Emergency response - ESTE - Fast running SW tool for source term evaluation and radiological impacts assessment

Transcription

1 Technical Meeting on Source Term Evaluation for Severe Accidents 21 to 23 October 2013, IAEA, Vienna, Austria Emergency response - ESTE - Fast running SW tool for source term evaluation and radiological impacts assessment Authors: Peter Čarný, Ľudovít Lipták, Eva Smejkalová, Monika Krpelanová, Dusan Suchoň, Miroslav Chylý, ABmerit, Slovakia

2 ESTE - tool for source term evaluation Source Term - EIA - EPZ determination - Severe accident management, prevention and mitigation - Emergency response IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

3 ESTE - tool for source term evaluation ESTE - tool for source term evaluation and radiological impacts assessment; - strong diagnostics modules and functions; - prepared and implemented for multi-unit NPPs: able to evaluate the ST in case of multi-unit events; - evaluation of the STs for SFP accidents; - impacts of multi-unit STs, releases at various heights above terrain and from various points in parallel or subsequent in time are evaluated to the same map of radiological impacts. IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

4 ESTE - tool for source term evaluation ESTE - for specific NPPs: - ESTE Bohunice (VVER-440)- at the Crisis Centre of NPP - ESTE Mochovce (VVER-440)- at the Crisis Centre of NPP - ESTE Temelin (VVER-1000) and ESTE Dukovany (VVER-440) - at the Crisis Centre of the Czech Regulatory Body, Prague - ESTE Kozloduy (VVER-1000)- at the Crisis Centre of NPP and at the Crisis Centre of the BNRA, Sofia, Bulgaria - module ESTE Dukovany v.austria and module ESTE Temelin v.austria at the Crisis Centre of the BMLFUW, Vienna, connected to ESTE systems in Prague IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

5 ESTE - tool for source term evaluation IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

6 ESTE - tool for source term evaluation Description of method of ST evaluation by ESTE: Considered pathways ( Initiating Event): Release to containment (LOCA, Transient) environment / and auxiliary building environment (or filtered stack release - environment) BYPASS of containment (I-LOCA, SGTR) auxiliary building or turbine building environment Spent fuel pool containment or building - environment (or filtered stack release - environment) IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

7 ESTE - tool for source term evaluation Diagnostics State of the core: - Release of coolant (spiking) - Coolant boiling (for PWR, some % of fuel can be partially uncovered) - Gap release, core uncovered - Core damage Events at spent fuel pool and during refuelling: - Partially damaged fuel in pool in connection with uncovering or melting (loss of coolant in spent fuel pool) - Mechanical damage of 1 fuel assembly IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

8 Diagnostics ESTE - tool for source term evaluation Spray system: - Working (there is flow rate at output of system) - Not working State of containment: -Tight -Untight (untightness = symptoms inside containment + degree of untightness estimated according to increase of response of dose rate monitors "at the fence" of NPP area) Inventory of core: - Calculated specifically for specific type (fuel, power) of given reactor (Scale 6.1/Origen) - End of fission IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

9 ESTE - diagnostics module: ESTE - tool for source term evaluation - e.g. of elementar functions which are diagnosed in process of ST evaluation IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

10 ESTE - diagnostics module: ESTE - tool for source term evaluation - each diagnostics function is operated automatically by measured input parameters and can be operated manually by crisis staff (example- level at pressurizer): IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

11 ESTE - diagnostics module: ESTE - tool for source term evaluation - more complex functions which are diagnosed in process of ST evaluation IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

12 ESTE - diagnostics module: ESTE - tool for source term evaluation - more complex functions which are diagnosed in process of ST evaluation IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

13 ESTE diagnostics module: the most important parameters which are diagnosed in process of ST evaluation

14 ESTE - tool for source term evaluation ESTE diagnostics module: the most important parameters which are diagnosed in process of ST evaluation IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

15 ESTE algorithm: -best prediction of the source term

16 Library of source terms in ESTE: - ~50-60 source terms; ESTE - tool for source term evaluation - combination of the IE (assumed release pathway), the state of the fuel, containment tightness, containment spray system; Example: Source term: LOCA, CD (in-vessel), spray system not in operation, containment tightness 5% / 24 h; or Source term: melted 1% of the spent fuel pool, release through stack filters; + knowledge of reactor core inventory, spent fuel pool inventory; (similar approach to severe accident phenomena and ST -in case of PWR, BWR, CANDU, AGR and RBMK) IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

17 Library of source terms in ESTE: - Impact of sprays, filters is modelled by equations (and efficiency/"decontamination" factors). ESTE - tool for source term evaluation - Deposit on floors and walls and pool scrubbing is considered by equations and factors. - NUREG-1228, NUREG-1465, NUREG-1150, NUREG 1940, NUREG/BR-0150, RG 1.183, NUREG/CR-6193, IAEA TECDOC-1594, IAEA TECDOC-955, + many papers on "CANDU severe accidents phenomena" (by Mathew, Simpson, Pethoukov, and others). IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

18 Prediction of the source term: ESTE - tool for source term evaluation - best-estimated ST = source term based on knowledge of actual state of the core, actual state of containment systems and release pathways (predicted with some agreed and reported level of conservatism) - worse case ST = source term based on assumption that state of systems and symptoms will get worse (core uncovered - CD, containment tigh - untight, filtered release - bypass or fault of filters) Radiological impacts to the area of NPP and to the EPZ are calculated and reported in parallel for both cases (best estimation and worse case). IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

19 ESTE semi-final output (GIS based): Actual Prognose is based on "best-estimated ST", Conservative Prognose is based on "worse case ST"

20 ESTE - tool for source term evaluation ESTE final output: -actual state of protective measures recommended for area of EPZ and for area of NPP IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

21 ESTE - tool for source term evaluation Predicted best-estimated ST (estimated with reported level of conservatism) is used for the EPZ (impacts assessment and urgent measures recommendation). Worse case prediction of ST is used for analyses of possible future trend and possible threat of urgent measures beyond the EPZ boundary (more than ~ e.g.20 km), etc. - these analyses must be done by experts in the crisis staff. IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

22 ESTE - tool for source term evaluation In addition - "really observed release" - is estimated and used by ESTE: - for calculation of radiological impacts of "real release - for implementation of measures beyond km zone from plant - for control of movement of monitoring groups, rescue system groups (including police, medical service...) IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

23 ESTE - tool for source term evaluation Estimation of "real" ST (really observed release) to the environment (estimated, in Bq/per time interval, by nuclides): - based on actual "best" prediction of the source term - based on response of dose rate monitors "at the fence" of NPP area,[gy/h] - based on knowledge of actual METEO measured on site assumed nuclide composition of "real release" is identical with actual best prediction of the source term calculated amount of the release is based on real measurements / on responses of dose rate monitors or activity monitors "at the fence" IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

24 START ESTE algorithm: -estimation of really observed release 15 min. step 30 s step INCREASED RESPONSE OF MONITORS? YES APPLY METEO DATA IS ANY PREDICTION OF SOURCE TERM GENERATED? NO NO YES ASSUME THE NUCLIDE COMPOSITION OF THE RELEASE ACCORDING TO THE BEST ESTIMATIED ST ASSUME THE NUCLIDE COMPOSITION OF THE RELEASE FROM THE DEFINITION SYMPTOMS OF RELEASE IN THE STACK? NO YES CALCULATE THE RESPONSE OF DOSE RATE MONITORS, WHICH WOULD CORRESPOND TO THAT RELEASE THROUGH THE STACK STACK RELEASE? NO YES APPLY CONVERSION FACTORS (MCNP) FOR THE STACK APPLY CONVERSION FACTORS (MCNP) FOR REACTOR BUILDING CALCULATE THE RELEASE in [Bq/15min] DURING LAST 15 min; by NUCLIDES, REALST

25 Example of dose rate monitors "at the fence" of NPP area. These monitors are exploited in the process of estimation of really observed release (application of conversion factors calculated by MCNP):

26 ESTE - tool for source term evaluation Conversion Factors for Dose Rate Monitors "at the fence" - gamma dose rate caused by released puffs; - conversion factors are defined for: a) each monitor; b) various meteo conditions (wind speed, stability category) described in model calculations by Briggs sigma functions; c) basic expected release points or heights (containment building, stack); d) radioactive nuclides assumed (up to 50). Figure: Dependence of the conversion factor on the distance from the release point (= containment building, 60m) and on the category of stability, for Cs-137. IAEA TM on ST Evaluation for Severe Accidents, Oct , /31

27 Conversion Factors for Dose Rate Monitors "at the fence" Figure: Dependence of conversion factor on release height, for Cs-137. Case 1: release at height 100 m (~stack); Case 2: release at height of 60 m (~ containment roof).

28 Conversion Factors for Dose Rate Monitors "at the fence" Figure: Dependence of conversion factor on distance from plume axis, for release at height of 100 m, for Cs-137. Case 1: axis of puff is directly above detector, Case 2: axis of puff is 50 m from detector (in horizontal direction); Case 3: axis of puff is 100 m.

29 Estimated real release (Bq/15 min) - examples Example: -response of (max) detector is 1 mgy/h; - event: LOCA, NON sprays; containment design leak Impact of non-exact knowledge of state of the core. Release at 100 m (~stack) puff above detector Release at 60 m puff above detector Release at 100 m (~stack) puff 50 m in horizontal direction 1/3 Uncovered Core fully uncovered 10 % core damage 100 % core damage (in-vessel) Total release 8.1E E E E I 3.0E E E E Cs 2.4E E E E+12 Total release 5.4E E E E I 2.0E E E E Cs 1.6E E E E+12 Total release 9.1E E E E I 3.4E E E E Cs 2.7E E E E+12

30 Estimated real release (Bq/15 min) - examples Example: -response of (max) detector is 1 mgy/h; - event: LOCA, NON sprays; containment design leak Impact of non-exact knowledge of ST timing. 1 st hour 2 nd hour 3 rd hour 1/3 Uncovered Core fully uncovered 10 % core damage 100 % core damage (in-vessel) Total release 8.1E E E E I 3.0E E E E Cs 2.4E E E E+12 Total release 1.3E E E E I 3.1E E E E Cs 2.5E E E E+12 Total release 1.9E E E E I 2.9E E E E Cs 2.3E E E E+12

31 ESTE - tool for source term evaluation Thank you for your attention Presented by: Peter Čarný, Ľudovít Lipták, Eva Smejkalová, ABmerit, Trnava, Slovakia carny@abmerit.sk IAEA TM on ST Evaluation for Severe Accidents, Oct , /31