ライブラリ登録: Guest

ISSN Online: 2688-7231

ISBN Online: 978-1-56700-478-6

Proceedings of the 24th National and 2nd International ISHMT-ASTFE Heat and Mass Transfer Conference (IHMTC-2017)
December, 27-30, 2017, BITS Pilani, Hyderabad, India

STUDY OF IN-VESSEL PHASE OF SEVERE ACCIDENT PHENOMENA OF VVER-1000/V412 WITH AND WITHOUT REFLOOD CONDITIONS

Get access (open in a dialog) DOI: 10.1615/IHMTC-2017.760
pages 551-556

要約

This paper highlights study of in-vessel phase of severe accident phenomena in VVER-1000/V412 reactor by using stand-alone calculations with ICARE/ASTECv2.0r3p3 for modeling the different components of reactor. The study has been carried out for different stages of degradation of fuel pins during in-vessel phase of severe accident. A Postulated Initiating Event (PIE) like Large Break LOCA with Extended Station Black Out (ESBO) has been considered with and without passive hydro-accumulator injection into Reactor Pressure Vessel (RPV). Degradation progression sequence of reactor core with and without reflooding of the core by passive Hydro Accumulators (HA) is required to develop an understanding on severe accident progression. Key parameters for severe accident progression without reflooding (e.g. large scale core heatup and structural material heat up, clad balloon and burst, hydrogen generation, relocation of melt in the lower plenum, RPV failure) are of interest to understand the degradation pattern. In addition to this, the influence of reflooding on the degradation parameters and adequacy of the reflooding flow rates to cool moderately/severely degraded core is also of interest. This study is helpful to establish verification of Severe Accident Management Guidelines (SAMGs) and generate insights for different operator actions for SAMGs.
The reference plant considered for this analysis is VVER-1000 (V412 model) of Kudankulam NPP-1&2 which includes enhanced passive emergency core cooling system (ECCS) comprising two stages of Hydro-Accumulators (HAs). HA-1 system having water inventory of 200 m3 actuates when primary pressure drops to 5.89 MPa. Later HA-2 actuates while system pressure falls below 1.5 MPa and this system has an inventory of 960 m3. In case of postulated Large Break LOCA with SBO, second-stage HA injects water into RPV up to 24 hours. Postulated Loss of Coolant Accident (LOCA) along with extended SBO scenario with two different conditions have been analyzed viz. (i) without any HA injection and (ii) with both HA-1 and HA-2 injection.
As the analysis considered large break LOCA, hence the inventory drops rapidly in RPV leading to a steam starved condition. The extent of zircaloy oxidation from steam is found to be very less leading to low chemical power generation. The major degradation is found to happen due to large decay heat. A core slump with vessel failure is predicted in this event. Reflooding analysis carried out illustrates that core does not undergo degradation up to the HA injection capacity (24 hrs). Heat transfer behavior during reflooding has been studied and different regimes of heat transfer have been identified. The paper describes the ASTEC specific modeling of RPV with internals, the analysis details and the study conclusion.