ML19261F241
| ML19261F241 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 06/10/1974 |
| From: | Arnold R METROPOLITAN EDISON CO. |
| To: | |
| References | |
| GQL-0060, GQL-60, NUDOCS 7910250665 | |
| Download: ML19261F241 (5) | |
Text
AEC L 3.I' 7 0'i FOR PART 50 DOCZET MA QT (TDiPORARY FORM)
CONTROL NO:
5293 FILE:A//,
FROM:
DATE OF DOC DAIZ REC'D LTR TWX RPT CTHER Metropolitan Edison Company Reading, Pa.
R. C. Arnold 6-10-74 6-13-74 X
TO:
ORIG CC OTHER SENT AEC PDR XXX Directorate of Licensina 1 signed CLASS JNCIASS PROP INFO INPUT NO CYS REC'D DOCKET NO:
XXX 1
50---289 DESCRIPTION:
ENCLOSURES:
74-5 of 5-31-74 inwhich a pinhole leak in the
$CKNOT gg Ltr furn info re abnormal occurrence #A0 50-289-
"B" makeup pump recirculation line orifice
-DO NOT REMOVE assembly was found......
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Director Directorate of Licensing U. S. Atcmic Energy C e ission p'
Washington, D.C.
20545
Dear Sir:
Operating License DPR-50 Docket #50-259 In eccordance with Technical Specifications for the Three Mile Island Nuclear Station Unit 1, paragraph 6.7.2.a.2, we are reperting the follow-ing abnor=al occurrence:
(1) Report Number: A0 50-289/74-5 (2a) Report Date: June 10, 1974 (2b) Occurrence Date: May 31, 1974 (3) Facility: Three Mile Island Nuclear Generating Statien, Unit 1 (4) Identification of Occurrence:
Title:
Pinhole leak in the "B" make-up pu=p recirculation line orifice assembly Type:
As defined by the Technical Specifications, paragraph 1.Se, in that the pinhole leak in the recirculation line orifice assembly of the "B" make-up pu=p resulted in an abnoz.al degradation cf one of the several boundaries which are designed to contain radioactive materials.
(5) Conditiens Prior to Occurrence: Reactor coolant system heatup in progress, with major plant parameters as follevs:
Power:
Core: O
}h Elec: 0
-Q-e }. 7mn--(Ju 7. Lt n.c gT ; T p tv y
- zoc, Q
3r og T
n
.g oc a
m 6
RC Flow:
104 x 10 #/hr. (3 RC pumps)
RC Pressure:
2150 psig RC Temp.:
430 F PRZR Level:
100" PRZR Temp.:
646 F (6) Description of Occurrence: At 1345 on May 31, 1974, during heatup of the reactor coolant system, an operator on a routine tour dis-covered a pinhole leak to be coming frem the recirculation line orifice assembly of the 1 "B" makeup pump. The 1 "A" makeup pu=p was immediately placed into service, the 1 "3" makeup pu=p secured and the leak isolated by valve closure.
Subsequent investigation revealed that the leak was located in the discharge end pipe portion of the pressure-reducing recirculation orifice, approximately one inch from where the orifice assembly is welded onto the recirculation line. Examinatien of the orifice assembly after its removal from the line revealed severe erosion of the pipe wall for approximately one ane' one-half inches down-stream of the last orifice element and almW ccmplete erosion of the last orifice element.
(7) Designation of Apparent Cause of Occurrence: Component Design, as indicated by subsequent discussions with the orifice vendor, in that erosion is a generic prob 1cm with orifices of this design and appears to be caused by excessively high exit velocities at the last stage of the orifice.
A related personnel problem, which could be censidered to have cen-cributed to the orifice assembly failure, was discovered during the post failure investigation. Due to a similar failure of the same type assembly at ANO-1, an untrasonic testing program was begun at TMI-1 to inspect the four suspect orifices on a bi-weekly basis.
This testing program failed to identify the faulty orifice, however, because testing personnel were not performing their inspections at the correct location. They had been directed to inspect the down-stream side of the suspect orifice assembly, while, in fact, they were inspecting the upstream side. Early idencification of the erosion problem might have made it possible to implement corrective actions prior to the orifice assembly failure.
(8) Analysis of Occurrence: The loss of integrity in the 1"B" make-up pu=p recirculation line orifice asse=bly did not represent a threat to public health or safety for a.
there was no resultant releace of radioactive materials, in that
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1.
there is a check valve installed in the discharge piping from each make-up pump discharge, and in each recircula-tion line, and 2.
there were no radioactive materials in the primary coolant system due to the reactor not having yet achieved initial criticality, and b.
the plant's safeguards system was not adversely affected, in that daring a LOCA 1.
only one of the three injection lines is required to provide core protection, 2.
two other make-up pumps (A & C) were available, and 3
the leaking orifice could have been quickly isolated during accident conditions.
(9) Corrective Action:
Immediate actions were as previously described.
The Plant Operations Review Committee (PCRC) met promptly after the incident and reco= mended to the Station Superintendent that a.
the failed orifice assembly be replaced, b.
the 1 "3" make-up pump then be returned to service, c.
radiograph inspections be conducted on the three similar orifices located elsewhere in the make-up and purification systems, d.
because of its relatively frequent usage, operational restrictions be placed on the 1 "A" make-up pump so that it will be used only on a limited basis, the ultrasonic inspection personnel who failed to properly inspect e.
the suspect orifices be appropriately instructed by supervisory quality assurance personnel, and f.
newly designed orifice assemblies (which are presently being manufactured and are on order) be installed in place of the faulty design asse=blies.
The Station Superintendent has reviewed and concurred with PORC's findings, and all corrective actions have been implemented except for installing the newly desigsed orifices which are not yet available.
(10) Failure Data:
Previous failures of the subject orifice assembly have been a.
noted at ANO - Unit 1.
Also, the radicgraph inspections of the other three assemblies installed elsewhere in t'.e make-up
s 4_
and purification systems indicated extensive erosion on 1 "A" =ake-up pu=p orifice, minor erosion on the letdevn orifice, and no erosion on the 1 "C" =ake-up pump orifice.
b.
The failed orifice asse=bly equipment identification is as follcws:
Manufacturer:
Bingham Pu=p Co.
Portland, Oregon Part Number:
B-26555 Orifice Type:
Seven stage, multiple plate Material:
304 SS Service:
BYPASS Manufacturer Drwg. #: A-44047 Sincerely, A
j_
w -
'R. C. Arnold Vice President - Generation RCA:DNG:eg cc:
Directorate of Regulatory Operations, Region 1 U. S. Atomic Energy Cc= mission 631 Park Avenue King of Prussia, Pennsylvania 194C6 File 20.1.1/7.7 3.5.1
.