ML20116B046
| ML20116B046 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 07/25/1996 |
| From: | Sellman M ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20116B049 | List: |
| References | |
| W3F1-96-0115, W3F1-96-115, NUDOCS 9607290079 | |
| Download: ML20116B046 (13) | |
Text
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ggy Entergy Operations. inc.
,v K:llona LA 700ff>-0751 Td 504 739 tMO
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Mike Sellman Pres on: Opeatens W3F1-96-0115 A4.05 PR l
July 25,1996 U.S. Nuclear Regulatory Commission j
Attn: Document Control Desk Washington, D.C. 20555
Subject:
Waterford 3 SES l
Docket No. 50-382 License No. NPF-38 Technical Specification Change Request NPF-38-180 Gentlemen:
l The attached description and safety analysis support a change to the Waterford 3 Technical Specifications (TSs). The proposed change modifies TS 3/4.7.4 Ultimate Heat Sink by incorporating more restrictive fan operability requirements and lower basin temperature. Several other administrative changes are incorporated to improve the human factors associated with this TS. The Waterford 3 corrective action program determined that system fouling had not been adequately addressed and analyzed within the thermal design performance calculations for the Ultimate Heat Sink (UHS). This proposed change seeks to modify the TS consistent with revised design basis calculations.
The proposed change has been evaluated in accordance with 10CFR50.91(a)(1) using criteria in 10CFR50.92(c) and it has been determined that this change does not involve a significant hazard. The bases for that determination is included in the attached submittal.
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e Technical Specification Change Request NPF-38-180 W3F1-96-0115 Page 2 July 25,1996 Waterford 3 requests that the implementation date for this change be within 60 days of NRC issuance of the amendment to allow for distribution and procedure I
revisions necessary to implement this change. Although this request is neither exigent nor emergency, your prompt review is requested.
Should you have any questions or comments concerning this request, please contact Mr. James Fisicaro at (504)739-6242.
Very truly yours,
.A vs M.B. Sellman Vice President, Operations Waterford 3 MBS/PLC/ssf
Attachment:
Affidavit NPF-38-180 cc:
L.J. Callan, NRC Region IV C.P. Patel, NRC-NRR R.B. McGehee N.S. Reynolds NRC Resident inspectors Office Administrator Radiation Protection Division (State of Louisiana)
American Nuclear Insurers
e JNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the matter of
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Entergy Operations, Incorporated
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Docket No. 50-382 Waterford 3 Steam Electric Station
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M.B. Sellman, being duly sworn, hereby deposes and says that he is Vice President Operations - Waterford 3 of Entergy Operations, incorporated; that he is duty authorized to sign and file with the Nuclear Regulatory Commission the attached Technical Specification Change Request NPF-38-180; that he is familiar with the content thereof; and that the matters set forth therein are true i
j and correct to the best of his knowledge, information and belief.
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4 M.B. Sellman Vice President Operations - Waterford 3 STATE OF LOUISIANA
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) ss PARISH OF ST. CHARLES
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Subscribed and sworn to before me, a Notary Public in and for the Parish and State above named this 28" day of JwT
,1996.
$ ew Notary Public My Commission expires W "" C
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DESCRIPTION AND SAFETY ANALYSIS j
OF PROPOSED CHANGE NPF-38-180 This proposed change modifies Technical Specification (TS) 3/4.7.4 Ultimate Heat Sink, to be consistent with revised design basis calculations that account
- for system fouling, and improve the human factors associated with the text and layout of this specification. Specific changes are as follows:
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Title 3/4.7.4 - added UHS acronym.
LCO 3.7.4 - revised to remove information provided in the BASES'.
l ACTION a. - revised to remove aspects addressed in the LCO.
1 ACTION b. - revised consistent with ACTION a.
. ACTION c. - oeleted and replaced with previous ACTION e.
ACTION d. - deleted and replaced with previous ACTION f.
i ACTION e. - changed to ACTION c and added increased fan operability.
ACTION f. - changed to ACTION d and modified to be consistent with revised i
Table 3.7-3.
4.7.4 - added UHS and removed " ultimate heat sink".
l 4.7.4.a - added "specified" and removed "their".
Table 3.7-3, - replaced the previous table to address new fan operability l
requirements and separate the WCT fan requirements from the DCT fan requirements.
i The associated UHS TS BASES has been revised to be consistent with the proposed change.
Existina Specification l
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See Attachment A l
Proposed Specification
- See Attachment B Description This amendment request contains two major changes; both concern system thormal performance and the associated impact on the ultimate heat sink (UHS).
These two major changes are,1) the proposed 89 F basin temperature, and 2) the modified fan operability requirements of Table 3.7-3. Other modifications to
- the UHS TS in this proposed change are administrative in nature.
The function of the UHS is to dissipate the heat removed from the reactor and its auxiliaries during normal unit operation, during refueling, or after a design basis accident.
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The UHS consists of two forced draft dry cooling towers (DCTs), two mechanical draft wet cooling towers (WCTs), and water stored in the WCT basins. Each of the two 100 percent capacity loops employs a dry and wet cooling tower. The dry towers are the primary heat sink for the Component Cooling Water System (CCWS) during normal operation and each DCT has been sized to dissipate to the atmosphere approximately 60% of heat removed by the CCWS after a Loss of Cooling Accident ( LOCA) assuming the worst case UHS meteorological condition (102 F dry bulb and 78 F wet bulb). During normal operation, the heat removal capacity of the DCT varies depending on the CCW inlet temperature, ambient dry bulb temperature and heat removed by the Auxiliary Component Cooling Water System (ACCWS). During accident conditions, the heat removal capacity of the DCT varies significantly depending on the CCW inlet temperature and ambient dry bulb temperature.
The DCTs are forced draft, dry type, parallel flow heat exchangers with each tower consisting of five separate cells. Each cell contains two O foot vertical cooling coils that in turn contairninred tubes that provide 42,255 square feet of net heat removal surface area per awer. The two sets of cooling coils (one cell),
p are arranged in a "V" shooe. Cooling air for each cell is provided by three 40 horsepower fans, for a total of 15 fans per DCT. DCT fans are started and shutoff automatically to maintain the CCWS temperatura at a predetermined setpoint. When the water outlet temperature of the CCW heat exchanger exceeds the predetermined setpoint or 100 F, the associated ACCW pump starts.
The cooling coils on three cells of each DCT (i.e. 60%) are protected from tornado missiles by grating located above the coils and capable of withstanding tornado missile impact. DCT fans and motors are located below grade, and are protected from tornado missiles by building walls and/or access platforms.
The WCTs are designed to operate whenever the heat rejection capacity of the DCT is exceeded or ambient conditions prohibit the DCT from rejecting its heat load. The WCTs can also be used to maintain the CCWS temperature below the range maintained by the DCT during normal operation. Each tower has a basin which is capable of storing sufficient water to bring the plant to safe shutdown under all accident conditions. Each WCT is sized to dissipate to the atmosphere approximately 40% of heat removed by the CCWS after a LOCA, assuming the worst case UHS meteorological condition (102 F dry bulb and 78 F wet bulb). The heat removal capacity of the wet cooling tower varies significantly, depanding on the component cooling water temperature to be maintained and atmospheric wet bulb temperature.
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e Each WCT consists of two cells, each cell is serviced by four induced draft 30 horsepower fans, for a total of 8 fans per WCT. There is a concrete partition i
between each cell that prevents eir recirculation between the fans of each cell.
l The wet cooling tower fans are started automatically whenever the water temperature in the tower basin exceeds a predetermined setpoint, and shut off j
by the operator. WCTs remove heat from the CCWS by the separate Auxiliary Component Cooling Water System (ACCWS). Unlike the DCTs, the forced air actually contacts ACCW during the heat removal process.- The ACCWS takes water from the WCT basin, pumps it through the CCW heat exchanger where its i
temperature is raised, and then to the WCT for heat dissipation to the atmosphere. ACCW enters the WCT and is sprayed downward towards the basin into fill modules which separates the water into droplets. Air is drawn i
upward through the modules and spray area by the fans located on top of the tower.
Backarovg i
The CCW heat exchangers supplement the DCTs in removing heat from the CCW system via the ACCW system.- There are two heat exchangers in the CCW system. They are shell and tube, horizontal, counterflow, straight tube, i
single pass heat exchangers made of carbon steel (shell side) with stainless steel tubes. CCW flows through the tubes with ACCW flowing through the shell.
CCW temperature can be automatically controlled by the DCT fans to maintain CCWS temperature between 88 F and 92 F or the ACCWS temperature control valve can be manually set below 88 F to allow ACCWS to modulate and control I
CCWS temperaNre. Post LOCA, CCW outlet temperature is raised to 115 F.
For the desigr. basis tornado event the limit for CCW outlet temperature is increased to 120 F.
During refueling cttage number 6 (RF-6), testing pursuant to Generic Letter 89-13
" Service Water System Problems Affecting Safety-Related Equipment", revealed fouling in the CCW heat exchangers that resulted in degraded system perforr:ance. The heat exchangers (shell side) were cleaned during RF-6 and a task force was established to incorporate a maximum fouling factor into the UHS design basis. The task for. e identified conservatism in the UHS design basis analysis to provide margin for fouling in the CCW heat exchangers.
While pursuing this action, it was also discovered that the minimum fan requirements in the TS were determined by using start-up test data and the design bases calculations did not include adequate margin to allow for system fouling that can occur during the life of the plant.
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Discussion The Waterford 3 UHS meets the requirements of Standard Review Plan (SRP)
Section 9.2.5 and Regulatory Guide (RG) 1.27, Ultimate Heat Sink For Nuclear Power Plants, Revision 2, January 1976. SRP 9.2.5 states that tne UHS must have the capability to dissipate the maximum possible heat load neluding LOCA under the worst combination of adverse environmental conditic.
" RG 1.27 requires that the meteorological conditions considered in the d^ $1 of a heat sink, to be selected with respect to the controlling parameters sod critical time l
periods unique to the sink. The following example is provided: "The controlling l
parameter (for a dry cooling tower) would be dry bulb temperature, and the critical time may be on the order of an hour. Therefore, an acceptable design basis l
meteorological condition for this sink would be the maximum observed ( based on i
regional climatological information) one hour dry bulb temperature." The RG further states that "the meteorological conditions resulting in minimum water l
cooling should be the worst combination of controlling parameters, including diurnal variations where appropriate, for the critical time period (s) unique to the I
specific design of the sink."
The Waterford 3 UHS employs a dry cooling tower and a wet cooling tower. The l
initial design basis calculation demonstrated that the UHS had sufficient capacity l
to dissipate the heat loads following a large break LOCA (limiting design basis accident) and assuming the historical highest dry bulb temperature (102 F) and highest historical wet bulb temperature (83 F). However, DCT performance is not affected by wet bulb temperature and WCT performance is not affected by dry bulb temperature. Since the historically high temperatures do not occur at l
the same time, the margin associated with this conservative assumption was l
reduced and used to determine the maximum fouling that can occur in the i
l CCWS heat exchanger. A coincident wet bulb temperature of 78 F is associated l
with the maximum dry bu5 temperature of 102 F and a coincident dry bulb of 98 F is associated with the maximum wet bulb of 83oF. As indicated below, the I
revised design basis calculations concluded the UHS is capable of dissipating l
the LOCA heat removal requirements for each of these meteorological conditions and determined that the most limiting meteorological condition was 102 F dry bulb with coincident 78 F wet bulb.
A heat balance was performed (see attached Figure A) to determine the actual l
heat rejected by the DCT, WCT and the CCW heat exchanger following a large l
break LOCA for each of the worst combination meteorological design i
parameters, maximum one hour dry bulb temperature / coincident wet bulb i
temperature or maximum one hour wet bulb temperature / coincident dev bulb temperature. For each of the meteorological design parameters, inlet CCW and ACCW tem,watures to the CCW heat exchanger will vary, thus the heat i
dissipated by the CCW heat exchanger will vary since the design CCW outlet 4
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temperature is constant and must be maintained at or below 115*F during a LOCA. The design basis of the UHS was based on the worst combination meteorological design parameter that produced the lowest CCW heat exchanger fouling factor needed to dicsipate its required heat load. The meteorological condition of 102*F dry bulb & 78'F wet bulb versus 98*F dry bulb & 83*F wet bulb for the UHS design basis proved to be more limiting to maintain a 115"F CCW outlet temperature to the plant auxiliaries following a large break LOCA.
The above methodology is consistent with Standard Review Plan Section 9.2.5 and Reg. Guide 1.27 which requires the UHS be designed at the worst meteorological condition that provides minimum CCW cooling.
Changing the UHS meteorological design basis requirea a reduced WCT basin temperature to provide an additional allowance for fouling in the CCW heat exchanger. Considering the previous design basis, the effectiveness of the CCW heat exchanger was optimum, therefore design WCT basin temperature was only requiled to be maintained at or below 95'F. Considering the new design t
basis, the allowance for CCW heat exchanger fouling requires the WCT basin temperature to be maintained at or below 89'F to preserve heat rejection capacity.
With the new operating points for the UHS determined, the impact on other design documents were evaluated for inclusion of the results. When evaluating the UHS Minimum Fan Requirements for ambient conditions, it was determined the analysis used the UHS start-up test performance. This did not provide an allowance for equipment fouling that can occur over the plant life. The UHS start-up test demonstrated the system is capable of dissipating accident heat loads above its design capability. However, failing to incorporate the equipment j
fouling factor resulted in less conservative UHS minimum fan requirements in Technical Specification Table 3.7-3. In addition, the pT :q/s analysis added additional heat load to the CCW heat exchanger when UNS fans are inoperable.
Since the new UHS design basis provided an additional allowance for CCW heat exchanger fouling, adding additional heat duty to the CCW heat exchanger would decrease this value. The new evaluation analyzed the Dry Cooling Tower (DCT) and Wet Cooling Tower (WCT) separately in order not to affect the CCW heat exchanger design basis fouling. In addition, evaluating the DCT and WCT fans separately preserves the design basis heat load that each UHS component is expected to dissipate following a large break LOCA. These heat loads are
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documented in FSAR Figure 9.2-4 and FSAR Table 9.2-9.
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5 The CCWS heat exchangers have been cleaned both tube and shell side. The DRY cooling tower fans (exterior) and tube bundles (interior) have also been cleaned. It is believed that this restoration has improved the current heat removal capacity of the UHS to the extent that the existing TS does not pose a threat to rSty. Nevertheless, the more restrictive requirements associated with basin y C temperature and fan operability are currently adhered to and included in plant administrative controls.
The proposed change also includes administrative changes as follows:
LCO 3.7.4 rernoves descriptive information associated with the UHS. This information is included in the Bases section and does not need to be in the LCO.
I Actions a. and b. are revised by removing specific parameters that may render a l
UHS train inoperable. Each UHS train is 100 percent capacity capable of removing design basis accident heat loads. Therefore, if a UHS train is inoperable for any reason the ACTION statement applies. Consistent with this approach there is no need for action requirements c and d. If the fan requirements of Table 3.7-3 are not met, entry into actions a or b is required.
Therefore, the proposed change deletes actions c and d.
ACTIONS e. and f. are revised to support the new requirements of TS Table 3.7-3 and changed to actions c and d.
The Bases has been revised consistent with the proposed TS change.
Modifications to the design basis calculations affected the 173,930 gallon value associated with WCT water evaporation and drift loss ( see FSAR Table 9.2-10).
The new value is 168,738 gallons.
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l Safety Analysis i
The proposed change described above shall be deemed to involve a significant hazards consideration if there is a positive finding in any of the following areas:
1.
' Nill operation of the facility in accordance with this prooosed change involve a significant increase in the probability or consequences of an l
accident previously evaluated?
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Response
No
't he proposed change modifies the UHS TS by revising WCT basin water -
temperature from less than or equal to 95 F to less than or equal to 89 F and incorporating more restrictive cooling tower fan operability requirements. These changes are necessary to adequately preserve the acsumptions and limits of the revised UHS design basis calculations.
These calculations conclude that the UHS is capable of dissipating the maximum peak heat load resulting from the limiting design bases accident (i.e., large break LOCA) and the most severe natural phenomena (i.e.,
tornado event). Other changes are purely administrative in nature. The proposed change does not directly affect any material condition of the plant that could directly contribute to causing an accident. The proposed change ensures that the mitigating effects of the UHS will be consistent with the design basis analysis. Therefore, the proposed change will not involve a significant increase in the probability or consequences of any accident previously evaluated.
2.
Will operation of the facility in accordance with this proposed change create the possibility of a new or different type of accident from any 1
accident previously evaluated?
Response
No.
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The proposed change modifies the UHS TS to be consistent with revised design basis calculations. These new calculations adjust margin to incorporate an additional allowance for fouling in the CCW heat exchangers and more restrictive UHS minimum fan requirements that were not adequately addressed in the initial design basis. This change also incorporates administrative changes that are intended to improve the application and use of this specification. The proposed change will not alter the operation of the plant or the manner in which the plant is operated. Therefore, the proposed change will not create the possibility of a new or different kind of accident from any accident previously
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evaluated.
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3.
Will operation of the facility in accordance with this proposed change involve a significant reduction in a margin of safety?
Response
No The proposed change modifies the UHS TS by revising WCT basin water temperature from less than or equal to 95*F to less than or equal to 89 F and incorporating more restrictive cooling tower fan operability requirements. Mcdifying the UHS meteorological design bases reduced WCT basin temperature requirement for operability, thus, providing an allowance for fouling in the CCW heat exchangers. The proposed change better preserves the margin of safety by ensuring that the UHS will maintain the CCW accident analysis temperature limit of 115 F.
Increased cooling tower fan operability requirements will ensure that the expected cooling efficiency is actually available and not unknowingly degraded due to fouling. Other changes requested herein are purely administrative in nature, do no affect safety margins and intended to improve the use and application of this specification. Therefore, the proposed change will not involve a significant reduction in a margin of safety.
Safety and Sionificant Hazards Determination Based on the above safety analysis, it is concluded that: (1) the proposed change 5s not constitute a significant hazards consideration as defined by 10CFR^.992: and (2) there is a reasonable assurance that the health and safety of the public will not be endangered by the proposed change; and (3) this action will not result in a condition which significantly alters the impact of the station on the environment as described in the NRC final environmental statement.
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f 109.3*F 5850 gpm m
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AUXILIARY COMPONENT COOLING 89'F WATER SYSTEM AL 101*F 850 gpm m
Wet Cooling Tower Auxiliary N
Og =59.3 x 10s BTU /Hr Component Cooling Water Pump Essential Chiller y
Qu =5.1 x 108 BTU /Hr 89'F g
M 110.7'F 5000 gpm m
3 89'F
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E 167.9'F 131.6*F
[
T 115*F m
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j CCW Heat Exchanger Qu =54.2 x 10s BTU /Hr N
Dry Cooling Tower j(
Qu =119.1 x 10s BTU /Hr COMPONENT COOLING WATER SYSTEM 167.9'F 4
m 115*F 6554 gpm m
Flant Loads Om =173.3 x 108 BTU /Hr Componont Cooling Water Pump ACCIDENT MODE Note: This Flow Diagram Shows Only One Train of the Redundant Ultimate Heat Sink
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