ML20127N592
| ML20127N592 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 12/08/1969 |
| From: | Vassallo D US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Boyd R US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 9212010318 | |
| Download: ML20127N592 (5) | |
Text
de% A E. d.,
UNITED STATES
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t, ATOMIC ENERGY COMMISSION 1 al p l' WASHINGTON. O C. 20$45 b
8 December 8, 1969 R. S. Boyd, Assistant Director for Reactor Projects, DRL 9[
THRU:
D. R. Muller, Chief, Reactor Project Branch #1, DRL ACCEPTABILITY OF JET PUMPS MONTICELLO NUCLEAR GENERATING PLANT CONTAINING CARBURIZED COMPONENTS In our report to the ACRS (Sections 1.2.3 and 4.4) we concluded that we would accept the jet pumps containing one remaining sub-component having a carburized surf ace with the stipulation that more frequent inservice inspection will be required. The remaining castings which contain the carburized surface are all part of the removable inlet-mixer subessembly, which consists of the 180*
elbow and nozzle castings shown in the attached sketch. For background our writeup in our report to the ACRS is attached.
The benefit of more f requent inservice inspection in this regard was questioned by the ACRS Subcommittee at the Monticello Sub-committee meeting held on November 28, 1969.
Upon further reflection and discussion with RT we believe that the only practical means for inspecting the inlet-mixer assembly is by removing it and then conducting the appropriate inspections.
We had in mind that this inspection should be done following the hot functional reactor test and after the first refueling shutdown, with a lower frequency of inspection thereafter. Although it is difficult to attribute any direct safety significance to cracking or f ailure of the inlet-mixer assembly, it is our judgment that it is not prudent to install components in a nuclear reactor that are known to be substandard. Considering this, and the fact that deficiencies were found in the quality assurance program under which the carburized castings were made, we feel that the castings in question should be replaced with non-carburized castings. In this regard, all carburized jet nump castings for the Dresden 2 and 3 and Millstone plants have been replaced with non-carburized castings.
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R. S. Foyd We believe that the applicant should make a commitment to do this before plant construction is completed. We would like to inform the applicant of this av soon as possible and prior to the ACRS meeting.
W D. B. Vassallo, Project Leader Reactor Project Branch #1 Division of Peactor Licensing Distribution:
Docket File RL Reading RPB-1 Reading D. J. Skovholt S. Levine F. Schroeder T. R. Wilson R. C. DeYoung RP Branch Chiefs CO (2)
D. B. Vassallo C. J. Hale N. M. Blunt
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WRITEUP ON JET' PUMPS PRESENTED IN REPORT-TO ACRS Some of the stainless steel castings in the Monticello jet pump assemtlies were found to be cracked. The principal cause of this cracking has been
'entified by CE as surface carburization.
All of the cracked castings have been replaced; however, some of the castings used still have a highly carburized surf ace.
The transition piece castings now installed were produced by a modified casting process which has been shown to prevent surface carburization.
Inspections performed by GE in accordance with an improved quality assurance program have shown these new castings to oc free of cracks.
The collar castings were repaired by nachining off the as-cast surfaces to the depth (0.10 inch) necessary to assure removal of the carburization. The remaining castings in the jet pump assemblies still have the carburized as-cast surfaces in those areas not machined for other purposes such es veld preparation or to form clamping surfaces. The applicant states that the-low stresses in these castings during normal operation and the fracture toughness of the base material (under the carburized skin) are adequate reasons to have confidence in the ability of these components to function without failure during the life of-the plant.
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The applicant concludes that with _ the corrective measures it has taken, the' jet pump castings are satisfactory for-reactor _use. -Further,-
the applicant states that all castings containing the carburized-condition are part of the removable portion of the jet pump-assembly, and can be replaced if conditions warrant it.
We find, however, that the analyses and ' tests upon which these-conclusions are based appear to be greatly oversimplified. We also find that there were obvious deficiencies in the quality assurance program under which the carburized ~ castings were made. Because of-these deficiencies, the inadequacy of the evaluations performed _and the record of f ailure involving these components, as part of the -
Technical Specifications we will require additional inservice inspection of all castings manufactured.
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Note: Cross-hatching denotes remaining carburized casting.
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