ML19316A489
| ML19316A489 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/15/1970 |
| From: | Case E US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 7912200743 | |
| Download: ML19316A489 (3) | |
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Peter A. Morris, Director Division of Reactor Licensing DEE POWER CONFANT, OCONEE NUct.xAR STATI5; DOCEET NOS. 50-269,#
50-270 AND 50-287 During the review of the Oconee applications by the Electrical Systems Branch, several items have been noted which do not meet our present day criteria.
These items were discussed at emetings with the appli-cant on April 2 and Usy 1, 1970.*
It appears that further discussion will not resolve the di" agreement between the applicant and DES on two of these items. The items and action recomumended for their resolution are discussed below:
a.
Oper;, tion With Less Than Four Pumps The applicant proposes to operate the Oconee units on only one loop if the two reactor coolant pussps in the other 5. cop are inoperable. In order to provide adequate protection during this mode of operation, the applicant proposes to taanually change several Reactor Protection System trip set points. The appli-cant ves informed that tha use of manual adjustments does not meet our interpretation of Section 4.15 of IEEE 279. The main point of the applicant's argument is that the adjustments are made while the reactor is shut down.
It is our judgment that since single loop operation is a planned mode of operation, the design must provide positive means of assuring that the more restrictive set pointr are used as required by IEEE 279. This is similar to the position taken by DEL on the Palisades, Robinson, and Indian Point No. 2 plants. The fact that single loop operation is preceded by a reactor shutdown does not make the Oconee design significantly different from that originally proposed for the above plants. We reconnend that DEL take the sans position on the Oconee design.
b.
Use of Automatic Transfer Functions In the Auxiliary Power Systes The design of the auxiliary power distribution system includes provisions for the automatic transfer of power to redundant 600 voit buses which supply engineered safety feature loads.
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This feature was not identified during the review of the construc-tion permit applications. Prior to the May 1 meeting, the applicant was requested to identify those loads for which automatic transfer is necessary in order to satisfy safety requirements. The only load so identified is one of the three contairement fan cooler
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units. It is our judgment that the use of an automatic transfer
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scheme unnecessarily reduces the independence of redundant ESF loads. Therefore, we reccesmond that the applicant be required to j
eliminate automatic transfer between redundant ESF buses except where its use is necessary to satisfy safety requirements.
As a result of discussions on the automatic transfer discussed above, a question regarding the design of the emergency power sup-i ply has been raised.
In each Oconee unit, each of the three ESF buses receive power via two common main feeder buses. In the event of an accident coincident with loss of offsite power, one preselec-ted hydro unit will supply power to the main feeder buses of the affected unit. If this hydro unit or its distribution circuit is inoperable, the other hydro unit will supply power to the main
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feeder buses via a different distribution circuit.
Although this design is similar to that proposed for the construction permit, it does not meet present day criteria which require that the ESF loads be separated into two, or more, redundant load groups with
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each group having access to a separate and independent emergency power source. In order to provide a Mais for accepting the pro-i posed design, it is requestad that the question in Enclosure 1 be transmitted to the applicant.
It is expected that the remaining items identified by the Electrical Systems Branch will be resolved by the answers to questions previously transmitted to the applicant and by discussions ce the technical specifications.
%cd :iw y E Q. Case ES3-26 Edsom G. Case, Director DRS:ESS :RDF Division of Rasetor Standards Inclosures:
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EM-15, Mano to Files Dated R. Follard April 16, 1970' 3.
IS3-23, Memo to Files Dated Distribution:
May 12, 1970 Suppl. (3)
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wast 10w To as TEAssxITTrD TO THE APF1.ICMrf We understand that the design of the Station Distribution System is such that each of the three engineered safety feature buses is connected to both of the unit's main feeder buses. We also understand that, when required, all three buses receive power from only one of the emergency power sources at a time. Thus, the redundant engineered safety feature loads are effectively connected in parallel regardless of the power source.
Provide an analysis of your design to show that the independence and reliability of the redundant engineered safety feature loada are comparable to the independence and reliability provided by a split-bus design such as that shown in Figure 1 of the
"?roposed IEEE Criteria for Class IE Electrical Systems For Nuclear Power Generating Stations," dated June, 1969.
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