VERIFIKASI MODEL KONDENSASI PADA RELAP5/SCDAPSIM/MOD 3.4

RELAP5/SCDAPSIM /MOD3.4 merupakan salah satu program komputer yang sering digunakan untuk menganalisis sistem keselamatan reaktor nuklir. Untuk mengetahui keakuratan program komputer ini dalam memprediksi koefisien perpindahan kalor kondensasi uap yang tercampur dengan gas tak-dapat terkondensasi, maka perlu dilakukan verifikasi model kondensasi yang ada di dalam program komputer tersebut. Verifikasi dilakukan dengan cara membandingkan prediksi nilai koefisien perpindahan panas kondensasi RELAP5/SCDAPSIM/MOD3.4 dengan nilai yang didapat dari hasil eksperimen. Perbandingan dilakukan dengan cara mensimulasikan fasilitas eksperimen PCCS ke dalam model input untuk RELAP5. Hasil verifikasi menunjukkan bahwa model kondensasi pada RELAP5 memprediksi koefisien perpindahan kalor kondensasi lebih rendah 20% dibandingkan dengan nilai hasil eksperimen walaupun mempunyai kecenderungan yang sama. Oleh karena itu diperlukan korelasi kondensasi yang lebih baik untuk diterapkan pada RELAP5/SCDAPSIM/MOD3.4 guna memperbaiki nilai koefisien perpindahan kalor kondensasi uap yang tercampur dengan gas tak-dapat terkondensasi.Kata kunci: model kondensasi, perpindahan kalor, tak-dapat terkondensasi, RELAP5/SCDAPSIM/MOD3.4, fasilitas eksperimen PCCS. RELAP5/SCDAPSIM/MOD3.4 is one of computer programs that is often used for performing nuclear reactor safety system analysis. In order to know the accuracy of this computer program in predicting condensation heat transfer coefficient of vapor mixed with non-condensable gas, it is necessary to perform verification of the condensation model in the computer program. The verification is done by comparing prediction of condensation heat transfer coefficient value of RELAP5/SCDAPSIM/MOD3.4 with condensation heat transfer coefficient value of experiment result.. The comparison was done by performing simulation PCCS experiment facility into RELAP5 input model. The verification results indicate that RELAP5’s condensation model predicts lower condensation heat transfer coefficient by 20 % compared to the experiment result although has the same tendency. Therefore, a new better condensation correlation is needed to be applied in the RELAP5/SCDAPSIM/MOD3.4 to improve the heat transfer coefficient value of vapor with noncondensable gases. Keywords: condensational model, heat transfer, non-condensable, RELAP5/SCDAPSIM/MOD3.4, PCCS experiment facilit

VERIFIKASI MODEL KONDENSASI PADA RELAP5/SCDAPSIM/MOD 3.4

RELAP5/SCDAPSIM /MOD3.4 merupakan salah satu program komputer yang sering digunakan untuk menganalisis sistem keselamatan reaktor nuklir. Untuk mengetahui keakuratan program komputer ini dalam memprediksi koefisien perpindahan kalor kondensasi uap yang tercampur dengan gas tak-dapat terkondensasi, maka perlu dilakukan verifikasi model kondensasi yang ada di dalam program komputer tersebut. Verifikasi dilakukan dengan cara membandingkan prediksi nilai koefisien perpindahan panas kondensasi RELAP5/SCDAPSIM/MOD3.4 dengan nilai yang didapat dari hasil eksperimen. Perbandingan dilakukan dengan cara mensimulasikan fasilitas eksperimen PCCS ke dalam model input untuk RELAP5. Hasil verifikasi menunjukkan bahwa model kondensasi pada RELAP5 memprediksi koefisien perpindahan kalor kondensasi lebih rendah 20% dibandingkan dengan nilai hasil eksperimen walaupun mempunyai kecenderungan yang sama. Oleh karena itu diperlukan korelasi kondensasi yang lebih baik untuk diterapkan pada RELAP5/SCDAPSIM/MOD3.4 guna memperbaiki nilai koefisien perpindahan kalor kondensasi uap yang tercampur dengan gas tak-dapat terkondensasi.Kata kunci: model kondensasi, perpindahan kalor, tak-dapat terkondensasi, RELAP5/SCDAPSIM/MOD3.4, fasilitas eksperimen PCCS. RELAP5/SCDAPSIM/MOD3.4 is one of computer programs that is often used for performing nuclear reactor safety system analysis. In order to know the accuracy of this computer program in predicting condensation heat transfer coefficient of vapor mixed with non-condensable gas, it is necessary to perform verification of the condensation model in the computer program. The verification is done by comparing prediction of condensation heat transfer coefficient value of RELAP5/SCDAPSIM/MOD3.4 with condensation heat transfer coefficient value of experiment result.. The comparison was done by performing simulation PCCS experiment facility into RELAP5 input model. The verification results indicate that RELAP5’s condensation model predicts lower condensation heat transfer coefficient by 20 % compared to the experiment result although has the same tendency. Therefore, a new better condensation correlation is needed to be applied in the RELAP5/SCDAPSIM/MOD3.4 to improve the heat transfer coefficient value of vapor with noncondensable gases. Keywords: condensational model, heat transfer, non-condensable, RELAP5/SCDAPSIM/MOD3.4, PCCS experiment facilit

PRELIMINARY ASSESSMENT OF ENGINEERED SAFETY FEATURES AGAINST STATION BLACKOUT IN SELECTED PWR MODELS

The 2011 Fukushima accident did not prevent countries to construct new nuclear power plants (NPPs) as part of the electricity generation system. Based on the IAEA database, there are a total of 44 units of PWR type NPPs whose constructions are started after 2011. To assess the technology of engineered safety features (ESFs) of the newly constructed PWRs, a study has been conducted as described in this paper, especially in facing the station blackout (SBO) event. It is expected from this study that there are a number of PWR models that can be considered to be constructed in Indonesia from the year of 2020. The scope of the study is PWRs with a limited capacity from 900 to 1100 MWe constructed and operated after 2011 and small-modular type of reactors (SMRs) with the status of at least under licensing. Based on the ESFs design assessment, the passive core decay heat removal has been applied in the most PWR models, which is typically using steam condensing inside heat exchanger within a water tank or by air cooling. From the selected PWR models, the CPR-1000, HPR-1000, AP-1000, and VVER-1000, 1200, 1300 series have the capability to remove the core decay heat passively. The most innovative passive RHR of AP-1000 and the longest passive RHR time period using air cooling in several VVER models are preferred. From the selected SMR designs, the NuScale design and RITM-200 possess more advantages compared to the ACP-100, CAREM-25, and SMART. NuScale represents the model with full-power natural circulation and RITM-200 with forced circulation. NuScale has the longest time period for passive RHR as claimed by the vendor, however the design is still under licensing process. The RITM-200 reactor has a combination of passive air and water-cooling of the heat exchanger and is already under construction. 

SENSITIVITY ANALYSIS ON THERMOHYDRAULIC CODE FOR MODIFIED PLATE-FUELED 2 MW TRIGA

SENSITIVITY ANALYSIS OF THERMOHYDRAULIC CODE FOR MODIFIED PLATE-FUELED 2 MW TRIGA. The plan to modify TRIGA 2000 Bandung from using regular TRIGA fuel to plate-type fuel should be supported by the use of appropriate computer codes. This research proposes three codes to design reactor thermohydraulics at transient condition. Analysis has been performed to identify code sensitivity using the same input and correlation. The codes used were COOLOD-N2, Heathyd, and PARET-ANL. The input was obtained from preliminary analysis of a flow rate calculation of 70 kg/s and a nominal power of 2 MW. The comparison of these three codes did not consider uncertainty factor for neutronic and technical aspects. The sensitivity analysis on thermohydraulic codes used to calculate heat transfer in the fuel plate of TRIGA reactor at steady state condition indicates similar temperature trend lines for the coolant, plate, and fuel meat. Temperature calculation results obtained from COOLOD-N2, Heathyd and PARET ANL give consistent sensitivity with the differences of coolant temperature from 2.83% to 12.5%; cladding temperature  from 2.14% to 31.30%; and fuel meat temperature  from 6.63% to 18.64%. The margins of flow instability were 5.03; 5.68 and 4.21, respectively for COOLOD-N2, Heathyd, and PARET-ANL. These values show that flow instability has not yet occurred. The results of the analysis show that the use of those three codes for steady state condition using the same input, in which uncertainty factor is neglected, give similar trend for coolant, cladding, and fuel meat temperature. As the modelling in each code is different, the values obtained are not exactly the same. Keywords: sensitivity analysis, TRIGA Plate, COOLOD-N2, Heathyd, PARET-AN

Simulation of Wickless-Heat Pipe as Passive Cooling System in Nuclear Spent Fuel Pool Using RELAP5/MOD3.2

The lesson learned from the severe accident of Fukushima Daiichi nuclear power plant shows that the residual heat generated from nuclear spent fuel should be cooled properly. In order to absorb that residual heat when station blackout occurs, wickless-heat pipe is proposed to be used as an alternative of the passive cooling system in nuclear spent fuel pool. The objective of this research is to simulation the effect of initial pressure and evaporator filling ratio as factors that influence the thermal performance of wickless-heat pipe. The simulation results will be validated with experiment results. The wickless-heat pipe model was built and simulated using nuclear thermal-hydraulic code RELAP5/MOD3.2. The wickless-heat pipe model is built similarly and it has same geometry with experiment test section. In the simulation, the initial pressure inside wickless-heat pipe and evaporator filling ratio are varied. The initial pressure is varied on -54 cm Hg, -64 cm Hg, and -74 cm Hg, and filling ratio of evaporator is varied on 40%, 60%, and 80%. The heat load of evaporator, coolant temperature, and coolant volumetric flow rate were kept constant. The results obtained show that thermal resistance of wickless-heat pipe simulation model is 0.005°C/W. It is showed that simulation model results have good agreement with experiment results, and it can be used to simulate wickless-heat pipe heat transfer phenomena with different values of the input parameter. The RELAP5/MOD3.2 simulation model has been verified by the experimental result on a steady state condition

ANALISIS KEJADIAN STEAM GENERATOR TUBE RUPTURE (SGTR) BERDASARKAN SKENARIO MIHAMA UNIT 2

Pada tanggal 9 Februari 1991, terjadi kecelakaan putusnya pipa pemanas pembangkit uap (Steam Generator Tube Rupture/SGTR) pada PLTN Mihama Unit 2. Dari kejadian tersebut, diperoleh catatan sekuensi kecelakaan berupa aktuasi sistem proteksi dan fitur keselamatan terekayasa dalam memitigasi kebocoran dari sistem primer ke sistem sekunder. Urutan sekuensi tersebut kemudian diterapkan pada PWR standar Jepang untuk disimulasikan menggunakan program perhitungan RELAP5/SCDAP/Mod3.2. Tujuannya untuk mengevaluasi konsekuensi yang terjadi bila kecelakaan tersebut terjadi pada PWR standar Jepang. Parameter yang dibandingkan adalah laju alir kebocoran, perubahan tekanan primer dan sekunder dan perubahan level di dalam pressurizer. Hasil simulasi menunjukkan perbedaan lama waktu kejadian SGTR hingga berhentinya kebocoran yang berlangsung lebih pendek pada PWR standar Jepang. Selain itu jumlah pendingin primer yang bocor dan jumlah uap yang terlepas dari MSRV tercatat lebih besar daripada PWR Mihama unit 2. Karakter aliran kebocoran, fluktuasi tekanan primer, dan level pressurizer sedikit berbeda pada tahap-tahap awal kejadian, namun relatif sama pada tahap akhir ketika aliran kebocoran dapat dihentikan. Hasil simulasi juga menunjukkan perlunya tindakan operator secara manual yang ditunjukkan dari isolasi sistem air umpan bantu (AFW) pada pembangkit uap yang bocor, aktuasi katup pelepas uap (MSRV) pada pembangkit uap yang utuh dan aktuasi auxiliary spray dan power operated relief valve (PORV) pada pressurizer untuk mengantisipasi kejadian sebagai bagian dari prosedur operasi darurat.Kata kunci: SGTR, PWR Mihama Unit 2, PWR standar Jepang On February 9,1991, a Steam Generator Tube Rupture (SGTR) took place at the Mihama Unit No. 2. From that event, the accident sequence representing the actuation of protection system and engineered safety feature to mitigate the leak from primary system to secondary system is recorded. That sequence is then applied on the Japanese standard PWR to be simulated using RELAP5/SCDAP/Mod3.2 thermal-hydraulic code. The purpose is to compare consequences resulted if this accident is occurred on the Japanese standard PWR. Parameter compared are break mass flow, fluctuation of primary and secondary pressure, and fluctuation of pressurizer level. The simulation result shown that the difference in the time duration from the initiation of rupture up to the leak termination, which takes place in shorter duration on the standard Japanese PWR. It is also shown that the total amount of the primary coolant leaked through the break nozzle to the secondary system that calculated is bigger than on the Mihama unit 2. The character of break mass flow, fluctuation of the primary system and level of pressurizer is slightly different in the beginning of the event, but is in similar trend in the end of event as the break flow is terminated. The simulation result also shows the necessity of operator action to manually isolate the auxiliary feedwater system in the affected steam generator, to actuate the main steam relief valves in the intact steam generator, and to actuate the auxiliary spray and power operated relief valve on pressurizer to anticipate the event as part of the emergency operating procedures. Keywords: SGTR, Mihama Unit 2,standard Japanese PW

ANALISIS KEJADIAN STEAM GENERATOR TUBE RUPTURE (SGTR) BERDASARKAN SKENARIO MIHAMA UNIT 2

Pada tanggal 9 Februari 1991, terjadi kecelakaan putusnya pipa pemanas pembangkit uap (Steam Generator Tube Rupture/SGTR) pada PLTN Mihama Unit 2. Dari kejadian tersebut, diperoleh catatan sekuensi kecelakaan berupa aktuasi sistem proteksi dan fitur keselamatan terekayasa dalam memitigasi kebocoran dari sistem primer ke sistem sekunder. Urutan sekuensi tersebut kemudian diterapkan pada PWR standar Jepang untuk disimulasikan menggunakan program perhitungan RELAP5/SCDAP/Mod3.2. Tujuannya untuk mengevaluasi konsekuensi yang terjadi bila kecelakaan tersebut terjadi pada PWR standar Jepang. Parameter yang dibandingkan adalah laju alir kebocoran, perubahan tekanan primer dan sekunder dan perubahan level di dalam pressurizer. Hasil simulasi menunjukkan perbedaan lama waktu kejadian SGTR hingga berhentinya kebocoran yang berlangsung lebih pendek pada PWR standar Jepang. Selain itu jumlah pendingin primer yang bocor dan jumlah uap yang terlepas dari MSRV tercatat lebih besar daripada PWR Mihama unit 2. Karakter aliran kebocoran, fluktuasi tekanan primer, dan level pressurizer sedikit berbeda pada tahap-tahap awal kejadian, namun relatif sama pada tahap akhir ketika aliran kebocoran dapat dihentikan. Hasil simulasi juga menunjukkan perlunya tindakan operator secara manual yang ditunjukkan dari isolasi sistem air umpan bantu (AFW) pada pembangkit uap yang bocor, aktuasi katup pelepas uap (MSRV) pada pembangkit uap yang utuh dan aktuasi auxiliary spray dan power operated relief valve (PORV) pada pressurizer untuk mengantisipasi kejadian sebagai bagian dari prosedur operasi darurat.Kata kunci: SGTR, PWR Mihama Unit 2, PWR standar Jepang On February 9,1991, a Steam Generator Tube Rupture (SGTR) took place at the Mihama Unit No. 2. From that event, the accident sequence representing the actuation of protection system and engineered safety feature to mitigate the leak from primary system to secondary system is recorded. That sequence is then applied on the Japanese standard PWR to be simulated using RELAP5/SCDAP/Mod3.2 thermal-hydraulic code. The purpose is to compare consequences resulted if this accident is occurred on the Japanese standard PWR. Parameter compared are break mass flow, fluctuation of primary and secondary pressure, and fluctuation of pressurizer level. The simulation result shown that the difference in the time duration from the initiation of rupture up to the leak termination, which takes place in shorter duration on the standard Japanese PWR. It is also shown that the total amount of the primary coolant leaked through the break nozzle to the secondary system that calculated is bigger than on the Mihama unit 2. The character of break mass flow, fluctuation of the primary system and level of pressurizer is slightly different in the beginning of the event, but is in similar trend in the end of event as the break flow is terminated. The simulation result also shows the necessity of operator action to manually isolate the auxiliary feedwater system in the affected steam generator, to actuate the main steam relief valves in the intact steam generator, and to actuate the auxiliary spray and power operated relief valve on pressurizer to anticipate the event as part of the emergency operating procedures. Keywords: SGTR, Mihama Unit 2,standard Japanese PW

PENENTUAN KOEFISIEN DISPERSI ATMOSFERIK UNTUK ANALISIS KECELAKAAN REAKTOR PWR DI INDONESIA

Atmosfer merupakan pathway penting pada perpindahan radionuklida yang lepas dari Pembangkit Listrik Tenaga Nuklir (PLTN) ke lingkungan dan manusia. Penerimaan dosis pada lingkungan dan manusia dipengaruhi oleh sourceterm dan kondisi tapak PLTN. Untuk mengetahui penerimaan dosis lingkungan untuk PLTN di Indonesia, maka diperlukan nilai koefisien dispersi untuk tapak potensial yang dipilih. Model perhitungan dalam penelitian ini menggunakan model yang diterapkan pada paket program pada modul ATMOS dan CONCERN dari PC-Cosyma yaitu model perhitungan segmented plume model. Perhitungan dilakukan untuk PLTN tipe PWR kapasitas 1000 MWe berbahan bakar UO2, postulasi kejadian untuk kecelakaan DBA, kondisi tapak kasar, untuk 6 tapak contoh tapak Semenanjung Muria, Pesisir Banten, dan tapak yang didominasi oleh stabilitas cuaca C,D,E, dan F. Koefisien dispersi dihitung untuk 8 kelompok nuklida produk fisi yang lepas dari PLTN yaitu: kelompok gas mulia, lantanida, logam mulia, halogen, logam alkali, tellurium, cerium, dan kelompok stronsium & barium. Perhitungan input menggunakan paket program ORIGEN-2 dan Arc View untuk penyiapan input perhitungan. Hasil pemetaan untuk parameter dispersi maksimum rerata diperoleh pada jarak radius 800 m dari sumber lepasan untuk nuklida dari kelompok logam mulia, logam alkali dan kelompok nuklida cerium. Parameter dispersi untuk Tapak Muria maksimum 1,53E-04 s/m3, Tapak Serang adalah 1,40E-03 s/m3, tapak dengan stabilitas C: 1,72E-04 s/m3, stabilitas D: 1,40E-04 s/m3, Stabilitas E: 1,07E-04 s/m3, dan tapak dengan stabilitas F : 2,14E-05 s/m3.Kata kunci: koefisien dispersi, atmosferik, PWR, kecelakaan, Indonesia The atmosphere is an important pathway in the migration of radionuclides transport from the Nuclear Power Plant (NPP) to the environment and humans. The dose accepted in the environment and humans is influenced by the sourceterm and NPP siting condition. Distribution of radionuclides in the atmosphere is determined by the dispersion coefficient. To find the environment dose acceptance for nuclear power plants in Indonesia, it is necessary to map the dispersion coefficient for Indonesia potential siting Model calculations in this study using Segmented plume model, which a model that is applied to the ATMOS and CONCERN module of PC-Cosyma software. The calculation has done for PWR 1000 MWe with UO2 fuel, DBA accident postulations, roughnes site conditions, for 8 example site such as Muria Peninsula, Coastal Banten, and the C, D, E, and F stability. Dispersion coefficient was calculated for the 8 fission product groups are: the noble gases, lanthanides, noble metals, halogens, alkali metals, tellurium, cerium, and strontium & barium groups. Input calculation using the program package Origen-2 and Arc View for the preparation of input calculations. The results of the dispersion parameter calculated are: the average maximum is obtained at a distance of 800 m radius from the source, for noble metals, alkali metal and cerium group nuclides. Dispersion parameters for maximum at Muria site is 1.53E-04 s/m3, Serang site is 1.40E-03 s/m3, site with stability C is 1.72E-04 s/m3, stability D is 1.40E-04 s/m3, stability E is 1.07E-04 s/m3, and site with the stability F is 2.14E-05 s/m3. Keywords: dispersion coefficient, atmospheric, PWR, accident, Indonesi

PRELIMINARY STUDY ON RELAP5 SIMULATION OF DVI LINE BREAK ACCIDENT IN THE ATLAS FACILITY USING BEST ESTIMATE PLUS UNCERTAINTY METHOD

The Best Estimate plus Uncertainty (BEPU) is a methodology, which was introduced in the deterministic safety analysis to evaluate limitations of codes in simulating realistic plant behavior by providing quantified uncertainty bands of calculation results. It has been already widely accepted in licensing nuclear power plant by regulatory bodies of United States (USNRC), Argentina, and Canada. The uncertainty evaluation in the BEPU method is performed by different approaches such as GRS, IRSN, ENUSA, AEAT, and UNIPI. Due to the complexity of other approaches, the purpose of this study is to present some key aspects of the BEPU process using the GRS methodology by selecting the ATLAS test facility to simulate 50% break of DVI line since any safety analysis performed so far was using deterministic best estimate approach only. As comparison of the best estimate simulation performed by RELAP5/SCDAP/Mod3.4, experimental data related to the event was used. After 100 simulations,  the uncertainty bands of peak heater of clad temperature and primary pressure transient obtained were only in a close agreement with the experimental data in the earlier period and less than 250 seconds during the transient condition. Therefore the overall accuracy of the best estimate simulation plays a key role on the final results of the uncertainty analysis because the propagation of any discrepancy in the best estimate with the experimental data will occur throughout the simulation. After that, selecting the important parameters to be randomly generated needs to be performed carefully by studying the important phenomena related to the event analyzed and associated plant model.Keywords: best estimate plus uncertainty, DVI line break, ATLAS facility, RELAP5, simulation STUDI AWAL SIMULASI KECELAKAAN PUTUSNYA JALUR DVI PADA FASILITAS ATLAS MENGGUNAKAN RELAP5 DENGAN METODE ESTIMASI TERBAIK DAN KETIDAKPASTIAN. Metode Best estimate plus uncertainty (BEPU) adalah metode analisis keselamatan deterministik yang bertujuan untuk melakukan evaluasi keterbatasan program perhitungan dalam mensimulasikan sifat-sifat fisis instalasi secara realistik dengan mengkuantifikasi rentang ketidakpastian dari hasil perhitungan. Metode tersebut telah diterima secara luas dalam perijinan PLTN oleh badan pengatur dunia seperti di Amerika (USNRC), di Argentina, dan Kanada. Evaluasi ketidakpastian dalam metode BEPU dilakukan dengan beberapa metode yang berbeda seperti GRS, IRSN, ENUSA, AEAT, dan UNIPI. Atas dasar kompleksitas metode-metode yang lain, tujuan makalah ini adalah untuk menggambarkan aspek penting dari proses BEPU dengan metode GRS dengan melakukan simulasi putusnya jalur DVI sebesar 50% luasan pada fasilitas ATLAS karena analisis keselamatan yang dilakukan selama ini baru berupa perkiraan terbaik secara deterministik. Sebagai perbandingan dari simulasi perkiraan terbaik yang dilakukan dengan RELAP5/SCDAP/Mod3.4 digunakan data-data eksperimen yang telah terdokumentasi. Setelah dilakukan 100 simulasi, rentang ketidakpastian dari transien temperatur puncak kelongsong pemanas dan tekanan primer hanya mendekati data eksperimen pada 250 detik di periode awal. Oleh karena itu keakuratan dari simulasi perkiraan terbaik secara keseluruhan memiliki peranan penting pada hasil akhir dari analisis ketidakpastian karena perambatan perbedaan dengan data eksperimen akan terus terjadi selama simulasi. Setelah itu, pemilihan parameter yang penting untuk dikembangkan secara random harus dilakukan secara cermat dengan mempelajari fenomena-fenomena penting yang terkait dengan kejadian yang dianalisis dan model instalasinya.Kata kunci: perkiraan terbaik dan ketidakpastian, putusnya jalur DVI, fasilitas ATLAS, RELAP5, simulas

PENENTUAN KOEFISIEN DISPERSI ATMOSFERIK UNTUK ANALISIS KECELAKAAN REAKTOR PWR DI INDONESIA

Atmosfer merupakan pathway penting pada perpindahan radionuklida yang lepas dari Pembangkit Listrik Tenaga Nuklir (PLTN) ke lingkungan dan manusia. Penerimaan dosis pada lingkungan dan manusia dipengaruhi oleh sourceterm dan kondisi tapak PLTN. Untuk mengetahui penerimaan dosis lingkungan untuk PLTN di Indonesia, maka diperlukan nilai koefisien dispersi untuk tapak potensial yang dipilih. Model perhitungan dalam penelitian ini menggunakan model yang diterapkan pada paket program pada modul ATMOS dan CONCERN dari PC-Cosyma yaitu model perhitungan segmented plume model. Perhitungan dilakukan untuk PLTN tipe PWR kapasitas 1000 MWe berbahan bakar UO2, postulasi kejadian untuk kecelakaan DBA, kondisi tapak kasar, untuk 6 tapak contoh tapak Semenanjung Muria, Pesisir Banten, dan tapak yang didominasi oleh stabilitas cuaca C,D,E, dan F. Koefisien dispersi dihitung untuk 8 kelompok nuklida produk fisi yang lepas dari PLTN yaitu: kelompok gas mulia, lantanida, logam mulia, halogen, logam alkali, tellurium, cerium, dan kelompok stronsium & barium. Perhitungan input menggunakan paket program ORIGEN-2 dan Arc View untuk penyiapan input perhitungan. Hasil pemetaan untuk parameter dispersi maksimum rerata diperoleh pada jarak radius 800 m dari sumber lepasan untuk nuklida dari kelompok logam mulia, logam alkali dan kelompok nuklida cerium. Parameter dispersi untuk Tapak Muria maksimum 1,53E-04 s/m3, Tapak Serang adalah 1,40E-03 s/m3, tapak dengan stabilitas C: 1,72E-04 s/m3, stabilitas D: 1,40E-04 s/m3, Stabilitas E: 1,07E-04 s/m3, dan tapak dengan stabilitas F : 2,14E-05 s/m3.Kata kunci: koefisien dispersi, atmosferik, PWR, kecelakaan, Indonesia The atmosphere is an important pathway in the migration of radionuclides transport from the Nuclear Power Plant (NPP) to the environment and humans. The dose accepted in the environment and humans is influenced by the sourceterm and NPP siting condition. Distribution of radionuclides in the atmosphere is determined by the dispersion coefficient. To find the environment dose acceptance for nuclear power plants in Indonesia, it is necessary to map the dispersion coefficient for Indonesia potential siting Model calculations in this study using Segmented plume model, which a model that is applied to the ATMOS and CONCERN module of PC-Cosyma software. The calculation has done for PWR 1000 MWe with UO2 fuel, DBA accident postulations, roughnes site conditions, for 8 example site such as Muria Peninsula, Coastal Banten, and the C, D, E, and F stability. Dispersion coefficient was calculated for the 8 fission product groups are: the noble gases, lanthanides, noble metals, halogens, alkali metals, tellurium, cerium, and strontium & barium groups. Input calculation using the program package Origen-2 and Arc View for the preparation of input calculations. The results of the dispersion parameter calculated are: the average maximum is obtained at a distance of 800 m radius from the source, for noble metals, alkali metal and cerium group nuclides. Dispersion parameters for maximum at Muria site is 1.53E-04 s/m3, Serang site is 1.40E-03 s/m3, site with stability C is 1.72E-04 s/m3, stability D is 1.40E-04 s/m3, stability E is 1.07E-04 s/m3, and site with the stability F is 2.14E-05 s/m3. Keywords: dispersion coefficient, atmospheric, PWR, accident, Indonesi