Computational Science and E-Systems Research

11-3 How Do Earthquake Waves Propagate into a Nuclear Facility?

=Realization of Precise Simulation of Building-Equipment Interaction during Earthquakes=Cnnection

Equipment
sideThe connection
interaction model
is setEquipment

Building
Non-linear spring arranged
distributedlyPresent
The connection interaction
model is set at theconnection surface

BuildingConventionalBuilding-equipment
connection are
assumed as fixed

0-50

B-100-10-50

Analyticalresult510

変位(mm)
Displacement(mm)

Intermediate heatexchanger (IHX)

50Primary pressurizedwater cooler (PPWC)

0-50-100-10-5Experimental
results
0510

Analytical model for whole numerical simulation ofprimary cooling system of HTTR

載荷点変位(mm)Displacement (mm)Reponces are reduced

6Acceleration (cm/s2)×104

Applicability of the model was confirmed bycomparing analytical results with experimental results
Resonance frequency was changed
during vibration

12A――
モデル無モデル有―― B

84

A: elastic
B: elastic-plastic

1020304050Frequency (Hz)

YZ

5432
10-1-2-3-4-5XYZTime (s)With the connection model

The time response of acceleration of non-linear
springs of the connection interaction model at point C

Applicability of the model was confirmed by checking theresonance frequencies

Fig.11-5 Connection interaction model between
buildings and equipment
We compared the analysis results from the suggested
connection interaction model with experimental results
and confirmed the applicability of the suggested modelto the real connection structure.

XTime (s)Without the connection model

00

5
4
3
2
10-1-2-3-4-5

Acceleration (cm/s2)×104

Force (kN)

A荷重（ ｋN50

Fourier Amplitude ×10

Secondarypressurizedwater cooler(SPWC)

100

100Force (kN)C

Fig.11- 6 Real entire -plant analysis with connection interaction model
We incorporated the connection interaction model into the real plantmodel and conducted earthquake response analysis. The results
indicate that the equipment response was reduced by absorption ofenergy as a result of the nonlinearization imparted by connection; thus,
we were able to confirm the effects of adopting the connection
interaction model.

Nuclear facilities are composed of a large number of
equipment, and it is necessary to evaluate realistic responsesof each of these equipment to earthquakes in order toascertain earthquake resistance safety. In particular, it isimportant to know which types of wave propagate into thebuilding through the connection; in other words, it isimportant to know the detailed wave propagation propertiesof the connection (wave transmission and reflection), because
equipment response is evaluated using building response.
Because the connection between buildings and equipment is aconcrete structure, it is usually assumed to be a fixedboundary to simplify the elucidation of its wave propagationproperties. However, recent experimental results havesuggested that a slight displacement or gap can occur at theconnection for large inputs, and it has become clear that theassumption of a fixed boundary is not appropriate in such
instances.
Therefore, we have attempted to express wave propagation
properties at the connection to model force-displacement
relationships based on experimental data. We devised forcedisplacement relationships for each micropart directly byarranging nonlinear springs dispersively on the boundary
surface in order to consider historical properties such as thepartial gap at the connection. We confirmed the applicabilityof the connection interaction model by comparing ouranalytical results with experimental results and confirmed theresonance frequencies before and after the nonlinearization of

the connection, as shown in Fig.11-5.
Furthermore, we conducted earthquake response analysisof the entire cooling structure of a nuclear facility
incorporating the connection interaction model using a large
earthquake input, for which part of the building-equipment
connection becomes nonlinearized, to confirm the applicabilityof the connection interaction model to the real plant. Fig.11-6
shows a model of the entire cooling structure of the hightemperature engineering test reactor (HTTR) and our analysis
results. We were able to confirm that the equipment response
was reduced because of historical energy absorption by
nonlinearization of the connection in the case with theconnection interaction model. On the basis of these results,
we were able to assess the potential for use of the connection
interaction model in earthquake resistance evaluation.
It is expected that more detailed analysis will be necessaryfor evaluation of the earthquake resistance of nuclear plants.
Furthermore, we expect that as the representation of thebehavior of nuclear facilities during earthquakes improves,
we will be able to share more detailed information with thegeneral public.
The present study is the result of the project entitled
Development of physical model describing the dynamic
interaction characteristics of component connections for theanalysis of an entire nuclear facility entrusted to the Japan
Atomic Energy Agency by the Ministry of Education,Culture, Sports, Science and Technology of Japan (MEXT).

Reference
Nishida, A. et al., Elastic-Plastic Connection Model Describing Dynamic Interactions of Component Connections, Progress in Nuclear Science andTechnology, vol.2, 2011, p.576-581.

104 JAEA R&D Review 2012