ML20097J849

Clarifies Re Method to Be Used to Enhance Moisture Removal If Request for Relief from 100 Psia Pcrv Pressure Restriction Granted.Helium Mass Flow Rate Through Circulator Differential Pressure Increased

ML20097J849
Person / Time
Site:	Fort Saint Vrain
Issue date:	09/13/1984
From:	Gahm J PUBLIC SERVICE CO. OF COLORADO
To:	Jay Collins, Johnson E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
P-84351, TAC-59936, NUDOCS 8409240059
Download: ML20097J849 (2)

Text

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of Odlendo 16805 WCR 19 1/2, Platteville, Colorado 80651 September 13, 1984 Fort St. Vrain Unit #1 P-84351 G20Ws W

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Mr. John T. Collins 1,J Regional Administrator SEP I 8124 U. S. Nuclear Regulatory Commission

,4 611'Ryan Plaza Drive, Suite 1000

~

3 Arli,.gton, Texas 76011 i

ATTN: Mr. Eric H. Johnson

SUBJECT:

PCRV Pressurization Above 100 psia REi-ERENCE:

1) PSC Letter, Lee to Johnson, Dated E

8/22/84,(P-84310)

2) NRC Letter,- Johnson to Lee, Dated 6/28/84,(G-84215)

Dear Mr.-Col' lins:

The purpose of this letter is to clarify statements that were made in Reference 1) regarding the method that we would employ to enhance moisture' removal should our request for relief from the 100 PSIA PCRV

. pressure res r ct i tion be granted.

The-current restriction of maintaining the PCRV pressure at

. <:100 psia has significantly reduced our capability. for removing remaining moisture from the primary coolant, particularij when it is combined with the low' circulator helium inlet temperatures that now exist.(< 100'F).

When moisture is introduced into the PCRV via the circulator bearing water auxiliary system, it accumulates in the insulation near the affected

. circulator.

The rate of moisture removal from the insulation is dependent on a number of variables, but the two major parameters, are the differential pressure across the circulator inlet to outlet plenums, and, less importantly, the temperature of the' primary coolant.

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,,.. Historically, we_ have determined that. the =best. mechanism for jincreasing the circulator differential pressure is to pressurize the TPCRV and then to. operate the affected circulator at a relatively high speed. This method of operation increases the helium mass flow rate through tne ~~ circulator diffuser, resulting in a higher circulator differential pressure and'an increase in the rate of moisture removal

'fromo the' insulation.

It also results in a larger-helium mass flow trate through the purification system.

-The above method can Lbe somewhat. enhanced, by-increasing the temperature of.the primary coolant..In order to accomplish this, auxiliary boiler steam is admitted to the reheat section of the steam generator (s) to heat the primary coolant as it passes over the steam

. generator. tubing.

. Typical.PCRV pressures. and primary. coolant temperatures are in the 150-300: psia' and.250-400*F ranges under the described moisture

. removal._ effort. Obviously, the exact pressures and temperatures are dependent,on a number of. plant conditions which may exist at _the time.

As always, the Fort St. Vrain Technical Specifications will govern our-activities..We will, of course, maintain the reactor in_a shutdown condition until released to startup by the NRC.

Since -restricting the. PCRV pressure to < 100 psia is in no way related to: the control rod-drive _ situation currently under investigation,' and.since continued high moisture levels in the PCRV

.are not desirable, we request relief from the 100 psia PCRV pressure restriction' imposed by Reference 2).

1. I f you have~ any' questions, please contact Mr. Chuck Fuller of my staff at (303) 785-2224.

Sincerely,-

J. W. Gahm Manager, Nuclear Production Fort St. Vrain Nuclear-Generating Station

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