ML20044A300

Forwards Update to 890817 Response to Bulletin 88-008,Suppl 3, Thermal Stresses in Piping Connected to Rcs. Unisolable Piping Connected to RCS Identified & Evaluated to Determine Which Piping Could Be Subj to Stratified Flow Phenomena

ML20044A300
Person / Time
Site:	Clinton
Issue date:	06/22/1990
From:	Jamila Perry ILLINOIS POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-88-008, IEB-88-8, JSP-0458-90, JSP-458-90, L30-90(06-22)LP, L30-90(6-22)LP, U-601693, NUDOCS 9006280315
Download: ML20044A300 (6)

Text

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WO (06-22 ) LP CLANTON l' OWE:R STATION. I'.O. DOX 678. CLINTON, ILLINOIS 61727 I h' J. STEPHEN PERRY. Vice President i i

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JSP-0458-90 i June 22, 1990 l

l f Docket No. 50 461 L U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555

Subject:

Clinton Power Station Response to Bulletin 88 08 Suoolege.ng J

Dear Sir:

The purpose of this letter is to provide an update to an August ,

17, 1989, letter (U 601492), which submitted the Illinois Power Company response to Nuclear Regulatory Commission (NRC) Bulletin 88-08 Supplement 3, " Thermal Stresses in Piping Connected to Reactor .

Coolant Systems". Attached are the review results, and a proposed- '

schedule for implementing any required actions.  ;

I hereby affirm that the information in this letter is correct _ t to the best of my knowledge.

Sincerely yours, J. S. Perry Vice President REL/alh Attachment cc: NRC Clinton Licensing Project Manager NRC Resident Office Illinois Department of Nuclear Safety Regional Administrator, Region III, USNRC 900628031"- 900622 //e PDR O

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As documented in Supplement 3 of NRC Bulletin 88 08, a recent event  ;

at a foreign reactor facility raised new concerns on thermal  !

stratification in unisolable piping connected to the Reactor Coolant  !

System (RCS). At this foreign facility, cracks were found in piping I connected to the RCS, The cracks resulted from tbstmal fatigue caused by hot water, which was drawn periodically from the RCS hot i leg, leaking through the packing gland of a Residual Heet Removal I (RHR) valve. The hot fluid flowed on top of the cool flyid in the L pipe and produced a temperature gradient between the top and bottom ,

i of the pipe resulting in thermal stresses on the pipe. The valve leakage and resultant thermal stresses were cyclic due to the thermal  ;

expansion and contraccion of the RHR valve disc.

This event is different than the event documented in the original NRC  ;

. Bulletin 88 08 where thermal stratification resulted from leakage of higher pressure cold water into hot RCS water. The NRC has requested j that the three actions in the original bulletin be addressed for the ,

event documented in Supplement 3. These actions are as follows: .!

A. Action 1 . Review systems connected to the RCS to determine j whether unisolable sections of piping connected to the RCS can be subjected to stresses from temperature stratification or temperature oscillations that could be induced by leaking i valves and that were not evaluated in the design analysis of the piping. For those addressees who determine that there are no unisolable sections of piping that can be subjected to such stresses, no additional actions are required. j B. Action 2 . For any unisolable sections of piping connected to l the RCS that may have been subjected to excessive thermal i

stresses, examine non destructively the welds, heat affected

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zones and high stress locations, including geometric discontinuities, in that piping to provide assurance that there s are no existing flaws.

C.. Action 3 . plan and implement a program to provide continuing assurance that unisolable sections of all piping connected to the RCS will not be subjected to combined cyclic and static i

thermal stresses and other stresses that could cause fatigue ,

! failure during the remaining life of the unit.

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' i k Evaluation for Clinton Power Station Response to Action 1 i

a The effects of stratified flow on Clinton Power Station (CPS) piping  !

systems connected to the RCS were evaluated as required by NRC  ;

Bulletin 88 08, Supplement 3. All unisolable piping connected to the j RCS was identified and evaluated to determine which piping could be h subjected to the stratified flow phenomena. The piping which was .

judged to be susceptible to this phenomena was then grouped into one  !

7 of three categories: 1) process piping. 2) instrumentation piping, )

and 3) vent and drain piping.  !

i The NRC Bulletin addressed leakage through the packing gland on wedge type gate valves. This study was expanded to postulate leakage jo past the seats for wedge type gate valves, stem leakage for globe i L valves and seat leakage for check valves. Leakage past the check valve and gate valve seats was postulated based on Irservice .

Inspection (ISI) and Technical Specification limits fer allowable ,

leakage. Stem leakage for globe valves was postulated baaed on industry experience. .

A summary of the results for each of the three categories is presented below: E

1. Process Piping l

Twelve process piping subsystems were determined to be '

susceptible to stratified flow. These subsystems and $

associated piping line numbers are tabulated below:

• Subsystem No. Pioine Line No.

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ILP 01 ILP02B/C (

ILP 21 ILP26A litP 01 litP02D/E litP 18 IllP23A 1Ril 01 1Ril03CA/DA 1Ril 03 1R1103CB/DB 1Ril 05 1R}{04B/C y 1R11 34 1R1109A/C 3 1Ril-60 1Ril59AA L 1Ril 68 1Ril59AB L 1Ril 76 1Ril49AC

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, Subsystem 1Ril 34 was selected for analysis since it most '

I directly reflected the configuration represented in the Bulletin. Subsystem 1LP 01 was selected and analyzed as a

!; representative sample for subsystems ILP 01, IllP 01, 1Rll 01, 1 :- 1Ril 03 and 1Ril 05.

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Subsystems ILP-21,1HP 18,1RH 60,1RH 68 and IRH 76 are the 3/4 inch equalizing lines for testing of the check valves in subsystems ILP-01, 1HP 01, 1RH 01, 1RH 03 and 1RH 05,

, respectively. These subsystems were not analyzed since it was judged that the results of the analysis for instrumentation lines and for vent and drain lines would be bounding for these ,

lines.

Subsystem 100 07 was not analyzed since its configuration was l not conducive to the cyclical type of stratification to which subsystems 1RH 34, ILP 01, 1HP 01, 1RH 01, 1RH 03 and 1RH 05  :,

may be subjected, The results of the analysis for subsystem 1RH 34 indicate that piping stresses, support loadings and penetration loadings resulting from this phenomena are acceptable. The results of the analysis for subsystem 1LP 01 indicate areas of high stress t and cyclical loadings beyond code allowable limits. Based on the maximum usage factor from the analysis, a conservative '

determination of the fatigue life of the piping system (to satisfy code allowables) with the occurrence of stratification '

is 4 years.

2. Instrumention Piping Seventy five instrumentation lines were judged to be susceptible to stratified floe. Of these lines, INB06BA/BB (piping subsystem INB 07) and INB06CA/CB (1NB 08) were selected v as a representative sample for instrumentation piping systems -

These subsystems were analyzed for two types of thermal stratification: 1) steady state stratification and 2) transient thermal stratification. The results of the analysis indicate that ateady state thermal stratification, characterized by gradual deterioration of the valve packing (greater than one  !

hour), is not detrimental to the integrity of the instrument lines. Transient thermal stratification, characterized by a i sudden failure of the valve packing (less than one minute), can I have an adverse effect on the piping; however, this type of <

stratification is judged to be an unlikely occurrence and therefore of no concern.

3. Vent and Drain Piping Twenty two vent and drain lines were judged to be susceptible ,

to thermal stratification. A typical representation of a vent  ;

and drain line was analyzed. The results of this analysis indicate that thermal stratification may increase the stress level in vent or drain lines; however, the increase is considered negligible and does not warrant further consideration. I l-l l

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,i' Response to Action 2 i

Action 2 ef NRC Bulletin 88 08, Supplement.3 requires that unisolable 6 sections of piping connected to the RCS that may have been' subjected to excessive thermal stresses be exasined. Examination requirements include Non. Destructive Examination of welds, heat affected zones o

and high' stress locations to provide assurance that there are no existing flaws.

) In order to. satisfy. the requirements of Action 2, the following welds a vill be examined during the second refueling outage (RF 2):

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Illinois Power Company Weld

. Subsystem No. _ Weld!No. Identification Isometric p

ILP 01 1 LP 1 10 A 23B 1 LP 1-11* A 23B 3/4" tap ndjacent A 23B i- to 1 LP 1 9 3 1-LP 1 7A A 23A

-1HP 01 1 HP 5 11 A 25A 1 HP 5 10 A 24 1 HP 5 7A A 24 1RH 01- 1 RH 18 4Q1 A 26A 1 RH 18 5Q1 A 26A 1 RH 18 18 A 26A 3/4" cap adjacent. A 26A to 1 RH 18 2 2Q1 1RH 03 1 RH 23 3B A 27A 1 RH 23 5 A 27B 1 RH 23 6 A 27B

, 3/4" tap adjacent A 27B l to 1RH 23 6 3 1RH 05 1 RH 12-19 A 28B 1 RH 12 12 A-280 1 RH 12 13A* A 280

• Denotes weld already scheduled for ISI during RF 2 The welds listed above are those welds for each subsyster that would be a concern if a stratified flow condition existed. It should be noted that those welds listed for subsystem 1LP 01 are based on the results of the thermal stratification analysis performed for that subsystem. The welds listed for the remaining subsystems were identified based on similarities between these subsystems and  !

1 subsystem 1LP 01, Examination of other unisolable process lines, instrumentation lines, vents and drains is not required for the reasons summarized above in Response to Action 1. j i

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Action 3 of NRC Bulletin 88 08 Supplement 3, requires that a program bM o '

be implemented to provide continuing assurance that unisolable

w. sections of piping connected to the RCS will not be subjected to  !

4' thermal stresses that could cause fatigue failure during th_o l remaining life of the unit. The ISI Program will be revised by the .i

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' start of the third refueling outage (RF.3) to' include the. inspection  !

. of susceptible welds once every two refueling outages for each of the. ,

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