ML20216E536
| ML20216E536 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/03/1997 |
| From: | NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML20216E532 | List: |
| References | |
| NUDOCS 9709100223 | |
| Download: ML20216E536 (4) | |
Text
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Docket No. 50-245 B16720 I
I Millstone Nuclear Power Station, Unit No.1 Retyped Bases Pages September 1997 9709100223 970903 P DP.
ADOCK 05000245 P
3.7 CONTAINMENT SYSTEMS BASES C.
Secondary Containment The secondary containment is designed to minimize any ground level release of radioactive materials which might result from a serious accident.
The reactor building provides secondary containment during reactor operation, when the drywell is sealed and in service; the reactor building provides primary containment when the reactor is shutdown and the drywell is open, as during refueling.
Because the secondary containment is an integral part of the complete containment system, secondary containment integrity is required at all times that primary containment is recuired.
Secondary containment integrity is also required when activities having the potential of significant fission products release, such as movement of the fuel cask, irradiated fuel, or other loads in containment are performed.
Administrative controls ensure that loads l
moved in containment, which may result in significant release of fission i
products, are evaluated to determine if secondary containment is required.
If secondary containment is inoperable in RUN, STARTUP/ HOT STANDBY or HOT SHUTDOWN, it must be restored to OPERABLE status within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> time provides a period of time to correct the problem that is commensurate l
with the importance of maintaining secondary containment integrity in RUN, STARTUP/ HOT STANDBY or HOT SHUTDOWN. This time period also ensures that the probability of an accident (requiring secondary containment OPERABILITY) occurring during periods where secondary containment is inoperable is minimal.
If secondary containment cannot be restored to OPERABLE status within the required time, the plant must be brought to a condition in which the LCO does not apply. An additional 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> are allowed to achieve this condition. The allowed times are reasonable, based on operating experience, to reach the required plant conditions from full power conditions in an orderly manner and without challenging plant systems.
l D.
Primary Containment Isolation Valves Double isolation valves are provided on lines penetrating the primary containment. Closure of one of the valves in each line would be sufficient to maintain the integrity of the pressure suppression system.
Automatic initiation is required to minimize the potential leakage paths from the containment in the event of a loss of coolant accident.
MILLSTONE UNIT 1 B 3/4 7-7 Amendment No. 101 0310
4.7 CONTAINMENT SYSTEMS BASES I
1 The frequency of tests and sample analysis are necessary to show that the HEPA filters and charcoal adsorbers can perform as evaluated.
In-place leak tests of the charcoal adsorbers with halogenated hydrocarbon refrigerant shall be performed in accordance with ANSI /ASME N510-1980.
Iodine removal efficiency tests shall follow ASTM D3803-1989, as well as the conditions and requirements specified in the technical specification.
The charcoal adsorber efficiency test procedures should allow for the removal of one adsorber tray, emptying of one bed from the tray, mixing the adsorbent thoroughly and obtaining at least two samples or removal of a test canister.
Each sample should be at least two inches in diameter and a length equal to the thickness of the bed.
If test results indicate removal efficiency less than 95%, all adsorbent in the system shall be L
replaced with an adsorbent qualified to ANSI /ASME N509-1980. The i
replacement tray for the adsorber tray removed for the test should meet the same adsorbent quality. The charcoal filter air flow distribution test is required only if inlet piping, filter plenum, or outlet piping geometry is altered, or if maintenance is performed that alters flow distribution. The flow distribution test is not applicable to the HEPA filters.
In-place leak tests of the HEPA filters with D0P aerosol shall be performed in accordance with ANSI /ASME N510-1980. Any HEPA filters found defective shall be replaced with filters qualified pu-suant to ANSI /ASME N509-1980. Although the SGTS design flow rate is 1100 SCFM, the D0P test at reduced flow rate is actually more sensitive because diffusion is the primary mechanism of small particle collection. The lower limit for test flow rate (500 SCFM) is based on test instrument sensitivity.
All elements of the heater should be demonstrated to be functional and operable during the test of heater capacity. Operation of the heaters will prevent moisture buildup in the filters and adsorber system.
Demonstration of the automatic initiation capability and operability of filter cooling is necessary to assure system performance capability.
Verifying that secondary containment access doors are closed ensures that the infiltration of outside air of such a magnitude as to prevent maintaining the desired negative pressure does not occur. Maintaining secondary containment OPERABILITY, in accordance with the definition for SECONDARY CONTAINMENT INTEGRITY, requires verifying at least one door in each access opening is closed. The access openings covered by Surveillance Requirement 4.7.C.l.b are the normal and emergency double-door accesses on Reactor Building elevation 14' 6" and the railroad track bay access' doors. The monthly frequency for the surveillance requirement
-is considered adequate in view of the other indications of door status that are available.
MIgLSTONEUNIT1 B 3/4 7-10 Amendment No. 77,75,101
4.7 CONTAIMENT SYSTEMS
,,, BASES D.
Primary Cor.tainment Isolation Valves Those large pipes comprising a portion of the reactor coolant system, whose failure could result in uncovering the reactor core, are supplied with automatic isolation valves (except those lines needed for emergency core cooling system operation or containment cooling).
The closure times specified in the Technical Requirements Manual (TRM). are adequate to prevent loss more coolant from the circumferential rupture of any of L
these lines outside the containment than from a steam line rupture.
Therefore, this isolation valve closure time is sufficient to prevent uncovering the core, l
In order to assure that the doses that may result from a steam line break
-do not exceed the 10 CFR 100 guidelines, it is necessary that no fuel rod perforation resulting from the accident occur prior to closure of the main steam line isolation valves. Analyses suggest that fuel rod clad-ding perforations would be avoided for main steam valve closure times, including instrument delay, as long as-10.5 seconds. However, for added margin, the Technical Specifications require a valve closure-time of not greater than five seconds.
The TRM lists the automatic primary containment isolation valves and l
their respective closure times. Also, remote manual or manual primary containment isolation valves that could be opened at power are listed.
The TRM includes administrative controls for opening normally closed remote manual and manual primary containment isolation valves on an intermittent basis during power operation. Administrative controls ensure that containment integrity is maintained during the time that the valves are open.
The ' addition, deletion, or. modification-of any primary containment isolation valve or related information is reviewed-under 10 CFR 50.59 ar.d is approved by the Plant Operations Review Committee.
For reactor coolant system temperatures less than 212'F, the containment could not become pressurized due to a loss of coolant accident. These valves-are highly reliable, have low service requirement and most are normally closed. The initiating sensors and associated trip channels are also checked to demonstrate the capability for automatic isolation.
Ref.
Section 6.2 and Tables 6.2-4 and 5 of the UFSAR. The test interval of once per operating cycle for automatic initiation results in a failure 4
probability of 1.1 X 10 that a line will not isolate. More frequent testing for valve operability results in a more reliable system.
The main steam line isolation valves are functionally tested on a more frequent interval to establish a high degree of reliability.
The containment is penetrated by a large number of small diameter instru-ment lines. A program for periodic testing and examination of the excess f1cw check valves in these lines is performed in accordance with Specification 4.7.D.I.b.
MILLSTONE UNIT 1 B 3/4 7-11 Amendment No. JJ, pp. 77, 101 031tL
.