05000272/LER-1995-017, :on 950718,CR Emergency Air Conditioning Sys Failed to Meet GDC 19 Criteria.Performed Calculactions to Identify Alternative Operating Mode for Eacs to Ensure That Requirements of GDC 19 Satisfied

:on 950718,CR Emergency Air Conditioning Sys Failed to Meet GDC 19 Criteria.Performed Calculactions to Identify Alternative Operating Mode for Eacs to Ensure That Requirements of GDC 19 Satisfied

ML18101A890
Person / Time
Site:	Salem
Issue date:	08/11/1995
From:	Zarechnak A Public Service Enterprise Group
To:
Shared Package
ML18101A889	List: 05000272/LER-1995-017, :on 950718,CR Emergency Air Conditioning Sys Failed to Meet GDC 19 Criteria.Performed Calculactions to Identify Alternative Operating Mode for Eacs to Ensure That Requirements of GDC 19 Satisfied ML18101A887
References
LER-95-017, LER-95-17, NUDOCS 9508170070
Download: ML18101A890 (4)

LER-1995-017, on 950718,CR Emergency Air Conditioning Sys Failed to Meet GDC 19 Criteria.Performed Calculactions to Identify Alternative Operating Mode for Eacs to Ensure That Requirements of GDC 19 Satisfied

Event date:
Report date:
2721995017R00 - NRC Website

text

NRC FORM 366 (4-95)

I LE(4)

U.S. N AR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

(See reverse for required number of digits/characters for each block)

OVED BY OMB NO. 3150-0104 EXPIRES 04/30/98 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTION REQUEST: 50.0 HRS.

REPORTED LESSONS LEARNED ARE INCORPORATED INTO THE LICENSING PROCESS AND FED BACK TO INDUSTRY.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH (T-6 F33), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT 05000-272

)

1OF4 FAILURE OF CONTROL ROOM EMERGENCY AIR CONDITIONING SYSTEM TO MEET GDC 19 CRITERIA A. Zarechnak 609 - 339 - 1755 11----+-----+------+-----+-----fll-----+----+----+------+------ll As a result of reviews being performed as part of corrective actions in LER-95-006 and other ongoing efforts, it was determined on July 18, 1995 that the GDC 19 requirements for control room habitability would have exceeded the 30 rem thyroid dose limit b¥ about 5 rem for a LOCA event at Salem.

This was reported on that date in accordance with 10 CFR 50.72.

The UFSAR uses an assumed value of 100 cfm for air in-leakage to the control room for calculating the dose.

The value used is considered to be much less than the current expected in-leakage.

Use of the realistic air in-leakage number results in an increased thyroid dose which exceeds the GDC 19 criteria when combined with ingress and egress dose.

Current Emergency Air Conditioning System configuration following a LOCA according to UFSAR section 9.4 is a 10 hour1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> recirculation/one hour pressurization cycle.

To meet GDC 19 criteria the Emergency Air Conditioning System needs to be placed and maintained in the pressurization mode within three hours of a LOCA event.

This is a change to the design basis and will be reflected in emergency procedures prior to restart of the unit.

The UFSAR will also be revised.

This issue is reportable under 10 CFR 50.73(a) was outside the design basis of the plant.

9508170070 950811 PDR ADDCK 05000272 NRC FORM 366 (4-95)

S PDR (2) (ii) as a condition that (4-95)

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET LER NUMBER (6)

SALEM GENERATING STATION, UNIT 1 05000-272 YEAR I <>C:.NUUMBE~AL I ra::=u'I 95 017 00 TEA l (If more space 1s required, use aaa1uona1 copies or NHi., Form.:sooA) (17 I.

PLANT AND SYSTEM IDENTIFICATION

Westinghouse -

Pressurized Water Reactor PAGE (3) 02 01-04 Energy Industry Identification System (EIIS) codes and component function identifier codes appear in the text as [xx/xx].

II. IDENTIFICATION OF OCCURRENCE The Salem Generating Station UFSAR describes the Control Room dose consequences following a loss-of-coolant accident in Chapter 15.4.1.4.

This describes the design of the Control Room Emergency Air Conditioning System (EACS)

[VI/-] being in a recirculation mode for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> followed by a one hour pressurization mode, and then returning to the recirculation mode.for another 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />.

The stated doses in the UFSAR are well below the limits specified in Footnote 2 of 10 CFR 100.

However, calculations to support response to one of the corrective actions in LER 95-006 indicate the current configuration of the Control Room envelope exceeds the UFSAR stated doses and further exceeds the 10 CFR 50 Appendix A, GDC 19 criteria for Control Room Habitability in modes 1, 2,and 3.

Doses are within acceptable values for the current configuration during modes 4 and 5.

III. CONDITIONS PRIOR TO OCCURRENCE Unit 1:

Unit 2:

Mode 5, Reactor Power 0 %,

Mode 5, Reactor Power 0 %

IV.

DESCRIPTION OF OCCURRENCE Unit Load 0 MWe Unit Load 0 MWe LER 95-006-00 reported a condition where the Unit 1 and 2 Control Room EACS would not have automatically actuated into the emergency recirculation mode in response to a high radiation signal.

One of the corrective actions in LER 95-006-00 stated "Before restart of either Salem Unit from the current self-imposed shutdown of both units~ the current design basis of the Control Room EACS and supporting radiation monitoring equipment will be appropriately documented.

Appropriate design changes will be implemented,* as necessary."

As part of the LER review and other ongoing efforts, the design bases of the Control Area Air Conditioning System (CAACS)/Emergency Air Conditioning System (EACS) were examined.

This review recognized the need to assess the ca~ability of the system operating in the Inside Air (recirculation) and Mixed Air (pressurization) modes.

Assessment results using current information and industry accepted practice indicate that doses exceed GDC 19 criteria of Appendix A to 10 CFR 50 for LOCA conditions.

The UFSAR uses an assumed value for air in-leakage to the control room for calculating dose.

The value used is considered to be much less than the current expected in-leakage.

Use of realistic air in-leakage values results in an increased thyroid dose which exceeds the GDC 19 criteria when comb.ined with ingress and egress dose. {4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET SALEM GENERATING STATION, UNIT 1 05000-272 TEXT (I more space is reqwred, use a ditiona copies of NRC Form 366 ) (17)

V.

APPARENT CAUSE OF OCCURRENCE U.S. NUCLEAR REGULATORY COMMISSION The need to reconstitute the design basis for the emergency air conditioning S¥stem was recognized ~n 1988 during the development of the Configuration Baseline Document. for the EACS.

Specifically, the control room dose calculations available were poorly documented and the control room air in-leakage basis was not sup~orted by specific calculations.

An engineering effort was initiated to reconstitute this information that resulted in the development of several proposed design basis calculations.

These calculations all showed that the design of the EACS satisfied the requirements of GDC 19.

However, none of the calculations were final accepted as design basis, primarily due to the limited technical basis for the control room air in-leakage.

Therefore the issue remained unresolved.

The most coinrnon presently accepted industry practice for calculating control room air in-leakage is the Standard Review Plan guidelines.

The control room air in-leakage was calculated in 1994 using this approach which increased the air in-leaKage to about 800 cfm during recirculation and about 450 cfm during pressurization compared to the original 100 cfm value assumed in the UFSAR.

However the effect on increased dose from the higher air in-leakage was not determined.

As a result of the LER 95-006 corrective action review and other ongoing efforts, the effects of the increased air in-leakage on the control room dose were calculated in mid July, 1995.

The increase in air in-leakage, used with the conservative methodology developed by Murphy and Campe (industry accepted practice) resulted in the calculated thyroid dose exceeding the requirements of GDC 19 by about 5 rem.

The extended period of time required to reconstitute the missing elements of the EACS design basis and recognize the link to possible effects on GDC 19 criteria is attributable to hllinan error by assigning a low priorit¥ to resolving this issue.

The lack of a questioning attitude concerning the potential significance that the increased air in-leakage had on the control room dose also contributed to the period required to resolve this problem.

VI.

PRIOR SIMILAR OCCURRENCE LER 91-038 This LER identified.a Control Room habitability concern from a postulated ammonium hydroxide releas.e.

In th_is instance there was a design change whereby the contents of a storage tank were changed to ammonium hydroxide.

Appropriate controls and evaluations were ~erformed to address this concern.

The methodology used in these evaluations does not use air in-leakage and therefore is not affected by the problem noted in this LER. {4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET SALEM GENERATING STATION, UNIT 1 05000-272 more space ts required, use additional copies of NRG Form 366 (17)

VII. SAFETY SIGNIFICANCE

.S. NUCLEAR REGULATORY COMMISSION Evaluation of the safety significance of this event has shown that the existing emergency air conditioning system configuration complied with the requirements of GDC 19 for all habitability concerns except thyroid dose.

In addition doses are within acceptable values for the current configuration during modes 4 and 5.

The control room thyroid dosage complies with the GDC 19 limits for the system operation and air in-leakage documented as the UFSAR licensing basis. When the estimates for the air in-leakage developed using the Standard Review Plan guidelines are combined with the original design basis for LOCA, the calculated thyroid dose exceeds the GDC 19 criteria by about 5 rem.

The design basis source term values are considered to be conservatively high.

Based on the source term definition accepted for the Advanced Light Water Reactor design, the NRC and the industry are evaluating the use of more realistic source term methodology for operating plants.

Use of realistic source term predictions and the current calculated air in-leakage indicate the GDC 19 criteria would not likely have been exceeded if an event had occurred.

VIII.CORRECTIVE ACTIONS Calculations were performed to identify an alternative operating mode for the EACS to ensure that the requirements of GDC 19 were satisfied.

Using the air in-leakage value for the control room area calculated in accordance with the Standard Review Plan methodology and a standard, conservative model of the dose impact of in-leakage, it was determined that the reguirements of GDC 19 are satisfied as long as the pressurization mode of EACS operation is implemented within three (3) hours of the LOCA event.

Continued operation of the EACS in the pressurization mode for the duration of the accident condition is also required.

Based on this evaluation, emergency procedures and the UFSAR will be revised to implement the pressurized operating mode as the design basis for the system.

The revised mode of operation for the EACS will be implemented prior to the restart of the Salem units.

An improved corrective action process for emergent issues has also been established for Salem Nuclear Generating Station.

This process, Corrective Action Program, Nuclear Administrative Procedure NC.NA-AP. ZZ-0006 (Q) Rev 9, includes a more rigorous initial operability assessment of each potential problem.

The Corrective Action Program requires a review by the Senior Nuclear Shift Supervisor for operability and reportability determinations whereas the previous engineering process did not require this review.

Existing plant issues are being re-evaluated for operability and safety significance by both the Engineering Review of Issues for Restart and the System Readiness Review Team.

This effort will ensure that the priority assigned to all existing issues reflects the significance of the issue. The existing issues will be resolved based on the priority assigned as a result of these two screenings.

These continuing efforts will ensure that any other significant issues receive appropriate attention for resolution.