United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-63: Loss of Safety Injection Capability

                                                            SSINS No.: 6835 
                                                                   IN 86-63 

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                            WASHINGTON, DC 20555

                               August 6, 1986

Information Notice No. 86-63:   LOSS OF SAFETY INJECTION CAPABILITY 

Addressees: 

All pressurized water nuclear power reactor facilities holding an operating 
license or a construction permit. 

Purpose: 

This notice is to alert recipients to a potentially significant problem 
pertaining to the loss of safety injection (SI) capability as a result of 
common-mode failure of SI pumps from crystallization of boric acid. The NRC 
expects that recipients will review this notice for applicability to their 
facilities and consider actions, if appropriate, to preclude a similar 
problem occurring at their facilities. However, suggestions contained in 
this notice do not constitute NRC requirements; therefore, no specific 
action or written response is required. 

Related Documents: 

AEOD Engineering Evaluation Report E606: "Loss of Safety Injection 
  Capability at Indian Point Unit 2," May 1986. 

NRR Generic Letter 85-16: "High Boron Concentrations," August 23, 1985. 

NRC "Report to Congress on Abnormal Occurrences," NUREG-0090, Vol. 8, No. 2,
  November 1985. 

Description of Circumstances: 

On December 28, 1984, during operations to top off the ECCS accumulators, 
the licensee at Indian Point Unit 2 observed discharge pressure to two SI 
pumps to drop from 1100 psig and 1500 psig, respectively, to about 700 psig 
corresponding to accumulator pressure. These pumps were secured from 
operation. The third SI pump could not be manually started. The licensee 
declared all the safety injection (SI) pumps inoperable and manually tripped
the reactor. The malfunction of the pumps was apparently caused by boric 
acid crystallization blocking pump suction and by possible gas binding of 
the pumps. 

Two parallel, leaky valves in the discharge line of the boron injection tank
(BIT) enabled highly concentrated boric acid to flow through the low 
pressure 



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                                                             IN 86-63 
                                                             August 5, 1986 
                                                             Page 2 of 3   

discharge line (SI pump suction) and to precipitate in the pumps, which were
not heat traced. Degassing of the nitrogen cover gas dissolved in the boric 
acid solution is believed to be one of the likely sources of gas found in 
the pumps. 

On May 10, 1974, a precursor to this event took place at Indian Point 2. In 
that event, two of the three SI pumps were rendered inoperable as a result 
of boric acid crystallization. No gas was noted in the pumps at that time. 

On June 1, 1984, while in cold shutdown, the licensee at San Onofre Unit 1 
found the two boric acid flow paths required by the plant's Technical 
Specifications to be blocked. The blockage was caused by crystallization of 
boric acid between the boric acid storage tank (BAST) and the charging 
pumps. There are two parallel lines, one having a transfer pump and the 
other a boric acid injection pump. Both were blocked. The operators were 
using highly concentrated boric acid from the BAST to rapidly make up to the 
refueling water storage tank (RWST) but failed to monitor concentration and 
solubility. Viable alternate flow paths were established by shifting the 
charging pump suction to the RWST and by using a manual bypass valve for the 
transfer pump. 

Discussion: 

These events demonstrate the potential for losing emergency safety injection
capability by common-mode failure resulting from either boric acid 
crystallization or gas binding of the pumps. As to the gas binding 
possibility in the December 1984 event at Indian Point 2, the licensee 
studied the possible sources of gas and concluded that the probable effect 
of gas evolution on pump performance would be minor. 

Originally in Westinghouse (W) plants, the addition of highly concentrated 
boric acid solution (20,00 ppm) to the reactor coolant system (RCS) 
following a design-basis main steam line break (MSLB) was intended to 
compensate for the addition of positive reactivity to the core by the sudden 
cooling of the RCS. In most W plants, the BIT (or equivalent) is located 
downstream of the SI pumps. On an SI signal, the pumps inject the BIT 
contents into the RCS, provided the RCS pressure is less than the SI system 
shutoff pressure. Indian Point Unit 2 is among the few W PWRs that has the 
BIT upstream of the SI pumps. Other plants with a source of Boric acid 
similarly located include San Onofre 1, Haddam Neck, Yankee Rowe, Point 
Beach 1 and 2, Prairie Island 1 and 2, Kewaunee, and Ginna. Of these plants, 
San Onofre 1, Haddam Neck, and Yankee Rowe use typically 2,000 ppm boric 
acid from the RWST for SI. Indian Point 2 uses a 20,000 ppm solution from 
the BIT, while Point Beach 1 and 2, Prairie Island 1 and 2, Kewaunee, and 
Ginna use a 20,000 ppm solution from the BAST for SI. 

Recent evaluations of the design-basis MSLB accidents in some W PWRs have 
revealed excessive conservatism regarding boric acid requirements. In some 
cases, it was shown that the requirements of 10 CFR 100 would not be 
exceeded if the BIT were eliminated or if the boric acid concentration were 
reduced. Following the Indian Point 2 event on December 28, 1984, NRR sent 
Generic 
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                                                             IN 86-63      
                                                             August 5, 1986 
                                                             Page 3 of 3   

Letter 85-16 to all licensees of W plants to encourage them to reevaluate 
their MSLB analysis and the need for the BIT. So far, in addition to Indian 
Point 2, at least the following plants have received NRR approval for 
removal of their BIT and/or for modifying technical specification 
requirements that would allow operation with reduced boric acid 
concentrations: 

Turkey Point 3 and 4
Harris 1 
Surry 1 and 2 
Beaver Valley 1 
South Texas 
McGuire l (McGuire 2 was licensed without a BIT) 
Catawba 1 and 2 
Callaway 
Farley 1 and 2 
Trojan 

For those plants that are still required to provide high boric acid 
concentrations for SI, plant-specific procedures normally provide for 
flushing the SI system after every SI actuation to prevent boric acid 
precipitation in the piping and for periodic sampling of the SI system. 

No specific action or written response is required by this information 
notice. If you have any questions about this matter, please contact the 
Regional Administrator of the appropriate regional office or this office. 


                                   Edward L. Jordan Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  Vern Hodge, IE
                    301-492-7275

                    Raji Tripathi, AEOD
                    301-492-4435

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