slides for 1/29/2013 u.s. epr public meeting with areva to … · 2013. 1. 29. · public meeting...

Public Meeting to discuss U.S. EPR Postulated Piping Rupture Blast Effects Evaluation Methodology and Design Approach and the Closure Plan for the U.S. EPR FSAR Open Items on Blast Effects

Rockville, Maryland January 29, 2013

Public Meeting to Discuss Blast Effect Methodology (RAI 354, Question 3.6.2-35) – 1/29/2013 2

AgendaTopic Presenter

Introductions AREVA/NRC

Purpose R. Wells

Background R. Wells

Discussion of the AREVA NP blast effects methodology and approach for RAI 354

C. McGaughy

• Discussion of the application of loads and frequencies)

• Description of changes to ANP-10318P

Closure Plan for RAI 354, Question 3.6.2-35 R. Wells• Path Forward Activities and Schedule

Summary/Next Steps R. Wells

Comments and Questions


Purpose

Present and obtain NRC feedback on the AREVA NP blast effects methodology and approach for RAI 354, Question 3.6.2-35

Outline path forwardReview closure plan for U.S. EPR RAI 354, Question

3.6.2-35Confirm agreement with the NRC on the path to closure


Background RAI 354, Question 3.6.2-35 (Blast Effect Methodology)

3/16/2010 - Initially issued by NRC 5/20/10 – Initial Draft Response of RAI 354, Question 3.6.2-35 sent to NRC 11/1/2010 – Public Meeting with NRC 1/5/2011 - Revised Draft Response of RAI 354, Question 3.6.2-35 sent to NRC 1/26/2011 – Comments received from NRC on Revised Draft Response of RAI 354, Question

3.6.2-35 2/28/2011 – Second revised Draft Response of RAI 354, Question 3.6.2-35 and Revision 0 of

AREVA NP Technical Report ANP-10318P, “Pipe Rupture External Loading Effects on U.S. EPR Essential Structures, Systems, and Components,” submitted to NRC

4/20/2011 – NRC/AREVA telecon to discuss NRC comments on second revised Draft Response of RAI 354, Question 3.6.2-35 and Revision 0 of ANP-10318P

8/9/2011 - NRC/AREVA telecon to discuss path forward on RAI 354, Question 3.6.2-35 8/30/2011 – Interim Response to RAI 354, Question 3.6.2-35 sent to NRC along with proposed

changes to ANP-10318P 10/17/2011 – Follow-up NRC/AREVA telecon to regarding RAI 354, Question 3.6.2-35 (AREVA

informed NRC we plan to use a simplified program to evaluate the blast effects for the Main Steam Valve isolation room and validate these results using CFD).

6/5/2012 – RAI 354 Suppl. 35 defers final response to Question 3.6.2-35 to 7/30/13 11/9/2012 - NRC/AREVA telecon on the status of the of the final Response to RAI No. 354,

Question 3.6.2-35 (AREVA informed NRC that we no longer planned to do the simplified program, rather we were just going to the CFD)

1/29/13 - Public Meeting/Telecon on Blast Effect Methodology


Background SER Open Items related to Blast Effect Methodology

RAI Question No.

Date of Final RAI Response

NRC Classification

Audit Topic

354 3.6.2-35 7/30/13 Open Item

NRC requested that AREVA clarify how the plan to be used that will account for the different fluid properties in an U.S. EPR blast (steam and/or water) compared to those of air considered in the Army/Navy/Air Force manual.

Discussion of the AREVA NP Blast Effects Methodology and Approach for RAI 354

Chris McGaughyAdvisory Engineer


Blast Effect MethodologyIntroduction

Goals:Develop a methodology to determine blast loadings

caused by ruptures in steam linesValidate the Computational Fluid Dynamics (CFD)

methods based on current literature


Blast Effect MethodologyVariability Sources

Selection of discretization in space Grid quality (grid angles, aspect ratios, etc.) Grid design (structured, unstructured, hybrid mesh) Grid size (error versus computational time)

Selection of discretization in time Time step size (error versus computational time)

Selection of convergence criteria Courant number (CFL criterion) Deviations in numerical approach Reasonable values for target variables (especially in

validations)

Input parameter uncertainty Sensitivity on variations of boundary conditions or fluid

properties


Blast Effect MethodologyModeling the Physics

Compressibility Density model: ideal gas law or real gas law

High-speed flow Viscous model: inviscid or turbulent flow

Flow discontinuities (shock wave) Solver formulation (coupled pressure-based or density-based) Numerical scheme: implicit or explicit Time discretization: implicit or explicit Dynamic mesh adaption (mesh refinement e.g. by pressure

gradient)

For validation, combustion and/or detonation Reaction model: one-step, Finite-Rate


Blast Effect MethodologyStrategy to Approach the Physics

As a first approach, simple models are chosen: Ideal gas law to model density of the gas mixture. Inviscid flow (inertial forces dominant in high speed flow)

Comparison to experimental data will show the need to change them


Blast Effect MethodologyV & V Cases

Literature review to identify cases for verification and validation (V&V)

Adequate cases for V&V are few in the open literature Examples for V&V to show the CFD code ability to

determine blast effects: Flow in a shock tube

• 1-D behavior (exact analytical solution available) 28-Inch shock tube

• 3-D behavior (more difficulty in achieving comparable results) Hydrogen combustion in confined vessel

• Similar to shock tube with multiple obstructions Blast wave on a solid box (detonation of propane)

• External wave propagation


Blast Effect Methodology V&V Case 1: Flow in a Shock Tube

The shock tube is a device in which a normal shock wave is produced by the sudden bursting of a diaphragm separating a gas at high pressure from one at lower pressure.

The problem tests the CFD code ability to handle rarefaction waves, contact discontinuities and shocks.

The basis for this study is the one-dimensional analytical solution of a shock tube.


Blast Effect MethodologyV&V Case 1: Flow in a Shock Tube

Pressure Ratio = 200

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

Dimensionless-X

Mac

h N

umbe

r

Fluent

Analytical

Expansion wave front

Expansion wave tail

Contact surface

Normal shock

CFD


Blast Effect MethodologyV&V Case 2: 28-Inch Shock Tube


Blast Effect MethodologyV&V Case 2: 28-Inch Shock Tube

The sudden bursting of a diaphragm separating the driver gas at high pressure (328 psi) from one at lower pressure (14.5 psi) produces a blast wave.

The problem tests the CFD code ability to calculate the blast wave in a large three dimensional geometry.

Measurements of the pressure as function of time in the shock tube are available.


Blast Effect MethodologyV&V Case 3: H2 Combustion in Confined Vessel

Homogeneous concentration of hydrogen

Flame direction: upwards 9 obstacles to generate

turbulence in the acceleration tube section

Pressure monitoring at the end of the tube



The hydrogen combustion in the confined ENACCEF vessel generates hot gases behind the flame which accelerates upwards. The pressure and temperature rise rapidly in the vessel.

The overpressure history as function of time is monitored and compared to the experimental data.

H2-combustion in the ENACCEF vessel is calculated with CFD to show the ability of the code to handle reactive flow and to predict the time-dependent pressure loads and pressure oscillations in the vessel.



Maximum pressure comparable to measured one or higher (conservative)

First and second rate of pressure rise (dp/dt) well-predicted Pressure oscillations well-predicted CFD Model considers adiabatic walls (heat losses unknown in the

experiments)

Decrease due to heat losses in experiments

ENACCEF RUN153 H2 Conc. 13%

0

1

2

3

4

5

6

0 0.1 0.2 0.3 0.4 0.5time (s)

pres

sure

(ba

r)


Blast Effect MethodologyV & V Case 4: Blast wave on a solid box


Blast Effect MethodologyV & V Case 4: Blast wave on a solid box

A three dimensional blast wave is generated by the explosion of propane

Pressure load on the solid wall is measuredGeometry not confined (free atmosphere)Calculation requires the modeling of combustion

reaction of propane


Blast Effect MethodologyConclusions for the shown V&V Cases

Flow in the tube shock CFD results agree well with the exact analytical solution

28-Inch shock tube Positive pressure section well-predicted Negative pressure section more difficult to match accurately

Hydrogen combustion in ENACCEF facility Predicted pressure loads in the vessel are reasonably captured

by the CFD model AREVA NP has long experience in modeling hydrogen

combustionBlast wave on a solid box

Detonation of propane is required (reaction model)


Blast Effect Methodology Rupture of steam lines

Pipe contains only pressurized steam Pipe rupture occurs at once, cross-section of pipe is open Only steam discharges (no phase change) Room is filled with air and there is a wall close to the break

Wall

Break

Pipe

P, x=1

air


Blast Effect Methodology Rupture of steam lines (Comparison to

method used in the report)CFD calculation of blast pressure loading for

following example: Description in Technical report ANP-10318P, page 34 Pipe geometry, target structure at 3 ft from break, P=1250psi

and x=1 Calculation focuses on the blast wave that follows a pipe

failure.


Blast Effect Methodology Rupture of steam lines (Comparison to

method used in the report)

Pipe conditions in CFD: Total pressure: 86.164 bar (1250 psi) Total Temperature: 264.91°C

P peak ~ 36 bar (522 psi), comparable to 540 psi as calc. in report


Discussion of the Application of Loads and Frequencies

Application of the Load Plate and Shell Models (Pressure Vessels and Walls) Overpressure applied to surfaces as a pulse with 0 rise time

and calculated duration (td) Beam Models (Structures and Components)

Overpressure applied as a distributed load along the length of the beam as a pulse with 0 rise time and calculated duration (td). Peak load calculated using peak overpressure multiplied by surface area.



Structural Analysis - Cutoff Frequency For a triangular pulse load with 0 rise time, the dynamic load

factor (DLF) is greatest when the pulse duration (td) is long, relative to the structure’s period.

With (td) typically being in the 1 ms range, the structure must have natural frequencies greater than 400 Hz for the DLF to be greater than 1 (Biggs - td/T=0.4). However, the DLF is applied to individual modes which, in high frequencies, usually have low effective masses and shapes that are not conducive to a distributed pressure loading.

Therefore, the cutoff frequency will be chosen such that 95% of the effective mass is accounted for. Remaining mass will be considered through the missing mass method.



Structural Analysis Damping

Although blast forces often cause nonlinear material behavior, damping is conservatively set to 1%, as for jet impingement.

LoadingLoading will be applied as a force time history using direct integration or modal integration, depending on geometric nonlinearities.


Discussion of Acceptance Criteria

Acceptance Criteria Using NRC approved code acceptance criteria for structural

evaluation of safety related target SSCPressure Vessels – ASME CodeSteel Structures – AISC N690 CodeConcrete Structures – ACI 349 Code


Description of Changes to ANP-10318P

Jet Impingement partial Intersection (Section 3.2.3) -Incorporated the calculation of jet area for use in determining partial intersection areas. Also included discussion of pressure distribution in the jet.

Compressible Jet Properties (Section 3.2.4) - Added new Section 3.2.4.3 describing pulse loading for jet impingement

Retitled Section 3.2.5 as Jet Dynamic Loading and Resonance

Clarified the maximum nozzle pressure ratio for jet resonance in 3.2.5 and 3.2.5.1



Blast Effects (Section 3.3) – Discussion updated to include CFD approach.

Structural Evaluation (Section 3.4) - Structural Evaluation of Typical Target Essential SSC (Section 3.4) – Added basic information concerning loading methodology.

Dynamic Finite Element Analysis (Section 3.4.1) – Added details

Loading Method (Section 3.4.1.3) – Separated into two subsections to define the loading for jet impingement and blast separately

Cutoff Frequency Criteria (Section 3.4.1.4) - Separated into two subsections to define the criteria for jet impingement and blast separately



Applicable Codes and Standards (Section 3.5) – Additional information is added to cover the possibility of nonlinear elastic-plastic analysis for blast loading of steel and concrete structures.

Steel Structure Code Requirements (Section 3.5.2) –Additional information is added concerning the use of ductility ratios based on code requirements.

Concrete Structure Code Requirements (Section 3.5.3) –Additional information is added concerning the use of ductility ratios based on code requirements.


Discussion of Results of Blast Effects Methodology

Based on review of past precedent (e.g., GE ESBWR SER) it does not appear that results of the blast effect methodology are needed for NRC to reach a reasonable assurance finding

ITAAC exist in the U.S. EPR FSAR Tier 1 Section 3.8 to require that the pipe break hazards analysis report demonstrates that SSCs are protected or qualified to withstand the dynamic and environmental effects of postulated failures, including cubicle pressurization effects.

Similar to the GE ESBWR SER, ANP-10318P will require that converged, worst-case loading scenarios be applied to SSCs and neighboring structures when using the CFD analysis approach. In addition, AREVA will benchmark the CFD analysis approach prior to applying it to U.S EPR designs.

Russ WellsLead Licensing Engineer

Path Forward Activities and Schedule


Path Forward Activities and Schedule

Submit revised interim response to RAI 354, Question 3.6.2-35 to reflect blast effect methodology including markups to ANP-10318P (Note: revised interim response may not be required if results of the CFD analysis are not required for NRC to close the open item).

Follow-up public meeting/telecon to address NRC comments, if any, on the revised interim response

Submit advanced copy of final response of RAI 354, Question 3.6.2-35 to NRC (including markups to ANP-10318P)

Resolve NRC comments, if any Submit final response of RAI 354, Question 3.6.2-35 to NRC

(including formal revisions to ANP-10318P) See timeline on following slide


29 31 15 11 15 31

Jan-13 March-13 Apr-13 June-13 July-13 July-13

NRC public meeting

Submit advanced copy of final

response of RAI 354, Question 3.6.2-

35 to NRC

Timeline for Open Item Closure

Send revised interim response to RAI 354, Question

3.6.2-35 to NRC

Public meeting/Telecon

with NRC on revised interim response for

RAI 354 Q3.6.2-35

Receive NRC comments on

advanced copy of final response of

RAI 354, Question 3.6.2-35

Submit final response of RAI

354, Question 3.6.2-35 to NRC


Summary/Next Steps

Complete Revisions to RAI 354, Question 3.6.2-35 using the methodology described in this presentation.

Timely NRC feedback is essential to achieving closure.”

Advanced and final response to RAI 354, Question 3.6.2-35 will be submitted in a timeframe to support NRC closure of open item.

slides for 1/29/2013 u.s. epr public meeting with areva to … · 2013. 1. 29. · public meeting...

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