ML20245L772
| ML20245L772 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 08/11/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20245L756 | List: |
| References | |
| NUDOCS 8908220298 | |
| Download: ML20245L772 (6) | |
Text
.,
q e
\\
L. c,
v
~. _ "
- g UNITED STATES k,,'
7L J,.;
. NUCLE AR REGULATORY COMMISSION 3g f
usmNcTON. D C. 20555
&A
)
1...'.
u.
.(
l
' ENCLOSURE 3 S UE v EVALUATIOf4 B) THE OFFICE OF NUCLEAR REACTOR REGULATION SLFPO? TING RENDMENT NC.123 TO FACILITY OPERATING LICENSE NO. OPR-77 AND AMEfiDtiENT NO. 112 TO FACILITY OPERATING LICENSE N0. DPR-79 TENNESSEE VALLEv AUTHORITY SEOP0YAH NUCLEAR PLANT, UNITS 1 AND 2 f.'
DOCKET NOS. 50-327 AND 50-328
- .E-INTRODUCTION Ey letter catec Accust 2, 1989, the Tennessee Valley Authority (TVA) requested exigert amendments tc the operating licenses for the Sequoyah Nuclear Plant, Dr.its 1 and :.
If approved, the amendments would temporarily. revise Surveil-lance Requireme,t (SR) 4.4.11.a. " Reactor Coolant System Vents." of the Seouoyah ' Technical Specifications (TS).
This is one of the SRs to detemine if.
tne reactor-vessel head vent system is operable.
The proposed changes are.to-act a foctnote to the requirement for each unit that the manual isolation valves for the reactor vessel head vent system must be locked open.
The footncte states that "the requirement to verify that the upstream manual 1 solation valves are locked in tne open position is waived until the cycle 4 refueling outage.
This waiver is granted on a one-time basis. At the first Mode 5' outage'follt 19 the issuance of the above waiver, a flow verification test will be perfcer, j to verify that the manual' isolation valves are open."
The changes would apply for both Units 1 and 2 until the next refueling outage, which is the Cycle 4 refueling cutage for both units.
The Cycle 4 refueling outages are scheduled for Spring of 1990 for Unit 1 ana Fall of 1990 for
. Unit 2.
This is TW TS change request 89-38.
As discussed below, the Commission determined, pursuant to 10 CFR 50.91, that these amenaments should be implemented as soon as possible. A Public Notice that. the NRC staff proposed to amend the operating licenses of Unit 1 and
. Unit 2 was published in the Chattanooga News-Free Press and the Chattanooga Times on Tuesday, August 6, 1989.
2.0 EVALUATION The purpose of the reacter vessel head vent system is to vent non-condensible gases and steam frcm the reactor coolant systi.3, if needed, to maintain core cooling.
These gases mey inhibit core cooling Juring natural circulation curing post-accident conditions.
The head vent system is connected to the reactor vessel heac by a pipe with two manual isolation valves in series.
The head vent syster is cownstreen of these manual isolation valves.
$$[2ggggg Q 7
P
e
.a ll 2
On July. 28,1989, TVA discovered that the two manual isolation valves upstream
)
of the reactor vessel head vent system for each unit were verified cpen before
< the restart of each unit from the last refueling outage but not locked open as required by the TS. Except for this, the head vent system is operable. The requirement that these valves be locked open did not exist at the time the units restarted.
The units were in compliance with their TS when they restarted from their las_t refueling outage but they came into non-compliance with their t
TS when the amer.cments issuing the new requirements on the head vent system s
were' issued on June 1, 1989.
The valves cannot now be locked because the-units are at 100% power and the valves are. inaccessible when the reactor is at power because of their proximity to the reactor vessel heaa and the high radiation levels in that area. Also,
.the missile shields above the reactor vessels would have to be removed. The TS.
require that if the manual isolation valves cannot be locked the units must be shut cown thirty.osys later, which would be August 27, 1989. The proposed changes would allow both units to continue operating with the manual isolation valves not.being lockea until the Cycle 4 refueling outage for each unit.
In its. letter dated August 2, 1989, TVA explained that flow verification tests of the head vent system conducted during startup for each unit provide further assurance that the manual isolation valves are open. Because of the relatively-short time between when the flow tests were run and when the valves became inaccessible during the startup of the units, it is unlikely that the valves could have been accidently closed. The manual isolation valves are inside containment for each unit and access to the containments is controlled.
However, in order to provide further verification that the manual isolation valves are open, TVA stated that it will perform a second set of flow verifica-tion tests on the head vent systems when each unit next enters Mode 5 or colo shutdown.
In its letter dated August 2, 1989, TVA provided the following details concerning its conclusion that the manual isolation valves are open. The manual isolation valves on Unit I were verified open on August 5, 1988 by a two-person sign-off. On August 26, 1988, flow was verified through the head vent system during performance of Surveillance Instruction (SI) 166.41 which incicates again that the manual isolation valve in Unit 1 are open.
Following the performance of S1-166.41, access to the manual isolation valves was restricted by removing the scaffolding from lower containment and setting the missile shield in place in preparation for entry into Mode 4.
The missile shield was set in place on September 24, 1988, and Unit 1 entered Mode 4 on September 27, 1988.
The manual isolation valves on Unit 2 were verified open on March 10, 1989 by a two-person sign-off. On March 26, 1989, flow was verit ied through the system during. performance of S1-166.41 which inoicates that the manual isolatior, valves in Unit 2 cre open.
Following the performance of SI-166.41, access to the manual isolatior valves was restricted by removing the scaffolding from lower containment anc' setting the missile shield in place in preparation for entry into Mode 4 The missile shield was set in place on March 26, 1969. The missile shield was removed to facilitate leakage repair work and reset on March 30, 1989, and Unit 2 cotered Mode 4 on April 5, 1989.
The manual isoletion valves on each unit have been verified open by two independent means and the head vent system is available to perform its intended
1; 1
3
(
l4 function. Therefore, it is concluded that locking the manual isolation ~ valves is not needed ic meet the underlying purpose of SR 4.4.11.a until the next refueling outage. A second flow test auring the next entry into Mode 5 would be a further verification that the valves are open. Requiring the flow verification tests to verify the manual isolation valves are open was not considered when the requirements on the reactor vessel vent system were added to the TS because they-were not proposed by TVA. -The proposed changes provide
. en alternative, reliable method to assure the manual isolation valves are open.
The two methods of-assuring the manual isolation valves are open are the following:
(1) lock the valves open and (2) conduct a flow verification test.
The two methods are comparably reliable. They are both conducted af ter the.
valves are verified open by'a two-person sign-off and before the valves are made inaccessible.
The first method assures that the position of the valves can not be accidently changed but it relies on the individuals doing the two-person sign-off correctly to assure the valves are open. The second method assures that the valves have been left open but it relies on the controlled eccess to the containment that the position of the valves is not accidentally changed.
The manual isolation valves would have to be locked open for each unit to return to power from the Cycle 4 refueling outage.
Based on the above, the staff concludes that the proposed changes are accept-able. The second set of flow verification tests will be conducted in Mode 5 to prevent overstressing the solenoid-operated valve actuators in the heaa vent system, which might occur if the tests were conducted at full system pressure.
3.0 EX1 GENT CIRCUMSTANCES The Commission has determined that these changes should be implemented as soon as possible. The amendments would permit the licensee to. continue operating the units until the Cycle 4 refueling outage. The proposed changes have no adverse effect on safety and would be beneficial to overall plant safety because the units would not be fcrced into an unnecessary shutdown. Although the manual isolation valves are open, they are not locked in this position. Therefore, the reactor vessel head vent system is considered inoperable and the TS require that power be removed f rom the system. The staff issued a Waiver of Compliance on July 31', 1989 to return power to the reactor vessel head vent system. This Waiver of Compliance from the TS is temporary until this amendment request is acted on. Consequently, the NRC staff has determined that exigent circumstances exist which justify reducing the public notice period normally provided for
-licensing amendments and proposes to issue the :mendment at the close of business of August 10, 1989.
4.0 FINAL NO SIGNIFICAliT HAZARDS CONSIDERATION The licensee and the NRC staff have evaluated these proposed changes with regard to the determination of whether or not a significant hazards consideration is involved. Operation of Sequoyah, Units I and 2, in accordance with the proposed amendment will not involve a si nificant increase in the probability 5
or consequences of an accident previously evaluated. The reactor vessel head vent system is designed to vent non-condensible gases and steam from the reactor coolant system, if needed, to maintain adequate core cooling following an accident. This system normally is not operated. The only purpose of the
4
('
marval isoletiomvalves is to isolate the head vent system from the reactor vessel. 'These valves must be open when the units.are operating for the head r
urt system to function. The assurance that the valves are open for both units is the double verification check of valve position and the flow verification test. The proposed changes provide an alternate, comparably reliable method to the locked valves to assure the manual isolation valves are open. Therefore,
.because the head vent system remains fully operational in the event of an accident, the proposed change does not affect the assumptions or consequences of any previously analyzed accident.
The proposed amendment will not create the possibility of a new or different kind of accident from any previously analyzed. The proposed change does not affect the function or the design of the head vent system or of any other safety system in either unit. The proposed changes only provide an alternative.
-method of assuring the manual isolation valves.are open. The head vent system remains avc Dable to perform its intended function.
The proposed amendment will nct involve a significant reduction in a margin of safety because the changes propose a comparably reliable method to assure valve position. The' head vent system is still available to perform its intended function.
The requested amenoment has been evaluated against the standards in 10 CFR 50.92 and the NRC staff has determined that the requested amendments involve no significant hazards considerations. The changes do not significantly~ increase the possibility or consequences of any accident previously considered, nor create the possibility of an accident of a different kind, nor significantly cecrease any margin of safets, 5.0 WA1VER OF COMPLIANCE On July;28,1989, the two manual isolation valves upstream of the head vent system for each unit were discovered to have been verified open before the restart of each unit from the last refueling outage but not locked open as required by the TS. The units were in compliance with their TS when they restarted from their last refueling outage but they came into non-compliance with their TS when the amendments issuing the new requirements on the head vent system were issued on June 1,1989. The valves car.not now be locked because the units are at 100% power and the valves are inaccessible when the reactor 'is at povfer. With the head vent system of each unit considered inoper-able, the TS require that power be removed from the solenoid-operated valve actuators in the_ head vent systems and, if the manual isolation valves cannot be locked, the units be shut down th1rty days later, which would be August 27, 1989. To comply with the TS, TVA removed the power frera the valve actuators on July 28, 1989.
By letter dated July 28, 1989, TVA requested the waiver of compliance to restore power to the valve actuators until it could submit this exigent TS change to prevent the plant shutcown on August 27, 1989 anc the NRC staff acts on the TS change. TVA stated that it was prudent to restore power to the four valve actuators because the configuration centrol process at Sequoyah provides assurance that the manual isolation valves are, in fact, open and the head vent systern woulo then be fully operational in the event of an accident.
t j
I
~
5 On July '31,1969, in a telephone conference, TVA staff explained that flow verifi-cation tests of the head vent system conducted during startup for each unit provides further assurance that the manual isolation valves should be open.
Because of the relatively short time between when the flow tests were run and j
when the valves became inaccessible curing the startup of the units, it is i
unlikely that the valves could have been accicently closed.
However, in order to provide firal verification that the manual isolation valves are open, TVA agreed to perform a seconc set of flow verification tests on the head j
vent systens when each unit next enters Mode 5 or cold shutdown. These flow l
tests would be conducted in Mode 5 to prevent overstressing the solenoid-oper-
)
ated valve actuators in the head vent system, which might occur if the tests J
were to be concucted at full system pressure.
]
The staff concluded that there was a basis for it to consider amending the TS 1
for Sequoyah to prevent the shutdown of both units.
It was, therefore, prudent
{
to return power to the solenoid operated valves in the head vent systems for i
both units because there is assurance that the manual isolation valves are open and it is not likely that they would have closed since the flow verification tests were perfornied even though they were not locked open. At 4:00 p.m. on July 31, 1989, the staff granted TVA the Waiver of Compliance to return power to the head vent systems for both units until the staff can act on the proposed TS change but for no later than August 27, 1989. This was documented in the staff's letter to TVA dated July 31, 1989.
6.0 CONSULTATION WITH THE STATE On August 7 and 10, 1989, the State of Tennessee was contact by telephone and the proposed amendment was discussed. A copy of the Public Notice issued by the staff with its preliminary determination of no significant hazards consideration was telecopied to the State. On August 10, 1989, the State contact had no comments on this determination.
7.0 RESPONSES FROM THE PUBLIC In The Public Notice for this proposed action, the NRC staff stated that all ccmnents received by the close of businss on August 10, 1989 would be considered in reaching a final determination of no significant hazards con-sideration. The staff received two telephone calls from the public before the close of business on August 10, 1989. There were no comments on the amendments and no requests for hearing.
8.0 ENVIRONMENTAL CONSIDERATION
These amendments involve a change to a requirement with respect to the installa-tion or use of a f actiity component located within the restricted area as defined in 10 CFR Part 20 and changes to the surveillance requirements. The staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed findir.g that these amendments involve no significant hazards consideration and there has been no public ctment on such finding. Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement nor environmental assessment need to be prepared in connection with the issuance of these emendments.
i l
1
g_.
6 9.0 CONCLUS10N' The staff has concluded, based on the considerations discussed above, that:
(1).tners'is reasonable assurance that the health and safety of the public will not be endangered by. operation in the proposed manner, and (2) 'such activities will be ccnducted in compliance with the Commission's regulations, and the issuance of the amendments will not be inimical to the common defense and security nor to the health and safety of the public.
Principal Contributor:
J. Donohew Dated: August 11, 1989 i
lw _
_ ___-