ML18017A894
| ML18017A894 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 09/29/1999 |
| From: | Alexander D CAROLINA POWER & LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-95-07, HNP-99-142, NUDOCS 9910060333 | |
| Download: ML18017A894 (21) | |
Text
Carolina Power & Ught Company Harris Nuclear Plant PO Box 165 New Hill NC 27562 SEP 2S (ggg SERIAL: HNP-99-142 United States Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 SHEARON HARRIS NUCLEAR POWER PLANT DOCKET NO. 50-400/LICENSE NO. NPF-63 RESPONSE TO REQUEST FOR ADDITIONALINFORMATIONREGARDING GENERIC LEITER 95-07, "PRESSURE-LOCKING AND THERMAL-BINDINGOF SAFETY-RELATED POWER-OPERATED GATE VALVES"
Dear Sir or Madam:
By letter dated April 14, 1999, the NRC requested that Carolina Power Ec Light Company (CP&L) respond by July 30, 1999 to a request for additional information regarding Generic Letter 95-07, "Pressure-Locking and Thermal-Binding of Safety-Related Power-Operated Gate Valves," for the Harris Nuclear Plant (HNP). By letter dated July 26, 1999, CPS'equested a due date extension of September 30, 1999.
A written report providing the requested information is enclosed. Questions regarding this matter may be referred to Mr. J. H. Eads at (919) 362-2646.
Sincerely,
%.b.M~ E D. B. Alexander Manager, Regulatory Affairs Harris Plant Enclosure c: Mr. J. B. Brady (NRC Senior Resident Inspector, HNP)
Mr. R. J. Laufer (NRR Project Manager, HNP)
Mr. L. A. Reyes (NRC Regional Administrator, Region II) 9910060333 990929 PDR ADOCK 05000400 P PDR 5413 Shearon Harris Road New Hill NC
t'q ry>p Enclosure to SERIAL: HNP-99-142 Page 1 of 5 SHEARON HARRIS NUCLEAR POWER PLANT DOCKET NO. 50-400/LICENSE NO. NPF-63 RESPONSE TO REQUEST FOR ADDITIONALINFORMATION REGARDING GENERIC LETTER 95-07, "PRESSURE-LOCKING AND THERMAL-BINDINGOF S~Y-RELATED POWER-OPERATED GATE VALVES" Re uested Information Item 1:
Your August 19, 1996 submittal states that the following valves are susceptible to pressure-locking and that a calculation was used to demonstrate that the valves would operate during pressure-locking conditions.
1SI-3 Boron Injection Tank Outlet 1SI-4 Boron Injection Tank Outlet 1SI-52 High Head Safety Injection (HHSI) to Reactor Coolant System Cold Leg 1RC-113 Pressurizer Power Operated Relief Block Valve 1RC-115 Pressurizer Power Operated Relief Block Valve 1RC-117 Pressurizer Power Operated Relief Block Valve 1SI-86 Normal HHSI to Reactor Coolant System Hot Leg 1SI-107 Alternate HHSI to Reactor Coolant System Hot Leg 1SI-359 Low Head Safety Injection to Reactor Coolant System Hot Leg The calculation assumed that leakage over a 6.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> period would partially depressurize the bonnet of the valves susceptible to thermally induced pressure-locking (1SI-86, 1SI-107, and 1SI-359). This leakage rate was based on testing performed by Commonwealth Edison (ComEd). You also stated that the calculation that is used to predict the thrust required to open the valves during a pressure-locking condition is a simplified version of the ComEd pressure-locking methodology that was developed by ComEd to demonstrate that these valves would operate during pressure-locking conditions.
During a telephone conversation conducted on April 8, 1999, you stated that you are no longer using the ComEd leak rate test results nor the ComEd pressure-locking prediction methodology to demonstrate that valves will operate during pressure-locking conditions. Explain your current methodology that is being used to demonstrate that valves will operate during pressure-locking conditions. Include in the discussion the margin between actuator capability and the calculated thrust value when using your new prcssure-locking prediction methodology, any limitations associated with the use of your new methodology, and any diagnostic test equipment accuracy requirements.
Res onse1:
The current Harris Nuclear Plant (HNP) methodology to demonstrate the above valves will operate under hydraulic pressure-locking conditions involves the addition of a pressure-locking force (PLF) to the calculated unwedging force determined by the Generic Letter (GL) 89-10 motor-operated valve (MOV) unwedging evaluation. This total required unwedging force is then
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Enclosure to SERIAL: HN 142 Page 2 of 5 corppared to the actuator capability. The PLF was developed by type-testing identical Westinghouse valves and applying adjustments to account for differences between the test valves and the installed valves. The test pressures were selected to closely represent the worst case potential locking pressures for the plant valves. Test equipment accuracy was determined to be 8.8%. Attachment 1 contains a more detailed description of the type-test program and how the results were applied to the installed valves, including conservatisms. Since the only valves tested were Westinghouse 1500 lb. class 3" and 10" flex-wedge gate valves, the test results are limited to applications involving these types of valves. To assure that the PLF is included in future evaluations or calculations for these nine valves, it is included as a factor in the HNP MOV unwedging calculation. Also, the MOV post-test evaluation procedure will require that future test data evaluations consider the effect of PLF.
Recent changes to the HNP GL 89-10 MOV calculation methodology, and application of recent test results, have resulted in new HNP actuator margins for the valves with a pressure-locking term. Modifications are planned for Refueling Outage (RFO) 9 in Spring 2000 to improve long-term margins for seven of the valves, as indicated in the table below. The specifics of the modifications are currently under plant review and thus subject to change. The modifications for 1SI-52, 86 and 107 are planned at present to include replacing the existing SMB-000 actuators with SMB-00 actuators, replacing the 10 ft-lb 1700 rpm motors with 15 ft-lb 1700 rpm motors and changing the actuator gear ratio from 36.5:1 to 109:1 by replacing the motor pinion and wormshaft gearing. The modification for 1SI-359 is currently planned to include changing the overall actuator gear ratio from 46.6:1 to 82.5:1 by replacing the motor pinion gear and wormshaft gearing. The modifications for 1RC-113, 115 and 117 are planned to include changing the motor pinion and wormshaft gearing such that overall actuator ratio increases from 41:1 to 109:1. The table below shows the PLF (from Attachment 1, Table 1), the total required unwedging force and actuator capability for each of the nine valves covered by this question.
Valve Pressure Calculated Total Required Actuator Unwedging Locking Force Unwedging Unwedging Capability Margin (lbs.) Force (lbs.) Force (lbs.) (lbs.) (%)
1SI-3 400 1,420 1,820 17,528 863 1SI-4 900 2,308 3,208 17,245 438 1SI-52 2,300 5,131 7,431 9,444 27.1 1SI-86 4,800 5,956 10,756 10,820 0.6 1SI-107 2,000 3,020 5,020 6,382 27.1 1SI-359 24,700 15,990 40,690 51,425 26.4 1RC-113 2,800 8,932 11,732 12,746 8.6 1RC-115 2,800 8,932 11,732 12,574 7.2 1RC-117 2,800 8,932 11,732 12,952 10.4 Notes:
- 1. Margin-enhancement modifications and testing are scheduled for RFO 9.
- 2. "Corrected PLF w/ margin & uncertainty removed" values from Attachment 1, Table 1.
- 3. Valve-specific test data not available for calculated unwedging force. This value is the maximum unwedging force of a group of 10 other 3" Westinghouse flex-wedge gate valves.
Enclosure to SERIAL: 142 Page 3 of 5 Re uested Information Item 2:
Your August 19, 1996 submittal states that the boron injection tank inlet valves, 1SI-1 and 1SI-2, are not susceptible to pressure-locking because it is acceptable for the valves to operate up to approximately 3 seconds at locked rotor conditions. At approximately 3 seconds, a charging pump develops full discharge pressure and the valves are no longer pressure-locked and open against a differential pressure. Explain how any reduction in actuator capability due to operation at locked rotor was accounted for, any testing that demonstrates that actuator capability will or will not degrade after operating at locked rotor. for up to 3 seconds, and any testing that verifies that the charging pumps can develop adequate discharge pressure in 3 seconds.
The NRC has accepted operation of actuators for 1 second or less at locked rotor conditions because testing performed by Idaho National Engineering and Environmental Laboratory (NUREG/CR-6478) demonstrates that the capability of the actuator does not degrade during the 1-second period.
Res onse2:
The 3 seconds of locked rotor time resulted from the HNP ECCS time response testing procedures. Based on discussion with the NRC, and review of responses of other Westinghouse plants, this time seemed very conservative. Subsequent timing of a charging safety injection pump (CSIP) start indicated 1.34 seconds from switch initiation to full discharge pressure. Since the time response testing results included safety injection (SI) signal processing time, the 1.5 seconds used by other plants is considered representative for HNP. A 1.5 second locked rotor period is not expected to degrade actuator capability. For conservatism, CP&L has evaluated the following three effects of a motor actuator at locked rotor for 3 seconds:
- 1) The locked rotor current will heat the motor stator reducing the torque capability. CP8cL has conservatively accounted for this effect by calculating the heating for 3 seconds and applying a torque degradation based on Limitorque "rate of temperature rise" curves. While the accuracy of these curves may be questioned due to lack of actual test data support, the conservative time assumption would bound any inaccuracies in the torque degradation. The reduced torque due to 3 seconds of heating still provides an unwedging margin of 23%.
Therefore, stator heating is not expected to significantly reduce torque capability.
- 2) Thermal overloads could trip rendering the actuator inoperable until manually reset. At HNP, while an SI signal is present, the thermal overloads are bypassed. The accident scenario that gives the locked rotor condition is a loss of coolant accident (LOCA) with loss of offsite power. In this scenario, an SI signal will be present. Therefore, the thermal overloads tripping is not a concern.
- 3) The locked rotor current could cause damage to the motor insulation. The motor operating temperature limit is 132 'C and the calculated motor temperature is only 78.3 'C for a 3-second locked rotor. Therefore, motor insulation damage is not expected.
P Enclosure to SERIAL: HN 142 Page 4 of 5 Based on the above, and the INEEL testing which showed no significant effect with a 1-second locked rotor, valves 1SI-1 and 2 are capable of opening after this short, 1.5-second locked rotor period.
Re uested Information Item 3:
The February 13, 1996 submittal states that residual heat removal (RHR) to charging and safety injection pump suction valves, 1RH-25 and 1RH-63, are susceptible to pressure-locking and, as corrective action, the valves are cycled during startup when the RHR system is aligned to the emergency core cooling mode of operation. Explain if the bonnets of these valves could be pressurized during the RHR pump injection mode of operation and whether these valves would be required to open later during the recirculation phase of an accident when pressure in the bonnets of the valves is greater than upstream and downstream pressures.
Res onse3:
The bonnets of valves 1RH-25 and 63 could become slightly pressurized during the injection mode post-LOCA when the RHR pumps are running at minimum flow recirculation conditions.
When the emergency core cooling system (ECCS) is realigned to the recirculation mode, the valves would be opened with the RHR pumps at approximately design flow conditions. The difference in pump discharge head between minimum flow recirculation and design flow is approximately 30 psi for the RHR pumps. This small differential is not likely to be trapped in the bonnet. Ifit were, it would not result in a significant unwedging force. The quarterly system performance test shuts down the RHR pump from minimum flow recirculation conditions, then strokes open 1RH-25 and 63. These actual test conditions would have approximately 130 psig in the bonnet and 30 psig on either side. The resulting 100 psi bonnet differential is much larger than the possible 30 psi bonnet differential during ECCS switchover. These valves have not failed to stroke during the quarterly testing, and there is not a maintenance history of failures or degradation that could be attributed to pressure-locking. Based on this information, pressure-locking is not a concern for these valves.
Re uested Information Item 4:
Your technical specifications (TS) require an operable emergency core cooling system injection flow path from the refueling water storage tank (RWST) to the reactor coolant system (RCS) via the RHR pump when RCS temperature is less than 350 'F. During the shutdown cooling mode of operation, the RHR pump suction valve to the RWST, 1SI-322 or 1SI-323, is shut. Is the valve required to be opened to realign the RHR pump to inject into the RCS? Ifso, explain why the valve is not susceptible to hydraulic or thermally induced pressure-locking.
Enclosure to SERIAL: 142 Page 5 of 5 Res onse4:
Valve 1SI-322 or 323 would be required to open to establish the flow path from the RWST to the RCS in Modes 4 and 5. This function is not required by Final Safety Analysis Report Chapter 15 accident analyses or Emergency Operating Procedures, but is required by TS. These valves are closed prior to pressurization and heatup of the RHR system for the shutdown cooling mode of operation. While the RHR loop is hot (350 'F maximum), these valves are susceptible to thermal pressure-locking. Ifthe RCS were to rapidly depressurize, they would be susceptible to mild hydraulic pressure-locking.
It is extremely unlikely that a large loss of inventory (beyond CSIP capability) would occur during the short periods of a plant cooldown or heatup. Nevertheless, these valves will be modified to preclude potential pressure-locking. Due to the low likelihood of pressure-locking, the low safety significance of this open function, and the close proximity of RFO 9 (Spring 2000), the modification of these valves will be scheduled for RFO 10 in Fall 2001. This will allow for orderly planning of the modification without adversely impacting the modification scope already in place for RFO 9.
Re nested Information Item 5:
Do your TS credit the use of a gravity boration path to the charging pumps? Ifso, are there any valves in the gravity boration path that may be susceptible to pressure-locking due to evolutions involving operation of the boric acid pumps?
Res onse5:
Yes, the HNP TS credit gravity flow to the charging pumps. There are no valves in this path susceptible to pressure-locking. The only valve in this path required to open is a diaphragm valve.
to SERIAL: 142 Page1of6 EVALUATIONAND APPLICATIONOF VALVEPRESSURE LOCKINGTEST RESULTS
Background:
In response to NRC Generic Letter 95-07, Carolina Power and Light Company (CP&L) based the evaluation of nine potentially susceptible valves on type-testing. In 1996, one 3" and one 10" Westinghouse 1500 lb. flex-wedge gate valves were tested for hydraulic pressure locking forces and bonnet pressure decay rates at the COL Central Dedication and Receiving Facility test lab. These valves were selected due to their similarity to the nine subject plant valves. Valve 1SI-359 is a 10" Westinghouse 1500 lb. flex-wedge gate valve with a SB-2 actuator. Valves 1SI-3, 4, 52, 86, 107 and 1RC-113, 115, 117 are 3" Westinghouse 1500 lb. flex-wedge gate valves with either SMB-000, SB-00, or SMB-0 actuators.
Calibrated VOTES diagnostic equipment, with an accuracy of 8.8%, was used for the test measurements. Seating thrust, unwedging force, motor amps, and appropriate pressure and time measurements were taken. The test pressures were selected to closely represent the worst case potential locking pressures for the plant valves, thus minimizing the need for interpolation. Static unwedging tests were typically run before and after the pressure locking tests to ensure appropriate consistency and repeatability. Typically three pressure locking runs were made at each test pressure point. The opening thrust results of the pressure locking runs as well as the static test results were averaged. The opening thrust test values were within 5% of the opening thrust averages, thus demonstrating repeatability. Since the tested and installed valves may have a different static unwedging force due to actuator type, torque switch setting, etc., the tested static unwedging component is subtracted from the tested opening thrust to give a tested pressure locking force (PLF).
Results are plotted on Figure 1 (3" test valve) and Figure 2 (10" test valve).
Evaluation:
This evaluation is divided into three sections. The "Pressure Locking Data" section addresses how the test data was converted to a specific PLF for each of the nine installed plant valves. The "Bonnet Pressure Decay Data" section develops an adjusted bonnet pressure for use in determining the PLF for valves 1SI-86, 107 and 359. The "Valves With Unequal Upsteam and Downstream Pressures" section describes how the PLF was determined for valves 1SI-52 and 1RC-113, 115 and 117.
Pressure Lockin Data Figures 1 and 2 chart the test results for those data points involving a zero upstream and downstream pressure. Each figure shows a 10% testing uncertainty line drawn above the "best fit" line. The PLF was determined from the uncertainty line to account for test equipment uncertainty. Actual test equipment uncertainty was 8.8% or less as described in the "Background" section above.
To compensate for possible variations in the disk-to-seat coefficient of friction between the tested and installed valves, a static friction correlation was developed for the test valves and installed valves. For valves of similar geometry and materials, the static zero pressure unwedging force (the "09" force as defined by the MOV Program) is essentially a function of the previous seating force to SERIAL: 142 Page 2 of 6 (the "C16" force as defined by the MOV Program) and the frictional forces between the disk and seat. Hence the ratio "R" of the static unwedging force ("09") to previous seating force ("C16") is proportional to the overall static coefficient of friction (CF). Since this same CF is acting under pressure locking conditions, it provides the means to adjust the PLF for installed valve CFs.
During the CP8cL pressure locking testing, a number of static unwedging runs were made. The test static unwedging ratio "R" was calculated by averaging the appropriate "09" and "C16" values and taking the ratio. The results are shown in Table 1. The "R" values for the installed valves were determined from recent in-situ testing under the HNP MOV program. These test results are also shown in Table 1.
A static friction correction factor "K"was determined by dividing the installed valve "R" by the tested valve "R". A 20% margin is included by multiplying the result by 1.2. Table 1 shows these "K"values for the installed valves.
The final corrected PLF for each installed valve is determined by multiplying the tested value for uncorrected locking force by the "K" above. This corrected force is the PLF to be used in the HNP MOV unwedging calculation. This calculation combines the actual installed valve static unwedging force and corrected PLF, to give the total unwedging load. Actuator capabilities and margins are then determined by the HNP unwedging calculation.
Using valve 1SI-3 as an example, the pressure locking conditions involve 2235 psig in the bonnet and 0 psig upstream and downstream. From Figure 1, the PLF (+10% line) at 2235 is 3520 lbs. The unwedging ratio "R" for the test valve is 0.369. The unwedging ratio for the installed SI-3 is 810 lbs /21,447 lbs = .038. The correction factor "K"is .038/.369 (1.2) = 0.124. The corrected PLF is 3520 lbs (0.124) = 436 lbs.
Bonnet Pressure Deca Data Once a gate valve bonnet has trapped pressure, this pressure has been observed to decay over time.
The decay rates are difficultto reliably predict, however, without testing a similar valve under similar conditions. The CP&L bonnet pressure decay testing is considered bounding for the installed valves because the test was conducted on new valves essentially identical to the installed ones. The condition of the new valve seats and disk would be expected to contain bonnet pressure better than a valve that has been in service for over 12 years.
The test data showed decay rates of approximately 4 psi/minute for the 10" valve and 3 psi/minute for the 3" valve at RCS pressure of approximately 2250 psig. The 3" valve was also tested with 1000 psi in the bonnet and showed a decay rate of 0.7 psi/minute. The 10" valve could not be tested at 1000 psi because at approximately 1200 psi, one of the disks unseated to the extent that the bonnet could no longer maintain pressure. The 3" valve leak rate rounded to 1 psi/minute was assumed at lower pressures.
From the original susceptibility evaluation for valve 1SI-359, there could be normal RCS pressure (2235 psi) trapped in the bonnet post LOCA with essentially 0 psi upstream and downstream. It
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to SERIAL: 142 Page 3 of 6 would be opened 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> later during the change from Cold Leg to Hot Leg recirculation. Since the bonnet pressure will decay over a band from 2235 psig to approximately 1200 psig, an average pressure decay rate of 4 psi/min at high pressure+ 1 psi/min at low pressure / 2 = 2.5 psi/min will be used. 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> of decay at an average rate of 2.5 psi/min gives a total decay of 975 psi or a remaining bonnet pressure of 1260 psi. The PLF is then read from Figure 2 and corrected in 'a manner similar to the SI-3 example above.
From the original susceptibility evaluation for valves 1SI-86 and 107, they could have normal CSIP discharge pressure (2750 psi) trapped in the bonnet post LOCA. The bonnet pressure will decay over a band from 2750 psig to approximately 1600 psig. The average pressure of approximately 2200 psi is close to the pressure for which the above 3 psi/min rate was obtained. Using the 3 psi/min decay rate gives a total decay in 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> of 1170 psi. The corresponding bonnet pressure would be 1580 psig. The PLF is then read from Figure 1 and corrected in a manner similar to the SI-3 example above.
Valves with Une ual U stream and Downstream Pressures Valves 1RC-113, 115 and 117 have a potential for a 2235 psi bonnet pressure with 1700 psi upstream and 0 psi downstream during a Steam Generator Tube Rupture scenario. The locking force in this case is determined by averaging the "before" and "after" tested static unwedging forces and subtracting the result (5477 lbs) from the test force (6489 lbs). The test force was chosen because it is the highest of the three test data points. The result is increased by 10% measurement uncertainties to give an uncorrected locking force of 1113 lbs. This force is corrected in a manner similar to SI-3 as shown in Table 1. Note a conservative "K" was chosen for these valves because they have not been static VOTES tested. VOTES testing is scheduled for Refueling Outage 9 (Spring 2000).
Valve 1SI-52 has the potential for a 2750 psi bonnet pressure (normal CSIP discharge pressure) with 2200 psi upstream (CSIP discharge pressure during LOCA injection mode) and 0 psi downstream (RCS pressure during LOCA). The locking force is determined in a manner similar to the PORV block valves above. The average static unwedging (5235 lbs) is subtracted from the highest total pullout (6421 lbs), increased by 10% to give an uncorrected locking force of 1304 lbs. Table 1 shows the subsequent corrections and the final locking force values.
F~ ' to Serial: HNP-99-142 Page4of6 Figure 1 - 3" W 1500 Ib Gate Valve Pressure Locking Test:
Pressure Locking Force vs Bonnet Pressure 4500 4000
+10% line 3500
~ 3000 0
u- 2500 c
+
~ 2000 r 1500 IL 1000 500 500 1000 1500 2000 2500 3000 Bonnet Pressure (psig)
to Serial: HNP-99-142 Page 5 of 6 Figure 2-10" W 15001b Gate Valve Pressure Locking Test:
Pressure Locking Force vs Bonnet Pressure 25000 20000
+10% line Q 15000 O
L, Ol a
O 0
I 10000 O.
5000 500 1000 1500 2000 2500 Bonnet Pressure (psig)
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I
, )I r
/
Attachment 1 to SERIAL: HNP-99-142 Page6of6 Table 1 - Pressure Locking Force Determination Valve Pressure Locking CCC1gl "09" Static Cgfl "K"Static Corrected Corrected PLF'LF Uncorrected C
Conditions Seating Unwed ging Unwed ging Friction PLF w/margin R (Upstream/Bonnet/
Force'lbs.) Force'lbs.)
Ratio Correction (lbs.) (nearest 100 lbs.) uncertainty removed Downstream psig) Factor (nearest 100 lbs.)
3" Test Valve N/A 14,784 5453 0.369 N/A N/A N/A N/A SI-3 0/2235/0 21,447 810 0.038 0.124 3520 400 300 SI-4 0/2235/0 20,281 1630 0.080 0.260 3520 900 700 SI-52 2200/2750/0 7626 4190 0.549 1.79 1304 2300 1800 RC-113 1700 / 2235 / 0 N/A N/A 0.772 2.51 1113 2800 2200 RC-115 1700/2235/0 N/A N/A 0.772 2.51 1113 2800 2200 RC-117 1700 /2235 /0 N/A N/A 0.772 2.51 1113 2800 2200 SI-86 0/ 1580/0 7080 5464 0.772 2.51 2480 6200 4800 SI-107 0/ 1580/0 7726 1932 0.250 0.813 2480 2000 1500 10" Test Valve N/A 53,441 7499 0.140 N/A N/A N/A N/A SI-359 0/ 1260/0 47,575 14,036 0.295 2.53 12,700 32,100 24,700 Notes:
- 2. No seating or static unwedging forces are available for these valves: most conservative "R" (0.772) is assumed.
- 3. Correction factor "K" includes a 20% margin: "K"= (installed Valve "R" / Test Valve "R") x 1.2.
- 4. Uncorrected PLF from Figure 1 for SI-3, 4, 86, and 107; Figure 2 for SI-359; Attachment write-up for SI-52, RC-113, 115, and 117.
- 5. Final PLF (to nearest 100 lbs.) to be used in HNP Unwedging Calculation.
- 6. Values in this column to be used for short term operability assessments only. "K"20% margin and 10% uncertainty have been removed.
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