ML20085B278
| ML20085B278 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 09/26/1972 |
| From: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20085B259 | List: |
| References | |
| NUDOCS 8307080073 | |
| Download: ML20085B278 (2) | |
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September 26,1J72 Cb
-4 Mr. John F. O' Leary, Director Re: Docket No 50-255 Directorate of Licensing License No DPR-20 US Atomic Energy Commission Washington, DC 20545
Dear Mr. O' Leary:
Our letter of September 8,1972, informed you of difficulties encountered on August 29 and 30, 1972, at the Palisades Plant with four control rod drive mechanisms (CRDM) during trip testing, corrective action taken and additional testing programs implemented to verify clutch operability. During a recent outage, additional work was per-fcmed on the CRIM clutches. This letter is written to inform you of that work and to describe our present CRDM testing program.
During the outage for modification of the main steam safety valve system, all CRDM clutch splines were relubricated. This relubri-cation involved removal of the original baked-on lubricant from the clutch splines by vapor blasting and then recoating the spline and rebaking on molybdenum disulfide lubricant to the original specifications. In addi-tion, a very thin coat of dry molybdenum disulfide powder lubricant was applied (similar to additional lubrication provided following the diffi-culties encountered with the four CRH4s). The relubrication was per-formed because of the previous operating history with the baked-on lubricant. The clutch splines were all refurbished with baked-on lub-ricant during late October 1971. The clutches performed with no failures until early June 1972 (refer to our letter dated June 12,1972).
Following reinstallation of the CRIN clutches, all CRDMs were h c2[
trip-tested eight times. The results of these trip tests were satis-factory. The failures that occurred on June 2 and August 29 and 30,1972, m
were attributed t_o__g_.q11ght breakdown of the lubricant.
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The Palisades Safety Audit and Review Board (SARB) has reviewed
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the relubrication of the clutch splines, the progress on the development of a modification that will provide a more nosithns of separating the clutch halves and the testing program. Based on the relubrication performed and the previous operating history, the Board concluded that a high degree of reliability be ascribed to the CRDMs for a period of operation of about six months. The Board established a new testing j
program, which consists of:
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53?5 T7 B307080073 721120 PDR ADOCK 05000255 S
PDR COPY SENT REGION
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Mr. John F. O' Leary 2
DocPs t No 50-255 e
License No DPR-20 September 26, 1972 1.
Trip test one peripheral CRDM on an alternating basis per day during plant operation.
2.
Trip test all CRIHs prior to returning the plant to service following a cold shutdown.
Again, this solution and testing program is temporary. It will remain in effect until a modification can be developed and tested which provides a more positive means of separating the clutch halves. Based on the progress to date and system requireuents, the tentative schedule for completion of development, testing and installation at the plant is approxi-mately four months.
We will keep both Directorate of Licensing and Directorate of Regulatory Operations representatives informed as to the progress with respect to proposed modifications. These modifications will be reviewed prior to installation at the plant and reported in accordance with the provisions of 10 CFR 50.59 and the Technical Specifications.
Yours very truly, Ralph B. Sewell (Signed)
RBS/ map Ralph B. Sewell Nuclear Licensing Administrator CC: BHGrier, USAEC
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