ML19332D609
| ML19332D609 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 11/29/1989 |
| From: | Richter M COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-008, IEB-88-8, NUDOCS 8912050020 | |
| Download: ML19332D609 (3) | |
Text
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) CommonweaNh Edloon JN #*
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",bX3dressEspTito: Post OIIEe BisI76T s
' 72 West Adams Street, Chicapo. Ilknots e
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\\N/ Chicago Encis 00690 0767.
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November 29, 1989 ye j.
U.S. Nuclear Regulatory Commission Attn: Document Control' Desk Hashington, D.C.
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Subject:
Byron Station Units 1 and 2 Braidwood Station Units 1 and 2 Supplemental Response to NRC Bulletin 88-08, Supplement 3 HRC Docket Nos. 50-414LiS1_And_10-456L452
Reference:
(a)' NRC Bulletin 88-08, Supplement 3, dated April 11, 1989.
(b)
M. Richter letter to U.S. NRC, W
dated July 17, 1989.
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Dear Sir:
Reference (a) described an event at a foreign reactor facility (Lenkai) which raised new concerns on thermal stratification in unisolable piping connected to the Reactor Coolant System (RCS).
The event in Reference (a) occurred due to a valve leakage phenomenon which was not previously considered in NRC Bulletin 88-08 (or Supplements I and 2).
Reference (a) requested that the Actions in NRC Bulletin 88-08 (Bullettn) be addressed.
As reported in Reference (b), Commonwealth Edison (Edison) identified two (2) lines (associeted with the Residual Heat Removal System) per unit at Byron and Braidwood Stations which may be susceptible to cyclic stratification due-to the yk1ve leakage phenomenon described in Reference (a).
To address Bullettn Actions 2 and 3 for Byron and Braidwood Stations, Edison indicated that an evaluation was-being performed which would supply the critical locations on the susceptible piping for inspection purposes, and the frequency of future inspections to ensure piping integrity.
This letter provides the results of the evaluation for Byron and Braidwood Stations for Bulletin Action 3.
Additionally, this letter provides the results of the examinations performed on the susceptible piping for Braidwood Unit 1 during its Fall 1989 refueling outage (Bulletin Action 2).
8912050020 891129 PDR ADOCK 05000454 N4 o
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'R l To address Bulletin Action 3, a detailed evaluation of the i
susceptible lines (suction lines to the Residual Heat Removal (RHR) pumps from i
the RCS hot legs) for Byron and Braldwood Units 1 and 2 has been completed.
i Although these lines are susceptible to the cycIlc valve leakage and resultant stresses, there are geometrical differences in the RHR suction piping, between Byron /Braidwood and Genkal, which provides assurance that cracking of the lines is unlikely.
However, to provide continuing assurance of RHR suction line integrity, the cyclic stratification transient for the Gankal event was postulated and analyzed for Byron and Braidwood Stations, j
r An analytical model of the leakage flow conditions associated with the transient which occurred at Genkai was developed for the configuration of the RHR suction lines at Byron and Braidwood Stations.
From this model, i
temperature profiles (and critical locations) for the lines were identified.
Using these temperature profiles and postulating leakage frequencies, stress, fatigue and fatigue crack growth analyses were performed.
The results of the analyses show that it would take a minimum of four (4) years for a crack to propagate to an unacceptable size, assuming valve leakage were to occur.
Therefore, if no indications are identified during the ultrasonic examinations (enhanced technique) for Bulletin Action 2 and the postulated transient was occurring, the structural integrity of the RHR suction lines would be maintained for at least two (2) fuel cycles.
i As indicated in Reference (b), Byron and Braidwood Stations will be performing non-destructive examinations on the susceptible RHR suction lines (at the critical locations) during the following refueling outages:
January 1990,
- Byron Unit 1
- Byron Unit 2 September 1990 September 1989 (reported in this letter).
- Braidwood Unit 1
- Braidwood Unit 2 March 1990.
Additionally, Byron and Braidwood Stations will adopt a long-term inspection program to ensure the integrity of the RHR suction lines.
The Inservice Inspection (ISI) Program at each station will be revised to include the inspection of these lines (at the critical locations) at a frequency of every other refueling outage. The analyses performed, coupled with the commitment to a long-term inspection program, provides the continued assurance of RHR suction line lategrity and fulfills Bulletin Action 3 for Byron and Braldwood j
Stations.
During the Fall 1989 refueling outage for Braidwood Unit 1 non-destructive examinations were performed on four (4) welds which were identified by the. evaluation as critical locations.
The welds examined were IRC-11-7, IRC-11-8 and IRC-11-9 on line IRC04AB (suction line to RHR Pump 1B from Loop 3 Hot Leg), and weld 151-02-43 on line IRC04AA (suction line to RHR Pump 1A from Loop 1 Hot Leg).
The examinations on the welds and associated i
heat affected zones were performed utilizing enhanced ultrasonic techniques which ensure increased sensitivity for the detection of cracks.
The results of these examinations for Braidwood Unit 1 revealed that there were no indications found.
The inspections performed fulfills Bulletin Action 2 for Braidwood Unit 1.
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r Please direct any questions that you may have on this response to l
this office.
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Respectfully, l
hN1 M.H. Richter J
Generic Issues Administrator i
t 0365k cc:
A.B. Davis - Regional Administrator, Region III Resident Inspector BY/BH t
L. 01shan - Byron Station Project Manager i
S. Sands - Braidwood Station Project Manager i
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-Subscribed and SwPrg to.
befo me.th d 4 C d y r
3 89 1E Notary Public/-
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