ML20205E440
| ML20205E440 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 10/21/1988 |
| From: | Hukill H GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| C311-88-2145, IEB-88-008, IEB-88-8, NUDOCS 8810270388 | |
| Download: ML20205E440 (5) | |
Text
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GPU Nuclear Corporation r U Nuclear
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M,ddletown, Pennsylvania 17057 717 944 7621 TELEX 84 2386 Writer's Direct Dial Number:
October 21, 1988 C311-88-2145 U.
S.
Nuclear Regulatory Commission Attn:
Document Control Desk Washington, DC 20555
Dear Sir:
Three Mile Island Nuclear Station, Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 GPUN Response to NRC Bulletin 88-08, "Thermal Stresses in Piping Connected to Reactor Coolant Systems" NRC bulletin 88-08, entitled "Thermal Stresses in Piping Connected to Reactor Coolant Systems" was issued as a result of a leak in an unisolable section of the Emergency Core Cooling System (ECCS) piping at Farley-2.
The leak was caused by high cycle thermal fatigue due to relatively cold water leaking through a closed globe valve at a pressure sufficient to open the check valvo connected to the Reactor Coolant System (RCS) cold leg.
Attached is GPUN's response to NRC Bulletin 88-08 (including Supplements 1 and 2).
This response documents the completion of Action Items 1 and 2 for TMI-1 and provides a schedule for the completion of Action Item 3.
TMI-1 was in its Cycle 7 Refueling (7R) Outage when NRC Dulletin 88-08 was roccived.
The 7R Outage was of short duration (60 days).
In accordance with Action 4 of tbc bulletin, Actions 2 and 3 are not required to be completed before the end of 3R.
HowcVer during the 7R outage we were able to completc the nondestructive examinations (NDB) in response to Action 2.
The results of these examinations (attached) provide assurance that there are no existing flaws in the HPI piping evaluated under this Bulletin.
.T.n accordance with the reporting requirements of the bulletin, a responso is requested within 30 days of completing Action 3.
We are currently evaluating the Makeup and P4trification System -
High Pressure Iniccrion (HPI) piping for pnr.cntislly being es102703ee 831021 PDR ADOCK 0500' 69 p
Gr U Nuclear Corporation is a subsidiary of the General Pubhc Utihties Corporaben
e C311-88-2145 October 21, 1988 subjected to unanticipated cyclic thermal stresses sufficient to cause fatigue failure.
This evaluation is scheduled for completion in June, 1989 and the results will be reportad to NRC by July, 1989.
Sincorcly, b
H. D. Hu.ill Vice President and Director, TMI-1 1.ttachment HDH/MRK cc:
J. Stolz R. Hernan R. Conto W.
Russell swornandsubscribedgo all before me th s/ %
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C311-88-2145 GPUN Response to NRC Bulletin 88-08 "Thermal Stresses in Piping Connected to Reactor Coolant Systems" Action 1:
,vw the systems connected to the RCS to determine 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 valves and that were not evaluated in the design analysis of the piping.
GPUN Response to Action 1:
The systems connected to the RCS were reviewed for applicability to this bulletin.
These systems are described below:
A. Makeup and Purification System This system, which includes the High Pressure Injection (HPI) System, has a configuration similar to the system described in NRC Bulletin 88-08.
There are unisolable sections of piping connected to the RCS which could be impacted by potential globe valve leakage from upstream since the pressure at the inlet of the valvo exceeds RCS i
pressure.
This system is evaluated as described in i
respense to Item 2 below.
B. Decay Heat. Removal (DHR) System This sysh.in is connected to the RCS, however the pressure on the decay heat removal side of the closed valves (DH-V1, 2, 3, and 4) la much lower than the RCS pressure and cold water flow to the RCS nozzle is not possible.
Thereforo, this bulletin does not apply to the DHR System.
C. Coro Flood Gystem This system is connected to the RCS, however the pressure in the core flood tank is 600 125 psig, which is lower than RCS pressure, 2155 psig.
Leakage cannot flow to the RCS from the core flood tanks through the valves, CF-V1A/B during normal operation.
Thorofore, this bulletin does not apply to the Core Flood Systein.
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C311-88-2145 Action 2.
For any unisolable sections of piping connected to the RCS that may have been subjected to excessive thermal stresses, examine nondestructively the welds, heat-affected zones and high stress locations, including geometric discontinuitics, in that piping to provido assurance that there are no existing flaws.
GPUN Response to Action 2:
There are two welds in the HPI piping betwoon the check valve and the RCS piping.
These welds are betwcon safe end to RCS nozzle and safe end to check valve.
The distance betwoon the welds is approximately 5 and 5/16".
The RCS piping material is composed of carbon stcol clad with austenitic stain 1 css steel.
The safe end is inconel and the HPI piping is stainless stccl.
All 8 wolds for the 4 HPI nozzles were examined nondestructively during the cycle 7 refueling (7R) outage (6/17/88 through 8/16/88) by ultrasonic tests (UT) and ponctrant tests (PT).
The base metal along with the thermal sleeve was observed using radiographic tests (RT).
UT of the 4 safe end to valve welds was performed on a best effort basis because of the valve and safe end configurations.
UT was the chosen nondestructive examination (NDE) method in this area because of its higher capability for thermal fatigue type flaw detection.
These wolds were inspected utilizing GPIIN's UT procedures which were specifically developed for the detcotion of intergranular stress corrosion cracking (IGSCC).
This proceduro exceeds the standard ASME Code requirements for UT.
Personnel who performed these inspections had passed the Electric Power Research Institute (EPRI) training on detection of IGSCC.
For the four valve to safe end wolds, the transducer angle was limited by geometry to allow only a 45' transducer beam angle for those inspections.
For the four safe end to nozzle welds, a 60* beam angle would have been possible but it was not considered to be necessary as determined by the results that were obtained using the 45* angle.
The other practicos l!.sted as 1, 3, and 4 in supplement 2 of NRC Bulletin 88-08 were followed.
No indications were observed from the UT and RT techniques.
The PT examination revealed 3 indications on the safe end to check valve wcld on the "C" Reactor Coolant Pump HPI line.
These indications, located on the outsido diameter at the valve sido of the wold, were removed by grinding.
In cach caso after grinding, the minimum wall thickness requirements were satisfied without the need for wcld buildup.
A2
s C311-88-2145 The.results of these examinations provide assurance that there are no
-existing flaws in the HPI piping evaluated under this Bulletin.
The three indications which were found on the outside. diameter of the safe f
end to check valve weld were not the result of thermal fatigue since thermal fatigue would have resulted in inside diameter indications.
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