ML20235U486
| ML20235U486 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 10/05/1987 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| NUDOCS 8710140110 | |
| Download: ML20235U486 (8) | |
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I TENNESSEE VALLEY AUTHORITY CH ATTANOOGA, TENNESSEE 374o1 SN 157B Lookout Place 1
00T 051987 I
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk l
Washington, D.C.
20555 l
Gentlemen:
In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - UNIT 2 - OVERVIEW OF HYDROGEN (H ) ANALYZER
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2 ISSUES The purpose of this submittal is to summarize the various issues currently l
outstanding for the SQN unit 2 H2 analyzers and to give a status of the respective corrective actions. These items were discussed with NRC management in our meeting of August 19-20, 1987. This overview is provided in accordance l
with your request.
H2 analyzer deficiencies were initially identified during an NRC inspection (327. -328/86-62) conducted between November 12-21, 1986. The following excerpt is transcribed from this NRC inspection report:
The field installation of the H2 monitors for both Units 1 and 2 did not implement the vendor (Comsip Delphi, Inc.) requirement regarding sample line slope and insulation.
The failure to properly route and insulate the sample line results in the condensation of moisture for the containment post-accident H2 sample in-route to the detector.
This installation can create two potential problems:
- 1) water traps present a torturous path for the H2 gas to reach the detector although the vendor did indicate, in a phone call, that the pump was capable of pumping any water that reaches the analyzer, 2) a true reading of containment vapor H2 concentration is not possible as long as actual containment moisture is greater than that the detector sees.
The adequacy of the installed system to satisfy the operability requirement of TS 3.6.4.1 is identified as Unresolved Item (URI 327/86-62-01, 328/86-62-08) pending NRR review, Several related items associated with the H2 analyzer installation were also identified. These items along with the inspector's concerns are listed on the next page:
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. U.S. Nuclear Regulatory Connission OCrf 051987 NUREG 0737 item II.F.1 (6) requires the H2 analyzer be a continuous monitor or be activated within 30 minutes af ter receiving a SI signal.
A review of the emergency instruction (EI)
E-0, " Reactor Trip or Safety Injection," indicated no reference to activation of the H2 analyzer within 30 minutes of the SI.
The inspector discussed this item with the group responsible for emergency procedures. The licensee indicated that task analysis has shown that if a true SI occurs, procedure E-0 will drive the operator to other procedures which will instruct the operator to activate the H2 analyzer equipment.
The inspector could find no time criteria established in any procedure review which would j
ensure the H2 analyzers are functioning within 30 minutes after j
an SI.
This item is identified as Inspector Followup Item I
(IFI 328/86-62-10).
Revision 3 of the Sequoyah FSAR changed the specified accuracy of the H2 Analyzer from the previous value to +/- 1.5% Hydrogen which is +/- 15% of scale for the instrument.
The inspectot requested that the licensee produce a 10 CFR 50.59 safety evaluation which should have been performed prior to changing the FSAR.
The annual update of the FSAR is to ensure plant modifications made during the year are accurately reflected in the l
l FSAR.
It appears that TVA has used the FSAR update process to correct problems identified in the FSAR.
It is the NRC position that changes to the facility as described in the FSAR, either physical or documentary, need to be supported by a 10 CFR 50.59 Safety Evaluation (TVA Unreviewed Safety Question Determination (USQD)). TVA was requested to provide the USQD for the identified change.
This item is identified as Unresolved Item (URI 327/86-62-03 and 328/86-62-11) pending receipt and review of the USQD.
Additionally, TVA has recognized other H2 analyzer discrepancies. These have been documented using the Condition Adverse to Quality Report (CAQR) process and were evaluated for deportability determinations.
CAQR SQP 870430 noted the removal of a train A containment leak test valve with the line subsequently left uncapped.
CAQR SQP 870431 identified that the train B containment leak test valves are located incorrectly. They are situated on the inboard side of the isolation valve and should be located outboard.
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. U.S. Nuclear Regulatory Commission OCrf 051987 CAQR SQP 870431 noted that the train A sample line was plugged with an unknown dry material.
CAQR SQP 870431 also noted that the train A sample line does not extend to upper containment, but ends in the pressurizer cubicle.
This is inconsistent with the SQN Final Safety Analysis Report (FSAR) because a representative sample of containment H2 concentration is required for evaluation.
Addressing each of these identified issues separately:
1.
Existence of sample line water traps that exceed vendor recommendations.
TVA conducted a walkdown, with the resident inspector, of the SQN unit 2 sample lines inside as well as outside of containment. The largest water trap outside containment was five feet, which is within the guidelines of the equipment vendor recommendations.
(Correspondence dated January 13, 1987 Comsip Inc., to G. Gupta, TVA,
" Inlet vacuum should not exceed a cumulative water head in excess of five (5) or six (6) feet ")
Inside containment, however, water traps of approximately seven feet for train B and 14 feet for train A were observed. TVA produced calculations demonstrating that the temperatures in the area of the train B sample lines inside containment are greater than the sampled atmosphere and thus will prevent moisture from condensing.
Accordingly, a water head greater than that specified by the vendor would not be formed.
These calculations were discussed with and given to the SQN resident inspector for review.
Train A inside containment lines, however, are routed in areas that are flooded post-loss of coolant accident (LOCA), and subsequently experience temperatures that are calculated to produce unacceptable moisture condensation.
To correct this condition. TVA has rerouted the sample lines inside containment to remove large traps. This action, although required only on train A, was taken on both trains in order that this issue expediently and unquestionably be resolved.
This rerouto has been completed by TVA.
The adequacy of the currently installed system to satisfy the operability requirements of technical specification 3.6.4.1 has therefore been assured. Further confirmation will be performed before mode 2, 2.
H2 analyzer actuation within 30 minutes of a Safety Injection (SI) signal.
A closure folder was assembled to address this issue and was presented to the SQN resident inspector.
After review, it was determined that this issue could be closed.
L j
. U.S. Nuclear Regulatory Comnission To summarize TVA's position:
Emergency Instructions (EI) and procedures were written to expeditiously and safely bring the power station to an orderly shutdown.
Each step has been defined based on necessary prerequisites being in place and a subsequent action then being required to mitigate an event.
Top priority is and should be the prompt acknowledgment and resolution of the situation at hand in the most orderly method possible.
TVA instructions are additionally based on the recommendations of the Westinghouse Owners' Group (WOG). These recommendations have been reviewed and accepted by the NRC staff. WOG instructions do not specify the imposition of intermediate time requirements for measurement of H2 concentration.
TVA writers guidelines for instructions and procedures and Institute of Nuclear Plant Operations Emergency Operating Procedures Writing Guideline also caution against the use of time to initiate operator actione.
Operator actions should be related primarily to plant parameters.
NRC has reviewed and commented on these guides.
EI E-0, " Reactor Trip or Safety Injection," admittedly does not reference activation of the H2 analyzer within 30 minutes of the SI signal.
It does, however, direct the operator to another instruction, E-1, " Loss of Reactor or Secondary Coolant." Step 17 of E-1 places the containment H2 analyzers in service. Step 25 of this same procedure transfers residual heat removal pump suction to the containment sump.
For the large break LOCA, with two trains of the engineered safety features operating, table 6.3.2-5 of the SQN FSAR ir.dicates that this action would have been performed within 14 minutes of initiation of the SI signal.
Given the above, TVA believes the establishment of an additional timeclock on activation of the H2 analyzer is not required.
3.
Revision to specified H2 analyzer accuracy in SQN FSAR.
The revision to the specified accuracy was discussed in a telephone conference call with NRR on May 19, 1987.
Originally, SQN's FSAR defined instrumentation accuracy as i 0.1 percent H2 or i 1 percent of scale. This reflected a vendor guarantee for the detector alone, not the entire system. TVA performed an instrumentation loop accuracy calculation that determined the entire instrument accuracy to be i i percent H2 or 10 percent of acale.
With account given to condensation effects, overall instrumentation accuracy is i 1.5 percent H2 or 15 percent of scale.
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. 'l U.S. Nuclear Regulatory Commission 00ff 051987 W
A USQD was performed for the subject FSAR change on March 26, 1987,.
l which concluded that the indicated accuracy of the H ' analyzers 2
would not exceed 1.5 pcreent. This item was reviewed in a recent inspection (50-327 -328/87-42) and dispositioned as follows:
" Licensee actions taken to resolve this specific violation and corrective steps taken'to avoid similar future violations (B45 861114 257 - DNE Program plan for Update FSAR Revisions;.
L44 870203 805-ECN Closeout and FSAR Updates) appear to be satisfactory."
4.
Removal of train A containment leak test valve.
CAQR SQP 870430 noted the removal of a train A containment leak test-valve with the line subsequently left uncapped. potential Reportable Occurrence (PRO) 2-87-011 evaluated this condition for deportability.
Copies of these determinations have been given to the SQN resident inspi ator for review.
The containment integrity aspects were evaluated.
It was determined that the valve was most likely removed after the last successful test of the system, which was conducted in August 1985 (during the current outage).
Consequently, containment integrity was not compromised, and this item was not reportable.
Valves and capa were replaced as part of Design Change Notice K00006.
The valve has been added to the. appropriate locked valve list and will be verified locked closed as part of the containment integrity surveillance.
5.
Train B containment leak test valve installation at incorrect. location.
CAQR SQP 870431 noted that the containment leak test valves for the H2 analyzer train B are located on the' inboard side of the isolation valve and should be on the outboard side.
A review was performed as a part of PRO 2-87-011, on April 3, 1987.
Determination was made that the configuration would not have resulted in an inability to leak test the closed loop Hydrogen Analyzer System 4
(HAS). This resolved the question of operability.
]
i Test valves have presently been relocated to their proper position, and design drawings revised accordingly.
6.
Train A samplo line blockage.
CAQR SQP 870431 indicated the blockage of the train A sample line with a foreign material.
.. U.S. Nuclear Regulatory Commission
}g Further investigation detenmined this to be a partial blockage as previous performance of SI-219 did not indicate the existence of a low.
l flow condition as no low-flow alarms were given.
The root cause of this condition will be determined when the material is properly analyzed.
In the interim, the blockage has;been removed; and the line will be checked.for flow in'accordance with TVA's commitment to confirm system performance, before mode 2.
PRO 2-87-58 has evaluated this condition and determined it to be reportable, in accordance with defined deportability procedures.
7.
Train A sample line does not extend to upper cont ainment.
CAQR SQP 870431 documented this condition. The sample line for train A did not run to upper containment as: required,-but rather ended in the top of the pressurizer cubicle. This routing did not allow for a representative sample of containment H2 concentration to be obtained.
PRO 2-87-58 determined this condition to be reportable. TVA has:since corrected this routing with the modification described in condition 1 on page 3.
The NRC inspector additionally questioned the upper containment sample point for analyzer train B.
This sample point is located 18 inches above the upper containment floor.
Concern was expressed that a representative H2 concentration would not.be obtained from this location. The SQN Hydrogen Collection System (HCS) withdraws air from the containment domeL and dead-ended compartments and mixes the containment atmosphere by way of the Containment Air Return Fans (CARF), thus' ensuring that any point in containment will yield a representative sample.
The'HCS is part of the CARF system and is described in FSAR section 6.2.
The mixing described in this section of the FSAR is different.from the mixing of upper and lower compartment samples obtained in the HAS itself. 'TVA maintains that HAS train B, as presently configured 'will therefore obtain a representative containment sample, i
b
. 00ff1)51987 U.S. Nuclear Regulatory Commission i.e In summary. the SQN unit 2 hydrogen analyzer system has been the subject of
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several varied deficiencies. While the operability of train A could admittedly be questioned, that of train B should not.
Corrective actions have l
been taken by TVA to amend all of the identified issues and prevent future' recurrence.
The NRC staff and inspectors will be apprised of the status for all corrective l
actions.
Very truly yours, TENNESSEE VALLEY AUTHORITY R.
ridley.. irector Nuclear Lice sing and Regulator Affairs Enclosure cc (Enclosure):
Mr. G. G. Zech. Assistant Director for Inspection Programs Office of Special Projects U.S. Nuclear Regulatory Commission 101 Marietta Street, NW, Suite 2900 j
Atlanta, Georgia 30323
^i Mr. J. A. Zwolinski, Assistant Director for Projects Division of TVA Projects Office of Special Projects o
a U.S. Nuclear Regulatory Commission 4350 East-West Highway EWW 322 Bethesda, Maryland 20814 1
Sequoyah Resident Inspector i
Sequoyah Nuclear Plant 2600 Isou Ferry Road Soddy Daisy, Tennessee 37379 l
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ENCLOSURE OUTSTANI(IRGCOMMITMENTS H2 ANhtiZER ISSUES
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Confirm adequate performance of the H2 analyzer system before mode 2.
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