ML20012C675

Summary of 900301 Meeting W/Bwr Owners Group MSIV & Leakage Control Committee in Rockville,Md Re Status of Work on Main Steam Line & Condenser Seismic Integrity

ML20012C675
Person / Time
Issue date:	03/12/1990
From:	Trottier E NRC
To:	NRC
References
NUDOCS 9003230042
Download: ML20012C675 (18)

Text

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March 12. 1990 MEETING

SUBJECT:

THIRD MEETING WITH BWROG M51V AND LEAKAGE CONTROL s

SYSTEM COMMITTEE DATE AND TIME: March 1, 1990 08 - 11:30 LOCATION:

One White Flint North 14 B 13 PURPOSE:

Discuss current status of BWROG work on main steam i

line and condenser seismic integrity I.

Background

This is the third meeting on this subject. The first meeting was held on 7 Dec. here in Rockville, and summarized the BWROG program to remove the MSIV LCS from the Tcchnical Specifications. The issues central to the BWROG program are theradiologicalaspects(sourceterm drywell assumptions, steam line plateout condenserholdup,mixingandplateoutl,andtheseismicintegrityofthesteam-lines and condenser (design and seismic experience). -The NRC and BWROG agreed to conduct future meetings on a single topic basis. Accordingly, the second meeting dealt exclusively.with the radiological aspects of MSIV leakage, and was held on January 25, in Rockville. That meeting resulted in the BWROG acknowledging that additional ~ work was required on the technical bases underlying

'their explanation of iodine holdup and plateout, and the mechanics of condenser

mixing, t

Severaldaysafterthesecondmeeting,the(GE)BWROGProjectManagercalled from San Jose' to advise that the GE ABWR group was receiving different radiological assumptions, bases and values from NRC ABWR reviewers, when

-compared to reviewers working with the BWR00.

It was not' clear to him why L

similar BWR containment and steam cycle designs would have such differing review criteria. An internal meeting has been scheduled to resolve, where l

possible, differences between ABWR and BWROG radiological assumptions. Where o

resolution is not possible, technical reasons for differences will be provided E, "m" f by.theresponsiblereviewgroup(s).(Thatinternalmeetingisscheduledat

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08-11:30 in Room 6 B 11 on Thursday, 15 March.)

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II. Meeting Highlights e ma 8E The meeting dealt exclusively with the mechanical integrity of main steam lines l

SW and condenser. The key question to be answered is "Will the main steam lines.

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and main condenser continue to provide a pressure boundary following a site-i specific seismic event?"

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The BWROG consultant on this task, EQE, presented a series of slides (enclosed)

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$ce that summarire their work to date and future plans. The slides generated JO geo-several questions from the staff.

NBC RE CErJIER COPY

Meeting Sumary.

Cor>cerning the 5 BWRs visited, the staff questioned the age spectrum and the design codes used, the architect / engineers employed, and the containment designs. The BWROG agreed to provide a complete and comprehensive breakdown of all relevant variables for the plants visited and plants whose design and constructionrecordsarereviewed(18todate).

The staff was particularly interested in BWROG research into the effects of seismic events on main steam piping and the main condenser. The BWROG stated that their research was comprehensive, and included virtually every nuclear plant and several large fossil plants--both here and abroad--that have under-gone significant seismic events.

In sumary, none has experienced any damage that threatened the pressure integrity of main steam piping or the main condenser.

In the worst case found so far, a valve experienced some damage by striking another structure during the event.

In most cases the only external damage noted was crushed piping insulation.

(ThisissimIlartotheeffectsofplant heatup when piping clearances are insufficient.) Although some condensers experienced minor tube leaks and seme internal damage, in no case was the pressure integrity of main steam piping or the main condenser compromised. The EWROG also noted that although seismic Category I ends at the outer MSIV (or steamshutoffvalve),mainsteampipingisdesignedtowithstandsomeseismic activity.

Further, all large main condensers are desigr.cd to the Unified L

!;uilding Code, which has a seismic requirement.

Other areas of interest to the staff included assurance that the BWROG surveyed the effects of a seismic event on mains steam and condenser branch piping, the effects of damage internal to the condenser, and leakage paths available after a less of vacuum (through stop and control valves'into and through the HP turbine, or upward from Lp sections of the condenser and thru the labyrinth shaftseals).

Neeting adjourned at 11:25 am.

DEllVERABLES:

BWROG--Submit draft final report on seismic aspects and functionality of main steam piping and main condenser in May, 1990, 1

FilTURE MEETINGS

1) Thursday, 15 March 90, 08:00 to 11:30 in 6 B 11. 0WFN.

Internal NRC staff meeting to discuss radiological aspects of ABWR and BWROG submittal reviews.

2) May, 1990--Review and discuss BWROG draft final report on seismic aspects and functionality of main steam piping and main condenser; working level meeting on radiological aspects stentative and in series with seismic meeting).

l Sumary prepared by Ed Trottier, 301-492-1427

Enclosures:

1.

BWROG(EQE)presentationslides l

2.

Attendance list l

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DIsiRIBUTION IMNHs#3 MRC PDR ~ "'

Local PDRs PDI-2 Reading T. Murley J. Snierek i:

J. Partlow S. Varga B. Boger ETrottier C. Haughney

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-E. Jordan B. Grimes A. Thadani F. Congel C. McCracken J. Cunningham L. Marsh J. kudrick J. Lee-D. Scaletti F. Witt C. Greves R. Anand J. Martin P. Kuo S. Hou S. Koscielny C. Nichols W. Butler K. Kniel L. Donate 11 C. Shiraki J. Maretis H. Bramer ACRS(10)

GPA/PA V. Wilson t.. Thomas J. Dyer, MS 17G21

K. Abraham, Region I M. O'Brien T. Green b

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Main Steam isolation Valve Issue a

Current status Survey of BWR plants

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Piping designs and design criteria l

Condenser designs and design standards k

EQE survey of earthquake experience j

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1 Future plane

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TechnicalTasks-Survey a sample of BWR designs for main steam j

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l piping and condensers t

Determ5ne common design and detailing practices

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Survey data base designs with the most similar a

design and detailing practices j

Establish design attributes to ensure good seismic a

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inclusion attributes for similarity Plant-specific installation attributes l

i Plant-specific engineering. comparisons if

. anyneeded Plant-specific evaluation and submittals to NRC by j

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m Piping Design Criteria and Methods a

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Five plant visited' a

Design documents reviewed for thirteen plants

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Main steam piping from MSIV to turbine and a

bypass to condenser is engineered j

Design code is B31.1 l

e Code dates vary from 1955 to 1973 1

Many incorporate Manufacturers

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' Standardization Society (MSS) standards for j

j design of supports-l SP-58 Pipe Hanger and Supports -

i Materials and Design l

LSP ' Pipe Hanger and Supports -

Selection and Application l

Application of B31.1 and MSS documents e

result in a safety factor of 4 to 5 on design '

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Codes and Standards for Other Attributes include:

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Materials-ASTM Allowable stresses - ASME Section VII Division 1 Welding-AWS, ASME Section IX i

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Design loadings-USC i

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bypass flow surges during start-up and

. shutdown Main steam, Bypass, and turbine stop valve e

l designs. reviewed have a range of flexibilities l

Some plants have fully rigid lateral l

support hardware including struts L

and snubbers

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.y support hardware in addition to rigid rods and variable springs Some plants are' detailed with only 1

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1 system, and at:many plants to the leakage j

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Condenser Design Criteria and Methods f

Condensers are large low pressure heat exchangers e

Condensers are designed to operate at pressures ranging l

a from near vacuum (1 to 3 inches HG abs) to 15 psi or l

greater BWR condensers are also designed for turbine bypass flow

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a surges during start-up and shutdown i

Condenser designs are based on various codes and a

standards relating to structural attributes The primary standard for condenser design is Heat t

a Exchanger Institute (HEI) " Standard for Steam Surface t

Condensers" j

HEl specifies hydrostatic shell testing to one foot above u

the condenser exhaust neck expansion joint For condensers greater than 34 feet high, hydrotest levels a

are established on a case-by-case basis Water boxes are hydrotested to 1.5 times design pressure a

l independently from the shell j

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e Condenser Designs' Condenser designs have thick shell and water box plates.

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Large circulating water lines are dcdy.ed with expansion m

joints tolimit loads to the shell Anchorage designs are governed by large uplift forces e

caused by operational vacuum Anchorage typicallyincludes e

A fixed anchor point j

Multiple support pads (4 to 8)

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Support pads all have vertical bolting (1-1/2-to 2-inch diameter bolts)

Anchorage configurations ranged from 16 to 50 bolts j

Some BWR condensers have seismic calculations u

These calculations show seismic loads ar 3 t

smallcompared to operationalloads EGE t

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--Survey is GE BWR Owners' Group on

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. performance of main steam piping and Condensers 1

Survey reviewed EQE data and open literature for

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a 18 earthquakes 29 sites ~

j 96 power plants i

Survey found no precedent for failure of s

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Condenser shell 1

Survey found damage to a

Piping insulation Valve.. operators l Piping supports '

-Condenser tube (Internal) 1 l

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Main Steam isolation Valve issue 1

Future Plans-a Survey of data base sites m

Review of design details for piping and condensers

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Collection of site and s'ructural i

response data j

Detail comparison of data base sites with BWR

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design attributes l

i Development of qualitative and quantitative a

seismic design attributes k

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