing systems that differ from the ones of the reference PWR. In this manner, the cost of the common components cancels out, and the uncertainty in the estimate is reduced. While this preliminary evaluation yet needs to be completed, the indications so far are that the I2S-LWR LCOE will be economically competitive with a standard PWR

OPTIMIZATION OF OPDT PROTECTION FOR OVERCOOLING ACCIDENTS

Overcooling accidents are typically resulting in power increase due to negative moderator feedback. There are more protection set points responsible for terminating power increase. OPDT protection set point is typically protection from exceeding fuel centre line temperature due to reactivity and power increase. It is important to actuate reactor trip signal early enough, but to be able to filter out events where actuation is not necessary. Different concepts of coolant temperature compensation as part of OPDT set point protection were studied for decrease of feedwater temperature accident and for small main steam line breaks from full power for NPP Krško. Computer code RELAP5/mod 3.3 was used in calculation. The influence of different assumptions in accident description as well as nuclear core characteristics were described

OPTIMIZATION OF OPDT PROTECTION FOR OVERCOOLING ACCIDENTS

Overcooling accidents are typically resulting in power increase due to negative moderator feedback. There are more protection set points responsible for terminating power increase. OPDT protection set point is typically protection from exceeding fuel centre line temperature due to reactivity and power increase. It is important to actuate reactor trip signal early enough, but to be able to filter out events where actuation is not necessary. Different concepts of coolant temperature compensation as part of OPDT set point protection were studied for decrease of feedwater temperature accident and for small main steam line breaks from full power for NPP Krško. Computer code RELAP5/mod 3.3 was used in calculation. The influence of different assumptions in accident description as well as nuclear core characteristics were described

CABLE AGING MANAGEMENT AS PART OF THE EXTENDED NUCLEAR POWER PLANT LIFESPAN PROGRAMME

Članak daje sveobuhvatan pregled procesa starenja kabela, od identifikacije mehanizama i procjene starenja te učinka na sigurnost nuklearnih elektrana do upravljanja samim procesom. Cilj je zaokružiti temu iz različitih perspektiva i dati informacije i zaključke utemeljene na iskustvu i pouzdanim rezultatima mjerenja.The article provides a comprehensive overview of the cable aging process, from mechanism identification and aging assessment and the effect on nuclear power plants’ safety to the management of the process itself. The objective is to round up the subject from different perspectives and provide information and conclusions based on experience and reliable measurement results

Dealing with Challenges of the European Energy Transition - Suočavanje s izazovima europske energetske tranzicije

U radu se daje osvrt na konferenciju pod naslovom Dealing with Challenges of the European Energy Transition (hrv. Suočavanje s izazovima europske energetske tranzicije) koja je u online obliku održana 20. studenoga 2020. godine u organizaciji Akademije tehničkih znanosti Hrvatske (HATZ) i Euro-CASE-a iz Pariza. Održiva proizvodnja i uporaba energije jedan su od najvažnijih izazova 21. stoljeća. Pružanje sigurne opskrbe čistom, konkurentnom i pristupačnom energijom za sve postavlja složena tehnička, ekonomska, socijalna i politička pitanja koja se moraju riješiti kako bi se osigurao održivi razvoj. Na konferencije Euro-CASE 2020 razmatrani su gore navedeni izazovi povezani s europskom energetskom tranzicijom

Dealing with Challenges of the European Energy Transition - Suočavanje s izazovima europske energetske tranzicije

U radu se daje osvrt na konferenciju pod naslovom Dealing with Challenges of the European Energy Transition (hrv. Suočavanje s izazovima europske energetske tranzicije) koja je u online obliku održana 20. studenoga 2020. godine u organizaciji Akademije tehničkih znanosti Hrvatske (HATZ) i Euro-CASE-a iz Pariza. Održiva proizvodnja i uporaba energije jedan su od najvažnijih izazova 21. stoljeća. Pružanje sigurne opskrbe čistom, konkurentnom i pristupačnom energijom za sve postavlja složena tehnička, ekonomska, socijalna i politička pitanja koja se moraju riješiti kako bi se osigurao održivi razvoj. Na konferencije Euro-CASE 2020 razmatrani su gore navedeni izazovi povezani s europskom energetskom tranzicijom