ML18136A439
| ML18136A439 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 01/24/1980 |
| From: | Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| 042, 42, NUDOCS 8001290287 | |
| Download: ML18136A439 (5) | |
Text
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I VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND,VIHGINIA 23261 January 24, 1980 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation Attn:
Mr. Darrel G. Eisenhut, Acting Director, Division of Operating Reactors U.S. Nuclear Regulatory Connnission Washington, D, C.
20555
Dear Mr. Denton:
Serial Number 042 PO/HEC/sjl Docket Numbers 50-280 50-281 License Numbers DPR-32 DPR-37 In our letter of May 9, 1977 (Serial Number 045/020177), we provide~
information describing a modification to the containment spray system required to update the system based on new meteorological data and to comply with the latest NRC requirements concerning site boundary dose.
This letter is to update information previously provided and to describe system changes to the containment spray system design since our last correspondence.
The information supplied here does not affect the intent of the modification to provide a containment spray system which will meet the limits of 10 CFR part 100 for site boundary dose.
The modified containment spray system, as originally proposed, included an eductor system for caustic addition to the containment spray.
In June of 1979, we were informed by our architect-engineer of potential computer modeling problems with the eductor system.
Specifically, eductor performance could not be modeled with sufficient certainty to ensure the appropriate range of spray pH throughout the duration of containment spray.
This problem was discovered by the architect-engineer during the computer modeling and analysis of a similar eductor system for another utility. Based on this information, we directed the architect-engineer to reevaluate the use of the eductor system and, if necessary to propose alternate systems for caustic addition.
As a result of this evaluation, two (2) alternate methods of caustic addition were pursued. The first alternative was a system utilizing positive displacement pumps to inject caustic into the containment spray pump suction lines to provide a constant rate of caustic addition.
The second alternative consisted of a gravity feed design which would intro-duce caustic directly into the spray pump suction line.
Each of these f
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e VIRGINIA ELECTRIC AND POWER COMPANY TO Mr. Harold R. Denton 2
alternatives was evaluated for its relative ability to assure adequate spray pH.
Other considerations were system complexity, availability of required safety related components, and construction time constraints.
Based on the above considerations, the gravity feed design was chosen as the best system for caustic addition.
A summary of the containment spray system modifications follows.
The caustic addition line changes discussed above are detailed in paragraph 2.
DESCRIPTION The containment spray (CS) system design change incorporates several modifications to increase the system iodine removal capability.
Drawing 11448-FKS-6, attached, is a flow diagram which indicates the extent of piping modifications. All new piping is designed and installed in accordance with the recent pipe stress reanalysis.
- 1.
CS System Spray Header Modifications An additional CS ring header is installed at elevation 95 ft. 6 in.
outside the crane wall.
The original CS pumps discharge in parallel to the new ring header via the original riser pipes.
Check valves are installed in each branch connection from the riser to the new ring header to limit system fill time, should one CS pump train fail to start.
New nozzles installed in the new common header are designed to balance flows with the original redundant ring headers to accommodate the different CS header elevations and CS pump combinations.
The new ring header is supported from the crane wall.
The spray nozzles on the original ring headers have been replaced with nozzles of a different design.
The new spray nozzles are fabricated of stainless steel and provide sufficient spray coverage and drop size distribution with the new system head flow character-istics.
The modifications to the spray headers increase the sprayed volume of the containment to 73 percent by creating a spray curtain in the containment annulus area and by increasing the cross-sectional area directly sprayed at the operating floor elevation 47 ft. 4 in.
The sprayed volume was determined considering the most severe single active failure.
- 2.
Caustic Addition Piping Modifications The Chemical Addition Tank (CAT) outlet line is rerouted directly to the CS pump suction located in the safeguards area instead of a mixing area in the Refueling Water Storage Tank (RWST).
The existing CAT outlet valves (MOV-CS-102A and B) are relocated adjacent to the
e VrnoINIA ELECTRIC AND PowER CoMPANY To Mr. Harold R. Denton 3
CS pumps where the caustic is directed to the suction line of the CS pumps.
The CAT circulating pump piping is also routed to the safeguards area and taps into the CAT outlet line to permit periodic circulation of the water in the tank and associated caustic addition piping.
The new arrangement of the chemical addition system piping provides a rapid feed of sodium hydroxide to the spray pumps and decreases the overall caustic spray delay time.
The rearrangement of the chemical addition piping and components is shown on Sketch 11448-FKS-6.
Restriction orifices in the caustic addition lines maintain the spray pH at 8.5 to 11.0 and ensure an ultimate sump pH of greater than 7.0.
Should one CS pump fail to run, its respective pair of chemical addition trip valves, MOV-CS-103A and C or MOV-CS-103B and D would be automatically activated to the closed position by pump discharge pressure sensing devices.
- 3.
RWST and Miscellaneous Piping Modifications The RWST mixing weir has been removed making the water outside the weir available for containment spray; thereby extending spray duration.
This water was originally designed to be used for the low head safety injection pump seal system after an accident.
The LHSI pump seal system has been modified to utilize a closed loop accumulator system similar to that presently installed for the outside recirculation spray pump seal system.
- 4.
Safety Injection, RWST, and Containment Spray System Instrumentation Modifications The RWST level instrumentation and Safety Injection (SI) system control circuits are modified to provide three methods for transferring SI from the RWST mode to the recirculation mode:
automatic at 161 inches RWST level, manual, and individual valve alignment.
The automatic transfer feature is employed during operation to ensure that sufficient water is available to operate the CS system for the duration of the LOCA containment pressure transient considering all combinations of SI and CS pump operation.
Four head sensing type level transmitters powered by four independent vital bus power supplies are installed on the RWST replacing the existing two level transmitters. Transmitters and piping are enclosed in heated, weatherproof enclosures.
Antifreeze protectio.n is also provided in each instrument enclosure.
Level indication is provided in the control room from each of these channels.
The automatic switchover referenced above is initiated by a two of four logic matrix from the new level instrumentation.
System modifications as described above are presently being implemented during the steam generator replacement outage of Surry Unit No. 2 and are scheduled for completion by February 19, 1980. Accordingly, we
VrnmNIA ELECTRIC AND PowEH CoMPANY To Mr. Harold R. Denton request that a meeting be held at your earliest convenience to discuss the new system design and to answer any questions you may*have.
Very truly yours,
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C. M. Stallings Vice President 4
Power Supply and Production Operations cc:
Mr. James P. O'Reilly, Director Office of Inspection and Enforcement Region II
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