ML20076D214

Proposed Tech Specs Re Design Pressure for Drywell Primary Containment Vessel

ML20076D214
Person / Time
Site:	Oyster Creek
Issue date:	07/22/1991
From:	GENERAL PUBLIC UTILITIES CORP.
To:
Shared Package
ML20076D209	List: ML20076D208 ML20076D211 ML20076D214
References
NUDOCS 9107260128
Download: ML20076D214 (6)

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OYSTER CREEE TECHNICAL SPECIFICATION CHANGE REQUEST NO. 198 REVISED TECHNIQAL SPECIFICATION PAGFE 9107260128 910722 PDR ALOCK 05000219 F' PIIR

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to conteinment cooling h:st exchangor performanco implicit in t?

containment cooling description. Since the loss-of-coolant accide while in the cold . shutdown condition would not require containment

_ spray, the system may be~ deactivated to-permit integrated leak rate

' testing of the primary containment while the reactor is in the cold shutdown condition.

The control rod - drive hydraulic system can provide high prowsure 'l 2

coolant injection capability. For break sizes up to 0.002 ft, ,

- single control rod drive pump with flow of 110 gpm is adequate for ,

maintaining the water level nearly five feet above the core,-thus l alleviating the necessity for auto-relief actuation (3). l l

The core spray. main pump compartments and containment spray pump compartments were provided with water-tight doors (4). Specification 3.4.E ensures that the doors are in place to perform their intended function.

Similarly, since a loss-of-coolant accident when primary containment integrity is not required would not result in pressure build-up in the drywell or torus, the containment spray system may be made inoperable under these conditions.

Esferences (1) Licensing Application, Amendment 34, Question 1 (2) Licensing Application, Amendment 32, Question 3 (3) Licensing Application, Amendment 18, Question 1 (4) . Licensing Application, Amendment 18, Question 4 OYSTER CREEK 3.4-7 Amendment No 21, 75

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• • rod worth- such that a rod drop would not result in any fuel damage. In

addition, in the unlikely event that an excursion did occur, the reactor . building - and standby gas treatment . system, which shall be operational during thia , time, of f er . a nef ficient - barrier to - koep 1

off-z3te doses well below 10 CFR 100 limits.

.o The. absorption chamber water volume provides the heat sink for'the reactor' coolant ' system energy released-following the loss-of-coolant accident. The core spray pumps and containment spray pumps are located

-in the . corner ' rooms and due. to their proximity to the torus,- the -

ambient temperature in those-: rooms could rise during the design basis accident. calculations (7) made, aseuming an initial torus water temperature of. 100*F and a minimum water - volume of 82,000. f t3, indicate that the corner room ambient temperature would not exceed the core spray and containment spray pump motor operating temperature

-limits and,-therefore, would not adversely affect the long-term core cooling capability. -The maximum water volume limit allows for an o

operating range without significantly affecting accident analyses with respect to free air' volume in the absorption chamber. For example, the cont?'ement capability (8) with a maximum water volume of 92,000 ft 3 is reduced : by = not more than 5.5% metal-water - reaction below the carcbility with 82,000 ft3 Exparimentalidata indicate that excessive steam condensing loads can be avoided if the-peak temperature of the suppression pool is-maintained Delow 160*F during any period of-relief valve operation with sonic conditions at the dischcrge exit. Specifications have been placed on the envelope of reactor operating conditions so that the reactor can be depressurized.. in-- a timely manner to avoid the regime of potentially

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high-. suppression chamber loadings.

-The technical specifications allow for torus repair work or inspections  !

that might require decining of the supprossion pool when all- irradiated fuel is removed or when the potential:for draining the reactor vessel

-has been minimized. This specification also provides assurance that the irradiated fuel has an adequate cooling water supply for normal and emergency conditions with the reactor mode switch in shutdown or refuel whenever the suppression pool is drained for inspection or repair.

The-purpose of the vacuum relief valves is to equalize the pressure between the drywell and suppression chamber, and suppression chamber and roactor building so that the containment external. design pressure -

limits are not exceeded.

. The vacuum relief system from the reactor- building to the pressure

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suppression chamber consists of two 100% vacuum relief breaker subsystems (2 parallel sets of 2 valves in series) . Operation of

-either subsystem will maintain the containment external pressure less-than the 2 psi external design pressure of the drywell; the external design pressure of'the suppression chamber is 1 psi (FDSAR Amendment l 15, Section 11).

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- The- capacity of the 14 suppressic1 chamber to drywell. vacuum relief valves is sized to limit tbs external pressure of the drywell during post-accident drywell cooling operations to the design limit of OYSTER CREEK 3.5-8 Amendment No.: 75

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4 o asie: In th3 cv:nt of c lor-of-cooltnt cccid:nt, tha petk drywall pressuro would be 38 peig which would rapidly reduce to 20 poig within 100 seconds following the pipe break. The total time the drywell pressure would be above 35 peig is calculated to be about 7 seconds.

Following the pipe break, absorption chamber pressure rises to 20 peig within 8 seconds, equalizes with drywell pressure at 25 peig within 60 seconds and thareaf ter rapidly decays with the drywell pressure decay. W The original design pressures of the dr ell and absorption chamber are 62 peig and 35 psig, respectively. ) The original calculated 38 peig peak drywell pressure was subsequently reconfirmed. W A 15% allowance was applied to revise the drywell design pressure to 44 peig. The design leak rate is 0.5%/ day at a pressure of 35 psig. As pointed out above, the pressure response of the drywell and absorption chamber following an accident would be the same after about 60 seconds. Bnsed on the calculated primary containment pressure response discussed above and the absorption chamber design pressure, primary containment pre-operational test pressures were chosen. Also, based on the primary containment pressure response and the fact that the drywell and absorption chamser function as a unit, the primary containment will be tested as a unit rather than testing the individual components separately.

The design basis loss-of-coolant accident was evaluated at the primary containment maximum allowable accident leak rate of 1.0%/ day at 35 poig. The analysis showed that with this leak rate and a standby gas treatment system filter ef ficiency of 90 percent for halogens, 95% for particulates, and assuming the fission product release fractions stated in TID-14844, the maximum total whole body passing cloud dose is about 10 rem and the maximum total thyroid does is about 139 rem at the site boundary considering fumigation conditions over an exposure duration of two hours. The resultant doses that would occur for the duration of the accident at the low population distance of 2 miles are lower than those stated due to the variability of meteorological conditions that would be expected to occur over a 30-day period. Thus, the doses reported are the maximum that would be expected in the unlikely event of a design basis loss-of-coolant accident. These doses are also based on the assumption of no holdup in the secondary containment resulting in a direct release of -fission product from the primary containment through the filters and stack to the environs. Therefore, the specified primary containment leak rate and filter efficiency are conservative and provide margin between expected of fsite doses and 10 CFR 100 guideline limits.

Although the dose calculations suggest that the allowable test leak rate could be allowed to increase to about 2.0%/ day before the guideline thyroid dose limit given in 10 CFR 100 would be exceeded, establishing the limit of 1.0%/ day provides an adequate margin of safety to assure the health and safety of the general public. It is further considered that the allowable leak rate should not deviate significantly from the containment design value to take advantage of the design leak-tightness capability of the structure over its service lifetime. Additional margin to maintain the containment in l Change 7, 27, l OYSTER CREEK 4.5-12 Amendment No.: 132 l

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Ths drywall sxterior was coated with Firebar D prior to concrote pouring during construction. The Firebar D separated the drywell steel plate from the concrete. After installation, the drywell liner was heated and expanded to compress the Firebar D to supply a gap between the steel drywell and the concrete. The gap prevents contact i of the drywell wall with the concrete which might cause excessive local stresses during drywell expansion in a loss-of-coolart accident. The surveillance program is being conducted to demonstrate that the Firebar D will maintain its integrity and not deteriorate throughout plant life. The surveillance frequenc -ic adequate to  ;

detect any deterioration tendency of the material. OI The operability of the instrument line flow check valves are demonstrated to assure isolation capability for excess flow aad to assure the operability of the instrument sensor when required.

Because of the large volume and thermal capacity of the suppression pool, the volume and temperature normally char.ges very slowly and monitoring these parameters daily is sufficient to establish any temperature trends. By requiring the suppression pool temperature to be continually monitored and also observed during periods of significant heat addition, the temperature trends will be closely followed so that appropriate action can be taken. The requirement for an external visual examination following any event where potentially high loadings could occur provides assurance that no significant damage was encountered. Particular attention should be focused on structural discontinuities in the vicinity of the relief valve discharge since these are expected to be the points of highest stress.

References (1) Licensing Application, Amendment 32, Question 3 (2) FDSAR, Volume I, Section V-1.1 (3) GE-NE 770-07-1090, " Oyster Creek LOCA Drywell Pressure Response," February 1991 (4) Technical Safety Guide, " Reactor Containment Leakage Testing and Surveillance Requirements," USAEC Division of Safety Standards. Revised Draft, December 15, 1966.

(5) FDSAR, Volume I, Sections V-1.5 and V-1.6 (6) FDSAR, Volume I, Sections V-1.6 and XIII-3.4 (7) FDSAR, Volume I, Section XIII-2 (8) Licensing Application, Amendment 11, Question 111-18 OYSTER CREEK 4.5-16 Amendment No.: 7,27

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5.2 201tTAIMiull A. The primary containment shall be of thb press' 'e suppression type .iaving a drywell and an absorption chamber constructed of steel. The drywell snal' have a volume of approximately 100,000 ft 3 and is designud to conform to ASME Boiler and Pressure Vessol Code,Section VIII, for an internal prob.;'tre of 44 peig at 175'F and an external pressure of 2 poig it l 150* F + o 20$

• F. The absorption changber shall have a tota 1 volume of approximately 210,000 ft . It is designed to conform to ASME Doller and Pressure vessel Code,Section VIII, tor an internal pressure of 35 psig at 150'T and an external pressure of 1 psig at 150'F.

D. Penetrations added to the primary containment shall be designed in accordance with standards cet forth in Section V-1.5 of the Facility Description and Ssfety Analysis Report . Piping passing through such penetrations shall have isolation valves in accordance with standards set forth in Section V-1.6 of the Facility Description and Safety Analysin neport.

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OYSTER CREEK 5.2-1

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