ML17290A548

Application for Amend to License NPF-21,requesting Change to Refueling Platform Load Limits by Adding New Values Resulting from Installation of Upgraded Refueling Mast (GE Model NF500)

ML17290A548
Person / Time
Site:	Columbia
Issue date:	07/29/1993
From:	Parrish J WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML17290A549	List: ML17290A548 ML17290A550
References
GO2-93-191, NUDOCS 9308050148
Download: ML17290A548 (25)

Text

'CCELERATEP DOCUIVIENT DISTRIBUTION SYSTEM REGULAT INFORMATION DISTRIBUTION+STEM (RIDE)

ACCESSION NBR:9308050148 DOC.DATE: 93/07/29 NOTARIZED: YES DOCKET FACIL:50<"397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME AUTHOR AFFILIATION PARRISH>J.V. Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION R

SUBJECT:

Application for amend to license NPF-21 requesting change to refueling platform load limits by adding new values resulting from installation of upgraded refueling mast D

. (GE model NF500) .

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NRR/DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 NUDOCS-ABSTRACT 1 1 OC/LFDCB 1 0 OGC/HDS1 1 0 EG FTQB E 01 1 1 EXTERNAL: NRC PDR 1 1 NSIC 1 1 D

D D

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'WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Bm 968 ~ $ 000 George Wasbtngton Way ~ Rtcbland, Wasbtngton 99352-0968 ~ (509) 372-5000 July 29, 1993 G02-93-191 Docket No. 50-397 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gentlemen:

Subject:

WNP-2, OPERATING LICENSE NPF-21 REQUEST FOR AMENDMENTTO TECHNICALSPECIFICATION 4.9.6, REFUELING PLATFORM LOAD LIMITS In accordance with the Code of Federal Regulations, Title 10 Parts 50.90 and 2.101, the Supply System hereby submits a request for amendment to the WNP-2 Technical Specifications. This proposal requests the following changes to Specification 4.9.6:

1) Refueling platform load limits be changed, as attached, to add new values resulting from the installation of an upgraded refueling mast (GE model NF500).

2) Correct an omission in the original Technical Specifications by adding a surveillance for the "overload cutoff" function of the frame mounted and monorail hoists. The present Surveillance (4.9.6.b) incorrectly specifies the "overload cutoff" for these two hoists as 485 + 50. By design 485 + 50 is the "loaded interlock" and should be noted as such in the surveillance. The "overload cutoff" should be 1000 + 50 as recommended in the vendor's manual.

3) Reorder the surveillances to place all the "overload cutoff'urveillances together and all of the "loaded interlock" surveillances together.

4) Change limit notation to eliminate specifying low limits and clearly indicate the appropriate trip setpoint. Presently the surveillances for the interlocks specify "when the load exceeds" a setpoint and a + tolerance value, for example 1200 + 50 pounds (Surveillance 4.9.6.a). Specifying the activation of an interlock when the value exceeds 1150 (1200 - 50) does not provide clear guidance to the operator. Because an upper limit is provided, "exceeds 1150" could be interpreted to mean less than 1150. However a load less than 1150 is not a safety issue. "Exceeds 1150" could also mean greater than 030082 93080SOi48 '930729 PDR *DOCK 05000397 P PDR

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'EQUEST FOR AMENDMENTTO TECHNICAL SPECIFICATION 4.9.6, REFUELING PLATFORM LOAD LIMITS 1150, for which an upper limit (1250) is provided. Hence to avoid confusion, this request also clarifies the interlock values to specify only an upper limit which, in all cases, is the safety concern. Also the phrase "when the load exceeds" is being replaced by "prior to the load exceeding." For example, 2000 satisfies a demonstration of operability "when the load exceeds" 1250 but the safety intent of the specification is that the trip occur before 1250. Therefore the new wording states where operability is to be demonstrated i.e., prior to exceeding the limit. This same philosophy is proposed for Specification 4.9.6.d. Instead of "(" 554 inches as indicated, "cutoff before" 554 inches as indicated is proposed. This change standardizes the intent of Specifications 4.9.6.a, 4.9.6.b, 4.9.6.d, 4.9.6.f, 4.9.6.g and the new surveillance for the overload cutoff added above. And finally,

5) Change the "slack cable cutoff" operability (4.9.6.e) from "less than 50 pounds" to "between 25 and 75 pounds." As reported in License Event Report 93-011 (April 9, 1993) practice at that time did not ensure that operability was shown >a 50 pounds decreasing load nor did it account for instrument accuracy and drift. Also, the ability to precisely set a trip on the cutoff sensing instrumentation is difficult.

With respect to the new mast, the Supply System intends to use the NF500 as the primary refueling mast. However, two values are specified in change 1. The higher values correspond to the NF500 and the lower values are applicable to the presently installed GE model NF400 (The NF400 mast will be retained as a spare.) Two values are specified so that the NF400 mast can be used if the NF500 becomes inoperable. This will eliminate the need for a subsequent license amendment should the use of the NF400 mast be necessary. It will also eliminate the need to maintain a more costly spare. The use of the NF500 is an enhancement to refueling operations that has no detracting refueling or operational characteristics.

The NF400 is a four segment, open frame, triangular mast, The NF500 is a four segment, solid, cylindrical telescoping mast, The NF500 mast has been approved for use at Grand Gulf and Fermi-2. The NF500 mast provides improved contamination control, by limiting the tendency for dripping onto the refueling platform, and the increased rigidity of the mast improves the ability to precisely locate the hoist where desired. Further, it is less prone to mast bowing which could result in structural damage or grapple misalignment. The use of the NF500 will not affect the function or operation of the fuel grapple hoist mechanism or the refueling platform. The auxiliary hoists (frame mounted and monorail) will also remain unaffected by the use of the NF500. The only design change having Technical Specification significance is the increased weight of the NF500 tubular mast sections relative to the NF400 triangular mast. The additional weight requires that certain interlocks dependent on total cable load be modified to ensure that protective features are activated when required. Total cable load includes the submerged weight of any suspended grapple loads (i.e., fuel assembly) and those portions of the mast supported by the cable and reel under the conditions for the interlock.

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'REQUEST FOR AMENDMENTTO TECHNICAL SPECIFICATION 4.9.6, REFUELING PLATFORM LOAD LIMITS The overload cutoff on the main hoist (Surveillance 4.9.6.a) is increased to 1700 pounds for the NF500. This interlock limits the lifting force of the main hoist to ensure that excessive force is not applied to a fuel assembly should it become stuck during handling operations, or to vessel internals should they become inadvertently engaged. The 1700 pound limit is below the lifting force on vessel internals expected to cause damage to stuck components. The mast supplier, General Electric (GE), has reviewed the reactor internals and GE fuel and determined that a maximum upward force relating to a cable tension of 2000 pounds is acceptable. Hence an overload cutoff of 1700 pounds provides adequate margin below the acceptable limit of 2000 pounds. Siemens Power Corporation (SPC) has also evaluated the specifications for use of the NF500 mast with this overload cutoff value and found it to be acceptable for use with SPC fuel at WNP-2. The present Technical Specification limits the allowable force on a fuel assembly to 1250 pounds for the NF400 mast. The additional approximate 400 pound weight differential (between the NF400 and NF500) and the physical manner in which the NF500 mast loads itself as the telescoping sections extend and retract raise this limit to 1700. The new value for the NF500 mast is not the addition of the approximate 400 pound weight differential to the value for the NF400 alone. In extending, as additional sections are sensed as a load, the loading measurement could potentially be abrupt causing the sensed value to exceed the approximate 400 pound differential weight. Hence the value for the NF500 is 50 pounds greater than the addition of the differential weight (400 pounds) to the NF400 value. The 50 pounds allows margin for this potential load measurement error yet does not allow excessive lifting forces to be exerted.

Again, a limit of 1700 pounds adequately protects against excessive lifting forces being applied to fuel and reactor internals.

The main hoist loaded interlock and redundant interlock values (Surveillances 4.9.6.f and 4.9.6.g) are provided to (1) initiate a control rod block when the hoist is loaded and located over the reactor vessel, (2) prevent raising the hoist when the platform is over the vessel with the hoist loaded and a control rod withdrawn, and (3) prevent raising the mast when the mast is under load but the grapple is not engaged. Limits for both of these interlocks are increased to 750 pounds. This value is calculated to account for the added submerged weight of the NF500 yet be sufficient to ensure initiation of these interlocks when the weight of a channeled fuel bundle is applied to the hoist. The difference of 400 pounds is not needed in the use of the NF500 because the sensed load at the time of fuel grapple will not include the entire weight of the mast. All the telescoped sections of the mast are not carried by the cable, and sensed by the load cells, until fully retracted. In extension, some of the weight of the mast is directly supported by the refueling platform, hence a difference of 400 pounds would not be an appropriate value to ensure correct operation of the interlocks.

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'EQUEST FOR AMENDMENTTO TECHNICAL SPECIFICATION 4.9.6, REFUELING PLATFORM LOAD LIMITS The only accident that could potentially be impacted by the change in masts is the Fuel Handling Accident (FHA). A FHA is postulated to occur as a consequence of a failure of the fuel bundle lifting mechanism. The most limiting FHA results in the dropping of a raised bundle onto fuel bundles loaded in the core. This accident is discussed in section 15.7.4 of the Final Safety Analysis Report (FSAR). However, the NF500 is designed to match or exceed all aspects of the NF400 mast now in use. The probability of failure of the NF500 and of the NF400 mast are both judged to be very small. For these reasons the consequences of a FHA with the NF500, using the assumptions contained in the WNP-2 FSAR, are not changed from the consequences of a FHA with the NF400.

No other interlocks or surveillances are affected by the use of the NF500 instead of the NF400 mast.

A review of the interlocks associated with the frame mounted and monorail hoists recently identified that the present Technical Specifications improperly describe the "overload cutoff" for these two hoists as 485 + 50 pounds. This is the value that should be used for the "loaded interlock." The "loaded interlock" is associated with recognizing when the hoist has a load on it. Accordingly it is set at a value low enough to ensure that it is satisfied at an appropriately low value with respect to the weight of a control rod, It provides a signal to prevent rod movement when the refueling platform is over the core, a control rod,is withdrawn, and a load is on the hoist. The "overload cutoff" is associated with ensuring that the hoist does not inadvertently apply an unacceptable upward force on a core internal or fuel bundle or over-range the capability of the hoist motors. The vendor manual specifies the "overload cutoff" to be 1000

+ 50 pounds. Accordingly a new surveillance has been added to ensure that the "overload cutoff's set correctly. The present wording could imply that the overload cutoff and loaded interlock should both be set at 485 + 50 pounds. If both were set at the 485 + 50 value it would impose excessive manipulation of the "overload cutoff" trips each time it was necessary to move loads greater than 485 + 50 but less than 1000 + 50 pounds. Obviously, each time the cutoff trip is adjusted an opportunity to damage the trip or set it improperly exists. To avoid this the new surveillance is proposed so that both setpoints are recognized and surveilled by the Technical Specifications. For ease of recognition it is proposed that the "loaded interlock" surveillance for the frame mounted and monorail hoists be placed with the loaded and redundant loaded interlock surveillances (4.9,6.f and 4.9.6.g).

This change does not impact the protective features of the "loaded interlock." The "loaded interlock" will continue to be set and surveilled at the correct weight thereby ensuring rod movement is restricted as per the WNP-2 design. The "overload cutoff", as recommended by the vendor, will be imposed to ensure that equipment is not damaged and core internals and fuel assemblies are not exposed to excessive forces. Both trips will be surveilled and tested as required by the Technical Specifications. A review of other plants having similar frame mounted and monorail hoists on similar refueling platforms indicates that the majority have "overload cutoff'nd "loaded interlock" surveillances with similar values. It appears that the

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Page Five REQUEST FOR AMENDMENTTO TECHNICAL SPECIFICATION 4.9.6, REFUELING PLATFORM LOAD LIMITS omission of an "overload cutoff" surveillance was an oversight in the WNP-2 Technical Specifications. Implementation of this additional surveillance, recognizing a higher value for the "overload cutoff'as no detracting aspects from the safety of refueling operations at WNP-2 because, as discussed above, a maximum upward force of 2000 pounds has been evaluated as acceptable for reactor internals at WNP-2. The 1000 + 50 value is sufficiently below that value so that excessive force will not be imposed. Further, the "loaded interlock" will also be effective should either of these hoists be inadvertently applied to a fuel bundle. Hence an "overload cutoff't 1000 + 50 pounds does not detract from safe refueling operations at WNP-2.

The fifth change being requested is to Surveillance 4.9.6.e which confirms operability of the slack cable cutoff on the main hoist "when the load is less than 50 pounds". The slack cable cutoff stops the hoist from lowering when a load cell on the hoist equipment senses a decreased load "less than 50 pounds." Because of the telescoping design of the hoist, a large portion of the hoist weight is suspended from the hoist until the last section of the hoist is extended. As the hoist is extended and the first two sections of the hoist extend fully, their weight is removed from the cable and carried by the refueling platform. At this point the slack cable cutoff load sensor begins sensing a decreased load. Hence the slack cable cutoff becomes effective as the hoist fully extends.

The reasons for a slack cable cutoff are:

1) As the load decreases the cable could unravel from the take up drum and drop free from the refuel platform,

2) a decreased load would allow detection of a fuel bundle hang-up in a timely manner,

3) prevent transfer of the entire weight of the lower mast section and grapple head to the fuel bundle, and

4) the cutoff provides additional indication that the grapple has made contact on down travel with the fuel bundle bail and is in position to connect to a bundle and begin a transfer.

During planning for installation of the NF500 a project engineer identified concerns with the surveillance testing and interpretation of surveillance requirement 4.9.6.e for the slack cable cutoff. It was noted that the setpoint for this feature did not account for instrument accuracy and drift. Further, it did not assure that the cutoff signal was generated at 50 pounds decreasing, In order to assure that 50 pounds decreasing is met the calibration must be set to a value higher than 50 pounds. Previous surveillance procedures did not account for instrument inaccuracies or the interpretation that required the interlock to be satisfied at no less than 50 pounds. The present phrase "less than 50 pounds" could accept 0 pounds as acceptable which is not the intent of the design.

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'EQUEST FOR AMENDMENTTO TECHNICAL SPECIFICATION 4.9.6, REFUELING PLATFORM LOAD LIMITS As a result, the calculation for the slack cable cutoff was revised. The calibration and surveillance procedures were revised to a value higher than 50 pounds in order to assure that the cutoff was satisfied at no less than 50 pounds.

However, the design of the cutoff was not made to the tolerances necessary to allow precisely "dialing in" a specific value. As a result, calibration becomes an iterative process until the surveillance is satisfied. Further, because of the design of the hoist, a precise 50 pound setpoint is difficult to attain. Two spring loaded hydraulic and control cable leads connected to the grapple on the end of the hoist provide a varying upward lift on the hoist and as the hoist extends into the water the load sensed decreases due to buoyant forces. Both of these characteristics combined with a "not less than 50 pounds" setpoint have the potential for causing the slack cable cutoff to activate too soon. In other words, the slack cable cutoff could actuate well before a true slack cable condition exists and stop movement of the main hoist. Refueling activities would therefore be unnecessarily delayed.

As a result GE, the refueling platform designer, was contacted to determine if a band of values would be acceptable. GE reviewed previous purchase specifications and previous GE guidance provided to plants with both the triangular mast, presently used at WNP-2, and the NF500 round mast. GE recommended 50 + 25 pounds as a range of acceptable values that could be used at WNP-2 without problem. The Supply System has reviewed the GE recommendation and proposes to use 50 + 25 pounds.

A slack cable cutoff set to actuate between 25 and 75 pounds will ensure that the protective functions of the cutoff remain viable. The upper value provides no protective feature. Use of a higher value for the cutoff would limit fuel movement (hoist travel) sooner so that movement as the cutoff value increased would be impossible and the most conservative situation. Use of the lower bound as the cutoff setpoint provides the protective features.

The tension (load) on the cable must be 0 to unwind the cable. The instrument calibration and setting process has an uncertainty of less than 5 pounds. With this uncertainty a cutoff set at 25 pounds will still protect against cable unravel as well as a cutoff set at 50 pounds would. The hoist down speed is such that a cutoff at 25 pounds, including uncertainty, stops travel well before the cable is unloaded enough to allow the cable to unwind from the drum.

Timely indication of a hung-up fuel bundle can also be provided by the 25 pound slack cable cutoff. The concern on a hung-up bundle is that it could be prematurely un-grappled thereby causing a dropped fuel bundle. Again, with an uncertainty of 5 pounds in the calibration and setting process, a 25 pound cutoff will still provide timely indication of a potentially hung-up fuel bundle before it could be un-grappled. Further, the hoist speed is such that the cutoff, uncertainty in setting, and hoist travel can not combine to unload the hoist given the cutoff signal at 25 pounds.

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'EQUEST FOR AMENDMENTTO TECHNICAL SPECIFICATION 4.9.6, REFUELING PLATFORM LOAD LIMITS A 25 pound cutoff setpoint will also avoid transferring the entire weight of the lower mast section and grapple head to the fuel bundle. Accounting for the most non-conservative application of the uncertainty would still leave 20 pounds of tension on the cable. This upward force on the cable will ensure that the fuel bundle will not see the downward force of the mast section and grapple head. Further, the lowering speed of the mast is such that, given the uncertainty, a positive tension on the cable willbe maintained thereby ensuring that the mast and grapple are not resting on a fuel bundle. A 50 pound setting for the cutoff provides no additional benefit.

With respect to the proposed Technical Specification changes resulting in the upgrade from an NF400 to NF500 mast the Supply System has evaluated these changes per 10 CFR 50.92 and determined that they do not represent a significant hazards consideration because they do not:

1) Involve a significant increase in the probability or consequences of an accident previously evaluated. The NF500 is designed to match or exceed all aspects of the NF400 mast now in use. The probability of failure of the NF500 and NF400 masts is judged to be very small. In addition, the consequences of a FHA using the assumptions contained in the FSAR are not changed, and are independent of the mast design in current use.

Further, an analysis by GE of a postulated accident in which the exposed portion of the NF500 mast is struck by a missile and severed while lifting a fuel bundle with both falling onto the top of the core has been completed. The conclusions are that this accident with the increased weight of the mast with the bundle is bounded by the current WNP-2 FSAR analysis for the fuel bundle only FHA.

For the "overload cutoff" value the setpoint changes allow only for the increased weight of the new mast and a small margin to allow for the sensing load changes as sections of the mast load onto the cable during extension and retraction. In other words, the

difference between the new setpoint and the current setpoint is approximately the same as the difference between the weights of the NF500 mast and the NF400 mast plus a small margin to account for instrument response. The new setpoint for the "overload cutoff", 1700 pounds, is well below the 2000 pounds maximum upward force on the reactor internals, found to be acceptable by the reactor internals vendor. Therefore, with the use of the NF500 mast and the revised "overload cutoff'alue, core internals will not be exposed to unacceptable lifting forces. The 1700 pounds limit has been evaluated by both WNP-2 fuel vendors and found to be acceptable for handling fuel at WNP-2.

The "loaded interlock" values for the NF500 account for the submerged weight of only a portion of the 400 pound difference due to the telescoping design of the NF500. The telescoping design loads a portion of the 400 pound differential weight onto the refueling platform at grappling so the interlock is set accordingly to actuate at a value correspond-ing to less than the value for the NF400 mast plus the proximate 400 pound weight difference. The value for the NF500 "loaded interlock" provides the same degree of protection as the present "loaded interlock" value for the NF400 mast.

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Page Right REQUEST FOR AMENDMENTTO TECHNICAL SPECIFICATION 4.9.6, REFUELING PLATFORM LOAD LIMITS "Hence because the masts are not significantly different in design and design function and the change in setpoints accounts for weight differences or portions thereof, between the two masts, no change in the probability or consequences of a previously evaluated accident as a result of these changes is credible.

2) Create the possibility of a new or different kind of accident from any accident previously evaluated. The NF500 is similar enough in design and function to the NF400 so as not to create the possibility of a new or different kind of accident. The refueling platform structural integrity is not degraded by the additional weight. Further, stress margins (including seismic) are not significantly changed. Therefore, the possibility of a new or different kind of accident as a result of upgrading the mast is insignificant.

3) Involve a significant reduction in a margin of safety. The changed cutoff and interlock values merely account for the increased weight of the mast, or a portion thereof, and still provide the intended protection as discussed in the WNP-2 Bases. No other interlocks are affected by the use of the NF500 mast. No margins or assumptions related to the fuel bundle drop analyses are changed as a result of using the NF500 mast. The "overload cutoff'etpoint ensures that excessive lifting forces, are not applied to core internals or fuel bundles. The "loaded interlock" limit still ensures that the associated interlocks are initiated when the weight of a channeled fuel bundle:is applied to the grapple. As such, the change to the upgraded mast design (NF500) does not involve a significant reduction in a margin of safety.

With respect to the proposed Technical Specification change correcting the "overload cutoff" surveillance to 1050 (1000 + 50) pounds and adding a surveillance for the "loaded interlocks" on the frame mounted and monorail hoists the Supply System has evaluated this change per 10CFR 50.92 and determined that it does not represent a significant hazards consideration because it does not:

1) Involve a significant increase in the probability or consequences of an accident previously evaluated, because this change maintains the degree of protection intended by the original plant design. The "loaded interlock" feature will continue to function correctly providing input to the refueling interlocks. The "overload cutoff" will provide an additional level of protection for plant equipment by ensuring that equipment is not exposed to excessive forces. Because this change maintains the original intent of the plant design the probability of an accident is not increased by this change, and because these hoists and the associated interlocks are not credited for mitigating the consequences of an accident there is no possible increase in the consequences of an accident previously evaluated due to the implementation of this change.

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Page Nine REQUEST FOR AMENDMENTTO TECHNICAL SPECIFICATION 4.9.6, REFUELING PLATFORM LOAD LIMITS

2) - Create the possibility of a new or different kind of accident from any accident previously evaluated, because no new modes of plant operation, new procedures, or plant modifications are introduced by this change, This change will continue to enforce the present plant refueling operations and surveillances. The addition of a surveillance to ensure that plant equipment will not be exposed to excessive forces does not limit any present capabilities of the plant. Hence this change does not create a new or different kind of accident from any previously evaluated.

3) Involve a significant reduction in a margin of safety. Because this change does not change the protection provided by the "loaded interlock" and does not allow plant equipment to be exposed to excessive forces, it does not represent a challenge to a margin of safety. The "overload cutoff" is set well below the acceptable value for maximum upward forces. It will eliminate the unnecessary manipulation of protective equipment in the event these hoists are required to lift equipment heavier than the "loaded interlock" value. Itrestores theoriginaldesignintentof theplant. Imposinga lower value on the "overload cutoff" unnecessarily requires manipulation of plant protective trip settings. By adding this additional surveillance this imposition is removed.

Therefore because this change recognizes the original design intent, conforms to the vendor's recommendations, and removes the necessity of manipulating plant protective features it does not represent a significant reduction in a margin of safety.

The Supply System has evaluated the change to replace the phrase "when the load exceeds 1200

+ 50 (485 + 50, 550 + 50, 1000 + 50)" with an upper value and the new phrase "prior to the load exceeding 1250 (535, 600, 1050)" and determined that it does not represent a significant hazards consideration because it does not:

1) Involve a significant increase in the probability or consequences of an accident previously evaluated. For example, the 4.9.6.a surveillance is met to ensure that excessive lifting forces are not applied to fuel bundles or vessel internals. A lower limit provides no credible protection to an excessive lifting force. The lower limit would ensure only that the interlock does not trip too soon. Tripping too soon is not a safety concern and does not contribute to the probability or consequences of a previously evaluated accident.

Surveillances 4.9.6.f and 4.9.6.g ensure that interlocks limiting rod and platform movement actuate before loads are excessive. Again a lower limit serves no purpose in ensuring the proper operation of the interlocks. The change in wording clarifies that the limit is to be met on the conservative side of the limit, prior to the limit, rather than an ambiguous "when the load exceeds" direction. Hence an increase in the probability or consequences of a previously evaluated accident as a result of this change is not credible.

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'EQUEST FOR AMENDMENTTO TECHNICAL SPECIFICATION 4.9.6, REFUELING PLATI~'ORM LOAD LIMITS

2) 'Create the possibility of a new or different kind of accident from any accident previously evaluated. The lower limits would serve only to ensure that the interlocks do not actuate too soon. Actuation of the interlocks is an event within the design bases of the plant.

The change in phrasing clarifies the conservative location of trip. Therefore, eliminating a lower limit value and providing a clearer description of where the trip is to be satisfied does not create the possibility of a new or different kind of accident from any previously evaluated.

3) Involve a significant reduction in a margin of safety. Because a lower limit provides no contribution to ensuring design loads are not exceeded the elimination of the lower limit cannot possibly result in a reduction in a margin of safety. The phrasing clarification preserves the margin of safety by eliminating the possibility of misinterpreting the setpoint to be a value that exceeds the accepted setpoint, As a result no margin of safety is impacted by the change in phrasing or the elimination of a low limit.

The Supply System has evaluated the change in the slack cable cutoff setting and determined that it does not represent a significant hazards consideration because it does not:

1) Involve a significant increase in the probability or consequences of an accident previously evaluated. A range of values between 25 to 75 pounds will ensure that the cutoff actuates in a timely manner and at an appropriate value preserving the original design intent while allowing flexibility in performing the operability surveillance. A setpoint at 25 pounds provides the same protection as 50 pounds against cable unravel, fuel bundle hang-up, setting the full weight of the grapple head and lower mast section on a fuel bundle and provides the same positive indication that the grapple is in position to grasp a fuel bundle. A 25 pound setpoint for the cutoff provides positive load on the cable at all times given the uncertainty in setting the cutoff trip. Further, hoist speed and travel is such that a positive load will remain on the cable given a cutoff at 25 pounds.

Because the 25 pound setting gives the same level of protection (a positive tension) and the design capability of the mast is not effected by the lower value there is no possibility that the change increases the probability of a previously evaluated accident. Further, the consequences of a previously evaluated accident are not affected because the cutoff setpoint and mast do not fulfillan accident mitigation function. For these reasons this change does not represent a significant increase in the probability or consequences of an accident previously evaluated.

2) Create the possibility of a new or different kind of accident from any accident previously evaluated. This change does not represent a change in modes of plant operation or require physical modifications. The change preserves the original slack cable cutoff design requirements. Therefore, because the intent of the slack cable cutoff is preserved and because no physical changes to plant systems or to plant modes of operation are involved in this change it does not create the possibility of a new or different kind of accident from any previously evaluated.

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Page Eleven REQUEST FOR AMENDMENTTO TECHNICAL SPECIFICATION 4.9.6, REFUELING PLATFORM LOAD LIMITS

3) 'Involve a significant reduction in a margin of safety. As discussed above, the change preserves the original design requirements and ensures adequate testing to confirm continued design capability. A positive load will remain on the cable given the uncertainty in load setting, mast down speed, and travel after the cutoff trip occurs. The load must go through 0 before impacting any design features. Hence a 25 pound setting provides adequate margin before impacting a design feature and the reduction in margin from 50 to 25 pounds is not significant given setting uncertainty, mast down speed, and travel. Therefore the margin of safety created by the slack cable cutoff is not significantly affected by this change.

As discussed above, the Supply System concludes that these changes do not involve a significant hazards consideration, nor is there a potential for a significant change in the types or significant increase in the amount of any effluents that may be released offsite, nor does the change involve a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed change meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(C)(9) and therefore, per 10 CFR 51.22(b), an environmental assessment of these changes is not required.

This Technical Specification change request has been reviewed and approved by the WNP-2 Plant Operations Committee and the Supply System Corporate Nuclear Safety Review Board.

In accordance with 10 CFR 50.91, the State of Washington has been provided a copy of this letter.

The Supply System intends to use the NF500 mast during the 1994 refueling outage scheduled to commence April 15, 1994. As such, approval of these changes by March 15, 1994, is requested so that the new mast can be ready for use in the event the Supply System is requested to start the outage early.

J. V. Parrish (Mail Drop 1023)

Assistant Managing Director, Operations PLP/bk Attachments CC: BH Faulkenberry - NRC RV NS Reynolds - Winston Ec Strawn JW Clifford - NRC DL Williams - BPA/399 NRC Site Inspector - 901A

STATE OF WASHINGTON )

Subject:

Request for Amend to TS 4.9.6

) Refuelin Platform d Limits COUNTY OF BENTON )

I, J. V. PARRISH, being duly sworn, subscribe to and say that I am the Assistant Managing Director, Operations for the WASHINGTON PUBLIC POWER SUPPLY SYSTEM, the applicant herein; that I have the full authority to execute this oath; that I have reviewed the foregoing; and that to the best of my knowledge, information, and belief the statements made in it are true.

DATE , 1993 J Parrish, Assistant Managing Director rations On this date personally appeared before me J. V. PARRISH, to me known to be the individual who executed the foregoing instrument, and acknowledged that he signed the same as his free act and deed for the uses and purposes herein mentioned.

GIVEN under my hand and seal this ~today of 1993.

sar ft

'fold'otary

\ Public in and for the STATE OF WASHINGTON Residing at Kennewick W hin on

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