IR 05000373/1986016

Insp Repts 50-373/86-16 & 50-374/86-24 on 860414-0807.No Violation or Deviation Noted.Major Areas Inspected: Functional Testing of safety-related Snubbers & Evaluation Performed for Test Failures

ML20212N142
Person / Time
Site:	LaSalle
Issue date:	08/22/1986
From:	Danielson D, James Gavula NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML20212N124	List: IR 05000373/1986016 ML20212N121
References
50-373-86-16, 50-374-86-24, NUDOCS 8608280102
Download: ML20212N142 (7)

Text

. .

-

U.S. NUCLEAR REGULATORY COMMISSION REGION III -

.

Reports No: 50-373/8601E(DRS); 50-374/86024(DRS)

Docket Nos: 50-373; 50-374 Licenses No: NPF-11; NPF-18

'

Licensee: Commonwealth Edison Company P. O. Box 767 Chicago, II'linois 60690 Facility Name: LaSalle County Station, Units 1 and 2 Inspection At: LaSalle Site, Marseilles, Illinois Sargent and Lundy Engineers, Chicago, Illinois (S&L)

USNRC Region III, Glen Ellyn, Illinois (RIII)

Inspection Conducted: April 24-25, l'J86, at the Site April 14, May 1, May 16, August 7, 1986, at S&L

'

.

May 7, 1986, at RIII Inspector: . . Gav'ula 8 O Approved By: n Materials and Processes Date 3hfi '

i Section Inspection Summary Inspection on April 14 through August 7,1986 (Reports No. 50-373/86016 (DRS);

No. 50-374/86024 (DRS))

Areas Inspected: Special announced inspection of the functional testing of safety-related snubbers and the evaluations preformed for-test failure Results: No violations or deviations were identifie '

- .

8608280102 860822 PDR O ADOCK 05000373 PDR

.

_ --

. , . .

,

. .

i DETAILS

'

1. Persons Contacted Commonwealth Edison Company (CECO)

+C. M. Allen, Nuclear Licensing Administrator, LaSalle -

+ D. Bishop, Services Superintendent, LaSalle

• +J. T. Fox, Station Nuclear Engineering Department

+D; L. Farrar, Nuclear L1cersing D.irector

+ Massin, Station Nuclear Encineering Department

+ R. Szumski, Technical Staff, LaSalle K. J. Harsing, Director of Quality Assurance Sargent and Lundy (S&L)

.

E. B. Branch, Mechanical Design Director

+G. T. Kitz, Engineering Mechanics Division, Head A. Derrenjian, Engineering Mechanics Division, Assistant Head

• +R. H. Pollock, Project Manager

• H. G. L. McCullough, Senior Quality Assurance. Coordinator

~

*A. Marcos', Quality Assurance Division, Assistant Head

*G. V. Mank, Project Supervisor, MDD J. F. Sidarous, Senior Engineering Specialist

~

R. Mahendranathan,iProject Engineer, EMD

• K. R. Panucci, Project Engineer, EMD '

• G. D. Schmalz, Lead Auditor, QAD 1 W. U. Choudhury, Mechanical Project Engineer

+ A. Gibrael, Supervisor, EMD U.S. NRC

+C. J. Paperiello, Director, 3f vision of Reactor' Safety, RIII

+J. J. Parrison, Chief, Engineering Branch, RIII-

+D. H. Danielson, Chief, Materials and Processes Section, RIII

+J. W. Muffett, Chief, Plant Systems Section, RIII

+ W. Defayette, Project Manager, RIII

, +I. T. Yin, Senior Mechanical Engineer, RIII .

,

+J. A. Gavula, Reactor Insler. tor-Mechanical, RIII

, + Denotes those attending the management meeting at RIII on May 27, 198 * Denotes these attending the exit meeting at Sargent and Lundy (S&L) on August 7, 198 . Snubber Testing and Failure Evaluation An inspection was conducted by the NRC on the functional testing and subsequent failure analyses for the safety-reined snubbers on LaSalle <

County Statien Unit 1. The testing and evaluation requirements performed by the licensee originate from the Plant's Techni, cal Specifications (Tech t

Specs).. As specified under Surveillance Requirements, functional tests

2

'

l

. _ -

-

. .

>

.

shall be performed on a representative sample of snubbers based on an established sampling plan. Furthermore, guidance is given for expanding the size of the sample based the number of snubbers which fail to meet the established acceptance criteria. Also stated in the Tech Specs are the requirements to perform an Engineering Evaluation on compo'nents to which any-inoperable snubber is attached. The purpose of this evaluation

, is to ensure' that the component remains capable of meeting its designed service. The initial portion of this effort was reviewed as documented in NRC Inspection Report No. 50-373/8601 ,

After the initial management meeting on March 17, 1986, between NRC Region III and CECO representatives (see above referenced inspection report), the following chronology of significant eve'its occurred:

March 25, 1986 Sample plan failure rate calls for 100% of all Unit 1. snubbers to be functionally teste April 14, 1936 NRC inspection at S&L offices to review i

preliminary results of transient analyses

on RHR System ,

. . April 24, 1986 NRC inspection at LaSalle site.to review snubber testing procedures and failure mode

,

determinatio April 28, 1986 Conference call between Ceco, NRR and

, Region III to discuss errors found in small

, bore thermal analyse May 1, 1986 NRC inspection at S&L offices to review th:e

,

small bore error proble May 2, 1986 Conference call between CECO, NRR, and ,

Region III to discuss the results of the small bore analysis proble May 16, 1986 NRC Inspection at S&L offices to review the results of the Unit 1 and 2 small bore problem and the evaluations of the

_

transient , snubber failure '

May 27, 1986 Manegement meetings between Region III and CECO representatives to discuss snubber i

testing conclusions and small bore design

> error summar August 7, 1986 NRC Inspection at S&L offices to review

'

the final results of the snubber failure unalyses and small bore design error problem.

,

\

. 3

_ _ _ _ _ . -_- _ ___._ __ _ - _- _n ,,..__~___ _.__ _ _ _ ___

.. __ . __

.

. .

-

2 The overall results of the functicnal testing for the 1235 Unit 1 snubbers indicated a total of 104 snubbers failed to meet the established

'

functional testing acceptance criteria. The probable cause fo'r.each testing failure was assigned to one of the following,four categories: , Installation Deficiencies - Defects which occurred during initial installation or subsequent construction activities. Typical flaws

] include weld spatter or tape residue on the inner support tube, blasting gr$t insice mechanism, twisted internals, bent support cylinder or dented housir.g from an external impact, Environmental Conditions - Defects caused by " normal" operational environment These flaws would include lubricant deterioration from excessive heat or internal corrosion due to excessive moistur Transient or Vibratory Loads - Defects caused by excessive load ,

application or cyclig motion from unanticipated sources. Causes include water hammer ~ events, steady state steam bubble collapse or flow induced vibration. Defects would inc1Lde excessive wear on ball screw shaft, damaged thrust bearings or buckled compression a

rod .

, Manufacturing Defects - Flaws traceable to the initial assembly of

- the snubber. These defects include excessive lubricant inside the mechanism, assembly errors or defective sub-assemblies.

i The distribution of failures relative to the probable causes was as

'

i follows:

i .

(a) Installation Deficiencies: 45 (b) Environmental Conditions: 20 (c) Transient or Vibratory: 29 i

'

(d) Manufacturing Defects: 10 Total 104 In the majority of cases, the criterion exceeded during the functional testing was the maximum drag load. For each excessive drag failure,  ;

an engineering evaluation was performed by S&L. In very few cases, the activation force was outside the established acceptance limit Since these cases did not pose any analytical problems, no evaluations were

,

performe ,

,

i For failures in Categories a, b, and d, the evaluation consisted of reanalyzing each of the associated piping systems with modified restraint

parameters for each failed snubber.' Actual drag loads ,found during

', the functional tests, or rigid constraint assumptions were used during these evaluations. In all but five cases the code stress allowables were met. By utilizing less conservative assumptions, or as-built field -

.

measurements the remaining five cases were brought within code limit '

I I

i I

,

l ,

f

_

-- . . - _ _ . , _ _..; _ , _ _ _ _ _. _ ___ __._ _ ._ _ _ _ _ _ _ _ , __ ._

T -' ,

.

.

. .

For Category c failures, a two part analysis was perfortre s Initially the piping systems were evaluated similar to Category a, b, and d failures using the failed snubber functional parameters for all the original design bacis loads. In most cases, the systems met code -

stress allowables. 'In a limited number of cases where the thermal stresses exceeded allowables, a conservative fatigue evaluation' was performe In these cases utilizing actual thermal cycles since start-up ample stress margin existed to assure that design capabilities were me The follow-up evaluations for Catergory c failures, postulated various _

transient loads for each system and correlated the predicted snubber failures with the actual failures found in the field. In almost every instance a high correlation was obtained between the predicted and .

actual failures. Using the postulated loads and relative magnitudes, the affected systems were evaluated and found to meet Level D >

requirements for Class 2 pipin In addition to the above evaluation a walkdown was performed on the transient failure systems to ensure that no additional damage occurred to other supports or supporting structures associated with the syste Test procedure LST 86-055 "RHR A and B Loop Piping Walkdown .

Unit 1 - First Refuel" was implemented by the station for this purpos Also, as an extra precaution, non-destructive examination (NDE) was perfo,rmed on the most highly stres' sed welds in several system The results of both the walkdown and NDE indicated that no additional damage had occurre As a result of the complications caused by the excessive snubber failures, an effort was made to eliminate the snubbers in environmentally h6 stile

-

locations or other troublesoma areas on a limited basi The implementation of this effoet utilized the NRC staff's authorization to use American Society of Mechanical Engineers (ASME) Code Case N-411. As a prerequisite,

. the staff specified four restrictions'to be applied for the use of this code cas ,

(a) The application of the Code Case shall be limited to piping systems -

analyzed by the response spectrum method onl (b) The alternate damping criteria of the Code Case shall be used in '

their entirety in any given analysis. Mixed application of the Code Case and Regulatory Guide 1.61 is not permitte (c) Due to the increased flexibility of the system, the user shall check '

all recalculated displacements to verify there is adequate clearance between the piping system and adjacent structures, components, and equipment, and to verify the ability of mounted' equipment to withstand the increased motio '

(d) The user shall clearly indicate whether the Code Case will be used for new analyses, for reconciltation work, or for support optin'ization .

'

. _ _

. - - - - . . -_. . , _ _ - . .- .- . . . - -. .- . .. .

-

. .

'

,

.

-

During the NRC inspectors review of the following documentation, associated with the deletion of one of the snubbers, it was observed that the information for the third restriction was not provida .

EMD-037817 Addendum D to Stress Report dated May 30, 1986, Residual Heat Removal Subsystem RH-08 " Documentation of Deletion of Snubber -

RH02-1024S" ECN PFL-245-LS dated May 19, 1986 s The above documents were reviewed and discussed with the S&L project engineer and no documentation was provided for the clearance adequacy with the new displacement information. Since a limited snubber reduction

, was performed and only a small number of snubbers were actually removed, the increase in piping displacements is expected to be small. However, this will be considered an Open Item until such infonnation is supplied

,

(373/86016-01). ,

.

All other documentation rev'ewed by the NRC inspector concerning the snubber failures and evaluations were considered acceptabl . (Closed) Small_ _Bor_e_ De_s_ign Er_r_or, Ev,alua_ tion _ (LER No. 86-024-00)

_

~

During the evaluation of three small bore lines with malfunctioning snubbers, it was inadvertently discovered that a potentially generic design error had occurred in S&L's calucations. This occurrence was documented in CECO's Licensee Event Report (LER) (86-024-00. The calculations

- in question were'for two inch and smaller safety lines that were originally analyzed using hand calculations for' thermal stress evaluations. Based on this information a review of all potentially applicable systems was initiate A total of 196 Small Bore Systems from both units were reviewed which had significant header motion and/or hot design temperatures. -A total of 66 systems were in some fashion outside the original analytical guidelines and required at least some additional simplified analysis to qualify the Of these 68 systems,16 required the use of a computer analysis to qualif In five of these situations, additional field information was required prior to qualification of the system. However, in one system (in addition to the three systems originally discovered) it was determined '

that a field modification was required to bring it within code allcwables. Engineering Change Notices were subsequently issued to remove the pipe restraints necessary to thermally " Free-up" the syste On this same subject, S&L performed the Generic Audit G-240 dated July 23, 1986. The scope of the audit covered all potentially affected units including LaSalle, Byren, Braidwood and Clinto The review included ,

95% of all the calculations involved with this analytical procedur No c.dditional discrepancies were discovered during this audi The above documentation concerning the evaluation and resolution to the problem was reviewed by the NRC inspector. No adverse observations were mad '

'

e

--

,

.. ..

..

- r

, Open Items '

Open' Items are matters which have been discussed with the -licensee, which will be reviewed further by the inspector, and which involves some action on the part of the NRC or Licensee or both. One Open Item disclosed during this inspection is discussed in Paragraph . Exit Interview The NRC inspector met with licensee representatives (denoted in Paragraph 1)

at the conclusion of the inspection. The inspector summarized the scope and findings of the inspection. The ,ir:spector also discussed the likely informational content of the inspection report with regard to documents

reviewed by the inspector during his inspection. The licensee representatives did not identify any such documents as proprietar .

p

.

l J

%

)

e

4

.

%