ML20024E756

Forwards Response to 830511 Request for Addl Info on Qualification of Automatic Depressurization Sys (Ads),Tmi Item II.K.3.28.Normal Supply to ADS Is from 8,000-gallon Nitrogen Storage Tank Connected to Vaporizer

ML20024E756
Person / Time
Site:	Cooper
Issue date:	08/26/1983
From:	Pilant J NEBRASKA PUBLIC POWER DISTRICT
To:	Vassallo D Office of Nuclear Reactor Regulation
References
TASK-2.K.3.28, TASK-TM LQA8300204, NUDOCS 8309070023
Download: ML20024E756 (6)

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LQA8300204 August 26, 1983 Director of Nuclear Reactor Regulation Attention : Mr. Domenic B. Vassallo, Chief Operating Reactors Branch No. 2 Division of Licensing U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

II.K.3.28 " Qualification of ADS Accumulators" Response to NRC Request

Reference:

1) Letter from D. B. Vassallo to J. M. Pilant dated May 11,1983, " Qualification of ADS Accumulators, Request for Additional Information"

Attachment:

1) Qualification of ADS Accumulators - Response to Request

Dear Mr. Vassallo:

The purpose of this letter is to respond to your letter of May 11,1983, (Reference 1) requesting additional information on i the qualification of ADS Accumulators. Shown as Attachment i l is the District's response to this request.

Should you have any questions concerning this response, please I do not hesitate to contact my office.

Sincerely, M

Jay M. Pilant Technical Staff Manager Nuclear Power Group JMP/gme:kr29/2 Attachment l

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Attachment:

1) Qualification of ADS Accumulators - ResponseLto Request'

. -1. 'At some specified percent of dryveii ' pressure -li.e., - 70l percent), ~ how mny actuations are the ADS valves capable 'of using only the accumulatora

' when considering leakage, harsh environment, and seismic evente.

Response: The ADS i accumulators will ' provide; the required actuation ' with leakage -of ' the safety relief valve actuator, accumulator,:and

-. associated piping taken' into ' account at -70 percent of drywell pressure. The accumulators, components, Land tubing .between the check valves and the safety relief valves are shown on plant process diagrams to be Class'I seismic. The above installation-was

As-Built" and is- being verified to be Class I seismic by .NPPD's architect engineer. The District is verifying that the electrical' components meet the qualification requirements of 10CFR50.49 in conjunction with the final environmental qualification.of the plant electrical equipment as described in a letter from J. M. Pilant to D. B..Vassallo dated May~20, 1983. The qualification of the mechanical components will follow 'a similar program and schedule set forth for the electrical components.

2. When taking into account ^ leakage, seismic evente and harsh environment, what is the length of time the accumulators are available to perfom

' their function, both at normal containment pressure and at a specified percent of dryveil pressure foiloving an accident? Does this meet the requirements specified in the plant'c FSAR?

Response: Per calculations performed by the District, the accumulators will perform the required relief valve actuation to depressurize the reactor at both normal containment pressure and at 70 percent of drywell pressure. The calculations performed are based in part on GE proprietary information and are therefore not being submitted as-part of this response. The accumulators are leak-tested at normal containment pressure each cycle for one hour to assure that the minimum accumulator pressure is maintained. This question is not

.specifically addressed in Cooper Station's FSAR.

3. Describe the ADS accumulator system and backup system design and operation (e.g., trains, air supply, capacity, alarms and instrumentation and their location, etc).

Response: The ADS accumulator system is shown on Flow Drawing CNS-IA-4 which is enclosed. The ADS accumulator system described in item I has two Class II seismic supplies which connect together and flow through a single line. The normal supply is from a 8,000 gallon liquid nitrogen storage tank connected to a vaporizer which provides the nitrogen gas to the accumulator system through a nitrogen supply regulator at 110-115 PSIG. The backup supply is the instrument air system which consists of three reciprocating air compressors acting in parallel. One compressor is used for the normal supply and two compressors are on standby. Two of the compressors are rated to deliver 600 SCFM at 115 PSIG and one compressor is rated to deliver 800 SCFM at 115 PSIG. There are pressure switches for each accumulator system located inside the drywell thich alarms the control room when a low pressure condition exists. ,

4. Definc the basis . for the allowable leakage criteria ' for ~ the ADS accumulator system (e.g., boundary conditions, environmental, and seismic parameters,: operator interface, margin, etc.).

Response: During an ~ accident condition the supply = to 'the check valves is assumed to'be' cut off and the-system boundary is considered to be from the check valve to the safety relief valve. The allowable

' leakage is' considered to.be such that the system will. maintain at least the minimum required pressure for one hour and still' provide more than adequate relief valve actuation time with the leakage of the relief valve actuator.taken into account. This portion of the system. will be. verified as Class I seismic and environmentally qualified as described in response to question 1, so no additional leakage for these parameters will be considered.

S. What margin is in the allowable leakage criteria to account for possible increase in leakage resulting from the effects of a harsh environment

.and/or a seismic event.

Response: As discussed in the response to question 4, this portion of the system is being verified to be' acceptable and additional leakage due to these parameters will not be considered. If an additional margin were necessary in the leakage criteria, the following applies: (1) the rise in . pressure in- the primary containment during the accident conditions will tend to lower the system leakage since the differential pressure between the primary containment and inside the pneumatic system will be less than at atmospheric pressure; whereas the leakage criteria was based on the results of ADS accumulator surveillance tests at atmospheric conditions and (2) the calculations performed by the District assumed that the 70 percent of drywell pressure which acts against the relief valve actuation remains constant during the accident; whereas lower containment presaure will allow the actuation to occur for a longer period of time.

6. A statement that test and/or analysis performed verified that a harsh environment and/or seismic event vould not increase the leakage rate.

Response: The harsh environment concern is currently being addressed by the District as shown in the response to question 1. Our preliminary review indicates that each of the components would function as required during an accident.

The tubing and components from the check valves to the safety relief valve are designated as Class I seismic in the original process diagram and installation contract. Since this portion is small diameter stainless steel tubing it was orig'nally span charted and the calculations are not readily available. The District has "As-Built" this portion of the system during the present refueling outage and submitted this information to the District's architect engineer to verify the installation meets Class I seismic requirements. These analyses will be done to provide assurance that the leakage rate will not increase.

A statement that verifies that no credit was taken for non-safety related

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equipment and instrumentation when establishing the allouable leakage criteria.

Response: 'All piping components from the check valves to the. safety relief valves are safety grade except the pressure switch. The pressure switch does not perform a safety function. The pressure switches are being analyzed per the schedule set forth in the equipment qualification program to assure . that they would maintain the pressure boundary during an accident condition.

8. Confirm that the backup system vitt meet the overait requirements of the ADS system, taking into account leakage, seismic events and a harsh environment.

Response: The system at CNS consists of two Class II . seismic supplies (nitrogen and instrument air) which tie to a common line outside primary containment as described in the response to question 1.

Each source is capable of supplying the minimum pressure required for the relief valve actuations. The boundary conditions that are required during an accident are described in the response to question 4.

9. A concise description of the testa performed on the backup system and their frequency.

Response: The three air compressors which provide the backup air supply are a part of the plant's preventive maintenance program.

10. A concise description of the surveillance performed, and hou frequent, on alarms and instrumentation associated with the ADS accumulator system and backup system.

Response: The ADS system surveillance tests are summarized as follows:

a) S.P. 6.2.2.2 ADS-Drywell Pressure Calibration and/or Functional Test (PC-PS-100 A, B, C, D). One of the signals required to initiate auto blowdown. Functional Test once per month, Calibration once per three months. Tech. Spec. Table 4.2.B and l 3.2.B.

i b) S.P. 6.2.2.3

ADS Timer Calibration and Actuation Functional Test. Timing relay calibration test and auto blowdown functional test vithout actually operating any of the valves. Functional test

( once per month, Calibration once per operating cycle. Tech.

Spec. Table 4.2.B and 3.2.B.

c) S.P. 6.2.2.4 ADS control monitor functional test. Functional test of the control power transfer. Power monitor functionally tested once per six months. Tech. Spec. Table 4.2.B.

d) S.P. 6.2.2.5 ADS pressure switch functional test. Functional test once per three months. No Tech. Spec, surveillance requirement.

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e) S.P. 6.2.2.6 q ADS. accumulator ' functional test. The -accumulator-Jis:

pressurized-and checked after one hour for leakage. Functional test "once ,per operating cycle. No Tech. . Spec. surveillance requirement. --

f) S.P.6.3.hl ADS'Manu 1lVa ve~ Actuation. Confirm operability of ADS relief valve. . Tech.fSpec. 4. 6 ~. D . 5. Test; once per operating cycle

@ >_100'psig' until3 main turbine bypass valves have closed to

. compensate for relief valve opening.

g) S.P. 6.3.2.2 ADS logic and7SRV solenoid continuity test. Simulate' high drywell pressure and low reactor water level to confirm relief valve - operability and check continuity of relief valve solenoids. Tech. Spec. 4.5.E.1. Test performed prior to start-up'after each refucling outage.

11. A statement that_ confirms that the backup system, associated equipment and control circuitry are seismically qualified.

Response: See response to question 8.

12. If the backup system usee the piping from the isolation valve outside containment to the ADS accicaulator check valve, confirm, via a statement that this section is seisitically_ qualified.

Response: See response to question 8.

13. A statement that confirms that the electrical and mechanical components in the ADS accumulator system and associated equipment and control circuitry are environmentally cualified for conditions ' associated with normal operation, maintenance, testing and postulated accidents.

Response: As stated in the response to question 1, the ADS accumulator system from the check valves to the safety relief valves is being further reviewed for the harsh environment concern. This portion is also being verified as Class I seismic as stated in the response to question 1.

14. A statement verifying that the ADS valves, accumulators, associated equipment and instrumentation are capable of performing their function during and following an accident situation while taking no credit for non-safety related equipment and instrumentation.

Response: The portion of the system discussed in our response to question 13 (that which is required to perform during an accident) is being further evaluated to ensure the systen can perform its function as required during an accident. Non-safety related equipment and instrumentation was addressed in the response to question 7.

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