ML032890314
| ML032890314 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 10/08/2003 |
| From: | Chernoff M NRC/NRR/DLPM/LPD2 |
| To: | Scalice J Tennessee Valley Authority |
| References | |
| TAC MB9480 | |
| Download: ML032890314 (6) | |
Text
Accumulators 3.5.1 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.5.1.1 Verify each accumulator isolation valve 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> is fully open.
SR 3.5.1.2 Verify borated water volume in each 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> accumulator is 7630 gallons and 5 8000 gallons.
SR 3.5.1.3 Verify nitrogen cover pressure in each 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> accumulator is 2 610 psig and 5 660 psig.
SR 3.5.1.4 -----------------NOTE------------------- 31 days The number of TPBARs in the reactor core is contained in the Core Operating AND Limits Report (COLR) for each operating cycle. *The number of TPBARs is limited ----- NOTE------
to no more than 240 based on TVA to NRC Only required Letter dated August 18, 2003. to be performed
________________________________________ for affected accumulators Verify boron concentration in each ---------------
accumulator is as provided below depending on the number of tritium Once within producing burnable absorber rods 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> after (TPBARs) installed in the reactor core each solution for this operating cycle: volume increase of
> 75 gallons, Number of TPBARs Boron Concentration Ranges that is not the result of 0-240* 3000 ppm and 3300 ppm addition from the refueling water storage tank (continued)
Watts Bar-Unit 1 3.5-2 Amendment 7, 21, 40, 48
RWST 3.5.4 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.5.4.1 ---------- NOTE----------------------
Only required to be performed when ambient air temperature is < 600 F or > 105 0 F.
Verify RWST borated water temperature is 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 2 600 F and 105 0F.
SR 3.5.4.2 Verify RWST brated water volume is 7 days Z 370,000 gallons.
SR 3.5.4.3 ----------------NOTE---------------------- 7-days The number of TPBARs in the reactor core is contained in the Core Operating Limits Report (COLR) for each operating cycle.
- The number of TPBARs is limited to no more than 240 based on TVA to NRC Letter dated August 18, 2003.
Verify boron concentration in the RWST is as provided below depending upon the number of tritium producing burnable absorber rods (TPBARs) installed in the reactor core for this operating cycle.
Number of TPBARs Boron Concentration Ranges 0-240* 2 3100 ppm and 3300 ppm Watts Bar-Unit 1 3.5-10 Amendment 7, 40, 48
Design Features 4.0 4.0 DESIGN FEATURES 4.1 Site 4.1.1 Site and Exclusion Area Boundaries The site and exclusion area boundaries shall be as shown in Figure 4.1-1.
4.1.2 Low Population Zone (LPZ)
The LPZ shall be as shown in Figure 4.1-2 (within the 3-mile circle).
4.2 Reactor Core 4.2.1 Fuel Assemblies The reactor shall contain 193 fuel assemblies. Each assembly shall consist of a matrix of Zircalloy or Zirlo fuel rods with an initial composition of natural or slightly enriched uranium dioxide (U02 ) as fuel material. Limited substitutions of zirconium alloy or stainless steel filler rods for fuel rods, in accordance with approved applications of fuel rod configurations, may be used. Fuel assemblies shall be limited to those fuel designs that have been analyzed with applicable NRC staff approved codes and methods and shown by tests or analyses to comply with all fuel safety design bases. A limited number of lead test assemblies that have not completed representative testing may be placed in nonlimiting core regions. For Unit 1, Watts Bar is authorized to place a maximum of 240 Tritium Producing Burnable Absorber Rods into the reactor in an operating cycle.
4.2.2 Control Rod Assemblies The reactor core shall contain 57 control rod assemblies. The control material shall be boron carbide with silver indium cadmium tips as approved by the NRC.
(continued)
Watts Bar Unit 1 4.0-1 Amendment 8, 40, 48
RWST B 3.5.4 BASES APPLICABLE required volume is a small fraction of the available volume.
SAFETY ANALYSES The deliverable volume limit is set by the LOCA and (continued) containment analyses. For the RWST, the deliverable volume is different from the total volume contained since, due to the design of the tank, more water can be contained than can be delivered. The minimum boron concentration is an explicit assumption in the main steam line break (ISLB) analysis to ensure the required shutdown capability. The maximum boron concentration is an explicit assumption in the inadvertent ECCS actuation analysis, although it is typically a nonlimiting event and the results are very insensitive to boron concentrations. The maximum temperature ensures that the amount of cooling provided from the RWST during the heatup phase of a feedline break is consistent with safety analysis assumptions; the minimum is an assumption in both the MSLB and inadvertent ECCS actuation analyses, although the inadvertent ECCS actuation event is typically nonlimiting.
The MSLB analysis has considered a delay associated with the interlock between the VCT and RWST isolation valves, and the results show that the departure from nucleate boiling design basis is met. The delay has been established as 27 seconds, with offsite power available, or 37 seconds without offsite power.
Technical Specification Surveillance Requirements 3.5.1.4, "Accumulators,' and 3.5.4.3, RWST,N match boron concentrations to the number of tritium producing burnable absorbers rods (TPBARs) installed in the reactor core. Watts Bar is authorized to place a maximum of 240 TPBARs into the reactor in an operating cycle. Generally, TPBARs act as burnable absorber rods normally found in similar reactor core designs. However, unlike burnable absorber rods which lose their poison effects over the life of the cycle, some residual effect remains in the TPBARs at the end of the cycle. When larger amounts of excess neutron poisons (as in the case with larger loads of TPBARs) are added to a core, there is competition for neutrons from all the poison and the negative worth of each poison (including the reactor coolant system (RCS) boron) decreases. The positive reactivity insertion due to the negative moderator coefficient that occurs during the cooldown from hot full power to cold conditions following a loss of coolant accident (LOCA) must be overcome by RCS boron. Because the RCS boron is worth less, it takes a higher concentration to maintain subcriticality.
For a large break LOCA Analysis, the minimum water volume limit of 370,000 gallons and the minimum boron concentration limit is used to compute the post LOCA sump boron concentration necessary to assure subcriticality. This (continued)
Revision 13 Watts Bar-Unit 1 B 3.5-26 Amendment 7, 48
RWST B 3.5.4 BASES APPLICABLE minimum value depends on the number of TPBARs in the core as SAFETY ANALYSES specified in the Core Operating Limits Report (COLR) for (continued) each operating cycle. The large break LOCA is the limiting case since the safety analysis assumes least negative reactivity insertion.
The upper limit on boron concentration of 3300 ppm is used to determine the maximum allowable time to switch to hot leg recirculation following a LOCA. The purpose of switching from cold leg to hot leg injection is to avoid boron precipitation in the core following the accident.
In the ECCS analysis, the containment spray temperature is assumed to be equal to the RWST lower temperature limit of 600 F. If the lower temperature limit is violated, the containment spray further reduces containment pressure, which decreases the rate at which steam can be vented out the break and increases peak clad temperature. The acceptable temperature range of 600 F to 105OF is assumed in the large break LOCA analysis, and the small break analysis value bounds the upper temperature limit of 1050F. The upper temperature limit of 105OF is also used in the containment OPERABILITY analysis. Exceeding the upper temperature limit will result in a higher peak clad temperature, because there is less heat transfer from the core to the injected water following a LOCA and higher containment pressures due to reduced containment spray cooling capacity. For the containment response following an MSLB, the lower limit on boron concentration and the upper limit on RWST water temperature are used to maximize the total energy release to containment.
The RWST satisfies Criterion 3 of the NRC Policy Statement.
LCO The RWST ensures that an adequate supply of borated water is available to cool and depressurize the containment in the event of a Design Basis Accident (DBA), to cool and cover the core in the event of a LOCA, to maintain the reactor subcritical following a DBA, and to ensure adequate level in the containment sump to support ECCS and Containment Spray System pump operation in the recirculation mode.
To be considered OPERABLE, the RWST must meet the water volume, boron concentration, and temperature limits established in the SRs.
APPLICABILITY In MODES 1, 2, 3, and 4, RWST OPERABILITY requirements are dictated by ECCS and Containment Spray System OPERABILITY (continued)
Watts Bar-Unit 1 B 3.5-27 Amendment 48
RWST B 3.5.4 BASES APPLICABILITY requirements. Since both the ECCS and the Containment Spray (continued) System must be OPERABLE in MODES 1, 2, 3, and 4, the RWST must also be OPERABLE to support their operation. Core cooling requirements in MODE 5 are addressed by LCO 3.4.7, "RCS Loops-MODE 5, Loops Filled," and LCO 3.4.8, RCS Loops-MODE 5, Loops Not Filled., MODE 6 core cooling requirements are addressed by LCO 3.9.5, "Residual Heat Removal RHR) and Coolant Circulation-High Water Level,'
and LCO 3.9.6, "Residual Heat Removal (RHR) and Coolant Circulation-Low Water Level."
ACTIONS A.1 With RWST boron concentration or borated water temperature not within limits, they must be returned to within limits within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. Under these conditions neither the ECCS nor the Containment Spray System can perform its design function. Therefore, prompt action must be taken to restore the tank to OPERABLE condition. The 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> limit to restore the RWST temperature or boron concentration to within limits was developed considering the time required to change either the boron concentration or temperature and the fact that the contents of the tank are still available for injection.
B.1 With the RWST inoperable for reasons other than Condition A (e.g., water volume), it must be restored to OPERABLE status within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.
In this Condition, neither the ECCS nor the Containment Spray System can perform its design function. Therefore, prompt action must be taken to restore the tank to OPERABLE status or to place the plant in a MODE in which the RWST is not required. The short time limit of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to restore the RWST to OPERABLE status is based on this condition simultaneously affecting redundant trains.
C.1 and C.2 If the RWST cannot be returned to OPERABLE status within the associated Completion Time, the plant must be brought to a MODE in which the LCO does not apply. To achieve this status, the plant must be brought to at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and to MODE 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The allowed Completion Times are reasonable, based on operating experience, to reach the required plant conditions from full (continued)
Watts Bar-Unit 1 8 3.5-28 Amendment 48