ML112991398

Technical Evaluation of Monticello Nuclear Generating Plant-Unique Analysis Rept

ML112991398
Person / Time
Site:	Monticello
Issue date:	09/30/1984
From:	Lehner J, Bienkowski G Brookhaven National Lab (BNL)
To:	NRC
Shared Package
ML112991396	List: ML112991398 ML20209E521
References
CON-FIN-A-3713 BNL-04243, BNL-4243, NUDOCS 8509190458
Download: ML112991398 (24)

Text

TECHNICAL EVALUATION OF THE MONTICELLO NUCLEAR GENERATING PLANT PLANT-UNIQUE ANALYSIS REPORT George Bienkowski John R. Lehner Reactor Safety Licensing Assistance Division Department of Nuclear Energy Brookhaven National Laboratory Upton, New York 11973 September 1984 FIN A-3713 BNL-04243 8509190458 PDR ADOCK P

650911 05000263 PDR

ABSTRACT This Technical Evaluation Report (TER) presents the results of the post-implementation audit.of the Plant Unique Analysis Report (PUAR) for the Monticello Nuclear Generating Plant.

The contents of the PUAR were compared against the hydrodynamic load Acceptance Criteria (AC) contained in NUREG-0661.

The TER summarizes the audit findings (Table 1), and discusses the nature and status of any exceptions to the AC, identified during the audit (Table 2).

ACKNOWLEDGEMENTS The cognizant NRC Technical Monitor for this program was Dr. Farouk Eltawila of the Containment Systems Branch (DSI) and the NRC Project Manager was Mr. Jack N. Donohew of the Technical Assistance Program Management Group of the Division of Licensing.

Mr. Byron Siegel of Operating Reactors Branch No. 2 (DL) was Lead Project Manager.

-ii-

List of Acronyms AC Acceptance Criteria BNL Brookhaven National Laboratory BWR Boiling Water Reactor CO Condensation Oscillation DBA Design Basis Accident DL Division of Licensing DSI Division of Systems Integration FRC Franklin Research Center FSI Fluid Structure Interaction FSTF Full Scale Test Facility LDR Load Definition Report LOCA Loss-of-Coolant Accident LTP Long Term Program NEP Non Exceedence Probability NRC Nuclear Regulatory Commission PUA Plant-Unique Analysis PUAR Plant-Unique Analysis Report QSTF Quarter Scale Test Facility RFI Request For Information SER Safety Evaluation Report SPTMS Suppression Pool Temperature Monitoring System SRSS Square Root of the Sum of the Squares S/RV Safety/Relief Valve S/RVDL Safety/Relief Valve Discharge Line STP Short Term Program TAP Torus Attached Piping TER Technical Evaluation Report

-iii-I

Table of Contents Page No.

ABSTRACT ACKNOWLEDGEMENTS ii LIST OF ACRONYMS iii

1. INTRODUCTION 1

2. POST-IMPLEMENTATION AUDIT

SUMMARY

3

3. EXCEPTIONS TO GENERIC ACCEPTANCE CRITERIA 10

4. CONCLUSIONS 17

5. REFERENCES 18

-iv-

1. INTRODUCTION The suppression pool hydrodynamic loads associated with a postulated loss of-coolant accident (LOCA) were first identified during large-scale testing of an advanced design pressure-suppression containment (Mark III).

These additional loads, which had not explicitly been included in the original Mark I containment design, result from the dynamic effects of drywell air and steam being rapidly forced into the suppression pool (torus).

Because these hydrody namic loads had not been considered in the original design of the Mark I con tainment, a detailed reevaluation of the Mark I containment system was required.

A historical development of the bases for the original Mark I design as tell as a summary of the two-part overall program (i.e., Short Term and Long Term Programs) used to resolve these issues can be found in Section 1 of Refer ence 1. Reference 2 describes the staff's evaluation of the Short Term Program (STP) used to verify that licensed Mark I facilities could continue to operate safely while the Long Term Program (LTP) was being conducted.

The objectives of the LTP were to establish design-basis (conservative) loads that are appropriate for the anticipated life of each Mark I BWR facility (40 years), and to restore the originally intended design-safety margins for each Mark I containment system.

The principal thrust of the LTP has been the development of generic methods for the definition of suppression pool hydrody namic loadings and the associated structural assessment techniques for the Mark I configuration.

The generic aspects of the Mark I Owners Group LTP were com pleted with the submittal of the "Mark I Containment Program Load Definition Re port* (Ref. 3) and the "Mark I Containment Program Structural Acceptance Guide" (Ref. 4), as well as supporting reports on the LTP experimental.and analytical tasks.

The Mark I containment LTP Safety Evaluation Report (NUREG-0661) presented the NRC staff's review of the generic suppression pool hydrodynamic load definition and structural assessment techniques proposed in the reports cited above.

It was concluded that the load definition procedures utilized by the Mark I Owners Group, as modified by NRC requirements, provide conservative estimates of these loading conditions and that the structural acceptance crite ria are consistent with the requirements of the applicable codes and standards.

The generic analysis techniques are intended to be used to perform a plant-unique analysis (PUA) for each Mark I facility to verify compliance with the acceptance criteria (AC) of Appendix A to NUREG-0661.

The objective of this study is to perform a post-implementation audit of the Monticello plant-unique analysis (Reference 5) against the hydrodynamic load criteria in NUREG-0661.

2. POST-IMPLEMENTATION AUDIT

SUMMARY

The purpose of the post-implementation audit was to evaluate the hydrodynamic loading methodologies which were used as the basis for modifying the pressure suppression system of the Monticello Nuclear Generating Plant.

The Monticello PUAR methodologies (Reference 5) were compared with those of the LDR (Reference 3) as approved in the AC of NUREG-0661 (Reference 1).

The audit procedure consisted of a moderately detailed review of the plant unique analysis report (PUAR) to verify both its completeness and its compliance with the acceptance criteria. A list of requests for further information was submitted (Reference 6), and answers were obtained at a meeting with the licensee (Reference 7).

Table 1 summarizes the audit results. It lists the various load categories specified in the AC, and indicates plant-unique information through the references, in the right-hand column, to the notes which follow in the text.

LOADS w2 Wy) g I

I CRITERIA MET NOr MET

-J oY 0-zo cr

~~0.

(n CONTAINMENT PRESSURE a TEMPERATURE 2.1 VENT SYSTEM THRUST LOADS 2.2 POOL SWELL TORUS NET VERTICAL LOADS 2.3 TORUS SHELL PRESSURE HISTORIES 2.4 VENT SYSTEM IMPACT AND DRAG 2.6 IMPACT AND DRAG ON OTHER STRUCTURES 2.7 FROTH IMPINGEMENT 2.8 POOL FALLBACK 2.9 LOCA JET 2.14.1 LOCA BUBBLE DRAG 2.14.2 VENT HEADER DEFLECTOR LOADS 2.10 TABLE 1. LOAD CHECKLIST FOR POff-IMPLEMENTATION AUDIT 0.

LOADS z-z W)

DO CRITERIA

-F---

MET' NOT MET w

0 0-w

- x 0

tu cr 0

CL 0 z CONDENSATION OSCILLATION TORUS SHELL LOADS 2.11.1 LOADS ON SUBMERGED STRUCTURES 2.14.5 VENT SYSTEM LOADS 2.11.3 DOWNCOMER DYNAMIC LOADS 2.11.2 CHUGGING TORUS SHELL LOADS 2.12.1 LOADS ON SUBMERGED STRUCTURES 2.14.6 VENT SYSTEM LOADS 2.12.3 LATERAL LOADS ON DOWNCOMERS 2.12.2 TABLE 1. (CONTINUED) 1

LOADS I

I ~

1" wz 0

0C to a9 W U) 0:

D~c CRITERIA MET NOT MET Id o

WX z<

cn I-0 z T-QUENCHER LOADS DISCHARGE LINE CLEARING 2.13.2 TORUS SHELL PRESSURES 2.13.3 JET LOADS ON SUBMERGED STRUCTURES 2.14.3 Z

AIR BUBBLE DRAG 2.14.4 THRUST LOADS ON T/0 ARMS 2.13.5 S/RVDL ENVIRONMENTAL TEMPERATURES 2.13.6 TABLE 1. (CONTINUED) 0 I

DESCRIPTION Z5 0

w 0:

z 0

(a Id U)

U CRITERIA MET NOT MET Y

~

I bJ 4i co 0Y z -j a.

0a-0 z SUPRESSION POOL TEMPERATURE 2.13.8 LIMIT SUPRESSION POOL TEMPERATURE 2.13.9

/

MONITORING SYSTEM 2

DIFFERENTIAL PRESSURE CONTROL SYSTEM FOR THOSE PLANTS USING A DRYWELL-TO-WET WELL PRESSURE 2.16 DIFFERENCE AS A POOL SWELL MITIGATOR SRV LOAD ASSESSMENT BY 2.13.9 v

IN-PLANT TEST

.(CONTINUED) 1 0

TABLE 1.

Notes to Table 1

1. For some structures Region 1 froth loads were calculated using the high speed QSTF movies. This alternative is outlined in Appendix A of the AC.

2. Instead of the equivalent cylinder procedure specified in the AC to calcu late acceleration drag volumes on sharp cornered submerged structures, the PUAR used an alternate modelling of the ring-beam structure. The discus sion in Section 3.1 explains the basis for accepting loads computed by the PUAR procedure, as modified in response to the staffs request for informa tion (Reference 7), as conservative.

3. To calculate CO and post-chug loads on the torus shell as well as on submerged structures the 50 individual harmonics were combined using a random phasing technique instead of the absolute summation specified in the AC.

The discussion of Section 3.2 describes why this alternate method was found acceptable.

4. To account for FSI effects for CO and chugging submerged structure loads the AC suggested adding the boundary accelerations directly to the local computed fluid accelerations. The applicant used a method to compute local FSI acceleration flow fields resulting from the specified boundary accelerations, and added these locally to the LDR specified fluid accelerations. This method, which has been accepted during previous PUAR reviews is discussed in Section 3.3.

5. Multiple downcomer lateral loads are based on non-exceedance probabilities that differ someWhat from the value specified in the AC. The difference between the PUAR and AC based loads is dependent upon the number of down comers chugging synchronously.

Section 3.4 describes why the alternate procedure was found acceptable in the specific Monticello application.

6.

The analytical model to calculate SRV torus shell loads approved in the AC was modified slightly to more closely bound the observed pressures in Monticello plant unique tests, on which the model is based. These changes have been found acceptable.

7. For SRV air bubble drag loads the PUAR modified the AC approved bounding factor of 2.5 to 1.75. This still bounds peak positive bubble pressure and maximum pressure differential in the Monticello test data.

In addition calibration factors for SRV drag loads were developed from in plant tests held at Monticello in 1977 and 1980. These modifications of the AC loads have been found acceptable and are discussed in more detail in Section 3.5.

8. The Monticello in plant tests of 1977 were the basis for the analytical model and bounding factors approved in the AC. Re-examination of those results and additional tests in 1980 were used to slightly modify the bounding factors, as well as, deduce calibration factors for certain SRV submerged structure loads (see Notes 6 and 7 above).

3. EXCEPTIONS TO GENERIC ACCEPTANCE CRITERIA Monticello is one of several plants analyzed by NUTECH Engineers, Inc.

based on an essentially common hydrodynamic loading methodology (Fermi, Duane Arnold, Dresden and Quad Cities are other plants in this group). The metho dology differs from the generic acceptance criteria of NUREG-0661 in five major areas Which are listed in Table 2.

In what follows, each of these areas is discussed in detail, and the bases for the resolution of the differences indicated.

Table 2:

Issues Identified During Audit as Exceptions to the Generic Acceptance Criteria Issue No.

Description Status Resolved Open

1.

Use of acceleration drag volumes which X

differ from those approved in the AC to determine drag on sharp cornered struc tures.

2.

Phasing of load harmonics used to analyze X

structures affected by CO and post-chug loads.

3.

FSI methodology used for CO and chugging X

submerged structure loads.

4.

Use of slightly modified non-exceedence X

probabilities for the computation of multi ple downcomer chugging lateral loads.

5.

Use of calibration factors developed from X

in-plant tests for use in defining SRV submerged structure drag loads.

3.1 Acceleration Drag Volumes for Sharp Cornered Structures The Acceptance Criteria 2.14.2 Section 2b in NUREG-0661 states that drag forces on structures with sharp corners (e.g. rectangles and 1" beams) must be computed by considering forces on an equivalent cylinder diameter Deq=2 1/ 2 Lmax is the maximum transverse dimension.

The intent of this criterion is to provide a conservative bound (based on very limited data) that includes non-classical flow effects such as vortex shedding on both the accel eration drag due to hydrodynamic mass and "standard" drag proportional to velocity squared.

Since the dominant load for the Ring Beam (the primary non-cylindrical structure) is acceleration drag, the issue concerns only the hydrodynamic mass or acceleration volume and not the drag coefficient in the Monticello plant-specific case.

The PUAR states that "published" acceleration drag volumes listed in Table 1-4.1-1 are used for sharp edged structures rather than the equivalent cylinder specified in the acceptance criteria.

The information in Appendix A and additional information supplied in response to the staff's request for information explains that modelling of the actual structure is necessary, and in particular, forces on the flange and the web of the ring beam are both obtained on the basis of the same acceleration volume (8.5 ft3 for Segment 7).

In order to evaluate the implications of this modelling, sample calcula tions were performed on the ring-beam flange and web-forces for the post-chug and SRV loading conditions.

For the sample (Segment 7) In-plane (flange) forces, the PUAR methodology produces loads which exceed by almost a factor of 4 those developed from the application of the hydrodynamic mass coefficient from Table 1.4.1-1 applied to a reasonable model of the flange portion of the structure.

This provides more than adequate margin for the non-classical effects that were the basis for the AC specification.

The out-of-plant (web) forces predicted by the PUAR methodology produce loads that are only 27% of those obtained by a realistic modelling of the structure and interference effects without inclusion of the nonclassical effects.

In response to the staff's RFI the applicant provided information (Refer ence 7) that in the critical load condition the ring-beam loads could be multiplied by a factor of almost 6 without exceeding allowables as long as loads can be combined by SRSS. The acceptability of load summation by SRSS for this case, as proposed by the applicant, is discussed in the FRC report on the structural aspects of the Monticello PUAR. This factor, which includes additional conservatism due to the unrealistically large flange forces, provides adequate margin to bound any non-classical. effects associated with the sharp corners of the structure. The staff, therefore, concludes that the revised application of the PUAR acceleration volume multiplied by the factor above is an acceptable exception to the AC specification.

3.2 CO and Post-Chug Harmonic Phasing The DBA condensation oscillation and the post-chug load definitions on the torus shell and on submerged structures, accepted in the NUREG-0661, were based on data from a series of blowdowns in the FSTF facility (NEDE-24539),

subject to additional confirmatory tests reported in the General Electric Let ter Report M1-LR-81-01 of April 1981.

The condensation oscillation load definition as described in NEDO-21888 is based on taking the absolute sum of 1 Hertz components of a spectrum from 0 to 50 Hz. Three alternative spectra are to be calculated with the one pro ducing maximum response used for load definition.

The procedure was found acceptable in-the supplement to the SER (NUREG-0661),

because the demonstrated high degree of conservatism associated with the direct summation of the Fourier components of the spectrum was sufficient to compensate for any uncertainties concomitant with the data available. The post-chug load definition is based on bounding FSTF chugging data but otherwise follows similar procedures to those used in the CO load definition.

The Monticello PUAR uses a factor of.65 to multiply the CO and post-chug loads on the torus and on submerged structures, computed on the basis of the absolute sum of the harmonic components. The justification is based on compari sons of measured and predicted stresses in the FSTF facility using statistical studies of different phasing models (References 8, 9, 10, 11).

The factor.65 is chosen to give 84% non-exceedance probability with a confidence level of 90%. The PUAR does use an additional spectrum, Alternate 4, for the CO loading, based on test M12 from the supplementary FSTF tests. The information supplied In Appendix A and in Table 1-4.1-4 of the PUAR provides additional justification to show that the computed loads (using the.65 factor and Alternates 1 through

3) bound the measured stresses at critical points in the FSTF facility by 11%

for axial shell stress to 69% for column force.

The use of Alternate 4 in the Monticello plant provides an additional conservatism of at least 10% to the shell response.

The procedure used in the PUAR is a conservative application of the phasing design rules evaluated in Reference 12 and is, therefore, found acceptable.

3.3 FSI Methodology for CO and Chugging Drag Loads A detailed discussion of the method used to account for FSI effects on con densation oscillation and chugging submerged structure loads is provided in Reference 13. The methodology described in this note is used to compute accel eration fields across a submerged structure anywhere in the torus resulting from FSI, based on knowing the torus boundary acceleration.

The method is presented as an alternative to the NRC Acceptance Criteria suggestion of adding the bound ary accelerations directly to the local fluid acceleration to account for FSI effects since the latter is deemed too conservative.

The review of the method outlined in Reference 13 has shown it to be rea sonable and acceptable. The equations derived for fluid accelerations and pres sure fields are plausible approximations for the conditions prevailing in the suppression pool.

Assumed boundary conditions including the driving one at the torus well are suitable. Overall trends as tell as the acceleration fields de picted in the selected results appear reasonable. Therefore, the alternate pro cedure used to account for FSI effects on submerged structures is considered ac ceptable in this application.

3.4 M1ltivent Chugging Downcomer Lateral Loads The multiple downcomer chugging specification given in Table 3.2.2-16 of the PUAR differs from the AC which is based on 10-4 NEP. This issue was addressed in the Fermi TER (Reference 14), and the staff concluded that the slightly reduced loads could be justified on the basis of a re-examination of the statistics of synchronized chugs within the FSTF data base. Similar conclusions can be applied to the Monticello PUAR loads. In response to the staff's RFI (Reference 6) the applicant demonstrated that the critical vent load is determined by 2 downcomers chugging synchronously. For that case, the Monticello value of 10.74 kips/downcomer falls within the AC specification of 10-4 NEP/LOCA.

3.5 Calibration of SRV Drag Loads Based on In-plant Tests The staff requested clarification of the detailed procedures used to derive the calibration factors from in-plant tests for SRV submerged-structure loads.

On the basis of this response, as well as those provided in other PUAR reviews of NUTECH plants, the staff considers the procedures as an acceptable modifica tion of the AC.

The SRV bubble pressure data from Monticello tests is shown to be bounded using a bounding factor of 1.75 instead of the 2.5 specified in the AC. In the Monticello plant, additional calibration factors for certain submerged struc tures were determined on the basis of comparisons of calculated to measured stresses at test conditions.

These factors are then applied to calculated SRV stresses at design conditions.

The staff considers these procedures to be a reasonable application of the In-plant test results, and considers any potential uncertainties associated with the limited data base to be bounded by other conservatisms associated with the design load calculation procedures.

4. CONCLUSIONS A post-implementation pool dynamic load audit of the Monticello PUAR has been completed to verify compliance with the generic acceptance criteria of NUREG-0661. Five major differences between the PUAR and the AC were identified along with some other minor issues needing additional clarification. Based on additional information supplied by the applicant, as detailed in the previous section, all of these issues were resolved.

The review of the Monticello PUAR has been completed with no issues or concerns outstanding.

5. REFERENCES References cited in this report are available as follows:

Those items marked with one asterisk (*) are available in the NRC Public Document Room for inspection; they may be copied for a fee.

Material marked with two asterisks (**) is not publicly available because it contains proprietary information; however, a nonproprietary version is avail able in the NRC Public Document Room for inspection and may be copied for a fee.

Those reference items marked with three asterisks (***) are available for purchase from the NRC/GPO Sales Program, U. S. Nuclear Regulatory Commission, Washington, D. C. 20555, and/or the National Technical Information Service, Springfield, Virginia 22161.

All other material referenced is in the open literature and is available through public technical libraries.

(1) 'Safety Evaluation Report, Mark I Long Term Program, Resolution of Generic Technical Activity A-7", NUREG-0661, July 1980.***

(2) "Mark I Containment Short-Term Program Safety Evaluation Report",

NUREG-0408, December 1977.***

(3) General Electric Company, "Mark I Containment Program Load Definition Re port", General Electric Topical Report NEDO-21888, Revision 2, November 1981.*

(4) Mark I Owners Group, "Mark I Containment Program Structural Acceptance Cri teria Plant-Unique Analysis Applications Guide, Task Number 3.1.3", General Electric Topical Report NEDO-24583, Revision 1, July 1979.*

(5) "Monticello Nuclear Power Generating Plant Plant-Unique Analysis Report",

Vols. 1-5, Prepared for Northern States Power Company by NUTECH Engineers, Inc., Rev. 1, November 1982.**

(6) Attachment to Letter from J. R. Lehner, BNL to F. Eltawila, NRC,

Subject:

-Monticello Request For Information, June 27, 1984.

(7) Attachment to Letter from David Musolf, NSP to Director Office of NRR,

USNRC,

Subject:

Responses to NRC Questions on the Monticello PUAR, September 4, 1984.

(8) General Electric Company, 'Mark I Containment Program, Evaluation of Har monic Phasing for Mark I Torus Shell Condensation.Oscillation Loads",

NEDE-24840, prepared for GE by Structural Mechanics Associates, October 1980.

(9) "Evaluation of FSTF Tests M12 and M11B Condensation Loads and Responses",

SMA12101.04-ROO1D, prepared by Structural Mechanics Associates for General Electric Company, 1982.

(10) R. P. Kennedy, "Response Factors Appropriate for Use with CO Harmonic Re sponse Combination Design Rules," SMA12101.04-RO02D, prepared by Structural Mechanics Associates for General Electric Company, March 1982.

(11)

R. P. Kennedy, "A Statistical Basis for Load Factors Appropriate for Use with CO Harmonic Response Combination Design Rules," SMA 12101.04-RO03D, prepared by Structural Mechanics Associates for General Electric Company, March 1982.

(12) G. Bienkowski, "Review of the Validity of Random Phasing Rules as Applied to CO Torus Loads", Internal BNL Memo, August 1983.

(13) A. J. Bilanin, "Mark I Methodology for FSI Induced Submerged Structure Fluid Acceleration Drag Loads", Continuum Dynamics Tech. Note No. 82-15, June 1982.*

(14) "Technical Evaluation of the Fermi 2 Plant-Unique Analysis Report,"

BNL-0461, Thermal Reactor Safety Division, BNL, September 1982. I