ML19323A965
| ML19323A965 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/10/1980 |
| From: | Rubenstein L Office of Nuclear Reactor Regulation |
| To: | Parris H TENNESSEE VALLEY AUTHORITY |
| References | |
| NUDOCS 8005090023 | |
| Download: ML19323A965 (9) | |
Text
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'<g UNITED STATES 8'
NUCLEAR REGULATORY COMMISSION p,
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APR 101980 Docket No.:
50-327 Mr. H. G. Parris Manager of Power Tennessee Valley Authority 500A Chestnut Street Tower II Chattanooga, Tennessee 37401
Dear Mr. Parris:
SUBJECT:
REQUEST FOR INFORMATION ON SEQUOYAH UNIT NO. 1
~ is the list of requests for information on the low power test program that was provided informally to your staff during the discussion on the proposed program. is the list of questions from R. Savio, Staff Engineer, for the ACRS. These items will be discussed at the next ACRS Subcommittee, tentatively scheduled for April 28th. Although some of tne questions are directed to the NRC staff, we request that you respond to all the listed items, to the extent possible, in order to assist us in the review of this matter. A response by April 22, 1980 would be appreciated.
Please call if there are questions.
Sincerely, Ciw ch $ <
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L. S. Kubenstein, Acting Chief Light Water Reactors Branch No. 4 Division of Prcject Management
Enclosures:
As stated l
cc w/ enclosures:
See next page.
Tennessee Valley Authority s
ccs:
Herbert S. Sanger, Jr. Esq.
General Counsel Tennessee Valley Authority 400 Commerce Avenue E llB 33 Knoxville, Tennessee 37902 Mr. E. G. Beasley Tennessee Valley Authority 400 Commerce Avenue, 249A H8B Knoxville, Tennessee 37902 1,r. Michael Harding
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Westinghouse Electric Corporation P. O. Box 355 Pittsburgh, Pennsylvania 15230 Mr. David Lambert Tennessee Valley Authority 400 Chestnut Street Tcwer II Chattanooga, Tennessee 37401 Mr. J. F. Cox Tennessee Valley Authority 400 Commerce Avenue, W10Cl31C 4
Knoxville, Tennessee 37902 Resident Inspector /Sequoyah NPS c/o U.S. Nuclear Regulatory Commiss,i_on P. O. Box 699 Hixson, Tennessee 37343
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ENCLOSURE 1
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SEQUOYAH SPECIAL TESTS 1.
Based on discussions during our meeting with TVA personnel on January 11,19S0, it is our understanding that the procedures for the special low pcwer tes:s t
you submitted are not intended to be self-sufficient, instead, tne special procedures 4150 requim use of the norr.al plant operating proc 4cm, the plant technical specifications, and special test exceptions to the tecnnical speci fications. This appmach has the advantage of providing additional operator training in the use of these nomal plant procedures, but does rake the operators' duties more complex during the low p:wer test program. Other potential difficulties include possible conflicts or ambiguities between the special procedures and the normal operating procedures, lack of clear instructions to the licensed operators regarding the actions they should take if specified limits are exceeded during testing, and any ambiguity as to tne responsibility and authority of the licensed operators relative to that of the test director.
The staff has concluded that TVA should prepare some type of lead or master document. This document should:
a.
Include an outline of the entire test program, defining the sequence in which the individual tests will be performed.
b.
Specify, for each individual test, wnich conditions snould be established or maintained, and what orders or instructions aoply during the peried the test is being perfomed, including the applicaale emergency procedures if an Acceptance Criterien is exceeded.
c.
Specify that at the conclusion of each individual. test that normal technical specifications and licensed plant conditions, including safety system settings, apply.
There may be some exemption for a specified short time period if the same test is planned to be repeated.
- d..$pecify that the plant administrative procedures will be followed when tests are being conducted so there will be no doubt that the licensed senior operator has the authority and msponsibility to direct the licensed operators in accordance with 10 CFR 55.4e.
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1.
Please ' provide for staff review a lead or master test document that covers the items listed above.
2.
The following coments and questions on the procedures for the special tests c.nly to o!1 of the special tests:
a.
Prerequisites should refer to any special arrangements of the plant that are not the same as called for by the normal operating procedums.
For example, any systems that mquire valve lineups that are different from normal should be noted in prerequisites.
b.
Why are only 4 in-core therinoccuples to be recorded on the trend recorder?
If there is the capability a record more this should be done.
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c.
In Appendix C, page 9, K0791 is stated to be equal to 0.075. This nu.ber T
is based on. four pumps operating.
We suspect this number will chance under low flow conditions. Will this invalidate the tests or give the j
operator an erroneous picture of what is happening?
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d.
The special test procedures and test exemptions should be thoroughly reviewed r.
relative to the nomal operating procedures and technical specifications to assure that there are no ambiguities that will arise durino testing.
Item 2.20 of Test !7 requires evacuation of construction personnel.
e.
Consideration should be given, in conducting other tests, to evacuating people from those areas in which they might, accidentally or othemise,,
i jeopardize safe caration or satisfactory test perfor: nance, f.
Where there are several valves to be operated in a single step, such as in item 5.10 of Test #7, there should be a signeff for each valve: This will help prevent nissing a necessary valve move ent.
The sare philosophy should be applied to similar multipie equiprent condition I
changes.
g.
Some notes and cautions are included in the procedures for some tests wnich appear equally applicable to tne other tests. These should be included in all the tests.
3.
The following questions and conraents apply to the procedures for the specific tests noted:
a.
Test 2.
Item 2.13 should specify the diesels to be cold so that their response is more typical of e.at would be exoected in an accident.
Item 5.24 should specify~ which header is to be verified as being wam.
b.
Test 3. (1) Item 5.11 should state the direction (increase or decrease) of change of charging flow and stear flow required to increase the saturation margin.
(2) Item 6.4, if satisfactorily achievec, should be the basis for preparing, later, a standard operating procedure for future use.
1 Test 7. (1) Item 5.67 discusses blo: king of safety injection between tests.
c.
TheapproachTVAhastakenappearstobencn-conservativeinthatl there may be significant time that passes between tests, thus leaving the plant without complete safety protection. When the end of the test is declared, the plant snould be placed back intt l a condition that satisfies the applicable Technical Specification and other l'icense conditions.
See Question 1.c.
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(2) Reference to the fourth sheet of Data Sheet 5.2 should be made
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maintained and checked at the required frequencies.
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Test 8. (1) Items 2.6 and 2.7 pemit disabling of two reactor trips.
What trips remain operable?
(2) Item 2.9.2 indicates that the reactor power and inter adiate range channels will be ronitored at 5-minute intervals.
We suggest they be conitored cuch r. ore often, preferable continuously.
(3) Item 2.10 indicates that 3 in-core therrocouples will be monitored.
All other tests use 4 thermocouples.
Please explain this inconsistency.
(4) Concerning the note following item 5.16, see our coment concerning Item 5.67 of Test 7 and Question 1.c.
e.
Test 9A.
From Item 2.5 it appears that the reactor coolant flow rates in
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loops 3 and 4 are not being recorded. Wny not?
4.
The low power test program you have proposed for' Unit l of Sequoyah includes
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a number of natural circulation tests with single pnase flow.
Each of the operating crews will obtain " hands-on" experience in performing each test.
which we agree will provide useful training.
However, we are concerned that G
this emphasis on single phase natural circulation will cause the operators to believe that this is the only condition that they would enco 9ter following an accident. We need the following information to determine if our concerns are valid.
I.9 there a small or intermediate si:e LOCA (including a stuck open a.
PORV) that would require heat transfer using the steam generator to remove U
decay heat and yet discharge enough mactor coolant inventory such that two phase conditions would exist in the RCS?
Your response should consider A
situations where there are no single failures as well as cases where R..:
one ECCS train is partially or totally inoperable.
i b.
If the answer to item (a) is yes, describe the training given to the operators to cope with this situation.
5.
Provide your schedule for submitting a safety analyses for each special test of your proposed low power test program.
6.
You have verbally agreed to perform tests to ootain base line data mgarding differential pressure across the elbow pressure taps in each reactor coolant loop for various cump combinations.
These tests should be conducted at~ isothermal conditions with the core installeo, out all cor tr l rod 7.ssemblies inserted.
o The reactor coolant system should t:e at about norral operating temperature and omssure.
The tests should be cerformd with one pump, two pumps and three cumps oparating. The differential pressure data should be obtained in all four loops; that is,'the loops with flow in the norami direction and the locos that wj have flow in the reverse direction.
Ptr.o data such as motor current and rpm (if possible) should be recorded.
Confim your co nitment to perfccm these tests and provide a brief test procedure for staff review.
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e 7.
There may be the need to perform some hot isothermal, :ero~ pcIer tests to f
meas 0re such items as normal system heat loss and rate of pressure ce:ay i;
due to heat losses in the pressuri:er in order to be able to.cornictly inttrpret
.f the data from the test procosed.
For example, in test 6, ;he eyerimntally determined change in the temperature of the reactor coolant W1 reflect j,o.ii the algebraic sum of the pit,p energy input, the heat losses enrougn t e insulation, and the heat removal capability of the charging and letdtvn system. Please review your overall test program and determine if there is a need to perform such supplemental tests.
8.
The instrucents for measuring hot leg and cold leg temperatures may be subiect to significant errors at the low flow rates tnat will exist during natural 3
circulation.
Under these flow conditions, heat losses to the environrent through the instrument mounts, combined with low heat transfer coefficients
- ' 'r at the sensor might lead to indicated temperature readings that are mch 1:wer than the actual bulk coolant temperature. This may make the control of the tests more difficult than anticipated.
Provide a description of tFie means you will use to confirm the accuracy of the hot and cold leg temperature measurerents. or alternate means of contr-lling these temperatures during testing.
If tne cold leg temperature masu enen-will be confirmed by using the temperature of the saturated fluid on :ne s. ell side of the steam generator, how will local subcooling, due to faccwater addition near the outlet of the Ustubes be controlled or limited?
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9.
Provide an evaluation which demonstrates that the radiation levels that will Tl exist after the low power test program is completed (including that frot c ud y,if deposits) will not preclude implementation of requirements steming
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from the NRR Lessons Learned Task Force, Xereny Comission, Rogovin Ccmission c.
or Task Action Plan.
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ENCLOSURE 2 QUESTIONS REGARDING THE LICENSING OF THE SEQUOYAH PLANT 1.
The general subject of the nitrogen in the UHI accumulator tank is of some interest.
The nitrogen is prevented from entering the primary system by active means (series valves).
What is the reliability which is associ-ated with this system and what would be the effect of ingesting large j
quantities of this gas in the primary loop after a very small break in the primary system or after a massive cooldown following a main steam line break with failure being failure to cut off the main feedwater.
Vortexi ng/ gas c.4 ingestion in the UHI tank would provide anotner mechanism for transferring gas into.the primary system even though the valves closed on signal.
What would be the uncertainty associated with the measures taken to prevent this event (hardware used and the tests results and analysis used to detennine setpoints).
2.
To what extent has the NRC reviewed the details of the design of the auxiliary control room, its capability for overriding the control room.
functions, and the vulnerability of the auxiliary control room to the eventse which would cause the loss of functions for the main control room.
3.
What are the reliability classes for the readout / indicating equipment in the control room?
Would the operator have a clear indication of the status of the-plant under emergency conditions?
How is operator action, in the event of conflicting instrument, indications, treated in the procedures?
4.
icenarios have been identified in which the ice condenser containment compartment drains may be plugged.
Has the additional structural load which would result from water accumulation been considered?
5.
To what extent is the ice condenser containment vulnerable to dynamic /-
static loadings which would result when the external pressure is higher than the interior pressure? For what events would this type of load be significant?
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.c 6.
Discuss the testing / analysis which has gone into establishing the operability of the containment purge valve.
What uncertainties woeld be associated with the operability of this system?
Are the dynamic forces on the ducting which are associated with the purge valve closure significant?
What physical tests are required?
7.
To what extent has the release of radioactivity from the containment into the auxiliary building during an accident by way of penetration / seal failures been considered?
How would access to the auxiliary building and -
adjacent structures be affected?
What capability exists for short te rm cleanup? To what extent is the control room environment protected from this and other accidents having potential consequences beyond the design bases?
Towhatextentarethepressurizek,heatersandassociatedsupportequip-8.
ment environmentally qualified for accident conditions?
To what extent are,
- the PORVs and associated equipment on primary-secondary systems environmen-tally qualified for accident conditions?
9.
The following questions apply to conditions during the base design flood:
ar' To what extent is the decay heat removal process dependent on natural
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convection and will the THI-2 experience lead to any change in the method for dealing with this event?
b.
Would the flood condition result in a release of any combustible fluids or toxic gases which are stored at the plant? How are these materials controlled to prevent fire and other damage?
10.
To what extent were plant design engineers involved in the writing of the emergency procedures?
11.
To what extent has TVA, independently of Westinghouse, looked at the syse/ design of the UHI?
What does TVA believe are the advantages /disadvant-ages of the UHI in a base loaded plant?
12.
Discuss the capability of the plant to withstand the loss ofs all AC power.
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- 13. Discuss the relative reliability of the various subsystems within the DC
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power system Does the redundancy in the number of banks of batterid5 dxtend
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through the whole system?
Are there cases, even with a large number of batteries, where certain redundant safety systems are served by just two t
batteries?
Are such systems normally on critical duty? To what extent has tae potential for other systems in the plant for causing failures of the DC power system been looked at?
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Is it cleer in light of the TMI-2 experience that the decay heat can be removed from the core without serious core damage af ter loss of the j
secondary loop?
What additional improvements could be made in existing j
primary side hardware which would increase the reliability of the decay heat removal process withouc assisance from the secondary loops?
Some specific topics to be considered would be improveme~s in the PORY system and pilot motors (on emergency power) on the reactor, coc.s at pumps..
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15.
Westinghouse has claimed that a significant capabiliy exists for the "sweepout" of noncondensible gases for high points in the primary system during the natural convection process.
What plans exist for the experimen-tal demonstration of this phenomena?
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