Transcript Analysis of the TMI-2 Accident Using ATHLET-CD

Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Analysis of the TMI-2 Accident
Using ATHLET-CD
Tilman Drath,
Ingo D. Kleinhietpaß, Marco K. Koch
Lehrstuhl für Energiesysteme und Energiewirtschaft (LEE)
(LEE)
B)
Ruhr-Universität Bochum (RU
(RUB)
0
11th International QUENCH Workshop
Forschungszentrum Karlsruhe, October 25-27, 2005
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
 TMI-2 Accident
 ATHLET-CD Short Description
 Modelling with ATHLET-CD
 Calculational Results
 Conclusions
1
Outline
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
TMI-2 Accident
 Three Mile Island Unit 2 (TMI-2):
 was planned by a number of organisations
(i.e. Babcock & Wilcox Inc.),
 is banked on the named-giving island in
the midst of the Susquehanna River near
Harrisburg, USA, beside Unit 1 being still
in commercial operation since September
1974,
 was completed as 2-Loop American PWR,
and
 started operation in the end of 1978 with
an electrical power of 0.9 GWel and a
thermal power of 2.7 GWth.
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Google Earth
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
TMI-2 Accident
 The TMI-2 accident was initiated by problems on the
secondary side of the plant.
 These problems finally led to:
 the loss of the main feed water pumps and the turbine,
 an insufficient low heat dissipation in the steam generators,
as well as
 a rise of the primary pressure, and finally
 the reactor shutdown on the 28th of March 1979
at 04:00:37 h local time.
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Ru h r -U n i v er si t ä t Bo ch u m
LEE
TMI-2 Accident
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Sequence of Events and Primary Pressure History
PORV Failure!
4
Ru h r -U n i v er si t ä t Bo ch u m
LEE
TMI-2 Accident
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Postulated Configurations of the TMI-2 Core
Before Reflood
(174 min)
Endstate
Configuration
After Reflood
and before
Relocation
(224 min)
5
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
 ATHLET-CD:
ATHLET-CD Short Description
Analysis of THermal-hydraulics of LEaks and
Transients – Core Degradation
Modular structured Code ATHLET-CD
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 The code is being developed by the Gesellschaft für Anlagen
und Reaktorsicherheit (GRS) mbH in Germany.
 It deals with the analysis of anticipated and abnormal plant
transients, small and intermediate leaks, as well as large
breaks in LWRs.
 The ATHLET code covers the spectrum of design basis and
beyond design basis accidents (without core degradation) for
PWRs and BWRs.
 The CD part represents an add-on to ATHLET with modules
describing core melting, fission product release, as well as
fission product and aerosol transport processes in the primary
system.
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
ATHLET-CD Short Description
Modular Structure of ATHLET-CD
7
Gesellschaft für Anlagen und Reaktorsicherheit (GRS) mbH
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Modelling of the TMI-2 Accident
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
ATHLET-CD Nodalisation of the Plant
Loop B
8
Loop A
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Modelling of the TMI-2 Accident
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
ATHLET-CD Nodalisation of the Core
Bypass
Core
Reflector
Bypass
9
ROD4
(Outer
Ring)
Cross
Connections
ROD3
ROD2 ROD1
(Inner
Ring)
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Results of the TMI-2 Calculations
Calculated and Measured Primary Pressure History
B-Pump Transient
High Pressure
Injection
Heat transfer to the coolant
is over-predicted due to the
under-estimation of core
degradation because of still
missing late phase models.
End of run using MESOCO!
10
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Results of the TMI-2 Calculations
Calculated and Measured Leakage Mass (PORV)
Measuring inaccuracy
during the trip due to the
operation beyond design
limits.
The mass flow rate is calculated
with the critical discharge model
and shows a qualitative good
result of the accumulated
leakage mass.
11
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Results of the TMI-2 Calculations
Calculated and Measured Pressuriser Water Level
Measuring inaccuracy
during the trip due to the
operation beyond design
limits.
Calculated mixture and water
level only differ, if the PORV
(block valve) is opened, which
means a good reproduction of
the pressuriser behaviour.
12
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Results of the TMI-2 Calculations
Calculated Water-/Steam Distribution History
13
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Results of the TMI-2 Calculations
Calculated and Postulated Core Configuration
before Reflood (174 min)
14
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Results of the TMI-2 Calculations
Calculated and Postulated Core Configuration
after Reflood and before Relocation (224 min)
Debris bed and molten
pool behaviour are not
calculable at present!
15
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Results of the TMI-2 Calculations
Calculated History of the Core Configuration
16
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Results of the TMI-2 Calculations
Calculated and Measured Hydrogen Production
The H2 generation is under-predicted
during the reflood due to:
1.) fuel rod failure and material relocation
into deeper core sections,
2.) temperatures being too low to
contribute significantly to the oxidation
rate in the lower core regions,
3.) no access of the coolant to the melt
because of blockage formation.
17
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Results of the TMI-2 Calculations
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Fuel rod failure:
ROD1 and ROD2!
Calculated Outer Oxide Layer Thickness (240 min)
Permanent
water level!
18
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Results of the TMI-2 Calculations
Calculated Fission Product and Structure Material Transport
into the Primary System (240 min)
Transport Rate
[%] of Initial Inventory
ATHLET-CD
2.0A/1.1K
Estimation of Akers et al.
I, Cs, Xe
53 %
50 %
Te, Sb
5%
1.6 %
(available for Sb only)
Sr
3%
3.5 %
0.4 %
-
Group of Species
U, Ag-St
19
(Nuclear Technology, Vol. 87, pp. 205-213)
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Conclusions
 The thermal-hydraulics are predicted quite well compared to the TMI-2
data, especially if the measuring inaccuracy during the trip due to the
operation beyond design limits is taken into account.
 The core configurations are calculated in good agreement compared to
the postulated status of the core at ascertained times of the sequence.
 The H2 generation is under-predicted during the reflood because of fuel
rod failure and material relocation into deeper core sections, where the
temperatures are too low to contribute significantly to the oxidation rate.
Additionally, no access of the coolant to the melt exists because of
blockage formation.
 The calculated fission product and structure material release as well as
their transport in the primary system represent plausible results.
 The calculation of the TMI-2 accident using ATHLET-CD in the current
program version 2.0A/1.1K shows a good overall code performance.
 But the code has, of course, still a potential of improvements in modelling
physical phenomena especially concerning the late phase of core
degradation and the behaviour and coolability in the lower head.
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Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Acknowledgement
 This work is sponsored by the German Federal
Ministry of Economics and Labour (BMWA 150 1241).
 The authors thank for support and interpretational
hints from Dr. Klaus Trambauer (GRS mbH).
 Special thanks to all colleagues from the FZK for
hosting the QUENCH Workshop.
21
Ru h r -U n i v er si t ä t Bo ch u m
LEE
Lehrstuhl für Energiesysteme
und Energiewirtschaft
Prof. Dr.-Ing. H.-J. Wagner
Analysis of the TMI-2 Accident
Using ATHLET-CD
Tilman Drath,
Ingo D. Kleinhietpaß, Marco K. Koch
Lehrstuhl für Energiesysteme und Energiewirtschaft (LEE)
(LEE)
B)
Ruhr-Universität Bochum (RU
(RUB)
22
11th International QUENCH Workshop
Forschungszentrum Karlsruhe, October 25-27, 2005