ML20077S584
| ML20077S584 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 01/19/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20077S587 | List: |
| References | |
| NPF-37-A-065, NPF-66-A-065 NUDOCS 9501240159 | |
| Download: ML20077S584 (1) | |
Text
REACTIVITY CONTROL SYSTEMS
,, BASES 3
B0 RATION SYSTEMS (Continued)
With the RCS temperature below 350*F, one Boron Injection System is acceptable without single failure consideration on the basis of the stable reactivity condition of the reactor and the additional restrictions prohibiting CORE ALTERATIONS and positive reactivity changes in the event the single Boron i
Injection System becomes inoperable.
The limitation for a maximum of one centrifugal charging pump to be OPERABLE and the Surveillance Requirement to verify all charging pumps except the required OPERABLE pump to be inoperable below 330*F provides assurance that a mass addition pressure transient can be relieved by the operation of a single PORV or an RHR Suction relief valve.
l The boron capability required below 200*F is sufficient to provide a SHUTDOWN MARGIN of 1% Ak/k after xenon depay and cooldown from 200*F to 140*F.
This condition requires either 740 (2,652 ) gallons of 7000-ppm borated water from the p)oric acid storage tanks or 2264 (11,840*) gallons of 2300-ppm (2000-ppm borated water from the refueling water storage tank (RWST).
A Boric Acid Storage Syy) tem level of 7% ensures there is a volume of greater than or equal to 740 (2652 gallons available. An RWST level of 9% ensures there l
is a volume of greater than or equal to 38,740 gallons available.
The contained water volume limits include allowance for water not available because of discharge line location and other physical characteristics.
The limits on contained water volume and boron concentration of the RWST also ensure a pH value of between 8.0 and 11.0 for the solution recirculated within l
containment after a LOCA.
This pH band minimizes the evolution of iodine and minimizes the effect of chloride and caustic stress corrosion on mechanical systems and components.
l The OPERABILITY of one Boron Injection System during REFUELING ensures that this system is available for reactivity control while in MODE 6.
The OPERABILITY of the automatic Boron Dilution Protection System ensures adequate capability for negative reactivity insertion to prevent a transient caused by tha cacontrolled dilution of the RCS in MODES 3, 4, and 5.
The functioning of the system precludes the necessity of operator action to prevent further dilution by terminating flow to the charging pump (s) from possible unborated water source; and initiating flow from the RWST. The most restrictive condition occurs shorf.ly after beginning of life when the critical boron concen-tration is highest, i.nd a 205 gpm dilution flowrate provides the maximum positive reactivity addition rate.
One reactor coolant pump in operation with all reactor coolant loop stop isolation valves open reduces the reactivity addition rate by
)
mixing the dilution through all four reactor coolant loops. A minimum count rate of ten counts per second minimizes the impact of the uncertainties associated with the source range nuclear instrumentation.
In the analysis of this accident, a minimum SHUTDOWN MARGIN of 1.3 Ak/k is required to control the reactivity tran-
.sient. Actions taken by the microprocessor if the neutron count rate is doubled iwill prevent return to criticality in these MODES.
- Not applicable to Unit 1.
Applicable to Unit 2 until completion of cycle 5.
9501240159 950119 PDR ADOCK 050004b4 i
P PDR BYRON - UNITS 1 & 2 B 3/4 1-3 AMENDMENT N0. 65