ML17339A407

Forwards Info Requested by NRC 781128 Ltr Re Analyses & Evaluations Performed to Resolve Containment Purge Issue. Results of Valve Integrity Evaluation Anticipated by June 1980

ML17339A407
Person / Time
Site:	Turkey Point
Issue date:	12/13/1979
From:	Robert E. Uhrig FLORIDA POWER & LIGHT CO.
To:	Schwencer A Office of Nuclear Reactor Regulation
References
L-79-346, NUDOCS 7912200508
Download: ML17339A407 (10)

Text

REGULAT INFORMATION DISTRIBUTION YSTEM (RIDS)

ACCESSION NBR: 7912200508 DOC ~ DATE: 79/12/13 NOTARIZED: NO DOC KK,T FACIL:50 250 Turkey Point Plant~ Unit 3p Florida Power and Light C 050 50 251 Turkey Point Plantg Unit Ar Florida Power and Light C 05000251 AUTH INANE AUfHOR A FFILI AT ION uHRIG,R;E; Florida P ower rr Light Co ~

REeIP. NAME REC IP IKN T AFFILIATION SCHRENCERiA ~ Opera'ti ng Reactors Branch 1

SUBJECT:

Forwards info requested by NRC 781128 tr re analyses 1 evaluations performed to resolve containment pur'ge issue, Results of valve integrity eva,luation anticipated by June 1980','ISTRIBUTION CODEo A034S COPIES RECEIVED:LTR ~ ENCL~ SIZEe TI L : Containment urg>ng N OT r=A ES ~~ >>~>>>>>>>>>>~>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>eereat>>>>>>>>ecto>>>>mes>>>>>>>>>>>>>>>>>>>>>>~swee+>>>>>>>>>>>>>>>>wteeawea~

RECIP IKNT COPIES RECIPIENT COPIES ID CODE/NAgE- 'Ef TR ENCL ID CODE/NAME. LTTR ENCL ACTION; 05 BC +R~ WI 7 7

• INTERNAL vi REG 1 1 0?. NRC PDR 1 1 1 IKE 2 2 14 TA/EDO 1 i5 CORE PERF BR 1 1 17 ENGR BR i i i8 ANZAC 8FTY BR 1 1, 19 PL'ANT SYS BR 1 20 EEB i 21. EFLT TAT SYS i 2? BRINKMAN 1 .?3 0 8HUM 1 24 K REEVES 1 EXTERNAL: 03 LPDR 1, '1 04 NSIC 25 ACRS 16 16 1'OTAL NUMBER OF COPIES REQUIRED ~ LTTR 39 ENCL 39

0 P.O. BOX 529100, MIAMI, FL 33152

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fAssA FLORIDA POWER (IL LIGHT COMPANY December 13, 1979 L-79-346 Office of Nuclear Reactor Regulation Attention: Mr. A. Schwencer, Chief Operating Reactors Branch ¹1 Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Dear Mr. Schwencer:

Re: Turkey Point Units 3 8 4 Docket Nos. 50-250 8( 50-251 Containment Pur e

References:

(1) NRC letter dated August 28, 1979 from A. Schwencer to R. E. Uhrig (applicable to Docket Nos. 50-250 8 50-251)

(2) NRC letter dated September 27, 1979 from Darrell G. Eisenhut to All Light Hater Reactors (3) NRC letter dated October 23, 1979 from A. Schwencer to R. E. Uhrig (applicable to Docket Nos.

50-250 8( 50-251)

In response to your letter of November 28, 1978, several analyses/evaluations have been performed in an effort to resolve the containment purge issue. A description of this effort, which is responsive to references (1) through (3),

is given below.

Attachment 1 contains Westinghouse Electric Corporation's evaluation of the effect of containment purgi ng on the Emergency Core Cooling System (ECCS) performance. The evaluation indicates that the effect of purge operation upon the calculated pellet cladding temperature is small.

An assessment of the incremental increase in radiological dose caused by containment purging during the initiation of a postulated Loss of Cooling Accident (LOCA) is presented in Attachment 2. The results clearly indicate the anticipated total LOCA dose to be well within the limits of 10 CFR 100.

A table of postulated containment purge valve failure modes is presented in . The unique scheme using double solenoid valves for the control air provides the assurance of purge valve closure in addition to the second valve in series. contains a response to the Reference (1) request for infonaation.

In order to demonstrate purge valve integrity and operability when subjected o~

to LOCA conditions, the valve manufacturer (Henry Pratt Company) has been 5

~exes 00 <<8'EOPLE... SERVING PEOPLE

Office of Nuclear R or Regulation Page 2 contracted to perform the necessary analyses. The results of the analyses are anticipated by June 1980. However, for the interim period, FPL, in consultation with Henry Pratt Company, has determined that satisfactory operability under accident transient conditions is expected when the purge valve opening is limited. A plant change/modification is being processed to.

implement a purge valve modification restricting the valve openi ng to a maximum of 50 degrees.

In addition, the containment purge system was previously evaluated with respect to I&E Bulletins 79-01 and 79-01A. The FPL response concerning the qualification of class 1E electrical equipment was sent to you on July 3, 1979 (L-79-182). As indicated then, the investigation for data identified problems relating to qualification documentation generic to the nuclear industry.

Those that apply to containment purging at the Turkey Point plant concern ASCO solenoid valves. The July 3, 1979 submittal provides justification for continued operation (section 3.3-6) until replacement solenoid valves (which have been ordered) can be installed.

In conclusion, Florida Power & Light Company intends to operate the containment purge system in compliance with our letter of June 8, 1979, a commitment to limit our combined contai nment purges for Turkey which'ontained Point Units 3 and 4 during power operation (>25 power) to 200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br /> per year for the site (200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br /> total for both units), until such time as the 50 degree modification is implemented. The effect of purging on ECCS performance and radiological dose has been shown to be minimal. The results of the valve integrity evaluation, to be performed by the valve vendor, are expected to be available by June, 1980.

We will keep you informed of our progress in this matter.

f Very truly yours, Robert E. Uhrig Vice President Advanced Systems & Technology REU/MAS/cph Attachments (4) cc: Mr. J. P. O'Reilly, Region II Harold Reis, Esquire

ECCS f Per ox~ar e Evaluation

.According to Branch Technical Posi'tion CSB6-4, evaluation of a containment purge.

system design should include "an analysis of the reduction in containment pressure resulting from the partial loss of contairment atmospnere during the accident for ECCS backpressure determination". Such an analysis has been performed for Turkey Point Units 3 and 4 based on the containment conditions defined in the limiting FAC analysis case (DECLG break, C = 0.4) assuming 22~

tube plugging using the modified February, 1978 Mestinnghouse Evaluate'ion Model.-

The containment isolation signal received in that analysis will initiate valve closure shortly after inception of the LOCA. The plant purge systems utilized during reactor operation consist of two lines, one 48 inches in diameter and one 54 inches in diameter. They are conservatively represented in this compu-tation as follows:

l. A 5 second isolation valve closure time is assumed. Credit is taken for the reduction in effective f1ow area which occurs whi'le the valve is in the process of closing. The flow area is reduced linear'ly with time as the valve position moves from fully open to fully closed.

2. The frictional resistance associated with duct entrance and exit losses, filters. ductwork bends and skin friction has not been considered.

3. Ho fan coastdown effects are considered.

4. Ho inertia is considered. Steady state flow out the purge system ducts is established immediately at the time of the LOCA.

A mixture of steam and air will exha~yt from the containm nt through the purge .

ljnes during the time that the isolation valves remain open. The effect of.

the composition of the gas being exhausted on containment pressure has been bounded by investigating the two extreme cases. air alone and steam alone.

Mithin several seconds of the inception of the LOCA. containment pressure will have increased to the point that critical flow will occur in the purge lines.

To conservatively bound the calculated containment gas mixture exhausted throuoh the purge lines, critical flow rates of steam and air were calculated during the C - 0.4 DECLG break transient, Using these flowrates critical flow was D

conservatively assumed to be in effect from time zero.. Eouation (4.18 in I

Reference (1), was employed to calculate the cr tical flow rate of air tnrou h the Turkey Point purge lines.

Figure 14 of Reference (2) was apolied to compute the critical flow rate of steam through the purge lines'. The total mass released during the tim period that, the valves are presumed open is conservatively calculated as 11299 lbs. air or 8588 lbs.

steam. The containment pressure reduction resulting from this loss of air is computed to be 1.84 psi; the pressure reduction associated with the loss of steam is 2.36'si.

The most recent ECCS performance analysis executed for Turkey Point resulted in a calculated peak clad temperature (PCT) of 2161 F at a peaking factor of 1.89. The effect 'of containment pressure upon the calcuated PCT of a plant whose PCT is computed'o occur during FLECHT cooling (i.e. flooding rate greater than 1 inch per second) is typically 5 F/psi. Applying this backpressure sensitivity factor t'o Turkey Point indicates the calculated PCT will continue to exhibit margin to 2200 F'for the limiting containment pressure reduction of 2.36 psi. Overall, the effect of purge operation upon the calculated PCT is small, and the most recent Turkey Point ECCS performan'ce analysis provides an appropriate basis for operation at an F value of 1.89 with no restrictions on the operation of the containment purge system.

REFERENCES:

1) Shapiro, A. H.. The Dynamics and Thermodynamics of Compressible Fluid Flow.

~

Volume 1, p. 85.

2. 1967 ASNE Steam Tables, p. 301.

At tachme>>t Page One

~Raddolo ical Assessment oi Containment Pur e The radiological doses due to a postulated Loss of Coolant Accident (LOCA) were originally presented in Section 14.3.5 of the FSAR. The original FSAR analyses assumed there was no containment purging occurring at the onset of the accident. A new evaluation was performed to determine the incremental radiological dose at the site boundary and low population zone assuming the purge valves are fully open when the accident initiates and close upon receipt of signal as designed. These incremental doses, when added to those presented in the FSAR, provide a maximum set of doses f'r a LOCA with containment purge. The results of this evaluation are presented in the following tab3 es:

THYROID DOSE (rem)

Location LOCA Increment due Total To Pur in Site boundary 93 10 103 (0-2 hour)

Low Population Zone 9 10 (0-2 hour)

Mhole Body (rem)

Site boundary (0-2 hour) 3.1 .002 3.1 Low Population Zone .4 .0002 .4 (0-2 hour)

The major assumptions which were used in the evaluation of the incremental dose are listed below:

1. The containment purge valves- are closed 5 seconds after the containrfknt high pressure signal is transmitted. There is a 2.7 second delay before the increased containment pressure is detected which results in a total of 7.7 seconds for valve closure (8 seconds was conservatively assumed) .

2. Radioactive releases. via the purge valves during 'closure is from the Reactor Coolant System only.

'3. The primary coolant iodine activity corresponds to the maximum limi't of 30 pCi/gm Dose Equivalent which is specified in the Turkey Point License.

At aehmunt, 2 Page Two

4. It is conservatively assumed during the initial 8 seconds that 50% of the blowdown (worst FSAR case) from the break flashes and becomes homogeneously mixed in the containment atmosphere. All of the iodine in the flashed steam is assumed to become airborne.

5. The flow through the purge valves is .assumed to be a mixture of steam and water. Frictionless flow through the valves is assumed.

6. FSAR meteorology is assumed.

7. Standard TID 14844 methodology was used to calculate the incremental doses.

The results clearly indicate that the anticipated dose caused by a LOCA with containment purging at the onset of the accident is well within the limits of 10 CFR 100.

t tacllm.'-.n t 3 CONTAINMENT PURGE VALVE S INGLE FAILURE ANALYS IS TABLE COMPONENT FAILURE MODE RESULTS Main Valve or Fails to close or 2nd purge air valve in series Operator fails to seat or signal will'provide the required to close not received. isolation.

Instrument Air Failure of air. Purge air valves are closed by Supply to the spring, air is NOT required for Operator closure.

Solenoid Valve Fails to operate Two solenoid valves in series (i.e., does NOT are used, thus 2nd solenoid isolate the operator valve would isolate air cylinder from air supply and dump operator air.

supply and does NOT Further back-up is provided provide air bleed off by the 2nd purge air valve for the cylinder). in series.

Attachnent 4 la) The non-seismic duct work, which has the opening" covered by expanded metal face plates ox by grilles and dampe s, provi.de limiei",d protection inside the cont:ainment against only low density debris sue" as foil insulation, paper, or rags. go missile protection is provM. d for duct woxk.

lb) Ho safety xeIated equipment is located in the flow stream beyond the outboard purge isolation valves, at the supply or exhaust: penetrations.

At Turkey 'Point the outboard valves axe outdoors. The safety related structuxes beyond the valves have been designed against tornado missiles as described in the PSAR, Section 5E.2.

lc) . The purge valves are listed among the five. types of penet:rations to

~

be given local leak detection tests at not less t:han 50 psig, using pressure decay, soap bubble, halogen detection, or equivalent methods, at each refueling (See, PSAR, Section 15, Technical Specificat:ion 4.4.2).

'he stated acceptance, criteria is that the sum of all local leak rate tests'shall not exceed 60 percent of the total containment allowable leak rat:e. PS&.'Figure 14.3.4-.2 indicates no pressure transient in excess of 50 psig fo- double ended, 6 squaxe feet, 3 square feet, and 0.5 square. feet pressure spectrum of potential breaks, against which

, the valves must close. Valve leakage is only applicable to a closed (zero flow)'valve. For release prior to closure see response to 7.d below>>

The total release thxough the containment purge system assuming

'initially fully open valves, .single valve failure, and conservat:ive low friction high flow rates, has been calculated for the spectrum of break sizes illustrated in PSAR Pigure 14.3.4-2,,titled "Contain-

'ent Pressgre Transients". The results of the calculation show that the 0.5 ft break resulted in less total release than the double ended break, taking into account t:he longer time scale due to slower pressure

• rise. Hence, the double ended break remains the worse c"'e for total release through the cont:ainment purge system. Plass xelease for the double ended break is less than t:he 17,000 lb. figure which was used in the dose calculations. Realistic valve flow calculations has resulted in a further mass flow reduct:ion to less than 9,000 lbs.

STATE OF FLORIDA )

) ss.

COUNTY OF DADE )

Robert E. Uhrig', being first duly sworn, deposes and says:

That he is a Vice President of Florida Power 6 Light, Company, the Licensee herein; That he has executed the foregoing document; that the state-ments made in this said document are true and correct to the best of his knowledge, information, and belief, and that he is authorized to execute the document on behalf of said Licensee.

Robert E. Uhrig Subscribed and sworn to before me this Wo'l day of 19~ rr NOTAR PUBLIC, in a d for the county of Dade, State of Florida Notary Public, State of Florida at Large My Commission Expires May 5, it98t Bonded thru Maynard Bonding Agency My commission expires: