ML20207S803

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Forwards Div of Engineering Plan for Resolution of Issues Re Design of Piping.Staff & Licensee Actions Necessary to Close Out Seven piping-related License Conditions Outlined. Related Documentation Encl
ML20207S803
Person / Time
Site: Diablo Canyon  Pacific Gas & Electric icon.png
Issue date: 04/27/1984
From: Vollmer R
Office of Nuclear Reactor Regulation
To: Harold Denton
Office of Nuclear Reactor Regulation
Shared Package
ML17325B782 List:
References
FOIA-84-741, FOIA-84-742 NUDOCS 8703200282
Download: ML20207S803 (21)
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![po*e.,,Io, UNITED STATES fE 7,

NUCLEAR REGULATORY COMMISSION

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..Y..* April 27, 1984 yh e MEMORANDUM FOR: Harold . Der n "'eci.or Office Nac ear Reactor Regulation .

FROM: Richard H. Vollmer, Director

  • Division of Engineering '

SUBJECT:

RESOLUTION OF DIABLO CANYON PIPING DESIGN ISSUES The Division of Engineering plan for resolution of issues related to design of piping at Diablo Canyon is enclosed. The plan outlines the staff and licensee actions necessary to close out the seven piping-related license conditions now in place by Commission order. Our current estimate of the resources necessary for timely resolution of these issues is 0.4 psy and 5120 K of contractor support.

Each of the seven conditions will be assigned to a specific group for review of the licensee's submittals, audits and plant walkdowns as y necessary and preparation of the SER input. The group leaders will be selected from the members of the peer review panel that was organized to review the concerns expressed by Mr. Yin. In addition to the assigned NRR, IE and Region I staff we have planned for participation by two individuals from each of Battelle Columbus Laboratories, INEL and ETEC.

For most of the license conditions, we anticipate a submittal from the licensee that will be reviewed as the basis for on-site audits. The v audits will be scheduled as soon as practicable.after the Itcensee has provided adequate documentation to assure that a meaningful audit is possible. Initial submittals from the licensee are expected on or shortly after April 27, 1984 Although our completion of these activities will depend on the timeliness and adequacy of the licensee submittals, our estimate based on current ,' [3 knowledge of licensee action on these issues is mid June.

after review of the first submittals, we will be in a better position toBy next Friday, ' # 'e a judge a completion date.

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x \ Resources and the time necessary to complete other Diablo Canyon pensibilities of DE including the scheduled inspection of the 10VP piping cw program, are included in this estimate.

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  • Harold R. Denton We would appreciate your feedback on the program we have outlined and the acceptability of the tentative schedule.

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' Richard H. Vollmer, Director Division of Engineering -

Enclosure:

As stated -

cc: E. Case D. Eisenhut J. Knight '

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License condition 1: Review of Computer Arelyi'ed Small acre Pipe / Supports  ;

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l. Staff develops aopicach to 62 folicded ir,,. 4 selecting audit sampir.,
2. PG&E notifies NRC that revic'.1 of computar analyzed small bore piping analysis is com-plete enough for audit. "

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3. Staff schedules audit at project offices. '

4.' NRC audit team selects approximately 15 supports for review. .

5. PG&E provides analysis packages for selected supports. Review by staff.
6. Staff completes review of initial 15, '

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', dis;usp . findings'and determines need to -

revies additi,onal supports, ~

7. Prepare SSER, assuming review beyond .

initial 15 is not required.

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License Condition- 2: Requirements for Closely Spaced Supports e .

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Item

1. PG&E submits to NRC a report on rigid rupports N >

installed in close proximity to rigid restraints or anchors. The report will i include a numerical breakdown of the cases e

involved, the shimming criteria to be uso: by .

PG&E, and a description of the program to be .

followed in the shimming process. PG&E will

":Q , provide their schedule for performance of shimming.

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2. Staff review of PG&E program.

. 3.. Staff schedules audit at site

4. Preparatory discussions at site. Observation of cases where shimming is not needed.

e s Selection of cases to be observed by staff where shimming is needed. Staff walkdown with PG&E to observe field preparations for shimming of approximately 8 cases.

i' L. Staf f independent verification of completed shimaing by PG&E of the 8 cases.

6. Prepare SSER.

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' License Condition 3: Review of Snubbers Close to Rigid Supports and Anchors

, Item .

J.. 1. PG&E submits a report to the NRC identifying l ',

all snubbers located in close? proximity to rigid supports and anchors,' describing their '

n snubber lock-up motion criteria, and demonstrating how piping and pipe support x licensing criteria are mer.

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2. Staff reviews PG&E report. -
3. Staff schedules audit at project. ,
4. Staff reviews five specific analyses at ._

project offices. This. effort will include a review of piping analyses and verification of the adequaiy of adjacent supports / anchors.

5. Prepare SSER.

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- Lkcense condition 4: Thermal Gaps Item

1. PG&E submits a -report-to NRC documenting tne

. pipe supports in which thermal gaps were r

included in the analysis. - The report will include a description of the analysiimethods where gaps are to be retained, and the proposed gap monitoring program. The report util also document' the cases in which retention of the .

gaps has been found to be unnecessary and 1

  • summary of the analyses that support thi: -

, conclusion. ,

2. ' Staff review of PG&E report.

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3. Staff schedules audit at project offices and site.
4. Staff reviews of approximately four pipe stress thermal analyses at project offices.

S. Staff travels to site from. project offices.

6. ' Staff walkdown for monitoring of thermal movements and observation of modifications to remove gaps.
7. Prepare SSER.

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__ License l Condition 5: Walkdown of Mainsteam and Main Feedwater Piping Systems Item -

1. PG&E notifies NRC of the schedule for hot walkdown of the mainsteam piping systems.
2. Staff schedules audit at project offices and site.
3. Staff reviews mainsteam piping thermal ~

analyses, hot walkdowr. procedures and .

locations identified by PG&E for taking -

. measurements of thermal movements.

4 ~. Staff travels to site from ' project offices. .

5. Staff observes PG&E walkdown and makes indepsndent observations of results as compared to predictions.
6. Staff discusses with PG&E the follow-up actions needed to reconcile observations with predictions and to alleviate any

' unintended restraints.

7. Prepare SSER, assuming additional observation of follow-up actions is not needed.

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License Condition 6: Quick Fix and DP Pr79 rams Item

1. PG&E submits program for revi&w of Quick Fix and DP activities.
2. Staff reviews PG&E program.
3. Staff schedules audit at project offices .

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4. Staff discusses with PG&E the implementation '

, of the Quick Fix and DP programs. PG&E provides documentation examples of the original Quick Fix and DP programs for NRC review.

5. Staff discusses PG&E approach to review of the programs per the license condition. Staff returns to Bethesda.
6. PG&E notifies NRC that review of DP and Quick Fix activities is sufficiently complete for audit of results. ,
7. Staff reviews sample Quick Fix and DP documentation to verify that the areas of

! concern identified in L.C. 6 have been properly treated.

8., Staff travels to site from project o'ffices.

!- 9. Staff performs site walkdown of qui'ck fix

! implementation on hardware.

10. Prepare SSER.

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License Condition 7: Resolution of Technical Topics Item ,

1. PG&E submits to NRC pr'oposed additions and modifications to design criteria . addressing the resolution of the technical topics (a) thru (f).
2. Staff reviews PG&E proposed resolutions. ,
3. Meating between staff and PG&E in Bethe::.'c .

to resolve differences and agree on -

implementation of modified design criteria.

4. PG&E notifies NRC that implementation of modified design criteria is sufficiently -

complete for audit.

5. Staff schedules audit at project offices.
6. NRC audit team selects approximately 15 ~

supports for review.

7. PG&E provides analysis packages for selected supports. Review by staff.

B. Sta'ff completes review of initial 15, discuss f.indings and determines need to review additional supports.

9 .* Prepare SSER, assuming review beyond initial 15 is not required.

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Sumary of Resources License Condition- Staff Cost

  • 1 0.13 psy $24.7k 2 ,

0,06 psy $10,8k 3 0.06 psy $11,5k 4 Q,06 psy $10,8k ,

o 5 Q 22 psy $39.6k .

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0,2 psy $37,5k 7 Q,18 psy $31,4k G,91 psy $166,3k Participatton in Addittenal Yin Inspections Q.43 176.4k Total Resources 1,34 $242,7k

  • Costs based on contractor rates for all aspects, although about 1/3 of review team personnel will be NRC staff.

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-Task: Allegation 39 (previously addressed in SSER 21)

ATS No.: RV 83A47 BN No.: 83-169 (10/20/83)

Characterization There is no control room annunciation provided to alert the operators (s) when the RHR letdown line has been isolated during Modes 4, 5, and 6 (hot shutdown, cold. shutdown, and refueling'respectively).

Related Allenations: 37, 40, 45, 177 Implied Significance to Plant Desion, Construction, or Operation Previously addressed in SSER 21.

Assessment of Safety Significance In SSER 21 the staff stated that indication provided in the control room of RHR letdown line isolation includes position indication for two valves in series as well as RPR system flow, nressure, and purp status information. Although these features provide a capability to assess RHR status, the staff has recognized the need for installation of a RHR low flow alarm. Accordinaly, the licensee was required to install a RHR low flow alarm durina the first refueling.

A.4-39.1

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Staff Position In SSER 21 the sta f stated that this allegation does not involve considerations that question plant readiness for power ascension testing or full power operation.

In a letter of February 15, 1984 the licensee committed to install the RHR low flow alarm prior to entering Mode 1, i.e. operation above 5 percent power. The licensee also provided the administrative controls and procedures .

that are now in effect. Based on this committment, the staff finds these controls and procedures acceptable for the interim, i.e. until installatier of the alarm.

The staff. concludes that the issue is resolved with regard to criticality and lower power operation.

Action Reauired The staff requires that the low flow alarm be installed prior to entering Mode 1 and that the licensee advise the staff of the completion of the in-stallation prior to Mode 1.

A.4-39.2

TASK: Allegation 45 (Previously addressed in SSER 21)

ATS NO.: RV 83A47 BN NO.: 83-169 (10/20/83)

Characterization:

Section 5.5 of the Diablo Canyon FSAR describes the autoclosure interlock for. the RHR suction line isolation valves (8701 and 8702).- Section 3.4.9.3.a of the Diablo Canyon Technical Specifications requries power to be removed from these isolation valve operators during Pode 4 (hot shutdown, RCS cold leg temperature is less than 323 F). Pode 5 (cold shutdown) and Mode 6 (refueling). This requirement defeats the function of autoclosure interlock for the valves.

Related Allegations: 37, 39, 40, 177 Imolied Significance to Plant Design, Construction or Operation As stated in SSER 21, as the result of Technical Specification Section 3.4.9.3.a, the isolation valves will be left in an open position& with petan pokw r removed

& f: dubr low ressure/ temperature operation gf the plant. The g automatic c os re e ' .

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f. ';d gthes e%isolation valves causMr hem to lose their design g fuction. This will result in a situation in which insufficient isolation capabilit.v exists to prevent an intersystem LOCA between high pressure RCS and the low pressure RHR system.

A.4 45.1

-2 Assessment of Safety Significance As stated in SSER 21, the staff concluded in Diablo Canyon SSER 13 that thelicenseeshouldberequiredtoprovideanalarmtoalerttheoperatorto a degradation in ECCS during long term recirculation. A low flow alarm was stated to be an acceptable method to satisfy this concern and the staff indicated that an alarm should be installed at the first refueling outage.

Until then, procedures and dedicated operators were to be implemented during long term recirculation to manage and monitor ECCS performance.

Staff Position As stated previously in SSER 21, to implement the staff position stated in SSER 13, the installation of a low flow alarm for RHR pump protection is being considered as a license condition in the Diablo Canyon full power license. Additionally, it is the staff position that power be available to the RHR M0Vs when in a shutdown condition. However, there is a question as to when these requirements should be implemented. If the low flow alarm were not installed until the first refueling outace, =**n ower to the psR eovs in the meantime wouie result in the autoclosure interlock be

-~h e,d na'bie to provide protection against intersystem LOCA.

A.4-45.2

In a letter dated February 15, 1984 the licensee committed to install the RHR low flow alarm prior to entering Mode 1, i.e. operation above 5 percent power.

The licensee also provided the administrative controls and procedures that are now in effect. Based on the committment the staff finds these controls and procedures acceptable for the interim, i.e. until installation of the alarm.

The staff concludes that this issue is resolved with regard to criticality and low power operation.

Action Pecuired The staff requries that the low flow alarm he installed prior to enterino "oda 3 and that the licensee advise the staff f,the, completion of the installatico ,

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e Task: Allegation 177 ATN No. None BN No.: None Characterization The allegation relates to the RHR pump common suction line valve control and a potential damage to RHR pumps due to loss of suction as a result of a single failure.

Related Alleoations: 37, 39, 40, 45 (previously discussed in SSER 71)

Imolied Sionificance to Plant Desian, Construction or Operation The RHR suction line from the RCS hot leg in the Diablo' Canyon design contains two isolation valves (8701 and 8702) in series that are normally closed durina power operation and hot standby condition (Modes 1,~2 and 3) The RHR suction line from the RCS hot leg is only used during Mode 4 (hot shut-down with RCS cold leg temperature less than 323 *F), Mode 5(cold shutdown) and Mode 6 (refuelina). A postulated inadvertent closure of either isolation valve (8701 or 8702) in the RHR suction line during plant shutdown could causa potential damage to both RHR pumps.

Diablo Canyon SSER 22 A.4-177.1

Assessment of Safety Significance This allegation ove,rlaps concerns previously expressed in Allegations 40 and 45 which have been addressed by the staff in Diablo Canyon SSER No. 21.

Thi,s concern also has been discussed by the staff at an ACRS meeting on February 10, 1984.

The potential damage of both RHR pumps due to loss of suction as a result of a single failure is prevented by the following provisions:

1. In response to the staff reovirement in SSER 21 regarding Allegation 45, PG&E has committed, in a letter dated February 15, 1984, to install the RHR low flow alarm prior to entry into power operation (i.e. Mode I with associated decay heat generation). The low finw alarm will be set so that sufficient time would be available to alert the operators to trip the RHR pumps before pump damage occurs.
2. The current Technical Specifications and operating procedures for Diablo Canyon linit I preclude the inadvertent closure of either of the two RHR pump suction line isolation valves (8701 and 8702) by maintaining the valves in an open position with power removed for the valve operators during Modes a, 5 and 6.

A.4-177.2

. . . _ - - - - _ = _ _ _ - _ , _ . -

The applicant stated at the ACRS meeting on February 10, 1984 that RHR pump damage could occur in 10 to 15 minutes following loss of suction flow.

Operating experience from the Calvert Cliffs Nuclear Power Plant showed that the RHR pump seals were damaged approxinately 15 minutes after loss of suction fl ow. The failure of both RHR pumps is an event beyond the design basis and its occurence is highly unlikely based on the plant specific design and administrative controls discussed above. However, if failure of both RHR pumps should occur during plant shutdown, the following steps could be taken to maintain a safe shutdown condition:

1. If both RHR pumps failed durino the period when the decay heat level is still relatively high, then the plant conditions would permit decay heat to be removed by the steam generator (s). Condensate supplied from the condensate storage tank, raw water reservior, and the auxiliary salt water system (unlimited supply) via temporary connections could provide a lona term source of auxiliary feedwater for decay heat removal.
2. If the steam generator (s) were not available, and the decay heat is relatively low, one RHR pump is generally used to remove decay heat with one pump in standby, in accordance with the requirements o# Technical i Specifications 3.9.8.2. In case the operating RHR pump is damaged due to closure of a suction valve, the standby RHR punp could be used to continue the decay heat removal function after the closed suction isolation valvels) i is manually opened by an operator. Analyses indicate that if all decay A.d-177.3

heat removal capability were lost at the time of reactor trip, at least 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> would be available for the operators to restore decay heat removal capability before core uncovery. If decay heat removal capability were lost while on RHR cooling, considerably more time than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> would be available for operator action to correct the situation.

3. If both RHR pumps were damaged while the steam generators were open for

. maintenance (or during any other period in which all steam genrators were unavailable), the charging pumps or safety injection pumps could be used to inject water into the RCS for core cooling. If the manways on the stean generator primary side were open for maintenance, water would ficw out the manways and onto the floor of the containment. The containment spray system and the fan coolers, which are independent from the RHR system, could be used to remove decay heat inside containment to the ultimate heat sink via the component cooling water or the essential service water system.

4. Diablo Canyon Operating Procedure No. E0P-17 addresses the emergency procedure under the condition that both RHR pumps are danaged during plant shutdown.

In summary, the staff recognizes that closure of either of the two isolation valves in series in the RHR hot leo wetion line would prevent the RHR system from performing its decay heat removal function and could result in damage to the RHR pumps if not corrected. Our evaluation has concluded that:

A.4-177.4

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a. Although the staff did not specifically evaluate the Diablo Canyon RHR system against the criteria of BTP RSB 5-1 at the time the system was reviewed, the staff concludes that the system meets the intent of BTP RSB 5-1 for Class 2 plant implementation. The only deviation we have identified is the lack of a qualified auxiliary feedwater supply in excess of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. However, there are other diverse auxiliary feedwater sources available, which, while not designed to safety grade standards, nontheless provide a high degree of assurance that an ample auxliary feedwater supply will be available. .

b) Technical Specifications and administrative procedures are in place at the plant to assure that the two series isolation valves in the RHR suction line are locked open with power sources removed from the valve operators.

fioreover, a RHR low flow alarm will be installed and made operational prior to power operation to ensure that the operators will be alerted to any low flow condition that would occur in the RHR suction line, such as could occur from a closed isolation valve. Given spurious isolation valve closure as an initiating event, the failure of the operators to follow administrative procedures and technical specifications, combined with a failure of the low flow alarn or the operators to take corrective action in the presence of a low flow alarm must be postulated in order for RHR pump damage to result.

The staff considers that the need to postulate two independent failures to lose the RHR capability meets the intent of the single failure criteria.

A.4-117.5

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