ML19295E448
| ML19295E448 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Arkansas Nuclear |
| Issue date: | 11/10/1980 |
| From: | Check P Office of Nuclear Reactor Regulation |
| To: | Novak T Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML093450149 | List:
|
| References | |
| FOIA-80-515, FOIA-80-555 NUDOCS 8011250051 | |
| Download: ML19295E448 (10) | |
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cDOCKET FILE ASB READING PCheck Docket No. 50-368 t'EI10RANDUM FOR: Thomas ti. ilovak, Assista46 Director for Operating Reactors, D0L FR0!!:
Paul S. Check, Assistant Director for Plant Systens, DSI gj 8UBJECT:
REQUEST FOR ADDITIONAL INFORMATION AND POSITI0 tis - ARVWiSAS NUCLEAR ONE, UNIT 2 (ANO-2) AUXILIARY FFED'AATER SYSTEM (4KF,!S)
Attached are our reauests for additional infornation and positions resulting from our reviea of the licensee's response of January 31, 1980, to our letter "NRC Requirenents for Auxiliary Feedwater System at Arkansas Nuclear One Unit 2" dated November 6,1979, and also from our review of the licensee's letter of September 17, 1980, on a oroposed Technical Specification change regarding verification of APAS normal flow path. The numbering schees utilized in the attachr.cnt is identifal to that utilized in Enclosure 1 to our requirements letter. The following items that were contained in our requirements letter are being reviewed by ICSB and RSB and will be the subject of separate correspondence:
- Short Term Recocmendation GS This recommendation concerns reouirements for control-grade autoaatic initiation of the APAS and is under review by ICSB.
- Additional Recommendation 3 - This recommendation concerns the safety-grade indication of APA flow to the steam generators and is under review by ICSS.
- Long Term Reco:mendation GL This recormendation concerns safety grade mquirements for automatic initiation of the AFWS and is under review by ICSB.
- Enclosure 2 - Basis for Auxiliary Feedwater Flow Requirements - The licen-see'r responses to this enclosure are under review by RSB.
In addition, Part D of the attachment contains four new questions. Two of these are based on recent AM0-2 licdnsee event reports (LERs) and the other two concern power diversity.
The licensee should be informed that the open itens in the attachment need to be resolved in a manner acceptable to the staff before the AP4S Safety Evaluation Reoort (SER) is issued.
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ATTACHMEi!T Request for Additional Information and Positions Auxiliary Feedwater System (AFWS)*
Arkansas Nuclear One, Unit 2 (ANO-2)
A.
Short Term Recommendation 1.
Recommendation GS-6 "The licensee should confirm flow path availaDility of an ARI system flow train that has been out of service to cerform periodic testing or maintenance as follows:
- Procedures should be implemented to require an operator to detemine that the AF.lS valves are properly aligned and a second operator to independently verify that the valves are properly aligned.
- The licensee should propose Technical Specifications to assure that prior to plant startup following an extended cold shutdown, a flow test would be performed to verify the normal flow path from the primary APd system water source to the steam generators.
The flow test should be conducted with AFAS valves in their nor al alignment."
In response to the first part of this reco:menda# ion, the licensee, in its January 31, 1980 letter, provided summaries of its procedures for realigning the 'JWS to its nomal coerating mode after testing or maintenance of the s ys tem. However, no mentien is made of indecencent verification of crocer valve alignment by a second coerator. Our cosition remains tnat this is a "he tem AF4S as used in this letter acclies to the ANO-2 Energency Feedwater System (E:'AS).
. requirement. The licensee should commit to revise its procedures accordingly, and the adequacy of the revised procedures will ce verified by the Office of Inspection and Enforcement.
In response to the second part of this recommendation, the licensee, in its letter of September 17, 1980, submitted a proposed addi tion to AFW Surveillance Requirerent 4.7.1.2.5, which would require verification of C:e normal flow path of the turbine driven AFW train from the primary AFW water source to the steam generators at least once per 18 months.
The second sentence of this proposed surveillance requirement states, "The provisions of Specification 4.0.4 are not apolicable." In its response letter of January 31, 1980, the licensee stated that the flow path of the motor driven pump train would be verified during startup since this pump normally supplies condensate-to the steam generators during plant startup. We conclude that the licensee's recommendation satisfies Recommendation GS-6 with regard to veri.fication of an EFW flow cath after a cold shutdown, subject to orovision of the basis for non-applicability of Specification 4.0.4.
2.
Recommendation 3 "The Surveillance Requirements section of the Technical Specifications should add oressure and flow acceptance criteria for the ceriodic (31-day) testing of the motor driven cumos."
In its response letter of January 31, 1980, the licensee indicated that the cump would be tested in accorde.ce with Section XI of the ASME Boiler and Pressure Vessel Code.
It is not clear whether the licensee intends to test the motor driven pumo every 31 days (Section XI scecifies inservice testing of pumos nominally every 3 months). ANO-2 Surveillance Require-ment 1.7.1.2 oresently requires a 31 day test for the turbine driven cumo to demonstrate its operability by verification of crocer discharge pressure and flow. There is not presently an equivalent soecification for the motor driven pump. It is our position that a Surveillance Requirement should be included for testing the motor driven puma every 31 days by verifying the develooed discharge cressure and flow rate.
B.
Additional Short Term Recommendations 1,
Recommendation 1 "The licensee should provide redundant level indica-tions and low level alarms in the control rcom for the API system primary water supply to allow the operator to anticipate the need to make up water or transfer to an altern.ite water sucply and prevent a low pump suction pressure condition from occurring. The low level alarm setooint should allow at least 20 minutes for operator action, assuming that the largest capacity AFW pump is operating."
In its response letter of January 31, 1980, the licensee stated that redundancy was provided by safety grade pressure switches located in the suction piping to the AFW pumps which alarm upon a decrease in pressure to 7 psig from its normal 10 psig, and switch the AFW supply to the service water system upon a further decrease in pressure to 5 psig.
This suoject is treated in detail in Long Term Reconmendation GL-2 (Item C.1).
2.
Recommenda tion
- "The licensee should cerform a 72-hour endurance test on all AFW system pumps, if sudi a test or continuous period of operation has not been accomplished to date. Following the 72-hour pump run, the Dumos should be shut down and cooled down and then restarted and run for one hour.
-es: acceptance ;"teria should inriuce demonstrating :nat :ne
4 pumps remain within the design limits with respect to bearing / bearing oil temperatures and vibration and that pump rocm amcient conditions (tempera-ture, humidity) do not exceed environmental qualification limits for safety-related equipment in the room."
Note: The licensee was suosequently infonned by an NRC letter dated December 13, 1979 that this test should be conducted for 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> rathe-than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. This letter also included test acceptance criteria and the information we require from the licensee recarding test results.
The licensee responded that the motor driven pump functioned continuously for over 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> during Unit 2 hot functional testing without exceeding design limits for bearing / bearing oil temperature and vibraticn. The steam driven pump would be tested subsequent to the cutage current at the time tnis response was crenared (Januarv 1480). We require that the licensee suomit reports on tne pumo performance tests to NRC for evalua-tion. For the steam criven pump the report should include the information required in our December 13, 1979 letter.
C.
Lonc Tern Recommendations 1.
Recommendation GL-2
" Licensees with plant designs in which all (primary acd alternate) wuter upplies to the AFW systems cass through valves in a single flow path snould install redundant carallel flow paths (piping and valves).
Licensees with plant designs in whicn the primary AFA system water supply passes througn valves in a single flow pa:h, but the alternate AFA system
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water supplies connect to the AF'd system pump suction piping downstream of the above valve (s), should install redundant valves parallel to the above valve (s) or provide automatic opening of the valve (s) from the alternate water supply upon low pump suction pressure.
The licensee should propose Technical Specifications to incorporate appropriate periodic inspections to verify the valve positions into the surveillance requirements."
This recommendation was not included in our requirements letter (Note:
e of Novemoer 6,1979.)
The normal AR4 pump water supply is from a condensate storage tank via a The ANO-2 single line containing i)oth motor operated and manual valves.
mi systm also includes automatic switchover of the AFW punn water suonly from the condensate tank to the service water system as described in The licensee must Additional Short Tem Recommendation 1 (item B.1).
demonstrate that the response time of the control systems and valvec utilized in switching the water supplies is adequate to protect the pumps from the effects of suction flow temination, and ' at the control Our primary concern is automatic system is redundant in all respects.
switchover resulting from inadvertent closure of a valve in the common As an alternative, the suction line from the condensate storage tank.
licensee must provide redundant carallel valves in the common suction line, as well as meeting the requirements of Additional Short Tem Recommendation I regarding redundant condensate tank level indication and s
k
6 low level alanns in the control room. Disabling the common valves by removing the valve internals would be an acceptable substitute for installing redundant parallel valves.
2.
Recommendation 2 "The Arkansas Unit 2 AR1 system design does not meet the high energy line break criteria in SRP 10.1.9 and Branch Technical Position 10-l' namely, that the APJ system should maintain the capability to supply the required APJ flow to the steam generator (s) assuming a pipe break anywhere in the AF4 pump discharge lines or other high energy line concurrent with a single active failure.
The licensee should evaluate the postulated pipe breaks stated above and (1) deternine any AFd system design changes or procedures necessary to detect and isolate the break and direct the reouired feedwater flow to the steam generator (s) before they boil dry or (2) describe how the plant can be brougnt to a safe shutdown condition by use of other systems wnich would be available following such postulated events."
The licensee responded in its letter of Janury 31, 1980, that if both AF4 trains were rendered inoperable, the ooerator would follow an emergency procedure whicn involves opening the pressurizer ECCS vent valves to lower reactor pressure anc provide greater HPSI flow.
It is our 30sition that this is not an acceptable alternative to meeting the lign energy line break criteria stated aDove. The licensee should demonstrate that eitner tne cresent AF45 design or procosed design revisions meet applicable parts of Branch Technical Position ASB 10-1, ASB 3-1 and *lE3 3-1.
. D.
New Questions 1.
Based on recent licensee event reports (LERs), the ANO-2 turbine driven AFN pump has been subject to a considerable number of trips, mainly due to overspeed, during both testing and plant shutdown. Discuss the effects of these trips on the overall reliability of the AFWS, and what measures are being taken to prevent recurrence of this croblem. S tate what equipment modifications and tests have been perfonned to date and are planned for the future, and provide the pump test results and conclusions.
2.
The ANO-2 AFWS is designed to utilize effluent from the startup and blow-down (SU/BD) demineralizer in parallel with the condensa e storage tank (CST). During an incident on April 7,1980, following loss of offsite power, the effluent temperature rose sufficiently to cause flashing at the AR4 pump inlet, with consequent cavitation and loss of pumo sucticn.
As a result the system ooerating and plant startup procedures were revised to require isolating the SU/BD deminerali:er effluent during plant startuo when 5',' power is reached. Discuss what additional long-term solutions to this problem, such as automatic closure of the motor-operated isola-tion valve in the demineralizer effluent line uoan receipt of an EFAS signal, routing the demineralizer effluent to the CST, or blanking off the line from the demineralizer to the ARi pump suction, are contemolated to increase system reliability.
(See also our SER of Septemoer 18, 1980, on this subject.)
,. 3.
The ANO-2 AF.4 turbine stean acmission valves are AC coerated.
They are locked open wi th power remover du--ing operation.
It would appear that for true power diversity as well as flexibility of ooeration they should be DC operated. Discuss ho., blowdown of both steam generators would be prevented in the event of a oice break downstrean of the check valves below these motor operated valves. Consider operator response time and accessibili ty to these valves af ter the postulated event.
4.
In accordance with the ANO-2 FSAR, section 9.2.1, the service water sys-tem (SUS) provides cooling for the AP.1 pump rooms. Since the SWS would not be available on loss of all AC cower, state whether the turbine operated AF.4 pump could function for two hours without room cooling.
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