ML20059A060
| ML20059A060 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 09/30/1993 |
| From: | Rosenblum R SOUTHERN CALIFORNIA EDISON CO. |
| To: | Faulkenberry B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| NUDOCS 9310260209 | |
| Download: ML20059A060 (4) | |
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,p a-Southem Califomia Edison Company 23 PARKER STREET 4RVINE, CAllroRNIA 92718 MlCHARD M. RoSENBLUM TELE PHONE September 30, 1993 Mr.
B. H. Faulkenberry Regional Administrator U.
S.
Nuclear Regulatory Commission, Region V
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1450 Maria Lane, suite 210 g
Walnut Creek, California 94596-5368
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_:J3 1 Dear Mr. Faulkenberryt W
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Subject:
Docket Nos. 50-361 and 50-362 M
Preoutage Work-shutdown Cooling System o
San Onofre Nuclear Generating Station, Units 2 and 3 Q
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The purpose of this letter is to discuss the basis for performing pre-O outage work on the Shutdown Cooling System (SDC) at SONGS Unit 3.
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amount of pre-outage work presently being done on Unit 3 is greater, in my opinion, than that which has historically been done on SONGS 2 and 3.
The work is being done in this instance because we believe that, carefully
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controlled, the overall level of plant safety can be enhanced and the exposure to plant workers reduced by performing appropriate aspects of a shutdown cooling system (SDC) design change with the plant on-line.
SCE is carefully contrclling the work which is being performed with the plant on-line and believes that an appropriate level of operational safety is being maintained.
.j P_urpose of the Desian Chance l-The design change now being implemented provides a cross-tie between the j
low pressure safety injection (LPSI) and containment spray (CS) systems.
This change provides greater flexibility to respond to post-accident equipment failures, doubles the number of available pumps for shutdown cooling, and similarly increases the number of pumps available for spent r
fuel pool cooling. We have determined that this design change will result in an an increase in both on-line and shut-down plant safety. We intend to utilize features of this design change during the upcoming Unit 3 Cycle 7
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Refueling Outage.
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PDR ADOCK 05000361 D
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B. H. Faulkenberry 2
Schedulina of the Work Since the design change had safety benefits as well as outage improvement benefits, once the decision had been made to implement the change, the-remaining question was when to do the work, such that the minimum plant risk would result. Completing portions of this design change prior to the refueling outage was viewed as the most prudent course of action since-performing the work in this manner had the following three advantages:
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ALARA - Radiation levels in the Safety Equipment Building (SEB) are higher during SDC operating periods than during plant operations. Since this work involves long piping runs in areas which will have higher radiation levels during shutdown. cooling operations, it was considered prudent to complete as much of the modification prior to shutdown cooling being placed in service to maintain dose ALARA.
Our evaluation indicates a 38% (8.9 person Rem for each unit) reduction in dose for this job due to performing the work pre-outage.
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WORK LOADING - Since other work activities are scheduled to be performed in these areas during the outage, (including MOVATS testing and a design change to LPSI pumps) performing portions of the cross-tie change beforehand minimized the+ number of work _
- 1 activities and groupu in the SE3 resulting in a higher level of
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overall safety while maintaining an outage of reasonable length.
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SHUTDOWN SAFETY - Although performing the work in'the SEB does pose some potential risk to standby safety equipment, we believe that this risk is minimal due to the. stringent construction j
safety controls in place. Additionally, the risk is less than
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that which would result were the change implemented during a
periods when the LPSI system was depended upon to provide the only source of core cooling.
I construction Safety I
Through the use of safe work practices, training, and procedural control, SCE is ensuring safe construction activities durf,i normal plant operations, with minimal risk to safety relat-u
,sonents.
Each work r
'ity is controlled by a construction Wori ehich has been reviewed r
a.m approved by Nuclear Construction, Quality <
N and Equipment control. Critical Component checkers and dedica,.
supervision are being utilized to assure that ongoing construction act.
es do not compromise
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plant safety.
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mu Mr.
B. H.
Faulkenberry 3
i A Construction Safety Evaluation (CSE), hac been prepared to provide
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specific guidance on precautions necessary to avoid damage to any permanent plant equipment, emphasizing safety rslated equipment, in the proximity of construction work.
Additionally, engineering has evaluated and provided calculations to support the use of temporary rigging methods necessary during the construction process.
Procedure Sol 23-I-1.13 provides lifting and rigging controls for significant loads.
I SCE's Nuclear Construction group provides constant oversight and assessment of the construction activities. This experienced core group is made up of personnel very familiar with SONGS procedures and practices.
For further conservatism, the Nuclear Oversight Organization is performing oversight of the construction activities on a heightened basis.
Review of Construction Safety Issues Based upon your concerns regarding the level of effort involved while the plant is in operation, we have conducted a re-review of our constru 'lon practices for this activity and, with one exception, continue to find them to be conservative and appropriate for the work activity.
Specifically, we have determined that our work practices did not consider design basis flooding.
For example, a rupture of a circulating water expansion joint at the main condenser inlet, with the then allowed combinations of water tight doors open and floor plugs removed, loss of safety equipment was postulated to occur if no action were taken in 10 minutes to turn off the circulating water pump. Based upon training and our experience in actual minor turbine building flooding events, Edison is confident that control room operators would turn off the pumps prior to actual loss of safety equipment.
When this deficiency was identified, we l'
'ed a special review by our Nuclear Engineering Design Organization.
1 this review, we have placed administrative restrictions on certain ors and floor plugs. We are completing our engineering assessment and examining our construction and maintenance activity review process. Our assessment will be the subject of a Licensee Event Report.
Conclusi4D The W;oing construction activities and associated risks have been carehdiy evaluated and Edison believes that the current course of action provides an adequate level of operational safety and is most appropriate-considering all relevant factors.
Mr. Harold Ray, our Senior Vice President, Mr.
J. T. Reilly, Manager of Nuclear Engineering and
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Mr. B. H.
Faulkenberry 4
Construction, and I have personally walked down the SEB and the current work in progress to assure ourselves that the ongoing work is appropriate and being performed with a high level of operational safety.
Should you have any questions, please contact me.
.i Sincerely,
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i cca NRC Document Control Desk M.
B. Fields, NRC Project Manager, San Onofre Units 2 and 3 Howard J. Wong, Region V NRC Resident Inspector Office, San Onofre Units 1, 2 and 3 r
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