ML20056E244
| ML20056E244 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 08/03/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20056E243 | List: |
| References | |
| NUDOCS 9308230057 | |
| Download: ML20056E244 (4) | |
Text
'
gaetc fl-UNITED STATES
[ (q Efi j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055E0001 g
,f g se j SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.108TO FACILITY OPERATING LICENSE NO. NPF-10 AND AMENDMENT NO. 97 TO FACILITY OPERATING LICENSE N0. NPF-15 SOUTHERN CALIFORNIA EDISON COMPANY SAN DIEGO GAS AND ELECTRIC COMPANY THE CITY OF RIVERSIDE. CALIFORNIA THE CITY OF ANAHEIM. CALIFORNIA SAN ONOFRE NUCLEAR GENERATING STATION UNITS 2 AND 3 DOCKET NOS. 50-361 AND 50-362
1.0 INTRODUCTION
By letter dated November 20,1994 [ sic 1992), Southern California Edison Company, et al. (SCE or the licensee) submitted a request for changes to the Technical Specification 3/4.4.5, " Reactor Coolant System Leakage," for San Onofre Nuclear Generating Station, Unit Nos. 2 and 3.
The proposed changes would revise the Surveillance Requirement 4.4.5.2.1.c to allow a transient evolution to continue and the required water inventory balance to be performed within 120 hours0.00139 days <br />0.0333 hours <br />1.984127e-4 weeks <br />4.566e-5 months <br /> of the previous balance in lieu of performing the water inventory balance every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
2.0 EVALUATION In part, the licensee has provided the following explanation and justification:
"The Reactor Coolant System Boundary Leakage Detection System is designed to ensure that expected inkage is limited, monitored, and separated from unidentified leakage.
TS 3/4.4.5.2, " Reactor Coolant System -
Operational Leakage," requires monitoring Reactor Coolant System (RCS) leakage, thereby providing additional assurance of detecting an impending failure of the RCS boundary.
The basis for TS 3/4.4.5.2 " Operational Leakage" is to ensure the unidentified portion of the leakage from the RCS is less than a threshold value of I gpm. This threshold value is sufficiently low to ensure early detection of leakage.
The limit of 10 gpm of identified leakage provides allowances for a limited amount of leakage from known sources whose presence will not interfere with the detection of unidentified leakage 9308230057 930B03 PDR ADOCK 0500 1
P
J and will be considered as a portion of the allowable limit..."
"The current [ Surveillance Requirement] (SR) 4.4.5.2.1.c requires a water i
inventory balance every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. To perform an accurate water inventory balance, the following plant conditions must be met:
Makeup operations to the volume control tank are secured.
Sampling of the RCS and interconnected systems are secured.
=
Venting and draining of the RCS and interconnected systems are secured.
Boration and dilution operations are secured.
i Purification ion exchanges and back-flushable filters shall not be shifted.
Letdown to radwaste diversion is secured.
Reactor power level variations are minimized, i
RCS temperature varations are minimized.
i Presurizer level setpoint is not to be changed during the performance of the water inventory balance.
i Safety injection tank levels shall be low enough to ensure that j
draining will not be required for the duration of the water inventory I
balance.
To meet these requirements, transient evolutions such as heat-ups, 3
cooldowns or power changes are interrupted and plant conditions stabilized every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. A transient power evolution, which is expected to be the limiting case, will cause a Xenon transient which can last up to 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. San Onofre Units 2 and 3 perform transient evolutions as part of normal operations. During a plant startup Xenon will build up and will take an additional 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> to reach equilibrium after reactor power is stabilized. This same phenomenon occurs when the reactor is returned to full power following the heat treatment of the circulating water system, which is performed every 6 weeks. These evolutions must be interrupted to allow for Xer:on equilibrium to occur prior to performing the water inventory balance. This 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> has to be a holding period for the plant to stabilize. This proposed change will allow the transient evolution to continue for an additional limited period of time before stabilizing the plant is required following the completion of the transient evolution.
In the worst case this change would allow 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for the transient evolution, 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> for stabilizing the plant, and 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> for performing the water inventory balance. Therefore, a water inventory balance will be performed within 120 hours0.00139 days <br />0.0333 hours <br />1.984127e-4 weeks <br />4.566e-5 months <br /> of the last water inventory balance.
~~ l
\\
r
. The main plant transients which are affected are plant startups and power changes for the circulating water system heat treatments.
The plant startup causes the largest Xenon oscillation. The power transients to support a heat treatment of the circulating water system would not normally cause as long a delay as a startup evolution, but they are performed every six weeks, a much greater frequency than a plant startup.
New wording for SR 4.4.5.2.1.c proposes to allow the transient evolution to continue and the required water inventory balance to be performed within 120 hours0.00139 days <br />0.0333 hours <br />1.984127e-4 weeks <br />4.566e-5 months <br /> of the last water inventory balance.
RCS leakage will be monitored during this time by the other three surveillances specified in Surveillance Requirement 4.4.5.2.1, which are:
i Monitoring the containment atmosphere gaseous or particulate a.
radioactivity monitor at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
j b.
Monitoring the containment sump inlet flow at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
i d.
Monitoring the reactor he&d flange leakoff system at least once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
The experience at San Onofre indicates that transients are not a primary cause of RCS leakage.
However, the potential does exist for transient i
j; induced leakage due to the transient stresses and fatigue. More
)
importantly, the water inventory balance is not the fir:t indicator of a leak because it is only performed once every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, lhe three addtional methods will continue to be employed, and if the leak rate limit is exceeded, as detected by any one method, the plant will be l
shutdown as directed by TS 3.4.5.
Additionally, experiences shows the first indication of a leak is normally an increase in the containment 5
sump l evel.... "
l j
"In summary, the three surveillances listed above provide the primary l
means of leak detection and we have demonstrated these will identify j
leaks in much less than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
Therefore, the water inventory balance l
is a confirmation method rather than an initial leak detection method."
)
i The staff has reviewed the licensee's evaluations and concluded that the
]
requested change is acceptable because the early. detection of unidentified leakage is assured by any one of three additional and independent monitoring 1
l requirements as identified in the licensee's discussion above.
Further, the staff agrees that the RCS water inventory balance provides only confirmation of the unidentified leakage identified by the other techniques; consequently, 4
delaying the procedure for 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> will not affect safe operation of the facility nor endanger the public health and safety.
i l
1 a
1
-r c
c
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the California State official was notified of the proposed issuance of the amendment.
The State official had no comments.
l
4.0 ENVIRONMENTAL CONSIDERATION
l The amendments change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR l
Part 20 and changes surveillance requirements. The NRC staff has determined i
that the amendments involve no significant increase in the amounts, and no i
significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards considera-tion, and there has been no public comment on such finding (58 FR 8784).
Accordingly, the amendments meet the eligibility criteria for categorical l
exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 CONCLUSION
f The Commission has concluded, based on the considerations discussed above, i
that (1) there is reasonable assurance that the health and safety of the i
public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, i
and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
1
(
Principal Contributor: John 0. Bradfute i
Date: August 3,1993 k
1 1
1 t
l l
o